Pipelines for Merge Requests
Introduced in GitLab 11.6.
In a basic configuration, GitLab runs a pipeline each time changes are pushed to a branch.
If you want the pipeline to run jobs only when merge requests are created or updated, you can use pipelines for merge requests.
In the UI, these pipelines are labeled as
detached. Otherwise, these pipelines appear the same
as other pipelines.
Any user who has developer permissions can run a pipeline for merge requests.
NOTE: Note: If you use this feature with merge when pipeline succeeds, pipelines for merge requests take precedence over the other regular pipelines.
To enable pipelines for merge requests:
- You must have maintainer permissions.
- Your repository must be a GitLab repository, not an external repository.
- In GitLab 11.10 and later, you must be using GitLab Runner 11.9.
Configuring pipelines for merge requests
To configure pipelines for merge requests you need to configure your CI/CD configuration file. There are a few different ways to do this:
rules to run pipelines for merge requests
rules, which is the preferred method, we recommend starting with one
workflow:rules templates to ensure
your basic configuration is correct. Instructions on how to do this, as well as how
to customize, are available at that link.
except to run pipelines for merge requests
If you want to continue using
only/except, this is possible but please review the drawbacks
When you use this method, you have to specify
only: - merge_requests for each job. In this
example, the pipeline contains a
test job that is configured to run on merge requests.
deploy jobs don't have the
only: - merge_requests parameter,
so they will not run on merge requests.
build: stage: build script: ./build only: - master test: stage: test script: ./test only: - merge_requests deploy: stage: deploy script: ./deploy only: - master
Excluding certain jobs
The behavior of the
only: [merge_requests] parameter is such that only jobs with
that parameter are run in the context of a merge request; no other jobs will be run.
However, you can invert this behavior and have all of your jobs run except for one or two.
Consider the following pipeline, with jobs
C. Imagine you want:
- All pipelines to always run
Cto run only for merge requests.
To achieve this, you can configure your
.gitlab-ci.yml file as follows:
.only-default: &only-default only: - master - merge_requests - tags A: <<: *only-default script: - ... B: <<: *only-default script: - ... C: script: - ... only: - merge_requests
Bare getting the
only:rule to execute in all cases, they will always run.
Cspecifies that it should only run for merge requests, it will not run for any pipeline except a merge request pipeline.
This helps you avoid having to add the
only: rule to all of your jobs
in order to make them always run. You can use this format to set up a Review App, helping to save resources.
Excluding certain branches
Pipelines for merge requests require special treatment when
except. Unlike ordinary
branch refs (for example
refs/heads/my-feature-branch), merge request refs
use a special Git reference that looks like
of this, the following configuration will not work as expected:
# Does not exclude a branch named "docs-my-fix"! test: only: [merge_requests] except: [/^docs-/]
Instead, you can use the
$CI_COMMIT_REF_NAME predefined environment
accomplish this behavior:
test: only: [merge_requests] except: variables: - $CI_COMMIT_REF_NAME =~ /^docs-/
Pipelines for Merged Results (PREMIUM)
Merge Trains (PREMIUM)
Read the documentation on Merge Trains.
Important notes about merge requests from forked projects
Note that the current behavior is subject to change. In the usual contribution flow, external contributors follow the following steps:
- Fork a parent project.
- Create a merge request from the forked project that targets the
masterbranch in the parent project.
- A pipeline runs on the merge request.
- A maintainer from the parent project checks the pipeline result, and merge into a target branch if the latest pipeline has passed.
Currently, those pipelines are created in a forked project, not in the parent project. This means you cannot completely trust the pipeline result, because, technically, external contributors can disguise their pipeline results by tweaking their GitLab Runner in the forked project.
There are multiple reasons why GitLab doesn't allow those pipelines to be
created in the parent project, but one of the biggest reasons is security concern.
External users could steal secret variables from the parent project by modifying
.gitlab-ci.yml, which could be some sort of credentials. This should not happen.
We're discussing a secure solution of running pipelines for merge requests that are submitted from forked projects, see the issue about the permission extension.
Additional predefined variables
By using pipelines for merge requests, GitLab exposes additional predefined variables to the pipeline jobs. Those variables contain information of the associated merge request, so that it's useful to integrate your job with GitLab Merge Request API.
You can find the list of available variables in the reference sheet.
The variable names begin with the
Two pipelines created when pushing to a merge request
If you are experiencing duplicated pipelines when using
rules, take a look at
the key details when using
which will help you get your starting configuration correct.
If you are seeing two pipelines when using
only/except, please see the caveats
related to using
only/except above (or, consider moving to
Two pipelines created when pushing an invalid CI configuration file
Pushing to a branch with an invalid CI configuration file can trigger the creation of two types of failed pipelines. One pipeline is a failed merge request pipeline, and the other is a failed branch pipeline, but both are caused by the same invalid configuration.
In rare cases, duplicate pipelines are created.
See this issue for details.