[Peter Eisentraut <peter.eisentraut@2ndquadrant.com>]

I think the recovery parameters

    archive_cleanup_command
    promote_trigger_file
    recovery_end_command
    recovery_min_apply_delay

can be changed from PGC_POSTMASTER to PGC_SIGHUP without any further
complications (unlike for example primary_conninfo, which is being
discussed elsewhere).

See attached patch.

-- 
Peter Eisentraut              http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

Attachments:

0001-Allow-some-recovery-parameters-to-be-changed-with-re.patch (text/plain, 5.8K) download
From 6e0777f4799bce027aa339629539cc101ed0f862 Mon Sep 17 00:00:00 2001
From: Peter Eisentraut <peter@eisentraut.org>
Date: Mon, 4 Feb 2019 09:28:17 +0100
Subject: [PATCH] Allow some recovery parameters to be changed with reload

Change

archive_cleanup_command
promote_trigger_file
recovery_end_command
recovery_min_apply_delay

from PGC_POSTMASTER to PGC_SIGHUP.  This did not require any further
changes.
---
 doc/src/sgml/config.sgml                      | 21 +++++++++++++++----
 src/backend/utils/misc/guc.c                  |  8 +++----
 src/backend/utils/misc/postgresql.conf.sample |  4 ----
 3 files changed, 21 insertions(+), 12 deletions(-)

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 9b7a7388d5..7e208a4b81 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -3081,8 +3081,7 @@ <title>Archive Recovery</title>
     <para>
      This section describes the settings that apply only for the duration of
      the recovery.  They must be reset for any subsequent recovery you wish to
-     perform.  They can only be set at server start and cannot be changed once
-     recovery has begun.
+     perform.
     </para>
 
     <para>
@@ -3161,6 +3160,10 @@ <title>Archive Recovery</title>
         database server shutdown) or an error by the shell (such as command
         not found), then recovery will abort and the server will not start up.
        </para>
+
+       <para>
+        This parameter can only be set at server start.
+       </para>
       </listitem>
      </varlistentry>
 
@@ -3202,6 +3205,10 @@ <title>Archive Recovery</title>
         terminated by a signal or an error by the shell (such as command not
         found), a fatal error will be raised.
        </para>
+       <para>
+        This parameter can only be set in the <filename>postgresql.conf</filename>
+        file or on the server command line.
+       </para>
       </listitem>
      </varlistentry>
 
@@ -3227,6 +3234,10 @@ <title>Archive Recovery</title>
         signal or an error by the shell (such as command not found), the
         database will not proceed with startup.
        </para>
+       <para>
+        This parameter can only be set in the <filename>postgresql.conf</filename>
+        file or on the server command line.
+       </para>
       </listitem>
      </varlistentry>
 
@@ -3863,7 +3874,8 @@ <title>Standby Servers</title>
           standby.  Even if this value is not set, you can still promote
           the standby using <command>pg_ctl promote</command> or calling
           <function>pg_promote</function>.
-          This parameter can only be set at server start.
+          This parameter can only be set in the <filename>postgresql.conf</filename>
+          file or on the server command line.
          </para>
         </listitem>
        </varlistentry>
@@ -4117,7 +4129,8 @@ <title>Standby Servers</title>
         </warning>
        </para>
        <para>
-        This parameter can only be set at server start.
+        This parameter can only be set in the <filename>postgresql.conf</filename>
+        file or on the server command line.
        </para>
       </listitem>
      </varlistentry>
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 8681ada33a..ea5444c6f1 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -2047,7 +2047,7 @@ static struct config_int ConfigureNamesInt[] =
 	},
 
 	{
-		{"recovery_min_apply_delay", PGC_POSTMASTER, REPLICATION_STANDBY,
+		{"recovery_min_apply_delay", PGC_SIGHUP, REPLICATION_STANDBY,
 			gettext_noop("Sets the minimum delay for applying changes during recovery."),
 			NULL,
 			GUC_UNIT_MS
@@ -3398,7 +3398,7 @@ static struct config_string ConfigureNamesString[] =
 	},
 
 	{
-		{"archive_cleanup_command", PGC_POSTMASTER, WAL_ARCHIVE_RECOVERY,
+		{"archive_cleanup_command", PGC_SIGHUP, WAL_ARCHIVE_RECOVERY,
 			gettext_noop("Sets the shell command that will be executed at every restart point."),
 			NULL
 		},
@@ -3408,7 +3408,7 @@ static struct config_string ConfigureNamesString[] =
 	},
 
 	{
-		{"recovery_end_command", PGC_POSTMASTER, WAL_ARCHIVE_RECOVERY,
+		{"recovery_end_command", PGC_SIGHUP, WAL_ARCHIVE_RECOVERY,
 			gettext_noop("Sets the shell command that will be executed once at the end of recovery."),
 			NULL
 		},
@@ -3474,7 +3474,7 @@ static struct config_string ConfigureNamesString[] =
 	},
 
 	{
-		{"promote_trigger_file", PGC_POSTMASTER, REPLICATION_STANDBY,
+		{"promote_trigger_file", PGC_SIGHUP, REPLICATION_STANDBY,
 			gettext_noop("Specifies a file name whose presence ends recovery in the standby."),
 			NULL
 		},
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index c7f53470df..ad6c436f93 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -244,9 +244,7 @@
 				# e.g. 'cp /mnt/server/archivedir/%f %p'
 				# (change requires restart)
 #archive_cleanup_command = ''	# command to execute at every restartpoint
-				# (change requires restart)
 #recovery_end_command = ''	# command to execute at completion of recovery
-				# (change requires restart)
 
 # - Recovery Target -
 
@@ -310,7 +308,6 @@
 #primary_slot_name = ''			# replication slot on sending server
 					# (change requires restart)
 #promote_trigger_file = ''		# file name whose presence ends recovery
-					# (change requires restart)
 #hot_standby = on			# "off" disallows queries during recovery
 					# (change requires restart)
 #max_standby_archive_delay = 30s	# max delay before canceling queries
@@ -329,7 +326,6 @@
 #wal_retrieve_retry_interval = 5s	# time to wait before retrying to
 					# retrieve WAL after a failed attempt
 #recovery_min_apply_delay = 0		# minimum delay for applying changes during recovery
-					# (change requires restart)
 
 # - Subscribers -
 
-- 
2.20.1