info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/product/ux/technical-writing/#assignments
As soon as you have code to review, have the code **reviewed** by a [reviewer](https://about.gitlab.com/handbook/engineering/workflow/code-review/#reviewer).
This reviewer can be from your group or team, or a [domain expert](#domain-experts).
When self-identifying as a domain expert, it is recommended to assign the MR changing the `.yml` file to be merged by an already established Domain Expert or a corresponding Engineering Manager.
- Team members working in a specific stage/group (for example, create: source code) are considered domain experts for that area of the app they work on.
- Team members working on a specific feature (for example, search) are considered domain experts for that feature.
When a suitable [domain expert](#domain-experts) isn't available, you can choose any team member to review the MR, or follow the [Reviewer roulette](#reviewer-roulette) recommendation.
- View the list of team members who work in the [stage or group](https://about.gitlab.com/handbook/product/categories/#devops-stages) related to the merge request.
- View team members' domain expertise on the [engineering projects](https://about.gitlab.com/handbook/engineering/projects/) page or on the [GitLab team page](https://about.gitlab.com/company/team/). Domains are self-identified, so use your judgment to map the changes on your merge request to a domain.
- Look for team members who have contributed to the files in the merge request. View the logs by running `git log <file>`.
- Look for team members who have reviewed the files. You can find the relevant merge request by:
1. Getting the commit SHA by using `git log <file>`.
1. Navigating to `https://gitlab.com/gitlab-org/gitlab/-/commit/<SHA>`.
1. Selecting the related merge request shown for the commit.
- Team members whose Slack or [GitLab status](../user/profile/index.md#set-your-current-status) emoji
is 🔵 `:large_blue_circle:` are more likely to be picked. This applies to both reviewers and trainee maintainers.
- Reviewers with 🔵 `:large_blue_circle:` are two times as likely to be picked as other reviewers.
- [Trainee maintainers](https://about.gitlab.com/handbook/engineering/workflow/code-review/#trainee-maintainer) with 🔵 `:large_blue_circle:` are three times as likely to be picked as other reviewers.
- People whose [GitLab status](../user/profile/index.md#set-your-current-status) emoji
is 🔶 `:large_orange_diamond:` or 🔸 `:small_orange_diamond:` are half as likely to be picked.
- It always picks the same reviewers and maintainers for the same
branch name (unless their out-of-office (`OOO`) status changes, as in point 1). It
removes leading `ce-` and `ee-`, and trailing `-ce` and `-ee`, so
| `~database` migrations or changes to expensive queries (*2*) | [Database maintainer](https://about.gitlab.com/handbook/engineering/projects/#gitlab_maintainers_database). Refer to the [database review guidelines](database_review.md) for more details. |
| `~UX` user-facing changes (*3*) | [Product Designer](https://about.gitlab.com/handbook/engineering/projects/#gitlab_reviewers_UX). Refer to the [design and user interface guidelines](contributing/design.md) for details. |
| Adding a new JavaScript library (*1*) | - [Frontend foundations member](https://about.gitlab.com/direction/ecosystem/foundations/) if the library significantly increases the [bundle size](https://gitlab.com/gitlab-org/frontend/playground/webpack-memory-metrics/-/blob/master/doc/report.md).<br/>- A [legal department member](https://about.gitlab.com/handbook/legal/) if the license used by the new library hasn't been approved for use in GitLab.<br/><br/>More information about license compatibility can be found in our [GitLab Licensing and Compatibility documentation](licensing.md). |
| A new dependency or a file system change | - [Distribution team member](https://about.gitlab.com/company/team/). See how to work with the [Distribution team](https://about.gitlab.com/handbook/engineering/development/enablement/systems/distribution/#how-to-work-with-distribution) for more details.<br/>- For Rubygems, request an [AppSec review](gemfile.md#request-an-appsec-review). |
| `~documentation` or `~UI text` changes | [Technical writer](https://about.gitlab.com/handbook/product/ux/technical-writing/#assignments) based on assignments in the appropriate [DevOps stage group](https://about.gitlab.com/handbook/product/categories/#devops-stages). |
| Changes to development guidelines | Follow the [review process](development_processes.md#development-guidelines-review) and get the approvals accordingly. |
| Only End-to-end changes (*4*) **or** if the MR author is a [Software Engineer in Test](https://about.gitlab.com/handbook/engineering/quality/#individual-contributors) | [Quality maintainer](https://about.gitlab.com/handbook/engineering/projects/#gitlab_maintainers_qa). |
| A new or updated [application limit](https://about.gitlab.com/handbook/product/product-processes/#introducing-application-limits) | [Product manager](https://about.gitlab.com/company/team/). |
| An addition of, or changes to a [Feature spec](testing_guide/testing_levels.md#frontend-feature-tests) | [Quality maintainer](https://about.gitlab.com/handbook/engineering/projects/#gitlab_maintainers_qa) or [Quality reviewer](https://about.gitlab.com/handbook/engineering/projects/#gitlab_reviewers_qa). |
| A new service to GitLab (Puma, Sidekiq, Gitaly are examples) | [Product manager](https://about.gitlab.com/company/team/). See the [process for adding a service component to GitLab](adding_service_component.md) for details. |
| Changes related to authentication or authorization | [Manage:Authentication and Authorization team member](https://about.gitlab.com/company/team/). Check the [code review section on the group page](https://about.gitlab.com/handbook/engineering/development/dev/manage/authentication-and-authorization/#additional-considerations) for more details. Patterns for files known to require review from the team are listed in the in the `Authentication and Authorization` section of the [`CODEOWNERS`](https://gitlab.com/gitlab-org/gitlab/-/blob/master/.gitlab/CODEOWNERS) file, and the team will be listed in the approvers section of all merge requests that modify these files. |
- (*1*): Specs other than JavaScript specs are considered `~backend` code. Haml markup is considered `~frontend` code. However, Ruby code within Haml templates is considered `~backend` code. When in doubt, request both a frontend and backend review.
This checklist encourages the authors, reviewers, and maintainers of merge requests (MRs) to confirm changes were analyzed for high-impact risks to quality, performance, reliability, security, observability, and maintainability.
Using checklists improves quality in software engineering. This checklist is a straightforward tool to support and bolster the skills of contributors to the GitLab codebase.
See the [test engineering process](https://about.gitlab.com/handbook/engineering/quality/quality-engineering/test-engineering/) for further quality guidelines.
1. I have self-reviewed this MR per [code review guidelines](code_review.md).
1. For the code that this change impacts, I believe that the automated tests ([Testing Guide](testing_guide/index.md)) validate functionality that is highly important to users (including consideration of [all test levels](testing_guide/testing_levels.md)).
1. If the existing automated tests do not cover the above functionality, I have added the necessary additional tests or added an issue to describe the automation testing gap and linked it to this MR.
1. I have considered the technical aspects of this change's impact on GitLab.com hosted customers and self-managed customers.
1. I have considered the impact of this change on the frontend, backend, and database portions of the system where appropriate and applied the `~ux`, `~frontend`, `~backend`, and `~database` labels accordingly.
1. I have tested this MR in [all supported browsers](../install/requirements.md#supported-web-browsers), or determined that this testing is not needed.
1. I have confirmed that this change is [backwards compatible across updates](multi_version_compatibility.md), or I have decided that this does not apply.
1. I have properly separated EE content from FOSS, or this MR is FOSS only.
1. I have considered that existing data may be surprisingly varied. For example, a new model validation can break existing records. Consider making validation on existing data optional rather than required if you haven't confirmed that existing data will pass validation.
1. I am confident that this MR does not harm performance, or I have asked a reviewer to help assess the performance impact. ([Merge request performance guidelines](merge_request_performance_guidelines.md))
1. I have added [information for database reviewers in the MR description](database_review.md#required), or I have decided that it is unnecessary.
- [Does this MR have database-related changes?](database_review.md)
1. I have considered the availability and reliability risks of this change.
1. I have considered the scalability risk based on future predicted growth.
1. I have considered the performance, reliability, and availability impacts of this change on large customers who may have significantly more data than the average customer.
1. I have confirmed that if this MR contains changes to processing or storing of credentials or tokens, authorization, and authentication methods, or other items described in [the security review guidelines](https://about.gitlab.com/handbook/engineering/security/#when-to-request-a-security-review), I have added the `~security` label and I have `@`-mentioned `@gitlab-com/gl-security/appsec`.
1. I have reviewed the documentation regarding [internal application security reviews](https://about.gitlab.com/handbook/engineering/security/#internal-application-security-reviews) for **when** and **how** to request a security review and requested a security review if this is warranted for this change.
##### Deployment
1. I have considered using a feature flag for this change because the change may be high risk.
1. If I am using a feature flag, I plan to test the change in staging before I test it in production, and I have considered rolling it out to a subset of production customers before rolling it out to all customers.
- [When to use a feature flag](https://about.gitlab.com/handbook/product-development-flow/feature-flag-lifecycle/#when-to-use-feature-flags)
1. I have informed the Infrastructure department of a default setting or new setting change per [definition of done](contributing/merge_request_workflow.md#definition-of-done), or decided that this is unnecessary.
merge request author. The author or [directly responsible individual](https://about.gitlab.com/handbook/people-group/directly-responsible-individuals/)
the code review lifecycle. If you are unable to set yourself as an assignee, ask a [reviewer](https://about.gitlab.com/handbook/engineering/workflow/code-review/#reviewer) to do this for you.
If there are any projects, snippets, or other assets that are required for a reviewer to validate the solution, ensure they have access to those assets before requesting review.
- Requesting maintainer reviews of merge requests with failed tests. If the tests are failing and you have to request a review, ensure you leave a comment with an explanation.
through Slack). If you can't add a reviewer for a merge request, `@` mentioning a maintainer in a comment is acceptable and in all other cases adding a reviewer is sufficient.
however, if one isn't available or you think the merge request doesn't need a review by a [domain expert](#domain-experts), feel free to follow the [Reviewer roulette](#reviewer-roulette) suggestion.
required approvers. If still awaiting further approvals from others, remove yourself as a reviewer then `@` mention the author and explain why in a comment. Stay as reviewer if you're merging the code.
- Write a detailed description as outlined in the [merge request guidelines](contributing/merge_request_workflow.md#merge-request-guidelines-for-contributors).
you should [request an initial review](../user/project/merge_requests/getting_started.md#reviewer) by selecting a reviewer based on the [approval guidelines](#approval-guidelines).
When a merge request has multiple areas for review, it is recommended you specify which area a reviewer should be reviewing, and at which stage (first or second).
This will help team members who qualify as a reviewer for multiple areas to know which area they're being requested to review.
For example, when a merge request has both `backend` and `frontend` concerns, you can mention the reviewer in this manner:
`@john_doe can you please review ~backend?` or `@jane_doe - could you please give this MR a ~frontend maintainer review?`
You can also use `workflow::ready for review` label. That means that your merge request is ready to be reviewed and any reviewer can pick it. It is recommended to use that label only if there isn't time pressure and make sure the merge request is assigned to a reviewer.
When your merge request receives an approval from the first reviewer it can be passed to a maintainer. You should default to choosing a maintainer with [domain expertise](#domain-experts), and otherwise follow the Reviewer Roulette recommendation or use the label `ready for merge`.
Sometimes, a maintainer may not be available for review. They could be out of the office or [at capacity](https://about.gitlab.com/handbook/engineering/workflow/code-review/#review-response-slo).
It is the responsibility of the author for the merge request to be reviewed. If it stays in the `ready for review` state too long it is recommended to request a review from a specific reviewer.
GitLab engineers who have capacity can regularly check the list of [merge requests to review](https://gitlab.com/groups/gitlab-org/-/merge_requests?state=opened&label_name%5B%5D=workflow%3A%3Aready%20for%20review) and add themselves as a reviewer for any merge request they want to review.
- There's a [Chrome/Firefox add-on](https://gitlab.com/conventionalcomments/conventional-comments-button) which you can use to apply [Conventional Comment](https://conventionalcomments.org/) prefixes.
- If the MR contains both Quality and non-Quality-related changes, the MR should be merged by the relevant maintainer for user-facing changes (backend, frontend, or database) after the Quality related changes are approved by a Software Engineer in Test.
To implement this policy in `gitlab-org/gitlab`, we have enabled the following
settings to ensure MRs get an approval from a top-level CODEOWNERS maintainer:
- [Prevent approval by author](../user/project/merge_requests/approvals/settings.md#prevent-approval-by-author).
- [Prevent approvals by users who add commits](../user/project/merge_requests/approvals/settings.md#prevent-approvals-by-users-who-add-commits).
- [Prevent editing approval rules in merge requests](../user/project/merge_requests/approvals/settings.md#prevent-editing-approval-rules-in-merge-requests).
- [Remove all approvals when commits are added to the source branch](../user/project/merge_requests/approvals/settings.md#remove-all-approvals-when-commits-are-added-to-the-source-branch)
There are scenarios such as rebasing locally or applying suggestions that are considered
the same as adding a commit and could reset existing approvals. Approvals are not removed
when rebasing from the UI or with the [`/rebase` quick action](../user/project/quick_actions.md).
- If the latest pipeline was created before the merge request was approved, start a new pipeline to ensure that full RSpec suite has been run. You may skip this step only if the merge request does not contain any backend change.
When reviewing merge requests added by wider community contributors:
- Pay particular attention to new dependencies and dependency updates, such as Ruby gems and Node packages.
While changes to files like `Gemfile.lock` or `yarn.lock` might appear trivial, they could lead to the
fetching of malicious packages.
- Review links and images, especially in documentation MRs.
- When in doubt, ask someone from `@gitlab-com/gl-security/appsec` to review the merge request **before manually starting any merge request pipeline**.
1. Add a comment to their MR saying you'll take it over to be able to get it merged.
1. Add the label `~"coach will finish"` to their MR.
1. Create a new feature branch from the main branch.
1. Merge their branch into your new feature branch.
1. Open a new merge request to merge your feature branch into the main branch.
1. Link the community MR from your MR and label it as `~"Community contribution"`.
1. Make any necessary final adjustments and ping the contributor to give them the chance to review your changes, and to make them aware that their content is being merged into the main branch.
1. Make sure the content complies with all the merge request guidelines.
1. Follow the regular review process as we do for any merge request.
- The [VP of Development](https://about.gitlab.com/job-families/engineering/development/management/vp/) ([@clefelhocz1](https://gitlab.com/clefelhocz1)) is the DRI for deciding if a merge request qualifies as customer critical.
- It is required to prioritize work for those involved on a customer critical merge request so that they have the time available necessary to focus on it.
- It is required to adhere to GitLab [values](https://about.gitlab.com/handbook/values/) and processes when working on customer critical merge requests, taking particular note of family and friends first/work second, definition of done, iteration, and release when it's ready.
- Customer critical merge requests are required to not reduce security, introduce data-loss risk, reduce availability, nor break existing functionality per the process for [prioritizing technical decisions](https://about.gitlab.com/handbook/engineering/development/principles/#prioritizing-technical-decisions).
- On customer critical requests, it is _recommended_ that those involved _consider_ coordinating synchronously (Zoom, Slack) in addition to asynchronously (merge requests comments) if they believe this may reduce the elapsed time to merge even though this _may_ sacrifice [efficiency](https://about.gitlab.com/company/culture/all-remote/asynchronous/#evaluating-efficiency.md).
- After a customer critical merge request is merged, a retrospective must be completed with the intention of reducing the frequency of future customer critical merge requests.
How code reviews are conducted can surprise new contributors. Here are some examples of code reviews that should help to orient you as to what to expect.
A good example of collaboration on an MR touching multiple parts of the codebase. Nick pointed out interesting edge cases, James Lopez also joined in raising concerns on import/export feature.
