Merge branch '23223-group-deletion-race-condition' into 'master'

Remove race condition while deleting groups

## What does this MR do?

The intended flow during a group deletion is:

```
  Soft-delete group (sync) -> Delete group projects (async) -> Hard-delete group (async)
```

The soft-delete was run in a transaction, which was committed only after
the async job (for hard-deletion) was kicked off. There was a race
condition here - the soft-delete transaction could complete _after_ the
hard delete completed, leaving a soft-deleted record in the database.

This MR removes this race condition. There is no need to run the
soft-delete in a transaction. The soft-delete completes before the async
job is kicked off.

This MR also adds a migration to delete all existing (soft-deleted) groups left in an inconsistent state
due to this bug.

- Closes #23223 
- EE merge request: gitlab-org/gitlab-ee!886

See merge request !7528

2 files changed, 17 insertions, 1 deletions

diff --git a/db/migrate/20161117114805_remove_undeleted_groups.rb b/db/migrate/20161117114805_remove_undeleted_groups.rb
new file mode 100644
index 00000000000..ebc2d974ae0
--- /dev/null
+++ b/db/migrate/20161117114805_remove_undeleted_groups.rb
@@ -0,0 +1,16 @@
+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class RemoveUndeletedGroups < ActiveRecord::Migration
+  DOWNTIME = false
+
+  def up
+    execute "DELETE FROM namespaces WHERE deleted_at IS NOT NULL;"
+  end
+
+  def down
+    # This is an irreversible migration;
+    # If someone is trying to rollback for other reasons, we should not throw an Exception.
+    # raise ActiveRecord::IrreversibleMigration
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index 42cf9515860..db2ce689afc 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20161113184239) do
+ActiveRecord::Schema.define(version: 20161117114805) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"