Build cascading train refs for parallel execution of Pipelines for merge trains
What does this MR do?
As we supported arbitrary refs creation in the previous merge request https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/14298, we can now create cascading merge refs in refs/train to run Pipelines for merge trains in parallel.
In this iteration, we support up-to 4 concurrent pipeline runs. Here is the overview of the process flow:
- User adds MR1, MR2, MR3, MR4 and MR5 to a train.
- The system creates the train ref
refs/merge-requests/1/trainfrommr1.diff_head_shaandmr1.target_branch_ref. - The system creates a pipeline run on
refs/merge-requests/1/train. - The system creates the train ref
refs/merge-requests/2/trainfrommr2.diff_head_shaandmr1.train_ref_path. - The system creates a pipeline run on
refs/merge-requests/2/train. - The system creates the train ref
refs/merge-requests/3/trainfrommr3.diff_head_shaandmr2.train_ref_path. - The system creates a pipeline run on
refs/merge-requests/3/train. - The system creates the train ref
refs/merge-requests/4/trainfrommr4.diff_head_shaandmr3.train_ref_path. - The system creates a pipeline run on
refs/merge-requests/4/train. - The system does not create any train refs
refs/merge-requests/5/trainbecause it's out of concurrency factor. - The system does not create any pipelines on
refs/merge-requests/5/trainbecause it's out of concurrency factor.
Related https://gitlab.com/gitlab-org/gitlab-ee/issues/11222 gitaly!1210 (merged)
Feature Flag
This behavior can be reverted by Feature.disable(:merge_trains_parallel_pipelines). After it's reverted, pipeline runs one at a time.
Extra datapoint
Today the number of projects which enables merge trains is still very low.
gitlabhq_production=> select COUNT(*) from project_ci_cd_settings WHERE merge_trains_enabled = true;
count
-------
28
(1 row)Does this MR meet the acceptance criteria?
Conformity
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Changelog entry -
Documentation created/updated or follow-up review issue created -
Code review guidelines -
Merge request performance guidelines -
Style guides -
Database guides -
Separation of EE specific content
Performance and testing
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Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process. - [-] Tested in all supported browsers
Security
If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:
- [-] Label as security and @ mention
@gitlab-com/gl-security/appsec - [-] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
- [-] Security reports checked/validated by a reviewer from the AppSec team
Merge request reports
Activity
changed milestone to %12.1
2 Warnings 
The title of this merge request is longer than 72 characters and would violate our commit message rules when using the Squash on Merge feature. Please consider adjusting the title, or rebase the commits manually and don’t use Squash on Merge. This merge request is quite big (more than 518 lines changed), please consider splitting it into multiple merge requests. Reviewer roulette
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Category Reviewer Maintainer backend Markus Koller ( @toupeira)Sean McGivern ( @smcgivern)test for spec/features/*No reviewer available No maintainer available Generated by
Edited by 🤖 GitLab Bot 🤖mentioned in merge request !14305 (merged)
Resolved by Shinya MaedaWe would need to set proper
commit_message.
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create-merge-train-ref - 3a048437 - Create refs/train and run a pipeline on it
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@oswaldo This MR is on top of https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/14298. It uses the extended
MergeToRefServicefor train ref creation.What do you think about this approach? Is there any concerns from your side?
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mentioned in merge request !11203 (closed)
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@smcgivern Would you mind reviewing as a backend maintainer? Thanks.
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Manual QA at
Thu Jul 11 12:28:37 UTC 2019Based on the https://gitlab.com/gitlab-org/gitlab-ee/issues/11222#note_190356236's conditions, I performed manual QA to the following cases:
Case 1: MR1 was merged into master branch.
Expectation:
- MR2 does not re-create pipeline for merge train.
- MR2 is merged after the current pipeline succeeded.
Result: Pass
Case 2: MR1 was dropped from the merge train.
Expectation:
- MR2 re-creates a pipeline for merge train.
- MR2 is merged after the recreated pipeline succeeded.
Result: Pass
Case 3: An emergent patch has been merged into master.
Expectation:
- Both MR1 and MR2 re-create a pipeline for merge train.
- MR1 is merged after the recreated pipeline succeeded.
- MR2 is merged after MR1 has been merged and the recreated pipeline succeeded.
Result: Pass
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@smcgivern Thanks. Back to you!
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