"standby follow": initial implementation of --dry-run option

GitHub #363.

doc/repmgr-standby-follow.sgml

@@ -48,6 +48,32 @@
     </para>
   </refsect1>
 
+  <refsect1>
+    <title>Options</title>
+    <variablelist>
+
+      <varlistentry>
+        <term><option>--dry-run</option></term>
+        <listitem>
+          <para>
+            Check prerequisites but don't actually follow a new standby.
+          </para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><option>-W</option></term>
+        <term><option>--wait</option></term>
+        <listitem>
+          <para>
+            Wait for a primary to appear.
+          </para>
+        </listitem>
+      </varlistentry>
+
+    </variablelist>
+  </refsect1>
+
   <refsect1>
     <title>Event notifications</title>
     <para>

repmgr-action-standby.c

@@ -1647,6 +1647,15 @@ do_standby_follow(void)
 		exit(ERR_BAD_CONFIG);
 	}
 
+	if (runtime_options.dry_run == true)
+	{
+		log_info(_("connected to node %i, checking for current primary"), primary_id);
+	}
+	else
+	{
+		log_verbose(LOG_INFO, _("connected to node %i, checking for current primary"), primary_id);
+	}
+
 	record_status = get_node_record(primary_conn, primary_id, &primary_node_record);
 
 	if (record_status != RECORD_FOUND)
@@ -1657,6 +1666,19 @@ do_standby_follow(void)
 		exit(ERR_BAD_CONFIG);
 	}
 
+	if (runtime_options.dry_run == true)
+	{
+		log_info(_("primary node is \"%s\" (ID: %i)"),
+				 primary_node_record.node_name,
+				 primary_id);
+	}
+	else
+	{
+		log_verbose(LOG_INFO, ("primary node is \"%s\" (ID: %i)"),
+					primary_node_record.node_name,
+					primary_id);
+	}
+
 	/* XXX check this is not current upstream anyway */
 	/* check replication connection */
 	initialize_conninfo_params(&repl_conninfo, false);
@@ -1673,6 +1695,10 @@ do_standby_follow(void)
 		PQfinish(primary_conn);
 		exit(ERR_BAD_CONFIG);
 	}
+	else if (runtime_options.dry_run == true)
+	{
+		log_info(_("replication connection to primary node was successful"));
+	}
 
 	/* check system_identifiers match */
 	local_system_identifier = get_system_identifier(config_file_options.data_directory);
@@ -1696,10 +1722,24 @@ do_standby_follow(void)
 		PQfinish(repl_conn);
 		exit(ERR_BAD_CONFIG);
 	}
+	else if (runtime_options.dry_run == true)
+	{
+		log_info(_("local and primary system identifiers match"));
+		log_detail(_("system identifier is %lu"), local_system_identifier);
+	}
+
+	/* TODO: check timelines*/
 
 	PQfinish(repl_conn);
 	free_conninfo_params(&repl_conninfo);
 
+	if (runtime_options.dry_run == true)
+	{
+		log_info(_("prerequisites for executing STANDBY FOLLOW are met"));
+		exit(SUCCESS);
+	}
+
+
 	initPQExpBuffer(&follow_output);
 
 	success = do_standby_follow_internal(primary_conn,
@@ -5426,6 +5466,7 @@ do_standby_help(void)
 	puts("");
 	printf(_("  \"standby follow\" instructs a standby node to follow a new primary.\n"));
 	puts("");
+	printf(_("  --dry-run                           perform checks but don't actually follow the new primary\n"));
 	printf(_("  -W, --wait                          wait for a primary to appear\n"));
 	puts("");
 

repmgr-client.c

@@ -1579,8 +1579,7 @@ check_cli_parameters(const int action)
 			case NODE_STATUS:
 				break;
 			default:
-				item_list_append_format(
+				item_list_append_format(&cli_warnings,
-										&cli_warnings,
 										_("--is-shutdown-cleanly will be ignored when executing %s"),
 										action_name(action));
 		}
@@ -1593,8 +1592,7 @@ check_cli_parameters(const int action)
 			case STANDBY_SWITCHOVER:
 				break;
 			default:
-				item_list_append_format(
+				item_list_append_format(&cli_warnings,
-										&cli_warnings,
 										_("--always-promote will be ignored when executing %s"),
 										action_name(action));
 		}
@@ -1608,8 +1606,7 @@ check_cli_parameters(const int action)
 			case NODE_REJOIN:
 				break;
 			default:
-				item_list_append_format(
+				item_list_append_format(&cli_warnings,
-										&cli_warnings,
 										_("--force-rewind will be ignored when executing %s"),
 										action_name(action));
 		}
@@ -1623,8 +1620,7 @@ check_cli_parameters(const int action)
 			case NODE_REJOIN:
 				break;
 			default:
-				item_list_append_format(
+				item_list_append_format(&cli_warnings,
-										&cli_warnings,
 										_("--config-files will be ignored when executing %s"),
 										action_name(action));
 		}
@@ -1638,6 +1634,7 @@ check_cli_parameters(const int action)
 			case PRIMARY_UNREGISTER:
 			case STANDBY_CLONE:
 			case STANDBY_REGISTER:
+			case STANDBY_FOLLOW:
 			case STANDBY_SWITCHOVER:
 			case WITNESS_REGISTER:
 			case WITNESS_UNREGISTER:
@@ -1645,8 +1642,7 @@ check_cli_parameters(const int action)
 			case NODE_SERVICE:
 				break;
 			default:
-				item_list_append_format(
+				item_list_append_format(&cli_warnings,
-										&cli_warnings,
 										_("--dry-run is not effective when executing %s"),
 										action_name(action));
 		}
@@ -1668,8 +1664,7 @@ check_cli_parameters(const int action)
 		if (used_options > 1)
 		{
 			/* TODO: list which options were used */
-			item_list_append(
+			item_list_append(&cli_errors,
-							 &cli_errors,
 							 "only one of --csv, --nagios and --optformat can be used");
 		}
 	}