We use Jenkins for verifying Gerrit patch sets under multiple configurations and conditions. The logfiles produced are a golden source of information. To keep Jenkins healthy and responsive, we needed to remove them all which sounded quite silly: would you just burn your cash because your wallet is too small?
Using the Logstash plugin and correlating the logs with Gerrit review data I have managed to keep everything and forever enabling a much richer data analysis and materialize back the logs with the same URL referenced in the Gerrit changes.
Slides are available on SlideShare
YouTube and transcript are available on GitEnterprise.me