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2020-06-14 Gitlab-Ci

Gitllab Runners

Gitlab Runners#

For a seemingly simple concept, gitlab runners are made to seem very complex especially when aided by the constant redirection in the gitlab docs.

Let’s try and simplify the concept.

Disambiguation#

Terms:

  • gitlab instance - this is where you host your projects and version control history
  • gitlab groups - like github organisations, groups can own projects, userc can be members of groups.

Gitlab runner:

  • A worker machine that executes your project’s GitLab CI jobs
  • Different runners have different capabilities
  • Tag runners and give jobs tags to match them up

A runner can be:

  • specific - to a chosen project
  • group - available to all projects in a group
  • shared - available to every project

A gitlab runner can also be seen as a service responsible for executing jobs and reporting their progress. It can execute the job on the same machine or a different machine. The machine might be launched on the fly in response to job submission.

Gitlab Runner Info#

When installed a gitlab runner generally runs as a long-running background service.

YOu can check the status with:

sudo gitlab-runner status

Registration#

There is a registration process for runners.

They continually poll a GitLab instance for jobs that match their tags, execute them, and communicate the progress and results back

Runners must be added incrementally with gitlab-runner register, which takes a registration token and exchanges it with the GitLab instance for a runner token that is stored in the configuration file

The registration token:

  • tells your GitLab Runner which GitLab instance to ask for jobs
  • tells your GitLab instance that it is allowed to assign your jobs to your GitLab Runner

Where to find the token you need depends on the type of Runner you want to register: shared, specific (project), or group

Executors#

Each Runner is configured with its own executor that defines how it executes jobs

  • shell executor - executes jobs on the same machine as the Runner
  • ssh executor - execute jobs on an existing remote machine
  • docker+machine executor - uses docker machine to launch cloud instances and execute jobs on those instances

With a fleet of runners it is important to assign tags for: size speed, OS and dependencies

Sources#