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Diffstat (limited to 'doc/development/background_migrations.md')
| -rw-r--r-- | doc/development/background_migrations.md | 29 |
1 files changed, 28 insertions, 1 deletions
diff --git a/doc/development/background_migrations.md b/doc/development/background_migrations.md index f83a60e49e8..5452b0e7a2f 100644 --- a/doc/development/background_migrations.md +++ b/doc/development/background_migrations.md @@ -215,14 +215,29 @@ same time will ensure that both existing and new data is migrated. In the next release we can remove the `after_commit` hooks and related code. We will also need to add a post-deployment migration that consumes any remaining -jobs. Such a migration would look like this: +jobs and manually run on any un-migrated rows. Such a migration would look like +this: ```ruby class ConsumeRemainingExtractServicesUrlJobs < ActiveRecord::Migration disable_ddl_transaction! + class Service < ActiveRecord::Base + include ::EachBatch + + self.table_name = 'services' + end + def up + # This must be included Gitlab::BackgroundMigration.steal('ExtractServicesUrl') + + # This should be included, but can be skipped - see below + Service.where(url: nil).each_batch(of: 50) do |batch| + range = batch.pluck('MIN(id)', 'MAX(id)').first + + Gitlab::BackgroundMigration::ExtractServicesUrl.new.perform(*range) + end end def down @@ -230,6 +245,15 @@ class ConsumeRemainingExtractServicesUrlJobs < ActiveRecord::Migration end ``` +The final step runs for any un-migrated rows after all of the jobs have been +processed. This is in case a Sidekiq process running the background migrations +received SIGKILL, leading to the jobs being lost. (See +[more reliable Sidekiq queue][reliable-sidekiq] for more information.) + +If the application does not depend on the data being 100% migrated (for +instance, the data is advisory, and not mission-critical), then this final step +can be skipped. + This migration will then process any jobs for the ExtractServicesUrl migration and continue once all jobs have been processed. Once done you can safely remove the `services.properties` column. @@ -254,6 +278,9 @@ for more details. 1. Make sure that background migration jobs are idempotent. 1. Make sure that tests you write are not false positives. +1. Make sure that if the data being migrated is critical and cannot be lost, the + clean-up migration also checks the final state of the data before completing. [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 +[reliable-sidekiq]: https://gitlab.com/gitlab-org/gitlab-ce/issues/36791 |