Run background migrations with a minimum interval

This adds a minimum interval to BackgroundMigrationWorker, ensuring
background migrations of the same class only run once every 5 minutes.
This prevents a thundering herd problem where scheduled migrations all
run at once due to their delays having been expired (e.g. as the result
of a queue being paused for a long time).

If a job was recently executed it's rescheduled with a delay that equals
the remaining time of the job's lease. This means that if the lease
expires in two minutes we only need to wait two minutes, instead of
five.

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/41624

1 files changed, 3 insertions, 3 deletions

diff --git a/spec/migrations/normalize_ldap_extern_uids_spec.rb b/spec/migrations/normalize_ldap_extern_uids_spec.rb
index 262d7742aaf..56a78f52802 100644
--- a/spec/migrations/normalize_ldap_extern_uids_spec.rb
+++ b/spec/migrations/normalize_ldap_extern_uids_spec.rb
@@ -27,11 +27,11 @@ describe NormalizeLdapExternUids, :migration, :sidekiq do
         migrate!
 
         expect(BackgroundMigrationWorker.jobs[0]['args']).to eq([described_class::MIGRATION, [1, 2]])
-        expect(BackgroundMigrationWorker.jobs[0]['at']).to eq(10.seconds.from_now.to_f)
+        expect(BackgroundMigrationWorker.jobs[0]['at']).to eq(5.minutes.from_now.to_f)
         expect(BackgroundMigrationWorker.jobs[1]['args']).to eq([described_class::MIGRATION, [3, 4]])
-        expect(BackgroundMigrationWorker.jobs[1]['at']).to eq(20.seconds.from_now.to_f)
+        expect(BackgroundMigrationWorker.jobs[1]['at']).to eq(10.minutes.from_now.to_f)
         expect(BackgroundMigrationWorker.jobs[2]['args']).to eq([described_class::MIGRATION, [5, 5]])
-        expect(BackgroundMigrationWorker.jobs[2]['at']).to eq(30.seconds.from_now.to_f)
+        expect(BackgroundMigrationWorker.jobs[2]['at']).to eq(15.minutes.from_now.to_f)
         expect(BackgroundMigrationWorker.jobs.size).to eq 3
       end
     end