Author:     Noah Misch <noah@leadboat.com>
Commit:     Noah Misch <noah@leadboat.com>

    [not for commit] Demonstrate 035_standby_logical_decoding.pl hang.
    
    There are three way XLOG_RUNNING_XACTS can show up:
    - SELECT pg_log_standby_snapshot()
    - CHECKPOINT
    - bgwriter LOG_SNAPSHOT_INTERVAL_MS
    
    An idle primary won't do the second two.  If you're unlucky enough for
    all three to happen before CREATE_REPLICATION_SLOT's
    DecodingContextFindStartpoint() call starts watching, then
    CREATE_REPLICATION_SLOT will hang indefinitely.

diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c
index f11ce27..07f987c 100644
--- a/src/backend/postmaster/bgwriter.c
+++ b/src/backend/postmaster/bgwriter.c
@@ -70,7 +70,7 @@ int			BgWriterDelay = 200;
  * Interval in which standby snapshots are logged into the WAL stream, in
  * milliseconds.
  */
-#define LOG_SNAPSHOT_INTERVAL_MS 15000
+#define LOG_SNAPSHOT_INTERVAL_MS 1
 
 /*
  * LSN and timestamp at which we last issued a LogStandbySnapshot(), to avoid
diff --git a/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c b/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c
index 9270d7b..0f170a4 100644
--- a/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c
+++ b/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c
@@ -1085,6 +1085,7 @@ libpqrcv_create_slot(WalReceiverConn *conn, const char *slotname,
 			appendStringInfoString(&cmd, " PHYSICAL RESERVE_WAL");
 	}
 
+	pg_usleep(1000 * 1000);
 	res = libpqrcv_PQexec(conn->streamConn, cmd.data);
 	pfree(cmd.data);
 
diff --git a/src/test/recovery/t/035_standby_logical_decoding.pl b/src/test/recovery/t/035_standby_logical_decoding.pl
index cebfa52..c371369 100644
--- a/src/test/recovery/t/035_standby_logical_decoding.pl
+++ b/src/test/recovery/t/035_standby_logical_decoding.pl
@@ -467,6 +467,7 @@ $psql_subscriber{run}->pump_nb();
 
 # Speed up the subscription creation
 $node_primary->safe_psql('postgres', "SELECT pg_log_standby_snapshot()");
+$node_primary->safe_psql('postgres', "CHECKPOINT");
 
 # Explicitly shut down psql instance gracefully - to avoid hangs
 # or worse on windows