The 187 Million Dollars Gmail Bug


The scene takes place at a multi-billion dollars company, running some of the most well known e-commerce sites in the world.

It’s a cold day of winter, as every last Tuesday of the month, it’s the on-boarding for new employees.

Teams and leaders are giving various presentations about the business, the teams, their products, the partners, the competitions and many more topics. Some talks are actually quite interesting.

One of the last presenter requests participants to use the service, find something we want and go through the purchase as if we were intending to buy it.

The point of this exercise is obviously to get some opinions and feedbacks…

I’ll spare you the full narrative of the session. Except, one insignificant details toward the end, one person in the back of the room saying she cannot login to the site.

If a decade of experience has taught me anything, it’s that for every user who complains, there can be another million who experience the same issue, making your product plain unusable for all of them. Always follow on feedback, no matter how stupid or irrelevant they seem, they can be the tree that hide the forest.

What can be so special that it doesn’t work with her? Let’s find out.


She cannot login, because she forgot her password. She did the “reset password” many times and it does NOT work.

Why would this not work? Let’s have her try and reset it one more time.

Forgot Password => Reset => “Instructions have been sent to …”

The email is allegedly sent… and it is received by her gmail.

screenshot gmail subject
New message in the inbox!

She opens it and click the reset link and it doesn’t work.

Why does this not work? The page says “invalid or expired link, try again to be sent a new email“.

So, let’s click again. Except this time, it’s my turn.

We open the gmail, it shows that there is a new unread message again. Great!

Looking carefully, there is something unusual on the bottom of the email conversation…

screenshot gmail hidden
New messages are not shown. They need to be manually expanded. (Desktop Client View)

The email is here. It’s just hidden!

It turns out that gmail is hiding new messages when they look too similar to the previous one.

All the password reset messages are there, hidden on the bottom, each with it’s own unique link. We try the latest one and it does work! Password resetted.

it's not a bug, it's a feature
Debugging complete

She’s been reading the same old email every single time. She never noticed the hidden messages on the bottom (note that they are quite difficult to spot on mobile).

Reset links are unique and invalidated when a new one is made, hence the errors about invalid links.

Let’s remember of that as a lesson in user accessibility. What may be noticed by one user may be missed by another.


This password reset procedure is for a billion dollar e-commerce site, used by millions of customers, in most of the countries in the world.

I should say that users buy things sparingly. They buy something once, go on with their lives, maybe come back one day far away. It’s reasonable to expect a sizeable user base to forget their password as often as “every single time“.

The issue is impacting all users who forgot their password (read: already registered on the site), use gmail (not sure about other clients) and don’t notice the hidden messages on the bottom.


Let’s see with the data team what’s the impact of this. Incidentally, they just introduced themselves during one of the presentations.

Assuming some percentages of some percentages of some statistics of our sales. (Sorry, private numbers ^^).

The direct impact of this bug is a direct loss of revenues of $187M dollars per year, simply accounting for people who are unable to login and place any order.


I should add that, as shown time and again during demonstrations, participants will switch to competitors within a few minutes of frustration, especially the ones who are already familiar with them. I don’t know if they are giving up faster or slower than regular users, either way that’s food for thought.

The impact accounting for direct losses, plus indirect losses, plus recurring losses, plus reputation loss, plus word of mouth loss, plus competitors stealing our business, well, recurrently stealing our business, etc, is hard to put an estimate on. It should be within some multipliers.


Last but not least. This is on a single business and we’ve got more than just one.

What else is impacted has yet to be determined. That will vary by how the password resets are done.


We need to force gmail to NOT collapse emails.

Having different subjects should do the trick.

Let’s append the current time to the subject. That is minor change in the line of code that generates the subject.

i dont often write code but when i do its 3m dollars per chara
What to say next time you’re asked to code in an interview


All the internet is potentially affected. You should check whether your business is.

pic - if google fixes google the internet could go up by 1percent of 1percent
There is a percentage of truth behind every meme.



What’s The Best Data Warehouse Solution? RedShift vs BigQuery vs Hadoop

That can be explained with a simple flowchart:

datawarehouse flowchart
Full Size ImagePDF Version


See also:


What’s The Best NoSQL Database? Cassandra vs MongoDB vs Redis vs ElasticSearch

That can be explained with a simple flowchart:

nosql flowchart
Full Size ImagePDF Version


See also:


Moby/Docker in Production: An Update

The previous article Docker in Production: A History of Failure was quite a hit.

After long discussions, hundreds of feedbacks, thousands of comments, meetings with various individuals and major players, more experimentation and more failures, it’s time for an update on the situation.

We’ll go over the lessons learned from all the recent interactions and articles, but first, a reminder and a bit of context.

Disclaimer: Intended Audience

The large amount of comments made it clear that the world is divided in 10 kind of people:

1) The Amateur

Running mostly test and side projects with no real users. May think that using Ubuntu beta is the norm and call anything “stable” obsolete.

I dont always make workin code but when I do it works on my machine
Can’t blame him. It worked on his machine.

2) The Professional

Running critical systems for a real business with real users, definitely accountable, probably get a phone call when shit hits the fan.

Didn’t work on the machine that served his 586 million customers.

What Audience Are You?

There is a fine line between these worlds and they clash pretty hard when they ever meet. Obviously, they have very different standards and expectations.

One of the reason I love finance is because that it has a great culture of risk. It doesn’t mean to be risk-averse contrary to a popular belief. It means to evaluate potential risks and potential gains and weight them against each other.

You should take a minute to think about your standards. What do you expect to achieve with Docker? What do you have to lose if it crashes all systems it’s running on and corrupt the mounted volumes? These are important factor to drive your decisions.

What pushed me to publish the last article was a conversation with a guy from a random finance company, just asking my thoughts about Docker, because he was considering to consider it. Among other things, this company -and this guy in particular- manages systems that handle trillions of dollars, including the pensions of millions of Americans.

Docker is nowhere ready to handle my mother’s pension, how could anyone ever think that??? Well, it seemed the Docker experience wasn’t documented enough.

What Do You Need to Run Docker?

As you should be aware by know, Docker is highly sensitive to the kernel, the host and the filesystem it’s using. Pick the wrong combination and you’re talking kernel panic, filesystem corruption, Docker daemon lock down, etc…

I had time to collect feedback on various operating conditions and test a couple more myself.

We’ll go over the results of the research, what has been registered to work, not work, experience intermittent failures, or blow up entirely in epic proportions.

Spoiler Alert: There is nothing with or around Docker that’s guaranteed to work.

Disclaimer: Understand the Risks and the Consequences

I am biased toward my own standards (as a professional who has to handle real money) and following the feedback I got (with a bias toward reliable sources known for operating real world systems).

For instance, if a combination of operating system and filesystem is marked as “no-go: registered catastrophic filesystem failure with full volume data loss“. It is not production ready (for me) but it is good enough for a student who has to do a one-off exercise in a vagrant virtual machine.

You may or may not experience the issues mentioned. Either way, they are mentioned because they are certified to be present in the wild as confirmed by the people who hit them. If you try an environment that is similar enough, you are on the right path to become the next witness.

The worst that can -and usually- happen with Docker is that it seems okay during the proof of concepts and you’ll only begin to notice and understand issues far down the line, when you cannot easily move away from it.


CoreOS is an operating that can only run containers and is exclusively intended to run containers.

Last article, the conclusion was that it might be the only operating system that may be able to run Docker. This may or may not be accurate.

We abandoned the idea of running CoreOS.

First, the main benefit of Docker is to unify dev and production. Having a separate OS in production only for containers totally ruins this point.

Second, Debian (we were on Debian) announced the next major release for Q1 2017. It takes a lot of effort to understand and migrate everything to CoreOS, with no guarantee of success. It’s wiser to just wait for the next Debian.



Docker on CentOS/RHEL 6 is no-go: known filesystem failures, full volume data loss

  1. Various known issues with the devicemapper driver.
  2. Critical issues with LVM volumes in combination with devicemapper causing data corruption, container crash, and docker daemon freeze requiring hard reboot to fix.
  3. The Docker packages are not maintained on this distribution. There are numerous critical bug fixes that were released in the CentOS/RHEL 7 packages but were not back ported to the CentOS/RHEL 6 packages.
ship crash shipt it revert
The only sane way to migrate to Docker in a big company still running on RHEL 6 => Don’t do it!


Originally running the kernel 3, RedHat has been back porting the kernel 4 features into it, which is mandatory for running Docker.

It caused problems at time because Docker failed to detect the custom kernel version and the available features on it, thus it cannot set proper system settings and fails in various mysterious ways. Every time this happens, this can only be resolved by Docker publishing a fix on feature detection for specific kernels, which is neither a timely nor systematic process..

There are various issues with the usage of LVM volumes, depends on the version.

Otherwise, it’s a mixed bag. Your mileage may vary.

As of CentOS 7.0, RedHat recommended some settings but I can’t find the page on their website anymore. Anyway, there are a tons of critical bugfixes in later version so you MUST update to the latest version.

As of CentOS 7.2, RedHat recommends and supports exclusively XFS and they give special flags for the configuration. AUFS doesn’t exist, OverlayFS is officially considered unstable, BTRFS is beta (technology preview).

The RedHat employees are admitting themselves that they struggle pretty hard to get docker working in proper conditions, which is a major problem because they gotta resell it as part of their OpenShift offering. Try making a product on an unstable core.

If you like playing with fire, it looks like that’s the OS of choice.

Note that for once, it is a case where you surely wants to have RHEL and not CentOS, meaning timely updates and helpful support at your disposal.


Debian 8 jessie (stable)

A major cause of the issues we experienced was because our production OS was Debian stable, as explained in the previous article.

Basically, Debian froze the kernel to a version that doesn’t support anything Docker needs and the few components that are present are rigged with bugs.

Docker on Debian is major no-go: There is a wide range of bugs in the AUFS driver (but not only), usually crashing the host, potentially corrupting the data, and that’s just the tip of the iceberg.

Docker is 100% guaranteed suicide on Debian 8 and it’s been since the inception of Docker a few years ago. It’s killing me no one ever documented this earlier.

I wanted to show you a graph of AWS instances going down like dominoes but I didn’t have a good monitoring and drawing tool to do that, so instead I’ll illustrate with a piano chart that looks the same.

Typical docker cascade failure in our test systems.

Typical Docker cascading failure on our test systems. A test slave crashes… the next one retries two minutes later… and dies too. This specific cascade took 6 tries to go past the bug, slightly more than usual, but nothing fancy.

You should have CloudWatch alarms to restart dead hosts automatically and send a crash notifications.

Fancy: You can also have a CloudWatch alarm to automatically send a customized issue report to your regulator whenever there is an issue persisting more than 5 minutes.

Not to brag but we got quite good at containing Docker. Forget about Chaos Monkey, that’s child play, try running trading systems handling billions of dollars on Docker [1].

[1] Please don’t do that. That’s a terrible idea.

Debian 9 stretch

Debian stretch is planned to become the stable edition in 2017. (Note: might be released as I write and edit this article).

It will feature the kernel 4.10 which is the latest LTS, published simultaneously.

At the time of release, Debian Stretch will be the most up to date stable operating system and it will allegedly have all the shiny things necessary to run Docker (until the Docker requirements change again).

It may resolve a lot of the issues and it may make a tons of new ones. We’ll see how it goes.


Ubuntu has always been more up to date than the regular server distributions.

Sadly, I am not aware of any serious companies than run on Ubuntu. This has been a source of much misunderstanding in the docker community because dev and amateur bloggers try things on the latest Ubuntu (not even the LTS [1]) yet it’s utterly non representative of production systems in the real world (RHEL, CentOS, Debian or one of the exotic Unix/BSD/Solaris).

I cannot comment on the LTS 16 as I do not use it. It’s the only distribution to have Overlay2 and ZFS available, that gives some more options to be tried and maybe find something working?

The LTS 14 is a definitive no-go: Too old, don’t have the required components.

[1] I received quite a few comments and unfriendly emails of people saying to “just” use the latest Ubuntu beta. As if migrating all live systems, changing distribution and running on a beta platform that didn’t even exist at the time was an actual solution.

Update: I said I’m never coming back to Docker and certainly not to spend an hour on digging up references but I guess I have to now that they are handed to me in spectacular ways.

I received a quite insulting email from a guy who is clearly in the amateur league to say that “any idiot can run Docker on Ubuntu” then proceed to give a list of software packages and advanced system tweaks that are mandatory to run Docker on Ubuntu, that allegedly “anyone could have found in 5 seconds with Google“.

At the heart of his mail is this bug report, which is indeed the first Google result for “Ubuntu docker not working” and “Ubuntu docker crash: Ubuntu 16.04 install for 1.11.2 hangs.

This bug report, published on June 2016 highlights that the Ubuntu installer simply doesn’t work at all because it doesn’t install some dependencies which are required by Docker to run, then it’s a see of comments, user workarounds and not-giving-a-fuck #WONTFIX by Docker developers.

The last answer is given by an employee 5 months later to say that the Ubuntu installer will never be fixed, however the next major version of Docker may use something completely different that won’t be affected by this issue.

A new major version (v1.13) just got released (8 months since the report), it is not confirmed whether it is affected by the bug or not (but it is confirmed to come with breaking changes).

It’s fairly typical of what to expect from Docker. Checklist:

  • Is everything broken to the point Docker can’t run at all? YES.
  • Is it broken for all users, of say a major distribution? YES.
  • Is there a timely reply to acknowledge the issue? NO.
  • Is it confirmed that the issue is present and how severe it is? NO.
  • Is there any fix planned? NO.
  • Is there a ton of workarounds of various danger and complexity? YES.
  • Will it ever be fixed? Who knows.
  • Will the fix, if it ever comes, be backported? NEVER.
  • Is the ultimate answer to everything to just update to latest? Of course.

AWS Container Service

AWS has an AMI dedicated to running Docker. It is based on an Ubuntu.

As confirmed by internal sources, they experienced massive troubles to get Docker working in any decent condition

Ultimately, they released am AMI for it, running a custom OS with a custom docker package with custom bug fixes and custom backports. They went and are still going through extensive efforts and testing to keep things together.

If you are locked-in on Docker and running on AWS, your only salvation might be to let AWS handles it for you.

Google Container Service

Google offers containers as a service. Google merely exposes a Docker interface, the containers are run on internal google containerization technologies, that cannot possibly suffer from all the Docker implementation flaws.

Don’t get me wrong. Containers are great as a concept, the problem is not the theoretical aspect, it’s the practical implementation and tooling we have (i.e. Docker) which are experimental at best.

If you really want to play with Docker (or containers) and you are not operating on AWS, that leaves Google as the single strongest choice, better yet, it comes with Kubernetes for orchestration, making it a league of its own.

That should still be considered experimental and playing with fire. It just happens that it’s the only thing that may deliver the promises and also the only thing that comes with containers AND orchestration.


It’s not possible to build a stable product on a broken core, yet RedHat is trying.

From the feedback I had, they are both struggling pretty hard to mitigate the Docker issues, with variable success. Your mileage may vary.

Considering that they both appeal to large companies, who have quite a lot to lose, I’d really question the choice of going for that route (i.e. anything build on top of Docker).

You should try the regular clouds instead: AWS or Google or Azure. Using virtual machines and some of the hosted services will achieve 90% of what Docker does, 90% of what Docker doesn’t do, and it’s dependable. It’s also a better long-term strategy.

Chances are that you want to do OpenShift because you can’t do public cloud. Well, that’s a tough spot to be in. (Good luck with that. Please write a blog in reply to talk about your experience).


  • CentOS/RHEL: Russian roulette
  • Debian: Jumping off a plane naked
  • Ubuntu: Not sure Update: LOL.
  • CoreOS: Not worth the effort
  • AWS Containers: Your only salvation if you are locked-in with Docker and on AWS
  • Google Containers: The only practical way to run Docker that is not entirely insane.
  • OpenShift: Not sure. Depends how good the support and engineers can manage?

A Business Perspective

Docker has no business model and no way to monetize. It’s fair to say that they are releasing to all platforms (Mac/Windows) and integrating all kind of features (Swarm) as a desperate move to 1) not let any competitor have any distinctive feature 2) get everyone to use docker and docker tools 3) lock customers completely in their ecosystem 4) publish a ton of news, articles and releases in the process, increasing hype 5) justify their valuation.

It is extremely tough to execute an expansion both horizontally and vertically to multiple products and markets. (Ignoring whether that is an appropriate or sustainable business decision, which is a different aspect).

In the meantime, the competitors, namely Amazon, Microsoft, Google, Pivotal and RedHat all compete in various ways and make more money on containers than Docker does, while CoreOS is working an OS (CoreOS) and competing containerization technology (Rocket).

That’s a lot of big names with a lot of firepower directed to compete intensively and decisively against Docker. They have zero interest whatsoever to let Docker locks anyone. If anything, they individually and collectively have an interest in killing Docker and replacing it with something else.

Let’s call that the war of containers. We’ll see how it plays out.

Currently, Google is leading the way, they are replacing Docker and they are the only one to provide out of the box orchestration (Kubernetes).


Did I say that Docker is an unstable toy project?

Invariably some people will say that the issues are not real or in the past. They are not in the past, the challenges and the issues are very current and very real. There is definite proof and documentation that Docker has suffered from critical bugs making it plain unusable on ALL major distributions, bugs that ran rampant for years, some still present as of today.

If you look for any combination of “docker + version + filesystem + OS” on Google, you’ll find a trail of issues with various impact going back all the way to docker birth. It’s a mystery how something could fail that bad for that long and no one writes about it. (Actually, there are a few articles, they were just lost under the mass of advertisement and quick evaluations). The last software to achieve that level of expectation with that level of failure was MongoDB.

I didn’t manage to find anyone on the planet using Docker seriously AND successfully AND without major hassle. The experiences mentioned in this article were acquired by blood, the blood of employees and companies who learned Docker the hard way while every second of downtime was a $1000 loss.

Hopefully, you can learn from our past, as to not repeat it.

mistake - it could be that the purpose of your life is only to serve as a warning to others

If you were wondering whether you should have adopted docker years ago => The answer is hell no, you dodged a bullet. You can tell that to your boss. (It’s still not that much useful today if you don’t proper have orchestration around it, which is itself an experimental subject).

If you are wondering whether you should adopt it now… while what you run is satisfactory and you have any considerations for quality => The reasonable answer is to wait until RHEL 8 and Debian 10. No rush. Things need to mature and the packages ain’t gonna move faster than the distributions you’ll run them on.

If you like to play with fire => Full-on Google Container Engine on Google Cloud. Definitive high risk, probable high reward.

Would this article have more credibility if I linked numerous bug reports, screenshots of kernel panics, personal charts of system failures over the day, relevant forum posts and disclosed private conversations? Probably.

Do I want to spend yet-another hundred hours to dig that off, once again? Nope. I’d rather spend my evening on Tinder than Docker. Bye bye Docker.

Moving On

Back to me. My action plan to lead the way on Containers and Clouds had a major flaw I missed out, the average tenure in tech companies is still not counted in yearS, thus the year 2017 began by being poached.

Bad news: No more cloud and no more Docker where I am going. Meaning no more groundbreaking news. you are on your own to figure it out.

Good news: No more toying around with billions dollars of other people’s money… since I am moving up by at least 3 orders of magnitude! I am moderately confident that my new immediate playground may include the pensions of a few millions of Americans, including a lot of people who read this blog.

docker your pension fund 100% certified not dockeri
Rest assured: Your pension is in good hands! =D

Career Advice and Salary Negotiations: Move Early and Move Often


This following are hard-earned experience for advancing a career quickly. It applies exclusively to tech hubs, in particular London, the Silicon Valley and New York.

Your mileage may vary, especially depending on your location, your experience and your skill.

Disclaimer: I’m seriously biased toward good performers. There are people who can fizz buzz and people who landed on that blog by accident.


The fastest way to advance your career is to move early and move often, especially when you’re young.

It’s a lot about money. The only way to get substantial raises is to leave your company. This is especially true when you just start out and/or you’re seriously undervalued (pick any combination: young, first job, naive, didn’t negotiate, just came from abroad, etc…).

It’s also about long-term savings. Not negotiating your jobs will cost you millions over your lifetime. You want to get to a decent level as quickly as possible, you’ll get to stay there for your future jobs.

It’s also about opening your eyes and widening your horizons. You learn the most when you change company, put in a completely different environment. Also, having had a lot of jobs gives you points of comparison to know whether you’re in a good place or not.

Disclaimer: This article will be about getting offers while threatening to quit your job. In business words, that’s call negotiating.

Lesson #1: ALWAYS negotiate.

Lesson #2: Negotiations are based on leverage.

Having a job and having competing offers are your leverage.

Chapter 1) Ground Rules

We’ll start with some ground rules and some myth busting.

Rules #1: You will NOT resign from your current job UNTIL you have a SIGNED contract with a new company.

(I’d put that as text size 20, bold, in flickering red if that blog allowed to do text formatting).

Rules #2: You already have a job.

Having a job is the stronger leverage you have. If a prospective employer doesn’t give you the terms you want, you stay where you are, you’ve not nothing to lose.

Rules #3: Leverage.

Leverage, leverage and more leverage!!! A negotiation is all about leverage. The person with the most leverage gets what he wants.

Rules #4: No one cares. No one is gonna get hurt.

The HR/manager is hiring 10 guys a week, he’s seeing and negotiating all day along, every day, he’ll have forgotten your name by the time you leave the room or hang the phone.

Rules #5: NEVER underwrite yourself. NEVER talk yourself down. NEVER give away your positions.

Ever heard sentences like “It’s pathetic to pay so little because you know I have a family to feed and I don’t have a choice” or “I would like xxx$…

… but I’m willing to negotiate [down]


You’re actively playing against yourself when you talk like that. Don’t do it!

Tip: Whenever this sort of non sense comes to your mind, slap yourself very hard in the face. Over time, your brain will learn to think better. (I am a strong believer in Positive Punishment).

(Also works if you think hard about slapping yourself, without actually slapping yourself).

Rules #6: Paper is real. Talk is cheap.

The only thing that matters is official papers with a signature on them. Talking doesn’t engage anyone into anything. If all you’ve got is a verbal promise then you’ve got nothing.

Corollary: Assume everything you’ll ever hear from a recruiter/HR/manager is a straight lie. (But what about the 20% bonus I’ve been promised? Ahah. Never existed!)

Rules #7: Be relentless, inflexible and never give up.

As one mentor taught me once, the secret to negotiations is to “be an asshole” [1]. In essence, that means to be relentless and inflexible.

Think about it for a minute. A sales person’s only goal is to close sales, a HR’s role is to hire people. They’re the same thing. If one is talking to you and is really close to getting  the sale (i.e. you) but not getting it, it’s a very frustrating position for him to be in. Remember, he HAS to sell. Eventually he’ll give up some slack to close the deal.

When you never lower your standards, you’ll never get less than your standards. But what if the negotiations goes wrong and everything is ruined? A negotiation cannot go wrong, at worst, you just call back the sales guy to accept the terms that he wanted to give you in the first place (and he’ll happily reply back because it’s closing a deal and that’s his job, he’s measured on that).

[1] Then he went on to negotiate $4M more in stock grants, while most of the employees had peanuts. It was a significant learning experience!

Rules #8: ALWAYS stay polite and courteous, no matter the circumstances.

When you receive an email that’s killing you. You write a response email that really puts that guy back in his place, then you go have a walk and take a breath. When you come back, you delete it and write the email you’re actually gonna send.

When I suggest to you stand up in an interview and leave the room (Who doesn’t love a dramatic exit?). In practice, it’s concluding in the middle of the 4th interview round that “We are not a fit for each other. Let’s stop the interview there and save both our afternoons, shall we?“, then standing up, saying goodbye to your interviewer(s) and asking politely the way to the exit.

Rules #9: Getting massive raises is fairly easy and common.

And the secret to achieve it is to start incredibly low. It’s really nothing to brag about.

Look around you for a minute. Let’s say you’re an American working at a typical tech company. Chances are that there are people earning $80k a year next to people earning $120k a year next to people earning $160k a year, for a similar position.

How does the former quickly become the later? That is definitely not by being nice and waiting patiently for a raise. One can only progress quickly by being good and being bold. Meaning, move early and move often.

Chapter 2) Be Goal Driven

Your single and only goal during a job search is to get offers, as in paper offers.

A contract is the guarantee that there is a job for you, at this place, at this moment, at this price, at these conditions. It’s both leverage and knowledge for YOU. You’re ready to go work at C company for £XX, assuming you sign.

If it’s satisfactory, you can sign and go there right away. (Once in a while, there’s a good offer on the first try). Otherwise, you can keep it in your offer letters collection. Who knows, maybe things will change in a year and you’ll reopen the conversation.

Whenever an interview process is stopped before the contract stage, it’s wasted time for everyone. You don’t know whether it would get real. You have incomplete information. You can’t sign it and work there. You can’t show it to other prospective employers.

Chapter 3) How Much Should You Ask For?

The only way to find out is to interview and get offers.

Basically, you need to perform a binary search. When you get an offer, you know that you can get at least that. Then you repeat the process a bit higher.

negotiation diagram
Binary Search applied to job offers

Note: Notice that the process goes on forever. In the real world, you have to stop at one point. Mastery is not achieved by knowing when to play (you’re always playing!) but by knowing when to close a play.

Chapter 4) Compensation Package

The only real thing in the universe is base salary. That’s the only thing you get at the end of the month for sure. That’s the first thing to negotiate.

Then comes the package which includes but is not limited to:

  • Base salary
  • Vacations, Sick days
  • Duration of your commute
  • Healthcare
  • Pension, 401k
  • Working hours
  • Food, Cafeteria
  • Shares, Stock, RSU
  • Bonus
  • Sign-on bonus

Some perks can only be known and guaranteed when in a contract (e.g. vacations). That’s why it’s very important to get to the contract stage. Some are variable and may disappear or worse, been a lie from the start (e.g. bonus, shares), these are very risky take and must be treated with caution.

You should negotiate base salary first, concrete perks (e.g. sign-on bonus, vacations) second, risky perks last (e.g. bonus, shares).

There are entire industries who get candidates by significantly over-promising and under-delivering (e.g. start-ups). To this day, I have never met a company that said they paid X amount of bonus and that amount was actually paid in full.

Usually, companies have a culture. Perhaps they promise 20% yearly bonus but in practice have been giving 10% to everyone for many years, the promise is oversold yet there is a non-negligible number that should be accounted for. The only way to have a clue is to get insider data, most of the time you can’t and you’ll have to take decisions partially blind.

Chapter 5) How Much Can You Charge?

There is no such thing as a “market rate” or a “fair compensation”. All there is are individual companies who run a specific business, generating a variable amount of cash, who’d get a variable gain from your service, with more or less favorable compensation policies.

At any point in time and space, there is always an endless supply of companies willing to hire for cheap. It’s fine when you first start out because your greatest quality is to be cheap and have low standards (we’ve all been there: you go where you can, not where you want).

As you mature and gain experience, you’ll request for more money and decent work conditions, there will be fewer places to work for.

Ultimately, if you’re a top performer and you’ve done your homework, you’ll reach a point where there is only a handful of acceptable companies in the area.

No matter where you are in your career, you should always know where will you send your resume next?

Never bother about the “how much?“. Your only concern should be the “where?”. You need to search, network and stay informed about worthwhile jobs and companies. 

Pick companies and go play binary search with them, it will tell you the how much. If you have no selection criteria (WTF?!), just pick whatever companies are in your area.

Note: The difficulty to get into a company has only a moderate correlation with how much it pays.

When there are 3 start-ups offering from $X to $2X and Goldman Sachs offering $3X. Your rate is $3*X +10% (cuz you negotiated!). It has little to do with an imaginary global tech market ruling the world and all to do with you pulling off your fingers and selling your service to the highest bidder like there’s no tomorrow.

if you want to have more you have to become more for things to improve you have to improve for things to get better you have to get better
One doesn’t get a rate, one makes it happen!

Chapter 6) Where To Work?

You gotta figure that out. Search, network, search some more.

For instance, let’s say I’m doing DevOps, SRE and system engineering for highly-scalable-low-latency-distributed-large-scale-systems.

In London, the easy money is usually in DevOps contracting (not to mention the neat flat tax rate). The hard money is usually in finance (ignoring that you can’t work in t-shirts). The usual big valley tech companies pay poorly (compared to contracting and finance).

For instance, if you hang around in the right pubs at the right time, you can overheard conversations like “A recruiter from Google contacted me to interview with them, I asked what’s their top range and they gave a number 40% less than I’m earning right now… Wow.“. Here in London all Google employees are easy fair pickings (please make sure your LinkedIn is updated!).

In SF/NY, the easy money is usually in big tech companies (Facebook, Google). A lot of the compensation comes from massive stock grant, so you have to negotiate stock hard and get it refreshed every year. (Note that the stock is liquid and publicly traded, it can be sold automatically monthly).

If you hang around on Hacker News for too long, you can find out conversations about Netflix not believing in stock and bonus. If you keep reading between the lines, you can figure out that they paid massive base salary in a big recruitment campaign to poach everyone from everywhere else.

Of course, not everything is about money, you may prefer a place with a shorter commute, less hours, or working from home 1 day a week to take care of your child. You’re considering a mix of compensation, personal criteria, location and qualifications.

Given my experience. There is no compromise to be made on compensation. The great companies are more successful all across the board, they pay more AND they have more money AND they treat their people better AND they have better work conditions AND more interesting projects AND …

Basically, there are the good organizations and the bad organizations, there is little middle ground. Given the choice, you always want to pick a 10x organization.

Chapter 7) Network, Network, Network…

Network in real life. Network online. Network at the pub. Network some more.

Do you know how much your current company pay other people around you? Well, you should!

Do you bring your co-workers one by one at lunch at a nearby pub to talk about secret compensations and office politics? Well, you should!

Do you have a LinkedIn up to date? Well, you should!

Do you have your previous co-workers on LinkedIn to follow-up on them and their new jobs, ready to message or be messaged if an opportunity pops up? Well, you should.

Do you regularly have drinks with your ex co-workers and ex-recruiters to keep up with the market and who’s where? Well, you should!

Chapter 8) Why Are We Doing All That?

We don’t negotiate salary because it’s easy, we negotiate because it’s important. Not negotiating your salary will cost you millions over your lifetime. Negotiate hard while you’re young and growing. It will impact the compensations of all your future jobs.

Have you ever asked around only to notice that 2 people performing the same work with the same qualifications have 30% difference in pay? Which one do you want to be?

when you life your life by poor standards you inflict damage on everyone who crosses your path especially those you love
Please negotiate your salary. It’s making the world a better place.

Chapter 9) Start-up Sucks

Disclaimer: I am in my “start-ups suck” phase.

Start-ups are a workaholics’ paradise. You’ll work a lot, for little money, with no healthcare and zero pension. All so you DO NOT make 1 million later because your company went bust, and if it didn’t your shares are worthless anyway.

The era of breaking the bank as a startup employee is long gone. Don’t expect to become a millionaire with that. The VC and the executives get all the returns if there are any, the employees get nothing. (Note that shares can have a negative value, they may cost you money to acquire and/or generate taxes).

Think for a minute about how much pay cut you took? Do you have bonus at all? How much your shares are REALLY worth? What’s your pension and healthcare plans? How often are you on call? How many hours a week do you work? When is the last time you had to work on a week-end?

While these issues are typical of start-ups, they can be found in any companies. Take a minute to think about your current situation and where you want to be (or not be). Would you be better off at a big tech company or a big financial institution?

Chapter 10) How Much Do You Want?

Question: “What salary do you want?”

The only acceptable answer is: “It will take xxx$ base salary to leave my current company.

Question: “What salary do you want?

Answer: “It will take xxx$ base salary to leave my current company.

Question: “What is your current salary?”

Answer: “It will take xxx$ base salary to leave my current company.

Question: “What is your current salary?”

Answer: “It will take $xxx base salary to leave my current company.

The only alternative answer is: “I need to know what kind of perks, hours and pension you have to give you a number? Let’s begin with what pension plans do you have?” [1]

You must figure out what you’re worth and you must ask for it. You won’t know at first, you’ll have no idea what their perks may be, you won’t know what you’ll work on. The entire point of this article is that you need to go get offers to find out. More interviews, more job offers, more binary search!

There is a myth that you should not give a number first, it’s 100% bullshit. If you let an employer gives a number first, he will low ball you every single time. It gets worse from there, the conversation is now anchored to that low number, it will be very difficult to negotiate up.

As a rule of thumb, if an employer says a number, it’s guaranteed 10% under what they were willing to pay without question.

Give a fix number, never give a range. Ranges are evil. Whenever a range comes up, the employer thinks of the bottom, the employee thinks of the top. You’re both pretending to be in agreement while really ignoring each other.

[1] I’m fairly confident I’ve got the best pension in town. I’m fairly confident I’ll reply to their reply with an egregious comment.

What do you have to lose by doing that? Absolutely nothing. Remember rules #1. You already have a job and you ain’t leaving until you get the terms you want written down in a contract. That’s your leverage.

I once had a conversation with an HR person in where he repeated the same question 9 times (the last 4 worded slightly differently). I repeated the same answer 8 times (then I changed the topic). This is a perfect example of being an asshole (read: relentless and inflexible).

Chapter 11) Move Early And Move Often

The average tenure for [young] qualified employees is around a year.

On the one hand, I can’t think of a single manager/HR who cares about keeping their employees. (I can think of many who pretend to care, but none who would actually lift a finger if necessary).

On the other hand, I can’t think of a single manager/HR who wouldn’t poach an employee from somewhere else [1].

The combination makes up for a very aggressive environment. Thus the best advice I can give to youngsters is to move early and move often. Don’t hate the player, hate the game.

[1] I loved that day when I joined a new job, only to find an email in my LinkedIn that evening from a Facebook recruiter inviting me to interview with them. [2]

[2] I loved that day when I interviewed with Facebook, only to get an email from a headhunter that evening to recruit for a recent finance shop in town managed by 2 well known ex-Goldman Sachs partners.

It seems that short tenure is an evolutionary trait of the industry as a whole. There is no sign of it ever getting longer any time soon.

In fast paced companies, a sizeable chunk of work can be done in 6-18 months delivered to millions of customers. It’s very project-oriented, a project is executed, quickly. In fact, even if people would like to stay, it’s not necessarily that simple, they may have to move internally or externally.

Despite the incredible turnover, it’s good enough to deliver and make huge profits. Sure it’s not optimal. A business only needs to be sustainable, not optimal.

Chapter 12) Should I Accept A Counter Offer?

Do you want to stay at your current company? If “YES”, then yes you should accept a counter offer. Otherwise, no.

Should you even bother asking for a counter offer? If you’d like to stay then yes.

Obviously, your life and your decisions depends on you so there is nothing we can say to help you there.

Please don’t trust articles which say that all people who accepted a counter-offer have left short afterwards anyway. These articles are written by recruiters who get a massive $20k-$100k commission only if you leave your company. They will say anything to get you to accept an offer with them, they are not acting in your interest. If you prefer to stay, stay!

Chapter 13) How To Ask For A Counter Offer?

Go to the people in the position of power, usually your manager (but not always, politics can be tricky). Tell him that you have a counter offer for $xxx, you’re fine here and you will stay provided by your compensation is adjusted, it’s only about money, he needs to match and he needs to match NOW because you’ve got the contract from the other company in your email ready to be signed (I love DocuSign) and you’re not gonna wait (I hate waiting).

If you’re a player: Print the half-page of the contract which contains the numbers to be matched, highlighted in bright pink, with the phone numbers written in the corner for your director and people he may want to call.

It should only take 3 minutes to expose the situation. Speak slow, speak calm. This is a perfectly normal business request. Businessmen do that all day along, every day of the year. (Don’t worry. You’re NOT doing anything wrong, you’re NOT taking anyone as hostage and you’re NOT hurting anyone by doing that. You’re just being an adult).

Don’t get into a discussion and don’t get into an argument. There isn’t a single thing he says that could matter. An experienced manager will probably have a script for that situation, don’t bother listening. It’s sure not the time to be manipulated into thinking the company has a limited raise pool or whatever he may invent.

Basically, he’s gonna need the day to talk to a few people and take a decision.

If he wants to keep you, he’ll pay. You should have a written salary amendment, signed, by the next day (2 days top). If you don’t get one, they’re not interested in keeping you.

If he doesn’t want to pay, the only two cards in his hands are to stall for time and to make [fake] verbal promises. An experienced bad-ass manager will never tell straight to your face that your request is denied, instead he’ll give excuses and talk about future raises. An alternative simple strategy is to make himself unreachable and unavailable to prevent you to talk any further and to hand your resignation (you can give it to any administrative person if needs be). Watch out for these red flags!

Chapter 14) Counter Offers Will Go Wrong

Disclaimer: I have biased toward good performers.

So far in my life, I have never seen a raise request or a counter offer go well. Or well, to be fair, I have seen a lot of 5-10% raises for a lot of people [1], and a few bigger ones.

There is a sizeable amount of them which are okay. There is also a sizeable amount of them which are for people who are seriously undervalued, who’ve been underpaid for years, still are after that raise, and would get outmatched easily by walking to the other shop across the street.

When you find out your company has undervalued you the whole time, the entire payroll is underrated, and the raise you’ve been given barely puts you on par with the low-end of the first company across the road. You are sure leaving the hell out of here.

Please refrain from sending an inflammatory goodbye email to reveal the true evil nature of your management. Stick to a short goodbye message and make sure to insert your contact info and LinkedIn so people can add you. This job is over, networking just begins!

[1] If you’ve got someone for a steal, ensuring they get a 5-10% yearly raise or a 5-10% one-off bonus is the cheapest way to make them feel appreciated and blind them just enough to the outside world.

herding sheeps
Resignations usually happen in waves.

A Personal Story:

I remember one raise I asked once, a meagre 33% that was perfectly reasonable (quite low as it turned out). They’ve invited me to a meeting with the other managers and it didn’t go as planned, I’ll spare you the details. At one point, my phone rang in the middle of the meeting. Some people barraged the request hard, be it for personal reasons or because it’s allegedly crazy to give a two digits raise to anyone. Everyone left the room in shock and despair.

I checked my phone, the missed call was from another company I interviewed with, to confirm I got the job. I called back to give my name/address and had a contract signed the next day for a substantial raise (plus additional bonus and perks).

My manager came to my office on the next Monday –interrupting me while I was setting up the printer to print my resignation letter– to say everything’s fine and I get half the raise I asked for. I nodded in acknowledgement… only to give him my resignation the next day (the printer was challenging!).

My last action at this job was to publish a job posting for my role at £120k base, which was more than any of us was earning. The rest of the team quit promptly.

gif - plane take off going wrong.gif
Didn’t plan to land a job that way.

That experience taught me 3 valuable lessons:

  1. Always have a backup plan.
  2. Imply only the single person that’s needed to bring the cash. More people can (and will) only cause troubles.
  3. Show a competing offer. Don’t talk and don’t argue. It can only go downhill.
  4. I’d be earning £120k soon.

Disclaimer: I’m looking forward to my 10th job in the industry, in the meantime, I’m just gathering materials for a future blog article: “A Retrospective on 10 Years of Salary Negotiations Gone Wrong: Still Counting“.

Chapter 15) Join The Recruitment Process

Become part of your recruitment process. That’s the best way to learn about recruiting, negotiations and one hundred other things.

For instance, after the 3rd dude in a row who failed to write a program to print number from 1 to 100, you’ll feel less like a fraud. Whereas there’s no such eyes opener as making an offer to a senior engineer who already has a job, only to have him reject you like a complete troll, stand up and leave the room.

Also, if you’re an idealist like me, that’s the only way to improve it: from the inside. And if you’re chaotic neutral idealistic like me, it can be a lot of fun, you get to see plenty of interesting people, while helping them, yourself and your company at the same time. (Chaotic Neutral Fact: Companies are ephemeral but what you learn for yourself is forever).

You’ll get a much better understanding of many things you couldn’t possibly dream of, with plenty of incredible and disastrous stories to tell (and recycle for your future negotiations).

yeah that aint happening
When you’ve been recruiting for a position you’re qualified to for 6 months and that’s the only answer you got, from the only candidate (out of 6) that passed the bar.

Look for the obvious signs, when this sort of things happen, it’s time to either get a raise or jump ship.


If you’re negotiating an offer, the thing that’s critical isn’t to be some kind of super genius. It’s enough to be pretty good, know what the market is paying, and have multiple offers.” — Dan Luu

Always be on the look out for better opportunities. Negotiate. Get competing offers. Get counter offers. Jump ship.

And remember that nothing can go wrong, you’ve already got a job, you’ve got nothing to lose.

the first year I was in London my compensation took 105 percent which really pissed me off because it was just shy of 10 percent a month
Shoot for the moon. Even if you miss, you’ll land among the stars.


Salary Negotiation: Make More Money, Be More Valued, patio11 blog.

Don’t Call Yourself A Programmer, And Other Career Advice, patio11 blog..

Big company vs. startup work and pay, Dan Luu blog.

Developer hiring and the market for lemons, Dan Luu blog.

Salary Negotiation and Job Hunting for Developers, Twilio blog.

H1B Salary Data, base salaries are public for all H1B visa, at all companies, in all USA cities.


Google Cloud is 50% cheaper than AWS

Let’s revisit Google and Amazon pricing since the AWS November 2016 Price Reduction.

We’ll analyse instance costs, for various workloads and usages. All prices are given in dollars per month (720 hours) for servers located in Europe (eu-west-1).

Shared CPU Instances

Shared CPU instances give only a bit of CPU. The physical processor is over allocated and shared with many other instances running on the same host. A shared CPU instance may burst to 100% CPU usage for short periods but it may also be starved of CPU and paused. Note that these instances are cheap but they are not reliable for non-negligible continuous workloads.

google cloud vs aws pricing shared CPU instances

The smallest instances on both cloud is 500MB and a few percent of CPU. That’s the cheapest instance. It’s usable for testing and minimal needs (can’t do much with only 5% of CPU and 500MB).

The infamous t2.small and it’s rival the g1-small are usually the most common instance types in use. They come with 2GB of memory and a bit of CPU. It’s cheap and good enough for many use cases (excluding production and time critical processing, which need dedicated CPU time).

The Cheapest Production Instances

Production instances are all the instances with dedicated CPU time (i.e. everything but the shared CPU instances).

Most services will just run on the cheapest production instance available. That instance is very important because it determines the entry price and the specifications for everything.

google cloud vs aws pricing cheapest production instances

The cheapest production instance on Google Cloud is the n1-standard-1 which gives 1 CPU and 4 GB of memory.

AWS is more complex. The m3.medium is 1 CPU and 4 GB of memory. The c4.large is 2 CPU and 4 GB of memory.

m3/c3 are the previous family generation (pre-2015), using older hardware and an ancient virtualisation technology. c4/m4 are the current generation, it has enhanced networking and reserved bandwidth for EBS, among other system improvements.

Either way, the Google entry-level instance is significantly cheaper than both AWS entry-level instances. There will be a lot of these running, expect massive costs savings by using Google cloud.

I’m a believer that one should optimize for manageability and not raw costs. That means adopting c4/m4 as the standard for deployments (instead of c3/m3).

Given this decision, the smallest production instance on AWS is the c4.large (2 CPU, 4GB memory), a rather big instance when compared to the n1-standard-1 (1 CPU, 4GB memory). Why are we forced to pay for two CPUs as the minimal choice on AWS? That does set a high base price.

Not only Google is cheaper because it’s more competitive but it also offers more tailored options. The result is a massive 68% discount on the most commonly used production instance.

Personal Note: I would criticize the choice of AWS to discontinue the line of m4.medium instance type (1 CPU).

Instances by usage

A server has 3 dimensions of specifications: CPU performances, memory size and network speed.

Most applications only have a hard requirement in a single dimension. We’ll analyse the pricing separately for each usage pattern.

google cloud vs aws pricing instances by usage

Network Heavy

Typical Consumers: load balancers, file transfers, uploads/downloads, backups and generally speaking everything that uses the network.

What should we order to have  1Gbps and how much will it be?

  • The minimum on Google Cloud is the n1-highcpu-4 instance (4 CPU, 4 GB memory).
  • The minimum on AWS is the c4.4xlarge instance (16 CPU, 30 GB memory).

AWS bandwidth allowance is limited and correlated to the instance size. The big instances -with decent bandwidth- are incredibly expensive.

To give a point of comparison, the c4|m4|r3.large instances have a hard cap at 220 Mbits/s of network traffic (Note: It also applies internally within a VPC).

Source: Network and cloud storage benchmark in 2015

All Google instances have significantly faster network than the equivalent [and even bigger] AWS instances, to the point where they’re not even playing in the same league.

Google has been designing networks and manufacturing their own equipment for decades. It’s fair to assume than AWS doesn’t have the technology to compete.


Typical Consumers: web servers, data analysis, simulations, processing and computations.

Google is cheaper per CPU.

Google CPU instances have half the memory of AWS CPU instances[1]. While that could have justified a 10% difference, it doesn’t justify double[2].

Note: The performances per CPU are equivalent on both cloud (though the CPU models and serial numbers may vary).

[1] A sane design decision. Most CPU bound workloads don’t need much memory. (Note: if they do, they can be run on “standard” instances).

[2] Pricing is mostly linked to CPU count. Additional memory is cheap.


Typical Consumers: database, caches and in-memory workloads.

Google is cheaper per GB of memory.

Google memory instances have 15% less memory than AWS CPU instances. While that could have justified a few percent difference, it sure as hell doesn’t justify double[2].

[2] Pricing is mostly linked to CPU count. Additional memory is cheap.

Local SSD and Scaling Up

There are software that can only scale up, typically SQL databases. A database holding tons of data will require fast local disks and truckloads of memory to operate non-sluggishly.

Scaling up is the most typical use case for beefy dedicated servers, but we’re not gonna rent a single server in another place just for one application. The cloud provider will have to accommodate that need.

Google allows to attach local 400GB SSDs to any instance type ($85 a month per disk).

Some AWS instances comes with small local SSD (16-160GB), you’re out of luck if you need more space than that. The only option to get big local SSD is the special i2 instances family, they have specifications in powers of 800GB local SSD + 4 CPU + 15 GB RAM (for $655 a month).

The Google SSD model is superior. It’s significantly more modular and cheaper (and more performant but that’s a different topic).

The requirements to fulfil are between parenthesis.

Disk Intensive Load: A job that requires high volume fast disks (i.e. local SSD) but not much memory.

AWS forces you to buy a big instance (i2.xlarge) to get enough SSD space whereas Google allows you to attach a SSD to a small instance (n1-highcpu-4). The lack of flexibility from AWS has a measurable impact, the AWS setup is 406% the costs of the Google setup to achieve the same need.

Database: A typical database. Fast storage and sizeable memory.

Bigger Database: Sometimes there is no choice but to scale up, to whatever resources are commanded by the application.

On AWS (i2.8xlarge) 32 cores, 244GB memory, 2 x 800 GB local SSD in RAID1 (+ 6 SSD unused yet gotta pay for it).

On Google Cloud (n1-highmem-32): 32 cores, 208 GB memory, 4 x 375 GB local SSD in RAID10.

This last number is meant to show that the lack of flexibility of AWS can (and will) snowball quickly. Only a very particular instance can fulfil the requirements, it comes with many cores and 4800 GB of unnecessary local SSD. The AWS bill is $4k (273%) higher than the equivalent setup on Google Cloud.

Custom Instances

Google offers custom machine types. You can pick how much CPU and memory you want, you’ll get that exact instance with a tailored pricing.

It is quite flexible. For instance, we could recreate any instance from AWS on Google Cloud.

Of course, there are physical bounds inherent to hardware (e.g. you can’t have a single core with 100 GB of memory).

Reserved Instances

Reserved Instances are bullshit!

Reserving capacity is a dangerous and antiquated pricing model that belongs to the era of the datacenter.

The numbers given in this article do not account for any AWS reservation. However, they all account for Google sustained use discount (30% automatic discount on instances that ran for the entire month).

If your infrastructure is so small that you can reserve all your 4 instances upfront, you should reconsider why you use AWS in the first place. There are more appropriate and cheaper options available.

If your infrastructure is big enough that you have dozens of servers (or thousands), you should already be aware that:

  1. Long term commitment is a huge risk. Most people underestimate it.
  2. Predictions are always off. Most people are overconfident in their predictions.
  3. You are no exception to most people.
  4. Reservation is a mess when having many AWS accounts (dev, staging, prod).
  5. Anything that is testing/transient is too short-lived to be reserved.
  6. Less than 50% of reservable stuff can actually be reserved (margin for change/error).

Most people managers are stubborn. If you your manager is stubborn and really insists on reserving instances, you should bet exclusively on “1 year full upfront“.

fishing with gr
Safety Warning: There is no confirmation button when you purchase reserved instances. You can absolutely spend $73185 without seeing nor confirming an invoice.


google cloud vs aws pricing summary relative costs

AWS was the first generation of cloud, Google is the second. The second generation is always better because it can learn from the mistakes of the first and it doesn’t have the old legacy to support.

2016 should be remembered as the year Google became a better choice than AWS. If 50% cheaper is not a solid argument, I don’t know what is.


Cloud Storage Performance, a benchmark with graphs on network performance.

Jupiter Rising: A Decade of Clos Topologies and Centralized Control in Google’s Datacenter Network, A Google Research Paper, the story on what powers their internal network.

Amazon does everything wrong, and Google does everything right, A message by an employee from Amazon than Google, not directly relevant but still a good read.

Before And After Docker: How To Deploy An Application

Docker is a packaging and deployment system. It allows you to package an application as a “docker image“, then deploy it easily on some servers with a single “docker start <image>” command.

Packaging an application

Packaging an application without Docker

built pipeline without docker
The Standard Build Pipeline
  1. A developer pushes a change
  2. The CI sees that new code is available. It rebuilds the project, runs the tests and generates a package
  3. The CI saves all files in”dist/*” as build artifacts

The application is available for download from “<project>/<build-id>/dist/

Packaging an application with Docker

build pipeline with docker
The Build Pipeline with Docker
  1. A developer pushes a change
  2. The CI sees that new code is available it. It rebuilds the project, runs the tests and generates a docker image
  3. The docker image is saved to the docker registry

The application is available for download as a docker image named “auth:latest” from the registry “”.

You need a CI pipeline

A CI pipeline requires a source code repository (GitLab, GitHub, VisualSVN Server) and a continuous integration system (Jenkins, GitLab CI, TeamCity). Docker also needs a docker registry.

A functional CI pipeline is a must-have for any software development project. It will ensure that your application(s) are automatically re-run, re-tested and re-packaged on every change.

The developers gotta write scripts to build their application, to run tests and to generate packages. Only the developers of an application can do that because they are the only ones to have the knowledge about how things are supposed/expected to work.

Generally speaking, the CI jobs should mostly consist into calling external scripts, like “./ && ./”. The scripts themselves must be part of the source code, they’ll evolve with the application.

You need to know your applications

Please answer the following questions:

  • What does the application need to be built?
  • What’s the command/script to build it?
  • What does the application need to run?
  • What configuration file is needed and where to put it?
  • What’s the command to start/stop the application?

You need to be able to answer all these questions, for all the applications you’re writing and managing.

If you don’t know the answers, you have a problem and Docker is NOT the solution. You gotta figure out how things works and write documentation! (Better hope the guys who were in charge are still working here and gave a thought about all that).

If you know the answers, then you’re good. You know what has to be done. Whether it will be executed by bash, ansible, DockerFile, spec or zip is just an implementation detail.

Deploying an application

Deploying an application without Docker

  1. Download the application
  2. Setup dependencies, services and configuration files
  3. Start the application
# ansible pseudo code 
hosts: hosts_auth
serial: 1 #rolling deploy, one server at a time
become: yes
  name: instance is removed from the load balancer
    elb_name: auth
    instance_id: "{{ ansible_ansible_id }}"
    state: absent
  name: service is stopped
    name: auth
    state: stopped
  name: existing application is deleted
    path: /var/lib/auth/
    match: "*"
    recursive: yes
    state: absent
  name: application is deployed
    destination:: /var/lib/auth
  name: virtualenv is setup
    requirements: /var/lib/auth/requirements.txt
    virtualenv: /var/lib/auth/.venv
  name: application configuration is updated
    src: auth.conf
    dst: /etc/mycompany/auth/auth.conf

  name: service configuration is updated
    src: auth.service
    dst: /etc/init.d/mycompany-auth
  name: service is started
    name: auth
    state: running
  name: instance is added to the load balancer
    elb_name: auth
    instance_id: "{{ ansible_ansible_id }}"
    state: present

Deploying an application with Docker

  1. Create a configuration file
  2. Start the docker image with the configuration file
# ansible pseudo code
hosts: hosts_auth
serial: 1 #rolling deploy, one server at a time
become: yes
  name: instance is removed from the load balancer
    elb_name: auth
    instance_id: "{{ ansible_ansible_id }}"
    state: absent
  name: container is stopped
    name: auth
    state: stopped
  name: configuration is updated
    src: auth.conf
    dst: /etc/mycompany/auth/auth.conf

  name: container is started
    name: auth
    state: started
  name: instance is added to the load balancer
    elb_name: auth
    instance_id: "{{ ansible_ansible_id }}"
    state: present

Notable differences

With docker, the python setup/virtualenv and the service configuration is done during the image creation rather than during the deployment. (The commands are the same, they’re just done in an earlier build stage).

The configuration files are deployed on the host and mounted inside Docker. It would be possible to bake the configuration file into the image but some configurations might only be determined at deployment time and we’d rather not store secrets in the image.


Docker is only a packaging and deployment tool.

Docker doesn’t handle auto scaling, it doesn’t have service discovery, it doesn’t reconfigure load balancers, it doesn’t move containers when servers fail.

Orchestration systems (notably Kubernetes) are supposed to help with that. Currently, they are quite experimental and very difficult to setup [beyond a proof of concept]. The lack of proper orchestration will limit Docker to only be a hype packaging & deployment tool for the foreseeable future.

Docker [even with Kubernetes] needs an existing environment to run, including servers and networks. It ain’t gonna install and configure itself either.

All of that has to be done manually. Order servers in the cloud. Create OS images with Packer. Configure VPC and networking with Terraform. Setup the servers and systems with Ansible. Install and deploy the applications (including docker images) with Ansible.

Cheat Sheet

  1. Figure out what is required and how to build the applications
  2. Write build, test and packaging scripts
  3. Document that in the README
  4. Setup a CI system
  5. Configure automatic builds after every change
  6. Figure out the application dependencies and how to run it
  7. Add that to the README
  8. Write deploy and setup scripts (with Ansible or Salt)


Packaging and deploying applications is a real and challenging job. A Debian package has some good practices and standards to follow whereas Docker comes with no good practices and no rules whatsoever. Docker is a [marketing] success in part because it gives the illusion that the task is easy, with a sense of coolness.

In practise though, it is hard and there is no way around it. You’ll have to figure out your needs and decide on a practical way to deploy and package your applications that will be tailored just for you. Docker is not the solution to the problem, it’s just a random tool among many others, that may or may not help you.

It’s fair to say that the docker ecosystem is infinitely complex and has a long learning curve. If you have neat applications with clear and limited dependencies, they should be relatively manageable and docker can’t make it any easier. On the contrary, it has the potential to make it harder.

Docker shines to package applications with complex messy dependencies (typical NodeJS and Ruby environments). The dependency hell is taken away from the host and moved into the image and the image creation scripts.

Docker is handsome for dev and test environments. It allows to run multiple applications easily on the same host, isolated from each other. Better yet, some applications have conflicting dependencies and would be impossible to run on a single host otherwise.

You should investigate a configuration management system (Ansible) if you don’t already have one. It will help you to manage, configure and setup [numerous] remote servers, à la SSH on steroid. It’s way more general and practical than Docker (and you’re gonna need it to install docker and deploy images anyway).

Reminder: In spite of the practical use cases, docker should be considered as a beta tool not quite ready for serious production.

Moby/Docker in Production: A History of Failure

April 2017: Updated the title. The Docker CEO decided to rename Docker to Moby overnight, without notice. I’ve tried to warn the world about unexpected Docker changes and breakages. That’s the order of magnitude you have to be prepared for.


My first encounter with docker goes back to early 2015. Docker was experimented with to find out whether it could benefit us. At the time it wasn’t possible to run a container [in the background] and there wasn’t any command to see what was running, debug or ssh into the container. The experiment was quick, Docker was useless and closer to an alpha prototype than a release.

Fast forward to 2016. New job, new company and docker hype is growing like mad. Developers here have pushed docker into production projects, we’re stuck with it. On the bright side, the run command finally works, we can start, stop and see containers. It is functional.

We have 12 dockerized applications running in production as we write this article, spread over 31 hosts on AWS (1 docker app per host [note: keep reading to know why]).

The following article narrates our journey with Docker, an adventure full of dangers and unexpected turns.

so it begins, the greatest fuck up of our time

Production Issues with Docker

Docker Issue: Breaking changes and regressions

We ran all these versions (or tried to):

1.6 => 1.7 => 1.8 => 1.9 => 1.10 => 1.11 => 1.12

Each new version came with breaking changes. We started on docker 1.6 early this year to run a single application.

We updated 3 months later because we needed a fix only available in later versions. The 1.6 branch was already abandoned.

The versions 1.7 and 1.8 couldn’t run. We moved to the 1.9 only to find a critical bug on it two weeks later, so we upgraded (again!) to the 1.10.

There are all kind of subtle regressions between Docker versions. It’s constantly breaking unpredictable stuff in unexpected ways.

The most tricky regressions we had to debug were network related. Docker is entirely abstracting the host networking. It’s a big mess of port redirection, DNS tricks and virtual networks.

Bonus: Docker was removed from the official Debian repository last year, then the package got renamed from to docker-engine. Documentation and resources predating this change are obsolete.

Docker Issue: Can’t clean old images

The most requested and most lacking feature in Docker is a command to clean older images (older than X days or not used for X days, whatever). Space is a critical issue given that images are renewed frequently and they may take more than 1GB each.

The only way to clean space is to run this hack, preferably in cron every day:

docker images -q -a | xargs --no-run-if-empty docker rmi

It enumerates all images and remove them. The ones currently in use by running containers cannot be removed (it gives an error). It is dirty but it gets the job done.

The docker journey begins with a clean up script. It is an initiation rite every organization has to go through.

Many attempts can be found on the internet, none of which works well. There is no API to list images with dates, sometimes there are but they are deprecated within 6 months. One common strategy is to read date attribute from image files and call ‘docker rmi‘ but it fails when the naming changes. Another strategy is to read date attributes and delete files directly but it causes corruption if not done perfectly, and it cannot be done perfectly except by Docker itself.

Docker Issue: Kernel support (or lack thereof)

There are endless issues related to the interactions between the kernel, the distribution, docker and the filesystem

We are using Debian stable with backports, in production. We started running on Debian Jessie 3.16.7-ckt20-1 (released November 2015). This one suffers from a major critical bug that crashes hosts erratically (every few hours in average).

Linux 3.x: Unstable storage drivers

Docker has various storage drivers. The only one (allegedly) wildly supported is AUFS.

The AUFS driver is unstable. It suffers from critical bugs provoking kernel panics and corrupting data.

It’s broken on [at least] all “linux-3.16.x” kernel. There is no cure.

We follow Debian and kernel updates very closely. Debian published special patches outside the regular cycle. There was one major bugfix to AUFS around March 2016. We thought it was THE TRUE ONE FIX but it turned out that it wasn’t. The kernel panics happened less frequently afterwards (every week, instead of every day) but they were still loud and present.

Once during this summer there was a regression among a major update, that brought back a previous critical issue. It started killing CI servers one by one, with 2 hours in average between murders. An emergency patch was quickly released to fix the regression.

There were multiple fixes to AUFS published along the year 2016. Some critical issues were fixed but there are many more still left. AUFS is unstable on [at least] all “linux-3.16.x” kernels.

  • Debian stable is stuck on kernel 3.16. It’s unstable. There is nothing to do about it except switching to Debian testing (which can use the kernel 4).
  • Ubuntu LTS is running kernel 3.19. There is no guarantee that this latest update fixes the issue. Changing our main OS would be a major disruption but we were so desperate that we considered it for a while.
  • RHEL/CentOS-6 is on kernel 2.x and RHEL/CentoS-7 is on kernel 3.10 (with many later backports done by RedHat).

Linux 4.x: The kernel officially dropped docker support

It is well-known that AUFS has endless issues and it’s regarded as dead weight by the developers. As a long-standing goal, the AUFS filesystem was finally dropped in kernel version 4.

There is no unofficial patch to support it, there is no optional module, there is no backport whatsoever, nothing. AUFS is entirely gone.

[dramatic pause]




How does docker work without AUFS then? Well, it doesn’t.

[dramatic pause]




So, the docker guys wrote a new filesystem, called overlay.

OverlayFS is a modern union filesystem that is similar to AUFS. In comparison to AUFS, OverlayFS has a simpler design, has been in the mainline Linux kernel since version 3.18 and is potentially faster.” — Docker OverlayFS driver

Note that it’s not backported to existing distributions. Docker never cared about [backward] compatibility.

Update after comments: Overlay is the name of both the kernel module to support it (developed by linux maintainers) and the docker storage driver to use it (part of docker, developed by docker). They are two different components [with a possible overlap of history and developers]. The issues seem mostly related to the docker storage driver, not the filesystem itself.

The debacle of Overlay

A filesystem driver is a complex piece of software and it requires a very high level of reliability. The long time readers will remember the Linux migration from ext3 to ext4. It took time to write, more time to debug and an eternity to be shipped as the default filesystem in popular distributions.

Making a new filesystem in 1 year is an impossible mission. It’s actually laughable when considering that the task is assigned to Docker, they have a track record of unstability and disastrous breaking changes, exactly what we don’t want in a filesystem.

Long story short. That did not go well. You can still find horror stories with Google.

Overlay development was abandoned within 1 year of its initial release.

[dramatic pause]




Then comes Overlay2.

The overlay2 driver addresses overlay limitations, but is only compatible with Linux kernel 4.0 [or later] and docker 1.12” — Overlay vs Overlay2 storage drivers

Making a new filesystem in 1 year is still an impossible mission. Docker just tried and failed. Yet they’re trying again! We’ll see how it turns out in a few years.

Right now it’s not supported on any systems we run. We can’t use it, we can’t even test it.

Lesson learnt: As you can see with Overlay then Overlay2. No backport. No patch. No retro compatibility. Docker only moves forward and breaks things. If you want to adopt Docker, you’ll have to move forward as well, following the releases from docker, the kernel, the distribution, the filesystems and some dependencies.

Bonus: The worldwide docker outage

On 02 June 2016, at approximately 9am (London Time). New repository keys are pushed to the docker public repository.

As a direct consequence, any run of “apt-get update” (or equivalent) on a system configured with the broken repo will fail with an error “Error Hash Sum mismatch

This issue is worldwide. It affects ALL systems on the planet configured with the docker repository. It is confirmed on all Debian and ubuntu versions, independent of OS and docker versions.

All CI pipelines in the world which rely on docker setup/update or a system setup/update are broken. It is impossible to run a system update or upgrade on an existing system. It’s impossible to create a new system and install docker on it.

After a while. We get an update from a docker employee: “To give an update; I raised this issue internally, but the people needed to fix this are in the San Francisco timezone [8 hours difference with London], so they’re not present yet.

I personally announce that internally to our developers. Today, there is no Docker CI and we can’t create new systems nor update existing systems which have a dependency on docker. All our hope lies on a dude in San Francisco, currently sleeping.

[pause waiting for the fix, that’s when free food and drinks come in handy]

An update is posted from a Docker guy in Florida at around 3pm (London Time). He’s awake, he’s found out the issue and he’s working on the fix.

Keys and packages are republished later.

We try and confirm the fix at around 5pm (London Time).

That was a 7 hours interplanetary outage because of Docker. All that’s left from the outage is a few messages on a GitHub issue. There was no postmortem. It had little (none?) tech news or press coverage, in spite of the catastrophic failure.

Docker Registry

The docker registry is storing and serving docker images.

Automatic CI build  ===> (on success) push the image to ===> docker registry
Deploy command <=== pull the image from <=== docker registry

There is a public registry operated by docker. As an organization, we also run our own internal docker registry. It’s a docker image running inside docker on a docker host (that’s quite meta). The docker registry is the most used docker image.

There are 3 versions of the docker registry. The client can pull indifferently from any:

Docker Registry Issue: Abandon and Extinguish

The docker registry v2 is as a full rewrite. The registry v1 was retired soon after the v2 release.

We had to install a new thing (again!) just to keep docker working. They changed the configuration, the URLs, the paths, the endpoints.

The transition to the registry v2 was not seamless. We had to fix our setup, our builds and our deploy scripts.

Lesson learnt: Do not trust on any docker tool or API. They are constantly abandoned  and extinguished.

One of the goal of the registry v2 is to bring a better API. It’s documented here, a documentation that we don’t remember existed 9 months ago.

Docker Registry Issue: Can’t clean images

It’s impossible to remove images from the docker registry. There is no garbage collection either, the doc mentions one but it’s not real. (The images do have compression and de-duplication but that’s a different matter).

The registry just grows forever. Our registry can grow by 50 GB per week.

We can’t have a server with an unlimited amount of storage. Our registry ran out of space a few times, unleashing hell in our build pipeline, then we moved the image storage to S3.

Lesson learnt: Use S3 to store images (it’s supported out-of-the-box).

We performed a manual clean-up 3 times in total. In all cases we had to stop the registry, erase all the storage and start a new registry container. (Luckily, we can re-build the latest docker images with our CI).

Lesson learnt: Deleting any file or folder manually from the docker registry storage WILL corrupt it.

To this day, it’s not possible to remove an image from the docker registry. There is no API either. (One of the point of the v2 was to have a better API. Mission failed).

Docker Issue: The release cycle

The docker release cycle is the only constant in the Docker ecosystem:

  1. Abandon whatever exists
  2. Make new stuff and release
  3. Ignore existing users and retro compatibility

The release cycle applies but is not limited to: docker versions, features, filesystems, the docker registry, all API…

Judging by the past history of Docker, we can approximate that anything made by Docker has a half-life of about 1 year, meaning that half of what exist now will be abandoned [and extinguished] in 1 year. There will usually be a replacement available, that is not fully compatible with what it’s supposed to replace, and may or may not run on the same ecosystem (if at all).

We make software not for people to use but because we like to make new stuff.” — Future Docker Epitaph

The current status-quo on Docker in our organization

Growing in web and micro services

Docker first came in through a web application. At the time, it was an easy way for the developers to package and deploy it. They tried it and adopted it quickly. Then it spread to some micro services, as we started to adopt a micro services architecture.

Web applications and micro services are similar. They are stateless applications, they can be started, stopped, killed, restarted without thinking. All the hard stuff is delegated to external systems (databases and backend systems).

The docker adoption started with minor new services. At first, everything worked fine in dev, in testing and in production. The kernel panics slowly began to happen as more web services and web applications were dockerized. The stability issues became more prominent and impactful as we grew.

A few patches and regressions were published over the year. We’ve been playing catchup & workaround with Docker for a while now. It is a pain but it doesn’t seem to discourage people from adopting Docker. Support and demand is still growing inside the organisation.

Note: None of the failures ever affected any customer or funds. We are quite successful at containing Docker.

Banned from the core

We have some critical applications running in Erlang, managed by a few guys in the ‘core’ team.

They tried to run some of their applications in Docker. It didn’t work. For some reasons, Erlang applications and docker didn’t go along.

It was done a long time ago and we don’t remember all the details. Erlang has particular ideas about how the system/networking should behave and the expected load was in thousands of requests per second. Any unstability or incompatibility could justify an outstanding failure. (We know for sure now that the versions used during the trial suffered from multiple major unstability issues).

The trial raised a red flag. Docker is not ready for anything critical. It was the right call. The later crashes and issues managed to confirm it.

We only use Erlang for critical applications. For example, the core guys are responsible for a payment system that handled $96,544,800 in transaction this month. It includes a couple of applications and databases, all of which are under their responsibilities.

Docker is a dangerous liability that could put millions at risk. It is banned from all core systems.

Banned from the DBA

Docker is meant to be stateless. Containers have no permanent disk storage, whatever happens is ephemeral and is gone when the container stops. Containers are not meant to store data. Actually, they are meant by design to NOT store data. Any attempt to go against this philosophy is bound to disaster.

Moreover. Docker is locking away processes and files through its abstraction, they are unreachable as if they didn’t exist. It prevents from doing any sort of recovery if something goes wrong.

Long story short. Docker SHALL NOT run databases in production, by design.

It gets worse than that. Remember the ongoing kernel panics with docker?

A crash would destroy the database and affect all systems connecting to it. It is an erratic bug, triggered more frequently under intensive usage. A database is the ultimate IO intensive load, that’s a guaranteed kernel panic. Plus, there is another bug that can corrupt the docker mount (destroying all data) and possibly the system filesystem as well (if they’re on the same disk).

Nightmare scenario: The host is crashed and the disk gets corrupted, destroying the host system and all data in the process.

Conclusion: Docker MUST NOT run any databases in production, EVER.

Every once in a while, someone will come and ask “why don’t we put these databases into docker?” and we’ll tell some of our numerous war stories, so far, no-one asked twice.

Note: We started going over our Docker history as an integral part of our on boarding process. That’s the new damage control philosophy, kill the very idea of docker before it gets any chance to grow and kill us.

A Personal Opinion

Docker is gaining momentum, there is some crazy fanatic support out there. The docker hype is not only a technological liability any more, it has evolved into a sociological problem as well.

The perimeter is controlled at the moment, limited to some stateless web applications and micro services. It’s unimportant stuff, they can be dockerized and crash once a day, I do not care.

So far, all people who wanted to use docker for important stuff have stopped after a quick discussion. My biggest fear is that one day, a docker fanatic will not listen to reason and keep pushing. I’ll be forced to barrage him and it might not be pretty.

Nightmare scenario: The future accounting cluster revamp, currently holding $23M in customer funds (the M is for million dollars). There is already one guy who genuinely asked the architect “why don’t you put these databases into docker?“, there is no word to describe the face of the architect.

My duty is to customers. Protecting them and their money.

Surviving Docker in Production

What docker pretends to be.
What docker really is.

Follow releases and change logs

Track versions and change logs closely for kernel, OS, distributions, docker and everything in between. Look for bugs, hope for patches, read everything with attention.

ansible '*' -m shell -a "uname -a"

Let docker crash

Let docker crash. self-explanatory.

Once in a while, we look at which servers are dead and we force reboot them.

Have 3 instances of everything

High availability require to have at least 2 instances per service, to survive one instance failure.

When using docker for anything remotely important, we should have 3 instances of it. Docker die all the time, we need a margin of error to support 2 crashes in a raw to the same service.

Most of the time, it’s CI or test instances that crash. (They run lots of intensive tests, the issues are particularly outstanding). We’ve got a lot of these. Sometimes there are 3 of them crashing in a row in an afternoon.

Don’t put data in Docker

Services which store data cannot be dockerized.

Docker is designed to NOT store data. Don’t go against it, it’s a recipe for disaster.

On top, there are current issues killing the server and potentially destroying the data so that’s really a big no-go.

Don’t run anything important in Docker

Docker WILL crash. Docker WILL destroy everything it touches.

It must be limited to applications which can crash without causing downtime. That means mostly stateless applications, that can just be restarted somewhere else.

Put docker in auto scaling groups

Docker applications should be run in auto-scaling groups. (Note: We’re not fully there yet).

Whenever an instance is crashed, it’s automatically replaced within 5 minutes. No manual action required. Self healing.

Future roadmap


The impossible challenge with Docker is to come with a working combination of kernel + distribution + docker version + filesystem.

Right now. We don’t know of ANY combination that is stable (Maybe there isn’t any?). We actively look for one, constantly testing new systems and patches.

Goal: Find a stable ecosystem to run docker.

It takes 5 years to make a good and stable software, Docker v1.0 is only 28 months old, it didn’t have time to mature.

The hardware renewal cycle is 3 years, the distribution release cycle is 18-36 months. Docker didn’t exist in the previous cycle so systems couldn’t consider compatibility with it. To make matters worse, it depends on many advanced system internals that are relatively new and didn’t have time to mature either, nor reach the distributions.

That could be a decent software in 5 years. Wait and see.

Goal: Wait for things to get better. Try to not go bankrupt in the meantime.

Use auto scaling groups

Docker is limited to stateless applications. If an application can be packaged as a Docker Image, it can be packaged as an AMI. If an application can run in Docker, it can run in an auto scaling group.

Most people ignore it but Docker is useless on AWS and it is actually a step back.

First, the point of containers is to save resources by running many containers on the same [big] host. (Let’s ignore for a minute the current docker bug that is crashing the host [and all running containers on it], forcing us to run only 1 container per host for reliability).

Thus containers are useless on cloud providers. There is always an instance of the right size. Just create one with appropriate memory/CPU for the application. (The minimum on AWS is t2.nano which is $5 per month for 512MB and 5% of a CPU).

Second, the biggest gain of containers is when there is a complete orchestration system around them to automatically manage creation/stop/start/rolling-update/canary-release/blue-green-deployment. The orchestration systems to achieve that currently do not exist. (That’s where Nomad/Mesos/Kubernetes will eventually come in, there are not good enough in their present state).

AWS has auto scaling groups to manage the orchestration and life cycle of instances. It’s a tool completely unrelated to the Docker ecosystem yet it can achieve a better result with none of the drawbacks and fuck-ups.

Create an auto-scaling group per service and build an AMI per version (tip: use Packer to build AMI). People are already familiar with managing AMI and instances if operations are on AWS, there isn’t much more to learn and there is no trap. The resulting deployment is golden and fully automated. A setup with auto scaling groups is 3 years ahead of the Docker ecosystem.

Goal: Put docker services in auto scaling groups to have failures automatically handled.


Update after comments: Docker and CoreOS are made by separate companies.

To give some slack to Docker for once, it requires and depends on a lot of new advanced system internals. A classic distribution cannot upgrade system internals outside of major releases, even if it wanted to.

It makes sense for docker to have (or be?) a special purpose OS with an appropriate update cycle. It may be the only way to have a working bundle of kernel and operating system able to run Docker.

Goal: Trial the CoreOS ecosystem and assess stability.

In the grand scheme of operations, it’s doable to separate servers for running containers (on CoreOS) from normal servers (on Debian). Containers are not supposed to know (or care) about what operating systems they are running.

The hassle will be to manage the new OS family (setup, provisioning, upgrade, user accounts, logging, monitoring). No clue how we’ll do that or how much work it might be.

Goal: Deploy CoreOS at large.


One of the [future] major breakthrough is the ability to manage fleets of containers abstracted away from the machines they end up running on, with automatic start/stop/rolling-update and capacity adjustment,

The issue with Docker is that it doesn’t do any of that. It’s just a dumb container system. It has the drawbacks of containers without the benefits.

There are currently no good, battle tested, production ready orchestration system in existence.

  • Mesos is not meant for Docker
  • Docker Swarm is not trustworthy
  • Nomad has only the most basic features
  • Kubernetes is new and experimental

Kubernetes is the only project that intends to solve the hard problems [around containers]. It is backed by resources that none of the other projects have (i.e. Google have a long experience of running containers at scale, they have Googley amount of resources at their disposal and they know how to write working software).

Right now, Kubernetes is young & experimental and it’s lacking documentation. The barrier to entry is painful and it’s far from perfection. Nonetheless, it is [somewhat] working and already benefiting a handful of people.

In the long-term, Kubernetes is the future. It’s a major breakthrough (or to be accurate, it’s the final brick that is missing for containers to be a major [r]evolution in infrastructure management).

The question is not whether to adopt Kubernetes, the question is when to adopt it?

Goal: Keep an eye on Kubernetes.

Note: Kubernetes needs docker to run. It’s gonna be affected by all docker issues. (For example, do not try Kubernetes on anything else than CoreOS).

Google Cloud: Google Container Engine

As we said before, there is no known stable combination of OS + kernel + distribution + docker version, thus there is no stable ecosystem to run Kubernetes on. That’s a problem.

There is a potential workaround: Google Container Engine. It is a hosted Kubernetes (and Docker) as a service, part of Google Cloud.

Google gotta solve the Docker issues to offer what they are offering, there is no alternative. Incidentally, they might be the only guys who can find a stable ecosystem around Docker, fix the bugs, and sell that ready-to-use as a cloud managed service. We might have a shared goal for once.

They already offer the service so that should mean that they already worked around the Docker issues. Thus the simplest way to have containers working in production (or at-all) may be to use Google Container Engine.

Goal: Move to Google Cloud, starting with our subsidiaries not locked in on AWS. Ignore the rest of the roadmap as it’s made irrelevant.

Google Container Engine: One more reason why Google Cloud is the future and AWS is the past (on top of 33% cheaper instances with 3 times the network speed and IOPS, in average).

Why docker is not yet succeeding in production, July 2015, from the Lead Production Engineer at Shopify.

Docker is not ready for primetime, August 2016.

Docker in Production: A retort, November 2016, a response to this article.

How to deploy an application with Docker… and without Docker, An introduction to application deployment, The HFT Guy.

Disclaimer (please read before you comment)

A bit of context missing from the article. We are a small shop with a few hundreds servers. At core, we’re running a financial system moving around multi-million dollars per day (or billions per year).

It’s fair to say that we have higher expectations than average and we take production issues rather (too?) seriously.

Overall, it’s “normal” that you didn’t experience all of these issues if you’re not using docker at scale in production and/or if you didn’t use it for long.

I’d like to point out that these are issues and workarounds happening over a period of [more than] a year, summarized all together in a 10 minutes read. It does amplify the dramatic and painful aspect.

Anyway, whatever happened in the past is already in the past. The most important section is the Roadmap. That’s what you need to know to run Docker (or use auto scaling groups instead).

How to present a GitHub project for your resume


Companies ask for a GitHub profile. Recruiters ask for a GitHub profile. The question “Do you contribute to open-source?” is now one of the most common questions asked in phone screens.

If people want a GitHub, we shall give them a GitHub. This article will explain how to present a GitHub project for use in a resume.

The given advice can be red from two point of views. As a candidate, it is what to write to introduce and present a software (not necessary on GitHub). As an interviewer (or a fellow developer), it is what to look for to judge the experience of the developer(s) and the quality of a software.

submit application form with a github link
When having a GitHub is mandatory, just like having a name.

Link to a specific project

Put a link to your GitHub in your resume and every application forms you have to fill.

That link must send directly to a project. Never link to the root of your GitHub profile, it doesn’t show anything useful and it’s hard to navigate from there.

It means that you must have ONE project to show. A single demonstration project is enough, don’t need more.

This project will be the “landing page” in web buzzword. This is the first page the employer will see. They will rarely go past it (and they shouldn’t have to) so the page should be a good enough by itself. If they go past it, it’s only because the page grabbed their interests and they wanted to see more.

We’ll write the project page to give a good first impression and show off skills as a software engineer.

Project Structure

A software project can be judged in 5 seconds by looking at the directory structure.

An inexperienced developer is easy to spot. His project doesn’t have any structure. Files are either in unpredictable places or all in the top directory.

There is one project structure to rule them all. There MUST be separate directories for source, test, libraries, compiled binaries, etc…

Whether the naming convention will be “doc” or “docs” is an unimportant detail. For example, here are Simple Folder Structure Conventions for GitHub projects:

├── build                   # Compiled files (alternatively `dist`)
├── docs                    # Documentation files (alternatively `doc`)
├── src                     # Source files (alternatively `lib` or `app`)
├── test                    # Automated tests (alternatively `spec` or `tests`)
├── tools                   # Tools and utilities
software project structure
A well-organized project


Have a README to:

  • Describe the purpose of the project
  • Screenshots/videos
  • Usage
  • Link to the installer/webpage

Have screenshots in the readme

A picture is worth a thousand words.

People are not going to install the application just to see it. Give them screenshots.

Have videos in the readme

A picture is worth a thousand words. A video is worth a thousand pictures.

There is nothing better than a video when it comes to giving a demonstration or showing off an application.

snake game preview animated gif
Great demo from a random snake project on GitHub

Note: GitHub does not allow to embed video files in the readme, use animated gif instead.

Link to a website or an installer

Link to the site if it’s a web application project. Of course, a web application should be running somewhere and publicly accessible, that’s the point of web applications.

Link to the installer if it’s a desktop application project. It’s unlikely that the user will install it but that looks professional, that’s how desktop applications are distributed after all.

Integrate GitHub tools

GitHub has a rich ecosystem of free tools for building, packaging, testing and much more. All these tools are mandatory for professional software development.

It used to be hell to setup the tooling but now everything is readily available for free through GitHub and the setup is dead simple. There is no excuse to not use the tooling.


This one is a sample C++ project for a Connect Four. From left to right:

  1. Build on Linux (Travis CI)
  2. Build on Windows (AppVeyor)
  3. Unit tests and coverage analysis (Coveralls)

What about the source code?

Nobody cares about your code. It was quite a shocking moment when I learned this in my programming career. I would take great care in polishing my code only to find out nobody actually cares. It’s not the code that counts, it’s the product. ” — Source

A paragraph to explain the purpose of the application is 10 times faster than guessing it. A quick start video of an [non-trivial] application is 100 times faster than figuring it out. A design diagram is 1000 times faster than reverse engineering the application. All of these could be achieved by reading the source code, at the cost of orders of magnitude more time and headache. It’s extremely slow and difficult to read code (or should we say to decode code). It should only ever be a last resort.

Lesson #1: Noone cares about your source code. Noone is gonna read it.

Lesson #2: Don’t expect people to read it. Don’t force them to.

What if I don’t have big projects to show?

Good. Smaller projects are easier to show, easier to explain and easier to understand for the interviewer. For instance, everyone can grasp a good old Connect Four.

It is not a trivial project despite what it looks like at first. Write a decent UI, put some colors, allow a two players option, add a “hint” to show the best next move, add an AI to play against.

While the game is conceptually simple there is a lot of work to turn it into a good and polished software. That leaves plenty of depth to talk about in a face-to-face interview.

Did you know that the first player in a connect four game always wins? [if playing perfectly] Did you know that the second player can always draw the game, if the first player doesn’t take the middle position as his first move?

Source: A Knowledge-based Approach of Connect-Four, The Game is Solved: White Wins, Victor Allis

Do interviewers really look at GitHub?

As a matter of fact: No, they don’t.

github traffic statistics
GitHub Traffic Statistics

We’ve done the tests. Here are the statistics after sending a bunch of resumes. The 3 views are from myself, I accessed the project while writing this article, without being authenticated to GitHub. Oops, my bad.

From personal experience from the last time I looked for a job. After a dozen of phone interviews (1 dev per call) and a couple of on-sites (4 to 7 devs per on-site), there was only 1 visit to my profile.

Conclusion: Noone cares about GitHub. Noone is gonna read it. Everyone is gonna ask for it nonetheless, cause it’s hype.

Bonus: Since noone will check the link they’re given, you too can refuse to participate in the GitHub masquerade by only linking to the ultimate hello world repository. (Worst case scenario: Just talk about this blog if the interviewers spot the trickery. They love candidates who read blogs).

Cheat Sheet

  1. Structure the project
  2. Have a README
  3. Write a paragraph to explain the purpose of the project
  4. Put screenshots and videos
  5. Distribute an installer (desktop app) or give the website (web app)
  6. Integrate development tools (CI, unit test, packager, etc…)

That’s good practices for software projects. It’s not limited to GitHub.