227 lines
8 KiB
Markdown
227 lines
8 KiB
Markdown
---
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stage: Verify
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group: Continuous Integration
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info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#designated-technical-writers
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type: reference, index
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last_update: 2019-07-03
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---
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# Pipelines for Merge Requests
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> [Introduced](https://gitlab.com/gitlab-org/gitlab-foss/-/issues/15310) in GitLab 11.6.
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In a [basic configuration](../pipelines/pipeline_architectures.md#basic-pipelines), GitLab runs a pipeline each time
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changes are pushed to a branch.
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If you want the pipeline to run jobs **only** on commits to a branch that is associated with a merge request,
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you can use *pipelines for merge requests*.
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In the UI, these pipelines are labeled as `detached`. Otherwise, these pipelines appear the same
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as other pipelines.
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Any user who has developer [permissions](../../user/permissions.md)
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can run a pipeline for merge requests.
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NOTE: **Note:**
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If you use this feature with [merge when pipeline succeeds](../../user/project/merge_requests/merge_when_pipeline_succeeds.md),
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pipelines for merge requests take precedence over the other regular pipelines.
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## Prerequisites
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To enable pipelines for merge requests:
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- Your repository must be a GitLab repository, not an
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[external repository](../ci_cd_for_external_repos/index.md).
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- [In GitLab 11.10 and later](https://gitlab.com/gitlab-org/gitlab-foss/-/merge_requests/25504),
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you must be using GitLab Runner 11.9.
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## Configuring pipelines for merge requests
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To configure pipelines for merge requests you need to configure your [CI/CD configuration file](../yaml/README.md).
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There are a few different ways to do this:
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### Use `rules` to run pipelines for merge requests
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When using `rules`, which is the preferred method, we recommend starting with one
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of the [`workflow:rules` templates](../yaml/README.md#workflowrules-templates) to ensure
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your basic configuration is correct. Instructions on how to do this, as well as how
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to customize, are available at that link.
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### Use `only` or `except` to run pipelines for merge requests
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If you want to continue using `only/except`, this is possible but please review the drawbacks
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below.
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When you use this method, you have to specify `only: - merge_requests` for each job. In this
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example, the pipeline contains a `test` job that is configured to run on merge requests.
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The `build` and `deploy` jobs don't have the `only: - merge_requests` parameter,
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so they will not run on merge requests.
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```yaml
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build:
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stage: build
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script: ./build
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only:
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- master
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test:
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stage: test
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script: ./test
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only:
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- merge_requests
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deploy:
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stage: deploy
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script: ./deploy
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only:
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- master
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```
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#### Excluding certain jobs
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The behavior of the `only: [merge_requests]` parameter is such that _only_ jobs with
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that parameter are run in the context of a merge request; no other jobs will be run.
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However, you can invert this behavior and have all of your jobs run _except_
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for one or two.
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Consider the following pipeline, with jobs `A`, `B`, and `C`. Imagine you want:
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- All pipelines to always run `A` and `B`.
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- `C` to run only for merge requests.
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To achieve this, you can configure your `.gitlab-ci.yml` file as follows:
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``` yaml
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.only-default: &only-default
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only:
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- master
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- merge_requests
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- tags
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A:
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<<: *only-default
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script:
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- ...
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B:
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<<: *only-default
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script:
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- ...
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C:
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script:
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- ...
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only:
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- merge_requests
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```
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Therefore:
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- Since `A` and `B` are getting the `only:` rule to execute in all cases, they will always run.
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- Since `C` specifies that it should only run for merge requests, it will not run for any pipeline
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except a merge request pipeline.
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This helps you avoid having to add the `only:` rule to all of your jobs to make
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them always run. You can use this format to set up a Review App, helping to
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save resources.
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#### Excluding certain branches
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Pipelines for merge requests require special treatment when
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using [`only`/`except`](../yaml/README.md#onlyexcept-basic). Unlike ordinary
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branch refs (for example `refs/heads/my-feature-branch`), merge request refs
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use a special Git reference that looks like `refs/merge-requests/:iid/head`. Because
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of this, the following configuration will **not** work as expected:
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```yaml
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# Does not exclude a branch named "docs-my-fix"!
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test:
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only: [merge_requests]
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except: [/^docs-/]
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```
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Instead, you can use the
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[`$CI_COMMIT_REF_NAME` predefined environment
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variable](../variables/predefined_variables.md) in
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combination with
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[`only:variables`](../yaml/README.md#onlyvariablesexceptvariables) to
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accomplish this behavior:
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```yaml
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test:
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only: [merge_requests]
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except:
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variables:
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- $CI_COMMIT_REF_NAME =~ /^docs-/
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```
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## Pipelines for Merged Results **(PREMIUM)**
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Read the [documentation on Pipelines for Merged Results](pipelines_for_merged_results/index.md).
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### Merge Trains **(PREMIUM)**
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Read the [documentation on Merge Trains](pipelines_for_merged_results/merge_trains/index.md).
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## Run pipelines in the parent project for merge requests from a forked project **(STARTER)**
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> [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/217451) in GitLab 13.3.
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By default, external contributors working from forks can't create pipelines in the
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parent project. When a pipeline for merge requests is triggered by a merge request
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coming from a fork:
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- It's created and runs in the fork (source) project, not the parent (target) project.
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- It uses the fork project's CI/CD configuration and resources.
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Sometimes parent project members want the pipeline to run in the parent
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project. This could be to ensure that the post-merge pipeline passes in the parent project.
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For example, a fork project could try to use a corrupted runner that doesn't execute
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test scripts properly, but reports a passed pipeline. Reviewers in the parent project
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could mistakenly trust the merge request because it passed a faked pipeline.
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Parent project members with at least [Developer permissions](../../user/permissions.md)
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can create pipelines in the parent project for merge requests
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from a forked project. In the merge request, go to the **Pipelines** and click
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**Run Pipeline** button.
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CAUTION: **Caution:**
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Fork merge requests could contain malicious code that tries to steal secrets in the
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parent project when the pipeline runs, even before merge. Reviewers must carefully
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check the changes in the merge request before triggering the pipeline. GitLab shows
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a warning that must be accepted before the pipeline can be triggered.
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## Additional predefined variables
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By using pipelines for merge requests, GitLab exposes additional predefined variables to the pipeline jobs.
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Those variables contain information of the associated merge request, so that it's useful
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to integrate your job with [GitLab Merge Request API](../../api/merge_requests.md).
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You can find the list of available variables in [the reference sheet](../variables/predefined_variables.md).
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The variable names begin with the `CI_MERGE_REQUEST_` prefix.
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## Troubleshooting
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### Two pipelines created when pushing to a merge request
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If you are experiencing duplicated pipelines when using `rules`, take a look at
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the [important differences between `rules` and `only`/`except`](../yaml/README.md#prevent-duplicate-pipelines),
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which will help you get your starting configuration correct.
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If you are seeing two pipelines when using `only/except`, please see the caveats
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related to using `only/except` above (or, consider moving to `rules`).
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It is not possible to run a job for branch pipelines first, then only for merge request
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pipelines after the merge request is created (skipping the duplicate branch pipeline). See
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the [related issue](https://gitlab.com/gitlab-org/gitlab/-/issues/201845) for more details.
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### Two pipelines created when pushing an invalid CI configuration file
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Pushing to a branch with an invalid CI configuration file can trigger
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the creation of two types of failed pipelines. One pipeline is a failed merge request
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pipeline, and the other is a failed branch pipeline, but both are caused by the same
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invalid configuration.
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