Why do we do Continuous Integration?

Continuous Integration is now very much a central process of most agile development efforts, but it hasn’t been around all that long. It may be widely regarded as a “development best practice” but some teams are still waiting to adopt C.I. Seriously, they are.

And it’s not just agile teams that can benefit from C.I. The principles behind good C.I. can apply to any development effort.

This article aims to explain where C.I. came from, why it has become so popular, and why you should adopt it on your development project, whether you’re agile or not.

Back in the Day…

Are you sitting comfortably? I want you to close your eyes, relax, and cast your mind back, waaay back, to 2003 or something like that…

You’re in an office somewhere, people are talking about The Matrix way too much, and there’s an alarming amount of corduroy on show… and developers are checking in code to their source control system….

Suddenly a developer swears violently as he checks out the latest code and finds it doesn’t compile. Someone’s check-in has broken the codebase.

He sets about fixing it and checking it back in.

Suddenly another developer swears violently….

Rinse and repeat.

CI started out as a way of minimising code integration headaches. The idea was, “if it’s painful, don’t put it off, do it more often”. It’s much better to do small and frequent code integrations rather than big ugly ones once in a while. Soon tools were invented to help us do these integrations more easily, and to check that our integrations weren’t breaking anything.

Tests!

Fossilized C.I. System

Fossil of a Primitive C.I. System

Excavations of fossilized C.I. systems from the early 21st Century suggest that these primitive C.I. systems basically just compiled code, and then, when unit tests became more popular, they started running unit tests as well. So every time someone checked in some code, the build would make sure that this integration would still result in a build which would compile, and pass the unit tests. Simple!

C.I. systems then started displaying test results and we started using them to run huuuuge overnight builds which would actually deploy our builds and run integration tests. The C.I. system was the automation centre, it ran all these tasks on a timer, and then provided the feedback – this was usually an email saying what had passed and broken. I think this was an important time in the evolution of C.I. because people started seeing C.I. as more of an information generator, and a communicator, rather than just a techie tool that ran some builds on a regular basis.

Information Generator

Management teams started to get information out of C.I. and so it became an “Enterprise Tool”.

Some processes and “best practices” were identified early on:

  • Builds should never be left in a broken state.
  • You should never check in on a broken build because it makes troubleshooting and fixing even harder.

With this new-found management buy-in, C.I. became a central tenet of modern development practices.

People started having fun with C.I. plugging lava lamps, traffic lights and talking rabbits into the system. These were fun, but they did something very important in the evolution of C.I. –  they turned it into an information radiator and a focal point of development efforts.

Automate Everything!

Automation was the big selling point for C.I. Tasks that would previously have been manual, error-prone and time-consuming could now be done automatically, or at night while we were in bed. For me it meant I didn’t have to come in to work on the weekends and do the builds! Whole suites of acceptance, integration and performance tests could automatically be executed on any given build, on a convenient schedule thanks to our C.I. system. This aspect, as much as any other, helped in the widespread adoption of C.I. because people could put a cost-saving value on it. C.I. could save companies money. I, on the other hand, lost out on my weekend overtime.

Code Quality

Static analysis and code coverage tools appeared all over the place, and were ideally suited to be plugged in to C.I. These days, most code coverage tools are designed specifically to be run via C.I. rather than manually. These tools provided a wealth of feedback to the developers and to the project team as a whole. Suddenly we were able to use our C.I. system to get a real feeling for our project’s quality. The unit test results combined with the static analysis could give us information about the code quality, the integration  and functional test results gave us verification of our design and ensured we were making the right stuff, and the nightly performance tests told us that what we were making was good enough for the real world. All of this information got presented to us, automatically, via our new best friend the Continuous Integration system.

Linking C.I. With Stories

When our C.I. system runs our acceptance tests, we’re actually testing to make sure that what we’ve intended to do, has in fact been done. I like the saying that our acceptance tests validate that we built the right thing, while our unit and functional tests verify that we built the thing right.

Linking the ATs to the stories is very important, because then we can start seeing, via the C.I. system, how many of the stories have been completed and pass their acceptance criteria. At this point, the C.I. system becomes a barometer of how complete our projects are.

So, it’s time for a brief recap of what our C.I. system is providing for us at this point:

1. It helps us identify our integration problems at the earliest opportunity

2. It runs our unit tests automatically, saving us time and verifying or code.

3. It runs static analysis, giving us a feel for the code quality and potential hotspots, so it’s an early warning system!

4. It’s an information radiator – it gives us all this information automatically

5. It runs our ATs, ensuring we’re building the right thing and it becomes a barometer of how complete our project is.

And we’re not done yet! We haven’t even started talking about deployments.

Deployments

Ok now we’ve started talking about deployments.

C.I. systems have long been used to deploy builds and execute tests. More recently, with the introduction of advanced C.I. tools such as Jenkins (Hudson), Bamboo and TeamCity, we can use the C.I. tool not only to deploy our builds but to manage deployments to multiple environments, including production. It’s now not uncommon to see a Jenkins build pipeline deploying products to all environments. Driving your production deployments via C.I. is the next logical step in the process, which we’re now calling “Continuous Delivery” (or Continuous Deployment if you’re actually deploying every single build which passes all the test stages etc).

Below is a diagram of the stages in a Continuous Delivery system I worked on recently. The build is automatically promoted to the next stage whenever it successfully completes the current stage, right up until the point where it’s available for deployment to production. As you can imagine, this process relies heavily on automation. The tests must be automated, the deployments automated, even the release email and it’s contents are automated.So what exactly is the cost saving with having a C.I. system?

Yeah, that’s a good question, well done me. Not sure I can give you a straight answer to that one though. Obviously one of the biggest factors is the time savings. As I mentioned earlier, back when I was a human C.I. machine I had to work weekends to sort out build issues and get working code ready for Monday morning. Also, C.I. sort of forces you to automate everything else, like the tests and the deployments, as well as the code analysis and all that good stuff. Again we’re talking about massive time savings.

But automating the hell out of everything doesn’t just save us time, it also eliminates human error. Consider the scope for human error in a system where some poor overworked person has to manually build every project, some other poor sap has to manually do all the testing and then someone else has to manually deploy this project to production and confidently say “Right, now that’s done, I’m sure it’ll work perfectly”. Of course, that never happened, because we were all making mistakes along the line, and they invariably came to light when the code was already live. How much time and money did we waste fixing live issues that we’d introduced by just not having the right processes and systems in place. And by systems, of course, I’m talking about Continuous Integration. I can’t put a value on it but I can tell you we wasted LOTS of money. We even had bugfix teams dedicated to fixing issues we’d introduced and not caught earlier (due in part to a lack of C.I.).

Conclusion

While for many companies C.I. is old news, there are still plenty of people yet to get on board. It can be hard for people to see how C.I. can really make that much of a difference, so hopefully this blog will help to highlight some of the benefits and explain how C.I. has been adopted as one of the most important and central tenets of modern software delivery.

For me, and for many others, Continuous Integration is a MUST.

 

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JDepend design metrics in CI

This article is intended to give the reader enough information to understand what JDepend is, what it does, and how to use it in a maven build. It’s a kind of cheat sheet, if you like.

What is it?

JDepend is more of a design metric than a code metric, it gives you information about your classes with regards to how they’re related to each other. Using this information you should be able to identify any unwanted or dubious dependencies.

How does it do that?

It traverses Java class files and generates design quality metrics, such as:

  • Number of Classes and Interfaces
  • Afferent Couplings (Ca) – What is this?? Someone probably feels very proud of themselves for coming up with this phrase. Afferent coupling means the number of other packages which depend on the package being measured, in a nutshell. JDepend define this as a measure of a package’s “responsibility”
  • Efferent Couplings (Ce) – Sort of the opposite of Ca. It’s a measure of the number of other packages that your package depends on
  • Abstractness (A) – The ratio of abstract classes to total classes.
  • Instability (I) – The ratio of efferent coupling (Ce) to total coupling (Ce + Ca)
  • Distance from the Main Sequence (D) – this sounds fairly wishy-washy and I’ve never paid any attention to it. It’s defined as: “an indicator of the package’s balance between abstractness and stability”. Meh.

 

To use JDepend with Maven you’ll need Maven 2.0 or higher and JDK 1.4 or higher. You don’t need to install anything, as maven will sort this out for you by downloading it at build time.

Here’s a snippet from one of my project POMs, it comes from in the <reporting> section:


 

<plugin>

    <groupId>org.codehaus.mojo</groupId>

    <artifactId>jdepend-maven-plugin</artifactId>

    <configuration>

        <targetJdk>1.6</targetJdk>

        <outputDirectory>build/maven/${pom.artifactId}/target/jdepend-reports</outputDirectory>

    </configuration>

</plugin>

 

What you’ll get is a JDepend entry under the project reports section of your maven site, like this:

project-reports-page

Maven Project Reports Page

 

And this is what the actual report looks like (well, some of it):

jdepend-report

jdepend report

Summary:

JDepend isn’t something I personally use very heavily, but I can understand how it could be used to good effect as a general measure of how closely related your classes are, which, in certain circumstances could prompt you to redesign or refactor your code.

I don’t think this sort of information is required on a per commit basis, so I’d be tempted to only include it in my nightly reports. However, I also use Sonar, and that has a built-in measure of afferent coupling, so if you’re only interested in that measurement and you’re already running Sonar, then JDepend is probably a bit of an unnecessary overhead. Also, Sonar itself has some good plugins which can provide architectural and design governance features, at least one of which I know implemented JDepend.

Sonar now supports Ant

Great news for Ant users, the new version of Sonar (2.6) now includes support for Ant. Previously it only supported Maven, which was a bit of a pity because it’s such a good tool, so it’s really good to hear that you can now get all the goodness of Sonar with Ant as well. There’s also talk of support for gradle too.

There’s a new Sonar Ant task so you can add Sonar to your ant scripts (details here).

Here’s the link to the release page for version 2.6 of Sonar.

 

Fun with FindBugs

We’ve just moved to a new master pom file in an effort to make our lives a bit easier, and to allow certain builds to carry on using the old master pom file which was basically quite rubbish. You see, the old master pom file just defined a load of plugins, mostly in the plugin management section, so they had to be referenced by the application poms anyway. The idea with the new master pom is that it enforces the use of certain plugins, and ALSO enfiorces certain standards for builds to pass – for instance, we included a cobertura coverage rate of 80% and made the builds fail if there were any findbugs issues. It sounded like a good idea at the time. So, we put these plugin definitions directly into the build section of the pom, like so:

<build>

<plugins>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<source>1.6</source>
<target>1.6</target>
</configuration>
</plugin>

<plugin>
<artifactId>maven-surefire-plugin</artifactId>
<version>2.4</version>
<configuration>
<testClassesDirectory>
build/maven/${artifactId}/target/test-classes
</testClassesDirectory>
</configuration>
</plugin>

<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>cobertura-maven-plugin</artifactId>
<version>2.4</version>
<configuration>
<formats>
<format>html</format>
<format>xml</format>
</formats>
<check>
<totalBranchRate>54</totalBranchRate>
<totalLineRate>75</totalLineRate>
</check>
</configuration>
<executions>
<execution>
<goals>
<goal>clean</goal>
<goal>check</goal>
</goals>
</execution>
</executions>
</plugin>

<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-pmd-plugin</artifactId>
<version>2.5</version>
<executions>
<execution>
<goals>
<goal>check</goal>
<goal>cpd-check</goal>
</goals>
</execution>
</executions>
<configuration>
<linkXref>true</linkXref>
<targetJdk>1.6</targetJdk>
<sourceEncoding>utf-8</sourceEncoding>
<failOnViolation>false</failOnViolation>
<outputDirectory>build/maven/${pom.artifactId}/target/pmd-reports</outputDirectory>
</configuration>
</plugin>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>findbugs-maven-plugin</artifactId>
<version>2.3.1</version>
<!– NOT USING THIS YET
<executions>
<execution>
<goals>
<goal>check</goal>
</goals>
</execution>
</executions> –>
</plugin>
</plugins>
</build>

The first thing I had to do (as you can see) is disable the check goal because it was causing findbugs to fail pretty much every build. The next thing I had to do was remove the whole of the following configuration section from the findbugs plugin:

<configuration>
<threshold>High</threshold>
<effort>Max</effort>
<xmlOutput>true</xmlOutput>
<xmlOutputDirectory>build/maven/${artifactId}/target/site</xmlOutputDirectory>
</configuration>

I’ve kept this section in the reporting section though.

The next thing I got was this error:

03-Nov-2010 09:53:03 [java] Java Result: 1
03-Nov-2010 09:53:03 [Fatal Error] findbugsTemp.xml:1:1: Premature end of file.
03-Nov-2010 09:53:03 [INFO] ————————————————————————
03-Nov-2010 09:53:03 [ERROR] FATAL ERROR
03-Nov-2010 09:53:03 [INFO] ————————————————————————
03-Nov-2010 09:53:03 [INFO] Premature end of file.
03-Nov-2010 09:53:03 [INFO] ————————————————————————
03-Nov-2010 09:53:03 [INFO] Trace
03-Nov-2010 09:53:03 org.xml.sax.SAXParseException: Premature end of file.

and that was fixed by changing this bit of the findbugs plugin configuration:

<effort>Max</effort>

to this:

<effort>Default</effort>

So, in short, using “Max” gives us java out of memory exceptions. Which is not exactly convenient. Not sure how to fix this though.