Multibranch Jenkins Pipelines Basics

(this post if part of the material I cover in my devops course)

Multibranch Pipelines

These pipelines automatically "build" the code for each branch that has a Jenkinsfile in it.
For example:

• In a feature branch, you may want to prepare (build image? run container?) and run unit tests alone
• in a develop branch, you may want to prepare more, and run some integration tests as well
• in master/main branch you will also want to deploy your code to production

Access token and credentials

• First, create an access token in github that allows you to do everything for this repository
  • go to: your github account->Settings->Developer settings->Personal Access Tokens
  • both types can do (classic and fine-grained), I prefer the fine grained
  • Generate a new token, give it a name and choose an expiration time
  • choose Only select repositories and select your repository
  • Give it all repository permissions (read/write)
  • When you see the secret text, make sure you keep that, because it will be there just once.
• Go to: Dashboard->Manage Jenkins->Credentials->System->Global Credentials
• Add a new credentials of the type Secret Text, of global scope, no ID, add a short description for it (e.g: myrep-PAM)
• Create another credential based on this text, now of type Username with Password.
  Use your github user, and the secret text as password.
  description example: myrep-content

Creating a multibranch pipeline job

• Click: NewItem -> (give it a name) -> Multibranch Pipeline -> OK
• Fill: Display Name + description
• Add source:
  • When you add source, you choose among several options (git, github, bitbucket etc.)
  • each option corresponds to the specific plugin that would handle accessing the specific repository.
    We'll demonstrate with github, so choose that
  • add HTTPS url of a repository that you have already prepared (that is, multiple branches with Jenkinfiles)
  • Add the myrep-content credential you have created above
  • hit Save

Basic usage

• After creating a multibranch pipeline, it automatically scans all branches in the repository, and finds all of those branches with a Jenkinsfile.

  

• If you go bacj to the pipeline status, you will see a list of the branches found
  (remember that these are the branches you'd like to build, branches with Jenkinsfile):

  

• You cannot "build" the multi-branch pipeline, you can build only branchse in it.

• Go into the master branch to see this:
  

  

• Hit the "Build Now" button to build each branch.

In the next post we will trigger buidling branch pipelines from github.