Opinions on building platforms

System Build Reproducibility

I’ve been on the receiving end of build reproducibility rants from developers at plenty of conferences. Their bile is usually aimed at Maven’s snapshot functionality. I’ve often questioned how reproducible their systems are; I’m usually met by a blank look.

I’ve always aimed to make system builds reproducible, but with little success. Gem, pear, pecl, rpm, license agreements, configure/make/make install: they all take their toll. This can lead to inconsistent builds between environments – or even in a single tier – due to scaling up/down.

As I’ve tended to use RPM-based systems (misspent youth), I’ve attempted, wherever possible, to get all non-configuration files on a server into RPMs. I’ve been more promiscuous with configuration management, moving from home grown, to Cfengine, via Puppet, to Chef. I’m currently using chef-solo, with tooling such as Noah and MCollective for orchestration. Don’t even mention the number of deployment/ALM tooling solutions I’ve been through(although Capistrano has never annoyed me to any great extent).

Even with long term usage of RPMs, build reproducibility has been far from simple. RH Satellite/Spacewalk should make this easy, but unfortunately it’s a bloated mess. I’ve usually resorted to simple apache/createrepo, but this poses its own problems. Do you have a repo per environment? How do you track which servers were built against which repo? How do you roll out updates in a manageable fashion?

I’ve created a simple setup called Yumtags! to address some of these issues. The basic idea is that you can drop RPMs in to a directory, and then “freeze” the directory at that point in time by creating and storing repository metadata against a tag. This tag can then be used, perhaps in a chef-solo-driven repository definition, to update, build, and reproduce systems in a known state. It currently features simple JSON-driven integration for CI systems, so RPM-based integration pipelines can be easily automated. There’s a million and one things missing from it, but now it does the basic story I’ve shared it for others to hack on.