Commit e597fa61 authored by Sean McGivern's avatar Sean McGivern

Add GitLab-specific concerns to code review guide

parent b6555693
...@@ -133,6 +133,55 @@ reviewee. ...@@ -133,6 +133,55 @@ reviewee.
tomorrow. When you are not able to find the right balance, ask other people tomorrow. When you are not able to find the right balance, ask other people
about their opinion. about their opinion.
### GitLab-specific concerns
GitLab is used in a lot of places. Many users use
our [Omnibus packages](https://about.gitlab.com/installation/), but some use
the [Docker images](https://docs.gitlab.com/omnibus/docker/), some are
[installed from source](https://docs.gitlab.com/ce/install/installation.html),
and there are other installation methods available. GitLab.com itself is a large
Enterprise Edition instance. This has some implications:
1. **Query changes** should be tested to ensure that they don't result in worse
performance at the scale of GitLab.com:
1. Generating large quantities of data locally can help.
2. Asking for query plans from GitLab.com is the most reliable way to validate
these.
2. **Database migrations** must be:
1. Reversible.
2. Performant at the scale of GitLab.com - ask a maintainer to test the
migration on the staging environment if you aren't sure.
3. Categorised correctly:
- Regular migrations run before the new code is running on the instance.
- [Post-deployment migrations](post_deployment_migrations.md) run _after_
the new code is deployed, when the instance is configured to do that.
- [Background migrations](background_migrations.md) run in Sidekiq, and
should only be done for migrations that would take an extreme amount of
time at GitLab.com scale.
3. **Sidekiq workers**
[cannot change in a backwards-incompatible way](sidekiq_style_guide.md#removing-or-renaming-queues):
1. Sidekiq queues are not drained before a deploy happens, so there will be
workers in the queue from the previous version of GitLab.
2. If you need to change a method signature, try to do so across two releases,
and accept both the old and new arguments in the first of those.
3. Similarly, if you need to remove a worker, stop it from being scheduled in
one release, then remove it in the next. This will allow existing jobs to
execute.
4. Don't forget, not every instance will upgrade to every intermediate version
(some people may go from X.1.0 to X.10.0, or even try bigger upgrades!), so
try to be liberal in accepting the old format if it is cheap to do so.
4. **Cached values** may persist across releases. If you are changing the type a
cached value returns (say, from a string or nil to an array), change the
cache key at the same time.
5. **Settings** should be added as a
[last resort](https://about.gitlab.com/handbook/product/#convention-over-configuration).
If you're adding a new setting in `gitlab.yml`:
1. Try to avoid that, and add to `ApplicationSetting` instead.
2. Ensure that it is also
[added to Omnibus](https://docs.gitlab.com/omnibus/settings/gitlab.yml.html#adding-a-new-setting-to-gitlab-yml).
6. **Filesystem access** can be slow, so try to avoid
[shared files](shared_files.md) when an alternative solution is available.
### Credits ### Credits
Largely based on the [thoughtbot code review guide]. Largely based on the [thoughtbot code review guide].
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment