Tag Archives: Continuous Integration

Starting with Continuous Integration

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In this post I look at things to consider when an organization wants to introduce Continuous Integration (CI). As in so many other situations the non-technical challenges are more difficult to solve than some nitty-gritty details.

Start Small Right Now

If ever there was a place for the proverb “the better is the enemy of the good” it is here. Waiting days, weeks, or months because you have not sorted out all details is the worst you can do. Instead you should start immediately by just installing a CI server (Jenkins is the de facto standard) and set up a simple job that does nothing but check out the source code from the VCS and compile it.

More advanced stuff like test automation, setting up delivery pipelines, integration with binary repositories like Artifactory or Nexus is not needed in the beginning.

Agile Automatically?

Most development teams that have not used CI so far are probably operating in a more or less non-agile fashion. That is fine and can stay as it is! Because while CI is virtually a prerequisite for agile development, that does absolutely not mean that teams following a waterfall model will not benefit considerably from CI.

So establishing CI can but does not have to be the first step of moving towards agile development. In fact I would argue that introducing CI is a large-enough step for an existing development organization. Only when this has been “digested”, you should think about moving towards agile. Otherwise too many things would be changed in parallel, similar to combining a new release of your own software with an upgrade of the underlying platform, e.g. the database server.

Frequency of Builds

This is the only part where I strongly recommend that you start at full throttle. What I mean by that is that you resist the temptation to run your builds only once a day or even less frequently. Ideally, every commit into the VCS triggers a build via a post-commit hook (here is more information for Git and Subversion). But polling the VCS every e.g. 10 minutes is a good-enough approximation in most cases. And it is also a little bit easier to set up when you just start on the whole topic.

Why am I so adamant on this particular point? I think that almost-instant feedback is at the very core of CI and the only way to deliver it is by running the build. All the points below change the amount of details that are provided or reduce the risk of introducing bugs into the code. But this hugely powerful feeling you get after your first commit triggers a build, is the important aspect for successful adoption in my view.

Test Automation

Start with “compilation works” as the lowest common denominator. When you want to start adding the use of “proper” test frameworks, feel free to do so. But is nothing you need on day one.

When you are ready to do more, you need to focus on those parts of your code that are most relevant for the business. Resist the temptation of striving for large test coverage of your code for the sake of it (having a KPI on this is a really bad idea). Otherwise people will start writing test for trivial helper functions, testing which on their own is of low relevance.

Instead take the critical parts of the business logic and develop a way to test them end-to-end (if possible without the GUI yet). With this approach you will implicitly cover all the lower-level stuff underneath automatically. Unless you have someone on your team with practical experience on integration testing frameworks (e.g. Citrus), I would not start with a full-blown approach but rather develop a few custom scripts.

The point in time when to start with more advanced topics, especially automated performance tests, depends on your individual situation and I will not make recommendations about it here. But what you should do as soon as possible, is read up on the subject and get an understanding about the different types of test and what they are good for. You do not need to implement everything now, but this will allow you to make informed judgements about the path you choose.

In Closing

You should now have an idea how to get started with CI quickly and in a way that delivers positive results pretty much from day one. Gaining traction in the organization should be your first priority in the beginning. There is a widespread misconception that things like CI, while theoretically the right to do, slow developers down. Nothing could be further from the truth. But unless you fight this impression fiercely, sooner or later management will ask for by-passing that “nice new thing” and get code out of the code faster using the old way.

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Start Working with a Version Control System

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Every so often I get asked about what to consider when introducing Continuous Integration (CI) to an organization. Interestingly though, most of the details discussed are about working with a version control system (VCS) and not CI itself. That is understandable because the VCS is the “gateway” for all developers. So here are my recommendations.

Use of Branches

It is important to distinguish between the goal (Continuous Integration) and the means (trunk-based development). Yes, it is possible to implement a system that facilitates frequent integration of code from various branches. On the other hand it is a considerably more complex approach than to simply work off trunk. So in most cases I would argue that simpler is better.

In any case I recommend to also look at using branches and can recommend this video on YouTube as a starting point. Whatever path you choose, it will always improve your understanding of the subject and you do not have to take my word for it.

Number of Commits

Most people that do not use a VCS will typically work through the day and create a file copy (snapshot-like) of their project in the evening just before they leave for the day. So it is a natural conclusion to transfer this approach like-for-like to the VCS. In practical terms this would mean to perform a single commit every day just before you go home. And the commit message would be similar to “Work for <DATE>” or “WIP”.

But instead of doing so, developers should commit as often as possible. In my experience 5 to 15 times for a full day of development work is a good rule-of-thumb. There will be exceptions, of course. But whenever you are far enough outside this ballpark-figure, you should analyze why that is.

Time to Commit

Instead of looking at time intervals, people should commit whenever the code has reached a stable state. Or in other words: It does not make sense to have people commit every 30 to 45 minutes. They should rather do this after e.g. having fixed a small bug (e.g. correction of a threshold). But for changes that require more than roughly 60 minutes of work, things need to be broken down. This will be looked at in detail in the next bullet point.

Especially when starting with a VCS, people will quite often miss to commit when they have completed a somewhat discrete piece of work. That is normal and happens to everybody. Even today, with more than ten years of experience on the subject, I still sometimes miss the point. Adding the step of committing a set of changes to your work routine, is something that really takes time. It is a bit like re-ordering your morning routine in the bathroom. Most people do things in the exact same order every day. Changing something there is just as difficult as performing a commit “automatically”.

What to do when you realize your miss, depends on the circumstances. If this is your personal pet project, you may just virtually slap yourself on the head and continue or do the infamous “WIP” commit. But if this a critical project for you organization and you collaborate with others, you need to undo the last couple of changes until you are back where you should have performed the commit in the first place. Yes, this is cumbersome and feels like a waste of time, especially if you are working under time pressure, i.e. always.

But there is no alternative and anyone who says differently (typically project managers without a solid background in software development) is just completely wrong. Because you need to be able to understand exactly who performed what change to the code base and when. But with messy commits this will not work in practice. Or to rephrase in management speak: It is much more time-consuming and error-prone to go through untidy changes every single time you try find something in the VCS, than to spend the effort only once and correct things. 

Split Up Larger Work Items

In many cases the effort to implement a new feature or fix a really nasty bug will exceed let’s say 60 minutes. In those cases the developer should have a rough a plan how the overall work be structured. For a new feature this could mean something like:

  1. Add test-cases that pass for the current implementation
  2. Re-factor in preparation without changing behavior
  3. Add test-cases for new feature
  4. Implement first half of new feature but ensure that it cannot be executed yet (think feature-toggle here)
  5. Finish new feature and enable execution

Working Code

The example above for how to structure the implementation of something larger has a critical aspect to it. Which is that at every point in time the code in the VCS must be in a consistent and operational (=deployable) state. If things look different (i.e. some parts are not working every now and then) in your development environment, as opposed to the VCS, that is ok. Although it has proven to make life easier when both the VCS and your environment do not stray too far apart from each other.

What I discovered for myself is that the approach has a really nice by-product: cleaner and more stable code. In hindsight I cannot say when this materialized for me. So there is a small chance that from a clean code perspective things got worse before they got better. But my gut feeling tells me that this was not the case. Because an always-working code also means a better structured code, which is by definition more stable due to reduced complexity (relative to a messy codebase).

Fix Immediately

This has been written about many times and I merely mention it for completeness here. Whenever a change breaks the code, and thus causes automated tests to fail, the highest priority is to get things back into a working state. No exceptions ever!

When NOT to Commit

A VCS is not a backup system for your code but a VCS. This also means that you should not simply commit at the end of the day before you go home, unless your code happens to be in a working state. Otherwise, if you feel the need or are obliged to do so, have a backup location and/or script that handles this. But please do not clutter the VCS with backups.

At least in the early days of CI (the early 2000s) it was a somewhat common phenomenon at the beginning of projects that at the end of the day people checked in whatever they had done so far and went home. In many cases this broke the code and tests failed on the CI server. Until the next morning it was not possible for others to work effectively because you cannot reasonably integrate further changes with an already broken codebase. That is bad enough if people are located in one timezone. But think about the effect it has on an organization that works with a follow-the-sun approach.

Commit Messages

The reason for commit messages, in addition to the technical details that the VCS records anyway, is to describe the intent of the change. It does not make sense to list technical details, because those can always be retrieved with much more precision from the VCS log. But why you performed the sum of those changes is usually hard to extract from the technical delta. So think about how you would describe the change in a way that allows you to understand things when you look at them in six months.

In Closing

These are just a few point I learned over the years and have been able to validate with various projects. They are practical and provide, in my view, a good balance between the ideal world and the reality you find in many larger organizations. Please let know if you agree or (more importantly!) disagree.

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webMethods Integration Server: Continuous Deployment

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For more than nine years I have been working on a package for webMethods Integration Server. With the experience gained there, I want to discuss a number of aspects about Continuous Deployment.

Versioning

I recommend the use of semantic versioning, which at its core is about the following (for a lot of additional details, just follow the link):

  • The version number consists of three parts: Major, minor, and patch (example v1.4.2).
  • An increase in the major version indicates a non-backwards-compatible change.
  • An increase in the minor version indicates a backwards-compatible change.
  • A increase in the patch version indicates bug fixes only, no functional changes at all.

It is a well-known approach and makes it very easy for everyone to derive the relevant aspects from just looking at the version number. If the release in question contains bug fixes for something you have in use, it is probably a good idea to have a close look and check if a bug relevant to you was fixed. If it is a minor update and thus contains improvements while being backwards compatible, you may want to start thinking about a good time to make the switch. And if it is major update that (potentially) breaks things, a deeper look is needed.

Each Integration Server package has two attributes for holding information about its “version”. One is indeed the version itself and the other is the build. The latter is by default populated with in auto-increase number, which I find not very helpful. Yes, it gives me a unique identifier, but one that does not hold any context. What I put into this field instead is a combination of a date-time-stamp and the change set identifier from the Version Control System (VCS). This allows me to see at a glance when this package was built and what it contains.

Build

Conceptually the work on a single package, as opposed to a set of multiple ones that comprise one application, is a bit different in that you simply deal with only one artifact that gets released. In many projects I have seen, people take a slightly different approach and see the entirety of the project as their to-be-released artifact. This approach is supported by how the related tools (Asset Build Environment and Deployer) work: You simply throw in the source code for several packages, create an archive with metadata (esp. dependencies), and deploy it. Of course you could do this on a per-package basis. But it is easier to have just one big project for all of them.

Like almost always in live, nothing comes for free. What it practically means is that for every change in only one of the potentially many packages of the application, all of them need a re-deployment. Suppose you have an update in a maintenance module that is somewhat unrelated to normal daily operation. If you deploy everything in one big archive, this will effectively cause an outage for your application. So you just introduced a massive hindrance for Continuous Deployment. Of course this can be mitigated with blue-green deployments and you are well advised to have that in place anyway. But in reality few customers are there. What I recommend instead is an approach where you “cut” your packages in such a way that they each of them performs a clearly defined job. And then you have discrete CI job for each of them, of course with the dependencies taken into account.

Artifact Storage

Once your build has been created, it must reside somewhere. In a plain webMethods environment this is normally the file system, where the build was performed by Asset Build Environment (ABE). From there it would be picked up by Deployer and moved to the defined target environment(s). While this has the advantage of being a quite simple setup, it also has the downside that you loose the history of your builds. What you should do instead, is follow the same approach that has been hugely successful for Maven: use a binary repository like Artifactory, Nexus, or one of the others (a good comparison can be found here). I create a ZIP archive of the ABE result and have Jenkins upload it to Artifactory using the respective plugin.

To have the full history and at the same time a fixed download location, I perform this upload twice. The first contains a date-time-stamp and the change set identifier from the Version Control System (VCS), exactly like for the package’s build information. This is used for audit purposes only and gives me the full history of everything that has ever been built. But it is never used for actually performing the deployment. For that purpose I upload the ZIP archive a second time, but in this case without any changing parts in the URL. So it effectively makes it behave a bit like a permalink and I have a nice source for download. And since the packages themselves also contain the date-time stamp and change set identifier, I still know where they came from.

Deployment

Depending on your overall IT landscape there are two possible approaches for handling deployments. The recommended way is to use a general-purpose configuration management tool like Chef, Puppet, Ansible, Salt, etc. This should then also be the master of your webMethods deployments. Just point your script to your “permalink” in the binary reposiory and take it from there. I use Chef and its remote file mechanism. The latter nicely detects if the archive has changed on Artifactory and only then executes the download and deployment.

You can also develop your own scripts to do the download etc., and it may appear to be easier at a first glance. But there is a reason that configuration management tools like Chef et al. have had such success over the last couple years, compared to home-grown scripts. In my opinion it simply does not make sense to spend the time to re-invent the wheel here. So you should invest some time (there are many good videos on YouTube about this topic) and figure out which system is best for your needs. And if you still think that you will be faster with your own script, chances are that you overlooked some requirements. The usual suspects are logging, error handling, security, user management, documentation, etc.

With either approach this makes deployment a completely local operation and that has a number of benefits. In particular you can easily perform any preparatory work like e.g. adjusting content of files, create needed directories, etc.

Summary

All in all, this approach has worked extremely well for me. While it was first developed for an “isolated” utility package, it has proven to be even more useful for entire applications, comprised of multiple packages; in other words, it scales well.

Another big advantages is separation of concerns. It is always clear which activity is done by what component. The CI server performs the checkout from VCS and orchestrates the build and upload to the binary repository. The binary repository holds the deployable artifact and also maintains an audit trail of everything that has ever been built. The general-purpose configuration management tool orchestrates the download from the binary repository and the actual deployment.

With this split of the overall process into discrete steps, it is easier to extend and especially to debug. You can “inject” additional logic (think user exits) and especially implement things like blue-green deployments for a zero-downtime architecture. The latter will require some upfront thinking about shared state, but this is a conceptual problem and not specific to Integration Server.

One more word about scalability. If you have a big-enough farm of Integration Servers running (and some customers have hundreds of them), the local execution of deployments also is much faster than doing it from a central place.

I hope you find this information useful and would love to get your thoughts on it.