在 Jenkins 中使用 pollSCM 和 Scan Multibranch Pipeline Triggers 有什么区别？

Question

I've been using Jenkins and I've seen a lot of Pipeline examples (declarative ones) and I've seen some using the pollSCM property in the Jenkinsfile to trigger a build, like this:

triggers {
        pollSCM('H/5 * * * *')
}

However, I've seen this Scan Multibranch Pipeline Triggers option when configuring a Multibranch pipeline. I'm not sure what's the difference between those.

All this problem came to me because I'm facing some cases where two builds are being triggered for the same job, and I thought it was because I have both these options configured.

Can anyone please help me understand this difference?

Thank you!

Answer 1

The 'Scan Multibranch Pipeline' trigger will scan the repository for new branches and changes in existing branches. By default it will trigger a new build for all branches which have been updated. However in the multibranch job configuration you can disable this automatic trigger for specific - or all - branches.

The 'Poll SCM' option is branch-specific. Within a Jenkinsfile you may configure different options for different branches. This option will never be able to trigger the very first build for a branch as it would need at least one build so the properties step gets executed and the 'poll SCM' option set. That is: Any change here will only get effective AFTER the next build.

Therefore I'd recommend to stick to the trigger based on the Multibranch branch scan - if possible. However in some special cases (eg first build on a new branch never be built automatically) it still might be useful to use the poll SCM feature. In that case you might want to disable the automatic trigger as required.

Last but not least the poll SCM feature sometimes uses a different plugin than the Scan Multibranch Pipeline, eg for Bitbucket. AFAIK for Bitbucket the multibranch trigger is little bit more flexible, allows to trigger a build on more events compared the the plain Bitbucket trigger.

Answer 2

I think pollSCM must be the jenkins plugin

https://wiki.jenkins.io/display/JENKINS/PollSCM+Plugin

Multibranch pipeline : This is the type of pipeline, where jenkins scan and pull from all the branch within the repository , so the build will trigger automatically when some code is checked in within the branch (if you have configured it)