Monday, November 24, 2014

Pinning mozharness from in-tree (aka mozharness.json)

Since mozharness came around 2-3 years ago, we have had the same issue where we test a mozharness change against the trunk trees, land it and get it backed out because we regress one of the older release branches.

This is due to the nature of the mozharness setup where once a change is landed all jobs start running the same code and it does not matter on which branch that job is running.

I have recently landed some code that is now active on Ash (and soon on Try) that will read a manifest file that points your jobs to the right mozharness repository and revision. We call this process to "pin mozhaness". In other words, what we do is to fix an external factor to our job execution.

This will allow you to point your Try pushes to your own mozharness repository.

In order to pin your jobs to a repository/revision of mozharness you have to change a file called mozharness.json which indicates the following two values:
  • "repo": "",
  • "revision": "production"

This is a similar concept as talos.json introduced which locks every job to a specific revision of talos. The original version of it landed in 2011.

Even though we have a similar concept since 2011, that doesn't mean that it was as easy to make it happen for mozharness. Let me explain a bit why:

  • For talos, mozharness has been checking out the right revision of talos.
  • In the case of mozharness, we can't make mozharness check itself out.
    • Well, we could but it would be a bigger mess
    • Instead we have made buildbot ScriptFactory be a bit more flexible
Coming up:
  • Enable on Try
  • Free up Ash and Cypress
    • They have been used to test custom mozharness patches and the default branch of Mozharness (pre-production)
Long term:
  • Enable the feature on all remaining Gecko trees
    • We would like to see this run at scale for a bit before rolling it out
    • This will allow mozharness changes to ride the trains
If you are curious, the patches are in bug 791924.

Thanks for Rail for all his patch reviews and Jordan for sparking me to tackle it.

Creative Commons License
This work by Zambrano Gasparnian, Armen is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported License.

Thursday, November 06, 2014

Setting buildbot up a-la-releng (Create your own local masters and slaves)

buildbot is what Mozilla's Release Engineering uses to run the infrastructure behind
buildbot assigns jobs to machines (aka slaves) through hosts called buildbot masters.

All the different repositories and packages needed to setup buildbot are installed through Puppet and I'm not aware of a way of setting my local machine through Puppet (I doubt I would want to do that!).
I managed to set this up a while ago by hand [1][2] (it was even more complicated in the past!), however, these one-off attempts were not easy to keep up-to-date and isolated.

I recently landed few scripts that makes it trivial to set up as many buildbot environments as you want and all isolated from each other.

All the scripts have been landed under the "community" directory under the "braindump" repository:

The main two scripts:

If you call with -w /path/to/your/own/workdir you will have everything set up for you. From there on, all you would have to do is this:
  • cd /path/to/your/own/workdir
  • source venv/bin/activate
  • buildbot start masters/test_master (for example)
  • buildslave start slaves/test_slave
Each paired master and slave have been setup to talk to each other.

I hope this is helpful for people out there. It's been great for me when I contribute patches for buildbot (bug 791924).

As always in Mozilla, contributions are always welcome!

PS 1 = Only tested on Ubuntu. If you want it to port this to other platforms please let me know and I can give you a hand.

PS 2 = I know that there is a repository that has docker images called "tupperware", however, I had these set of scripts being worked on for a while. Perhaps someone wants to figure out how to set a similar process through the docker images.

Creative Commons License
This work by Zambrano Gasparnian, Armen is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported License.