Over the past month, my colleague Kurtis and I have been engineering a fully environment. This article discusses the requirements that we had for our deployment system.  I eventually hope to discuss the entire thing, how we built it, and what revisions we make.

Why Deploying Can Be Painful

Most programmers hate deploying code. I certainly did until this past year. Deploying code is (often times) much harder than writing the code itself. Deploying requires a great deal of knowledge: OS configuration and setup, cloud provider APIs or physical server installation quirks, numerous software components, system monitoring, access lists, and a lot of other things.

It’s a pain.

At my work, we operate with a variety of technologies and tools, which makes deployment even more complex, as there is no one-solution-fits-all approach to managing our various components easily.

Since it can be difficult and frustrating (especially for small teams like mine, where we don’t have any dedicated sysadmins), many people tend to ignore deployment, or put it off till the last minute. This is the way I used to operate–I would work on my code for weeks at a time, and then once I had some features finished and bugs removed I would manually copy my code over to each production server, carefully update my project files, and then restart the necessary services and manually test like crazy to make sure I wasn’t breaking anything.

The approach I used to take was awful for numerous reasons. Among other things:

• It made me scared to deploy code frequently. This means users get slower updates, bugs get fixed slower, and every suffers.
• Deploying code would often cause downtime. One accidental cp or rm, and your code is gone. It’s hard to recover from production mistakes.
• It is time consuming. Deploying code shouldn’t take hours.
• It made it difficult to test for code correctness. Infrequent deployment = infrequent testing = infrequent integration with other team member’s code. When we deployed, it would often cause other code issues that were unseen in our development environments.

When Kurtis and I started discussing these issues, we decided it was time to do something about it. We wanted to build a deployment system to make our lives easier, our coding more effective, and our company more efficient.

Our Requirements

When we started planning out our deployment system and doing research, we generated a list of requirements that (more or less) must be met by the system of our choosing. Here they are:

• We should have three distinct environments: development, staging, and production. There should never be any versions of code running on the incorrect systems.
• Our development systems should always be running the latest version of or develop git branch.
• Our staging systems should always be running the latest version of our master branch.
• Our production systems should always be running the latest version of our master branch (but only if tests pass on staging).
• We should have a continuous integration system watch our git repositories, and when changed, check out the latest version of our code, run tests on it and if the tests pass deploy it to the appropriate environment.
• We should be able to run multiple levels of tests: unit tests, integration tests, performance tests, and deployment tests, with each commit.
• We should be able to get meaningful statistics and notifications when we break stuff, so that we can get it working again.
• Our system should be as self-healing as possible. If something goes wrong, it should try to fix it, and only if it can’t figure out what to do should we be notified.

Those are the main requirements we had. And I’d like to think that they are still pretty solid. With those features, we should be able to focus on code, and let everything else happen naturally.

The three distinct environments are important. They can vary greatly from organization-to-organization. For us, our development environment is local for each developer. We write and test most of our code on our home boxes with a combination of Rackspace boxes and Virtualbox environments as helpers. Our staging and production environments are both in the same cloud, and identical in almost every way. We use our staging as a live fail over for production, and it serves as a great test bed for production code before putting it live.

We use git flow at work, which explains our git branching model. Basically, all our branches have standard naming convention, which allows us to do stuff like say that all code in the master branch should be deployed straight to staging / production, and that all code in develop should be deployed straight to development.

The continuous integration (and deployment) system should be able to run tests and deploy code. This step has the biggest impact on our work flow. Knowing that every time I git commit, my code is automatically tested and deployed to all development, staging, and production boxes (depending on the git branch) is an awesome feeling. This enables us to do a lot of cool things. Push bug fixes out immediately, push features out immediately, instantly test for problems, discover pain points earlier, etc.

The ability to run multiple levels of tests is also extremely important. Most folks (those who do any sort of testing, anyhow) will stop at unit tests. However, especially when you are designing large scale systems with databases, you need to test for concurrency problems, and many other factors that simple unit tests won’t catch. This means that we need the ability to launch performance test suites, and other remote tests that MUST run against a live development or staging environment to be useful.

Our requirement to get feedback is a no-brainer. What is the point of automating stuff if you can’t get reports when things don’t work?

And lastly, we chose to build in the self-healing requirement so that we would not end up wasting our time dealing with issues that are best solved automatically.

Conclusion

What are your experiences with deployment? I’m extremely glad that we decided to tackle this issue recently. We’ve still got quite a while to go before our system is perfect, but we’re making a lot of good progress, and have already saved hundreds of man hours with some fairly simple automation.

Sometime in the next week or so I’ll throw up another article on our deployment system, and dive into some technical details.