aaronang / rusty_jenkins

Rusty Jenkins

This repository is an experiment to observe and document the behavior or Jenkin's build discarder.

The default implementation of Jenkin's BuildDiscarder is called LogRotator. The LogRotator accepts four arguments: daysToKeepStr, numToKeepStr, artifactDaysToKeepStr, artifactNumToKeepStr. According to the documentation, the arguments have the following semantics.

daysToKeepStr: History is only kept up to this days.
numToKeepStr: Only this number of build logs are kept.
artifactDaysToKeepStr: Artifacts are only kept up to this days.
artifactNumToKeepStr: Only this number of builds have their artifacts kept.

The parameter names and documentation may seem obvious but can be deceptive. For example, when numToKeepStr is set to 10, every branch and pull request allows 10 builds to persist. Therefore, given a repository with three branches:

$ git branch
  development
  documentation
* master

The maximum allowable number of persisted builds is 3 * 10 = 30.

Deep Dive

Assuming Jenkins was installed according to the "Installing Jenkins" guide, Jenkins stores build logs and artifacts in the location /var/jenkins_home/jobs/<repository>/branches. For each branch and pull request Jenkins creates a directory to store build logs and artifacts. For example, given the branches master, development, documentation, and one pull request, Jenkins will have the following directory structure:

$ pwd
/var/jenkins_home/jobs/<repository>

$ tree branches
branches
├── PR-1
├── development
├── documentation
└── master

Inside one of the directories, the tree structure looks something like:

$ pwd
/var/jenkins_home/jobs/<repository>/branches

$ tree master
master
├── builds
├── config.xml
├── lastStable
├── lastSuccessful
├── name-utf8.txt
├── nextBuildNumber
├── scm-polling.log
└── scm-revision-hash.xml