Friday, February 27, 2015

Pipes as Code

Finally we have started to move away from having build pipes as a chain of Jenkins jobs. There has been alot written of the subject that CI systems arnt well suited to implement CD processes. Let me first give a short recap on why before I get into how we now delivery our Pipes as Code.

First of all pipes in CI systems have bad portability. They are usually a chain of jobs set up through either a manual process or through some sort of automation based on a api provided by the CI system. The inherrited problem here is that the pipe executes in the CI system. This means that it is very hard to test and develope a pipe using Continuous Delivery. Yes we need to use Continuous Delivery when implementing our Continuous Delivery tooling otherwise we will nto be able to deliver our CD Processes in a qualitative, rapid and reliable way.

Then there is the problem of that data that we collect during the pipe. By default the data in a CI system is stored in that CI systems. Often on disk on that instans of that CI server. Adding insult to injury navigation of the build data is often tided to the current implementation of the build pipe. This means that a change to the build pipe means that we can no longer access the build data.

For a few years now we have been off loading all the build data into different types of storages depending on what type of data it is. Meta data around the build we store in a custom database. Logs go to our ELK stack, metrices to Graphite and reports to S3.

Still we have had trouble delivering quality Pipes. Now that has changed.

We still use a CI Server to trigger the Pipe. On the CI server we now have one job "DoIt". The "DoIt" job executes the right build pipe for every application. Lets talk a bit on how we pick the pipe.

Each git repo contains a YML file that says how we should build that repo. Thats more or less the only thing that has to be in the repo for us to start building it. We ingore all repos without the YML files. So we listen to all the gerrit triggers and ignore ones withouth

The YML is simply pretty much just

pipe: application-pipe
jdk: JDK8

We describe our build pipes in YML and implement our tasks in Groovy. Here is a simple definition. 

     - do: setup.Clean     - do: setup.Init
     - do: build.Build     - do: test.Test
     - do: log.ReportBuildStatus
     - do: notify.Email

Each task has a lifecycle of first, main, last. The first section is always executed and all of the "do´s" in the first section are executed regardless of result. In the main secion the "do´s" are only execute if everything has gone well so far. Last is always executed regardless of how things went.

The "do´s" are references to groovy classes with the first mandatory part of the package stripped. So there is a com.something.something.something.setup.Clean class.

A Context object is passed through all the execute methods of the "do´s". By setting context.mock=true the main executing process adds the sufix "Mock" to all "do´s". This allows us to unit test the build pipe inorder to assert that all the steps that we expect to happen do happen in the correct order.

When alot of things start happening its not really practicall to have a build task all that verbose especially since we have multiple pipes that share the same build task. So we can create a "build.yml"  and a "notify.yml" which we then can include like this.

    ref : build
     - do: notify

So this is how our build pipes look and we can unit test the pipe, the tasks and each "do" implementaiton.

Looking at a full pipe example we get something like this.

    ref: init
            ref: build.deployable
            ref: provision.create-test-environment  
    ref: deploy.deploy-engine
        ref: test.functional-tests
        ref: test.load-tests
            ref: release.publish-to-nexus
            ref: bake.ami-with-packer
            ref: provision.destroy-test-environment

            ref: end

Thats it.!

This pipe builds, functional tests, load tests and publishes our artifacts as well as baking images for our AWS environments. All the steps report to our meta data database, elk, graphite, s3 and slack.

And ofcourse we use our build pipes to build our build pipe tooling.

Continuous Delivery of Continuous Delivery through build Pipes as Code. High score on the buzzword bingo!