standby promote: in --dry-run mode, display promote command which will be used

For PostgreSQL 12 and later, explicitly note whether repmgr user has
execution permissions on the pg_promote() function.

HISTORY

@@ -15,8 +15,9 @@
         repmgr: consolidate replication connection code (Ian)
         repmgr: check permissions for "pg_promote()" and fall back to pg_ctl
           if necessary (Ian)
-        repmgr: accept option -S/--superuser for "node check"; GitHub #612 (Ian)
+        repmgr: in --dry-run mode, display promote command which will be used (Ian)
         repmgr: enable "service_promote_command" in PostgreSQL 12 (Ian)
+        repmgr: accept option -S/--superuser for "node check"; GitHub #612 (Ian)
 
 5.0     2019-10-15
         general: add PostgreSQL 12 support (Ian)

doc/appendix-release-notes.xml

@@ -49,6 +49,14 @@
       <title>General improvements</title>
       <para>
         <itemizedlist>
+          <listitem>
+            <para>
+              <link linkend="repmgr-standby-promote"><command>repmgr standby promote</command></link>:
+              when executed with <option>--dry-run</option>, the method which would be used to promote the node
+              will be displayed.
+            </para>
+          </listitem>
+
           <listitem>
             <para>
               <link linkend="repmgr-standby-follow"><command>repmgr standby follow</command></link>:
@@ -67,7 +75,7 @@
           <listitem>
             <para>
               <link linkend="repmgr-node-check"><command>repmgr node check</command></link>:
-              accept option <option>-S</option>/<option>--superuser</option> GitHub #621.
+              accept option <option>-S</option>/<option>--superuser</option>. GitHub #621.
             </para>
           </listitem>
         </itemizedlist>

doc/repmgr-standby-promote.xml

@@ -115,6 +115,10 @@
       <function>pg_promote()</function>, &repmgr; will fall back to using &quot;<command>pg_ctl promote</command>&quot;.
     </para>
     <tip>
+      <para>
+        Execute <command>repmgr standby promote</command> with the <option>--dry-run</option>
+        to check whether the &repmgr; user has permission to execute <function>pg_promote()</function>.
+      </para>
       <para>
         If the <literal>repmgr</literal> user is not a superuser, execution permission for this
         function can be granted with e.g.:

repmgr-action-standby.c

@@ -2409,6 +2409,37 @@ do_standby_promote(void)
 		}
 	}
 
+	/*
+	 * In --dry-run mode, note which promotion method will be used.
+	 * For Pg12 and later, check whether pg_promote() can be executed.
+	 */
+	if (runtime_options.dry_run == true)
+	{
+		if (config_file_options.service_promote_command[0] != '\0')
+		{
+			log_info(_("node will be promoted using command defined in \"service_promote_command\""));
+			log_detail(_("\"service_promote_command\" is \"%s\""),
+					   config_file_options.service_promote_command);
+		}
+		else if (PQserverVersion(local_conn) >= 120000)
+		{
+			if (can_execute_pg_promote(local_conn) == false)
+			{
+				log_info(_("node will be promoted using \"pg_ctl promote\""));
+				log_detail(_("user \"%s\" does not have permission to execute \"pg_promote()\""),
+						   PQuser(local_conn));
+			}
+			else
+			{
+				log_info(_("node will be promoted using the \"pg_promote()\" function"));
+			}
+		}
+		else
+		{
+			log_info(_("node will be promoted using \"pg_ctl promote\""));
+		}
+	}
+
 	if (runtime_options.dry_run == true)
 	{
 		PQfinish(local_conn);