Merge branch 'sh-fix-issue-52176' into 'master'

Disable replication lag check for Aurora PostgreSQL databases

Closes #52176

See merge request gitlab-org/gitlab-ce!22786

app/models/postgresql/replication_slot.rb

@@ -4,6 +4,15 @@ module Postgresql
   class ReplicationSlot < ActiveRecord::Base
     self.table_name = 'pg_replication_slots'
 
+    # Returns true if there are any replication slots in use.
+    # PostgreSQL-compatible databases such as Aurora don't support
+    # replication slots, so this will return false as well.
+    def self.in_use?
+      transaction { exists? }
+    rescue ActiveRecord::StatementInvalid
+      false
+    end
+
     # Returns true if the lag observed across all replication slots exceeds a
     # given threshold.
     #
@@ -11,6 +20,8 @@ module Postgresql
     #       statistics it takes between 1 and 5 seconds to replicate around
     #       100 MB of data.
     def self.lag_too_great?(max = 100.megabytes)
+      return false unless in_use?
+
       lag_function = "#{Gitlab::Database.pg_wal_lsn_diff}" \
         "(#{Gitlab::Database.pg_current_wal_insert_lsn}(), restart_lsn)::bigint"
 

changelogs/unreleased/sh-fix-issue-52176.yml

+---
+title: Disable replication lag check for Aurora PostgreSQL databases
+merge_request: 22786
+author:
+type: fixed

spec/models/postgresql/replication_slot_spec.rb

@@ -3,7 +3,27 @@
 require 'spec_helper'
 
 describe Postgresql::ReplicationSlot, :postgresql do
+  describe '.in_use?' do
+    it 'returns true when replication slots are present' do
+      expect(described_class).to receive(:exists?).and_return(true)
+      expect(described_class.in_use?).to be_truthy
+    end
+
+    it 'returns false when replication slots are not present' do
+      expect(described_class.in_use?).to be_falsey
+    end
+
+    it 'returns false if the existence check is invalid' do
+      expect(described_class).to receive(:exists?).and_raise(ActiveRecord::StatementInvalid.new('PG::FeatureNotSupported'))
+      expect(described_class.in_use?).to be_falsey
+    end
+  end
+
   describe '.lag_too_great?' do
+    before do
+      expect(described_class).to receive(:in_use?).and_return(true)
+    end
+
     it 'returns true when replication lag is too great' do
       expect(described_class)
         .to receive(:pluck)