From a16877bf24fd80a421cf96d8807dea6953accb94 Mon Sep 17 00:00:00 2001
From: Masahiko Sawada <sawada.mshk@gmail.com>
Date: Mon, 17 Apr 2017 10:57:09 +0900
Subject: [PATCH 2/2] Add a new GUC parameter apply_worker_launch_interval.

Specify the inteval of launching logical replication apply worker.
---
 doc/src/sgml/config.sgml                      | 22 +++++++++++++++++-----
 src/backend/replication/logical/launcher.c    | 16 +++++++++-------
 src/backend/utils/misc/guc.c                  | 13 +++++++++++++
 src/backend/utils/misc/postgresql.conf.sample |  1 +
 src/include/replication/logicallauncher.h     |  1 +
 5 files changed, 41 insertions(+), 12 deletions(-)

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index f584431..92e8b0f 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -3420,11 +3420,6 @@ ANY <replaceable class="parameter">num_sync</replaceable> ( <replaceable class="
       Their values on the publisher are irrelevant.
      </para>
 
-     <para>
-      Note that <varname>wal_retrieve_retry_interval</varname> configuration parameters
-      affects the logical replication workers as well.
-     </para>
-
      <variablelist>
 
      <varlistentry id="guc-max-logical-replication-workers" xreflabel="max_logical_replication_workers">
@@ -3497,6 +3492,23 @@ ANY <replaceable class="parameter">num_sync</replaceable> ( <replaceable class="
       </listitem>                                                                 
      </varlistentry>                                                              
 
+     <varlistentry id="guc-apply-worker-launch-interval" xreflabel="apply_worker_launch_interval">
+      <term><varname>apply_worker_launch_interval</varname> (<type>integer</type>)
+      <indexterm>
+       <primary><varname>apply_worker_launch_interval</> configuration parameter</primary>
+      </indexterm>
+      </term>
+      <listitem>
+       <para>
+        Specify the number of milliseconds after which a logical replication apply
+        worker launched.
+       </para>
+       <para>
+        The default value is 5 seconds. Units are milliseconds if not specified.
+       </para>
+      </listitem>
+     </varlistentry>
+
     </variablelist>
     </sect2>
 
diff --git a/src/backend/replication/logical/launcher.c b/src/backend/replication/logical/launcher.c
index 2d663f6..6db8793 100644
--- a/src/backend/replication/logical/launcher.c
+++ b/src/backend/replication/logical/launcher.c
@@ -58,6 +58,7 @@
 
 int	max_logical_replication_workers = 4;
 int max_sync_workers_per_subscription = 2;
+int	apply_worker_launch_interval = 5000;
 
 LogicalRepWorker *MyLogicalRepWorker = NULL;
 
@@ -684,9 +685,9 @@ ApplyLauncherMain(Datum main_arg)
 
 		now = GetCurrentTimestamp();
 
-		/* Limit the start retry to once a wal_retrieve_retry_interval */
+		/* Limit the start retry to once a apply_worker_launch_interval */
 		if (TimestampDifferenceExceeds(last_start_time, now,
-									   wal_retrieve_retry_interval))
+									   apply_worker_launch_interval))
 		{
 			/* Use temporary context for the database list and worker info. */
 			subctx = AllocSetContextCreate(TopMemoryContext,
@@ -714,7 +715,7 @@ ApplyLauncherMain(Datum main_arg)
 					logicalrep_worker_launch(sub->dbid, sub->oid, sub->name,
 											 sub->owner, InvalidOid);
 					last_start_time = now;
-					wait_time = wal_retrieve_retry_interval;
+					wait_time = apply_worker_launch_interval;
 					/* Limit to one worker per mainloop cycle. */
 					break;
 				}
@@ -729,11 +730,12 @@ ApplyLauncherMain(Datum main_arg)
 		{
 			/*
 			 * The wait in previous cycle was interrupted in less than
-			 * wal_retrieve_retry_interval since last worker was started,
-			 * this usually means crash of the worker, so we should retry
-			 * in wal_retrieve_retry_interval again.
+			 * apply_worker_launch_interval since last
+			 * worker was started, this usually means crash of the worker,
+			 * so we should retry in apply_worker_launch_interval
+			 * again.
 			 */
-			wait_time = wal_retrieve_retry_interval;
+			wait_time = apply_worker_launch_interval;
 		}
 
 		/* Wait for more work. */
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 378bad2..31e76e9 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -2547,6 +2547,19 @@ static struct config_int ConfigureNamesInt[] =
 	},
 
 	{
+		{"apply_worker_launch_interval",
+			PGC_SIGHUP,
+			REPLICATION_SUBSCRIBERS,
+			gettext_noop("Sets the time to wait before launching aply woker."),
+			NULL,
+			GUC_UNIT_MS,
+		},
+		&apply_worker_launch_interval,
+		5000, 1, INT_MAX,
+		NULL, NULL, NULL
+	},
+
+	{
 		{"log_rotation_age", PGC_SIGHUP, LOGGING_WHERE,
 			gettext_noop("Automatic log file rotation will occur after N minutes."),
 			NULL,
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 20b5bb7..7bebd63 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -280,6 +280,7 @@
 #max_sync_workers_per_subscription = 2	# taken from max_logical_replication_workers
 #apply_worker_timeout = 60s		# time that apply worker waits for
 					# communication from publisher#
+#apply_worker_launch_interval = 5s	# time to wait before start apply worker
 
 
 #------------------------------------------------------------------------------
diff --git a/src/include/replication/logicallauncher.h b/src/include/replication/logicallauncher.h
index 060946a..696a9e5 100644
--- a/src/include/replication/logicallauncher.h
+++ b/src/include/replication/logicallauncher.h
@@ -14,6 +14,7 @@
 
 extern int max_logical_replication_workers;
 extern int max_sync_workers_per_subscription;
+extern int apply_worker_launch_interval;
 
 extern void ApplyLauncherRegister(void);
 extern void ApplyLauncherMain(Datum main_arg);
-- 
2.8.1