How can I have unique build numbers across branches with Jenkins & the Pipeline Multibranch Plugin
You can get the Git branch name from $GIT_BRANCH and add this to $BUILD_NUMBER to make an ID that's unique across branches (as long as your company doesn't do something like get themselves taken over by a large corporation that migrates you to another Jenkins server and resets all the build numbers: to protect against that, you might want to use $BUILD_URL).
Only snag is $GIT_BRANCH contains the / character, plus any characters you used when naming the branch, and these may or may not be permitted in all the places where you want an ID. ($BUILD_URL is also going to contain characters like : and /) If this is an issue, one workaround would be to delete unwanted characters with tr:
export MY_ID=$(echo $GIT_BRANCH-$BUILD_NUMBER | tr -dc [A-Za-z0-9-])
(-dc means delete the complement of these characters, so A-Z, a-z, 0-9 and - are the characters you want to keep.)
Maybe instead of a unique (global numeric) build number you might want to try a unique (global) build display name?
According to "pipeline syntax: global variables reference" currentBuild.displayName is a writable property. So you could e.g. add additional information to the build number (in order to make it globally unique) and use that string in subsequent artifact/application build steps (to incorporate that in the application's version output for your desired traceability), e.g. something like:
currentBuild.displayName = "${env.BRANCH_NAME}-${currentBuild.id}"
Using the build's schedule or start time formatted (currentBuild.timeInMillis) as a readable date, or using the SCM revision might be also useful, e.g. resulting in "20180119-091439-rev149923".
See also:
- https://groups.google.com/forum/#!msg/jenkinsci-users/CDuWAYLz2zI/NLxwOku4AwAJ
- https://support.cloudbees.com/hc/en-us/articles/220860347-How-to-set-build-name-in-Pipeline-job