Gomatic - scripting of GoCD configuration

Gomatic has been released - it is a Python API for configuring ThoughtWorks GoCD. I worked on it with my colleague Hilverd Reker. There isn't any documentation yet - we'll add some. For the moment, I thought I'd just post a very brief article here to announce it and to show a simple example of using it.

Limitations

We wrote it for our purposes and find it very useful; however, it has limitations (e.g. only really supports "Custom Command" task type) and allows you to try to configure GoCD incorrectly (which GoCD will refuse to allow). We will continue to work on it and will address its current limitations.

It has only been tested using GoCD version 14.2.0-377 - I think it doesn't yet work with other versions.

Install

We've written it using Python 2 (for the moment - should be simple to port to Python 3 - which we might do in the future). You can install it using "pip":

sudo pip install gomatic

Create a pipeline

If you wanted to configure a pipeline something like that shown in the GoCD documentation then you could run the following script:

#!/usr/bin/env python
from gomatic import *

go_server = GoServerConfigurator(HostRestClient("localhost:8153"))
pipeline = go_server \
    .ensure_pipeline_group("Group") \
    .ensure_replacement_of_pipeline("first_pipeline") \
    .set_git_url("http://git.url")
stage = pipeline.ensure_stage("a_stage")
job = stage.ensure_job("a_job")
job.add_task(ExecTask(['thing']))

go_server.save_updated_config()

Reverse engineer a pipeline

Gomatic can reverse engineer a gomatic script for an existing pipeline.

If you run the following (we will make it easier to run this rather than having to write a script):

#!/usr/bin/env python
from gomatic import *
go_server = GoServerConfigurator(HostRestClient("localhost:8153"))
pipeline = go_server\
    .ensure_pipeline_group("Group")\
    .find_pipeline("first_pipeline")
print go_server.as_python(pipeline)

this will print out the following text:

#!/usr/bin/env python
from gomatic import *

go_server_configurator = GoServerConfigurator(HostRestClient("localhost:8153"))
pipeline = go_server_configurator\
    .ensure_pipeline_group("Group")\
    .ensure_replacement_of_pipeline("first_pipeline")\
    .set_git_url("http://git.url")
stage = pipeline.ensure_stage("a_stage")
job = stage.ensure_job("a_job")
job.add_task(ExecTask(['thing']))

go_server_configurator.save_updated_config(save_config_locally=True, dry_run=True)
This produces a script which does a "dry run" so you can run it to see what changes it will make before running it for real.

So what?

I don't have time to write about why this is a Good Idea, or the consequences of being able to script the configuration of your CI server - but will do soon.

[This article slightly updated as a result of a new release of gomatic]

Copyright © 2014 Ivan Moore