Commit 433b6fed authored by Grzegorz Bizon's avatar Grzegorz Bizon
Browse files

Copy-edit background migrations guidelines

parent f3758fcbea73
......@@ -40,7 +40,7 @@ and idempotent.
See [Sidekiq best practices guidelines](https://github.com/mperham/sidekiq/wiki/Best-Practices)
for more details.
Make sure that in case that your migration job is going to be retried a data
Make sure that in case that your migration job is going to be retried data
integrity is guarateed.
## How It Works
......@@ -227,18 +227,24 @@ the `services.properties` column.
## Testing
It is possible to test a background migrations scheduling migration and a
cleanup migration using `:migration` RSpec tag. See README in specs/migration/
directory.
It is required to write tests for background migrations' scheduling migration
(either a regular migration or a post deployment migration), background
migration itself and a cleanup migration. You can use the `:migration` RSpec
tag when testing a regular / post deployment migration.
See [README][migrations-readme].
When you do that, keep in mind that `before` and `after` RSpec hooks are going
to migrate you database down and up, which can result in another background
to migrate you database down and up, which can result in other background
migrations being called. That means that using `spy` test doubles with
`have_received` is encouraged, instead of using regular test doubles, because
your expectation defined in a `it` block can conflict with what is being
called in RSpec hooks. See gitlab-org/gitlab-ce#35351 for more details.
your expectations defined in a `it` block can conflict with what is being
called in RSpec hooks. See [gitlab-org/gitlab-ce#35351][issue-rspec-hooks]
for more details.
## Best practices
1. Make sure that background migration jobs are idempotent.
1. Make sure that tests you write are not false positives.
[migrations-readme]: https://gitlab.com/gitlab-org/gitlab-ce/blob/master/spec/migrations/README.md
[issue-rspec-hooks]: https://gitlab.com/gitlab-org/gitlab-ce/issues/35351
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