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authorSean McGivern <sean@gitlab.com>2017-09-25 12:39:30 +0100
committerSean McGivern <sean@gitlab.com>2017-09-25 12:48:07 +0100
commit989ccd7171113a6dc1fa42ef68bab391dbcd2816 (patch)
tree73cf7d5a7f79ca3595c66364feb616314fd9031c /doc
parent7da72a0de296e430378c7eb85fc486a01f3163bd (diff)
downloadgitlab-ce-989ccd7171113a6dc1fa42ef68bab391dbcd2816.tar.gz
Document manual cleanup after background migration stealingdocument-background-migration-stealing
Diffstat (limited to 'doc')
-rw-r--r--doc/development/background_migrations.md29
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