Fix Geo Log Cursor not restarting after pgbouncer dies

If pgbouncer dies, then the connection may get stuck in `PQsocket() can't get
socket descriptor` state. Wrap the query in a transaction to allow the
connection to return to the pool and recover. This also potentially prevents
idle-in-transaction cancellations.

Closes #5145

ee/changelogs/unreleased/sh-fix-geo-log-cursor-reconnect.yml

+---
+title: Fix Geo Log Cursor not reconnecting after pgbouncer dies
+merge_request: !4866
+author:
+type: fixed

ee/lib/gitlab/geo/log_cursor/daemon.rb

@@ -34,7 +34,11 @@ module Gitlab
         end
 
         def run_once!
-          LogCursor::Events.fetch_in_batches { |batch| handle_events(batch) }
+          # Wrap this with the connection to make it possible to reconnect if
+          # PGbouncer dies: https://github.com/rails/rails/issues/29189
+          ActiveRecord::Base.connection_pool.with_connection do
+            LogCursor::Events.fetch_in_batches { |batch| handle_events(batch) }
+          end
         end
 
         def handle_events(batch)