Revert First, Ask Questions Later
By Adrian Sutton
The key to making continuous integration work well is to ensure that the build stays green – ensuring that the team always knows that if something doesn’t work it was their change that broke it. However, in any environment with a build pipeline beyond a simple commit build, for example integration, acceptance or deployment tests, sometimes things will break.
When that happens, there is always a natural tendency to commit an additional change that will fix it. That’s almost always a mistake.
The correct approach is to revert first and ask questions later. It doesn’t matter how small the fix might be there’s a risk that it will fail or introduce some other problem and extend the period that the tests are broken. However since we know the last build worked correctly, reverting the change is guaranteed to return things to working order. The developers working on the problematic change can then take their time to develop and test the fix then recommit everything together.
Reverting a commit isn’t a slight against its developers and doesn’t even suggest the changes being made are bad, merely that some detail hasn’t yet been completed and so it’s not yet ready to ship. Having a culture where that’s understood and accepted is an important step in delivering quality software.