repmgr: set "synchronous_commit" to "local" by default

Rather than set this for individual connections, we'll change the setting
each time a connection is made (except replication connections), which will
obviate the need to take this into consideration when making connections
in the application code.

Resolves GitHub #276.

dbutils.c

@@ -35,6 +35,14 @@ char repmgr_schema_quoted[MAXLEN] = "";
 static int _get_node_record(PGconn *conn, char *cluster, char *sqlquery, t_node_info *node_info);
 static bool _set_config(PGconn *conn, const char *config_param, const char *sqlquery);
 
+/*
+ * _establish_db_connection()
+ *
+ * Connect to a database using a conninfo string.
+ *
+ * NOTE: *do not* use this for replication connections; use establish_db_connection_by_params() instead.
+ */
+
 PGconn *
 _establish_db_connection(const char *conninfo, const bool exit_on_error, const bool log_notice, const bool verbose_only)
 {
@@ -78,6 +86,20 @@ _establish_db_connection(const char *conninfo, const bool exit_on_error, const b
 		}
 	}
 
+	/*
+	 * set "synchronous_commit" to "local" in case synchronous replication is in use
+	 */
+
+	if (set_config(conn, "synchronous_commit", "local") == false)
+	{
+
+		if (exit_on_error)
+		{
+			PQfinish(conn);
+			exit(ERR_DB_CON);
+		}
+	}
+
 	return conn;
 }
 
@@ -117,8 +139,12 @@ PGconn *
 establish_db_connection_by_params(const char *keywords[], const char *values[],
 								  const bool exit_on_error)
 {
-	/* Make a connection to the database */
+	PGconn	   *conn;
-	PGconn	   *conn = PQconnectdbParams(keywords, values, true);
+	bool	    replication_connection = false;
+	int	   	    i;
+
+	/* Connect to the database using the provided parameters */
+	conn = PQconnectdbParams(keywords, values, true);
 
 	/* Check to see that the backend connection was successfully made */
 	if ((PQstatus(conn) != CONNECTION_OK))
@@ -132,6 +158,27 @@ establish_db_connection_by_params(const char *keywords[], const char *values[],
 		}
 	}
 
+
+	/*
+	 * set "synchronous_commit" to "local" in case synchronous replication is in
+	 * use (provided this is not a replication connection)
+	 */
+
+	for (i = 0; keywords[i]; i++)
+	{
+		if (strcmp(keywords[i], "replication") == 0)
+			replication_connection = true;
+	}
+
+	if (replication_connection == false && set_config(conn, "synchronous_commit", "local") == false)
+	{
+		if (exit_on_error)
+		{
+			PQfinish(conn);
+			exit(ERR_DB_CON);
+		}
+	}
+
 	return conn;
 }
 

repmgr.c

@@ -3022,18 +3022,6 @@ do_standby_clone(void)
 				strncpy(recovery_conninfo_str, upstream_node_record.conninfo_str, MAXLEN);
 			}
 		}
-
-		/* Finally, set `synchronous_commit` to `local` to avoid problems
-		 * if synchronous commit is in use.
-		 */
-
-		if (primary_conn != NULL && PQstatus(primary_conn) == CONNECTION_OK)
-		{
-			if (set_config(primary_conn, "synchronous_commit", "local") == false)
-			{
-				exit(ERR_DB_QUERY);
-			}
-		}
 	}
 
 	if (mode == barman && PQstatus(source_conn) != CONNECTION_OK)
@@ -4857,8 +4845,6 @@ do_standby_follow(void)
  *
  * TODO:
  *  - make connection test timeouts/intervals configurable (see below)
- *  - add command line option --remote_pg_bindir or similar to
- *    optionally handle cases where the remote pg_bindir is different
  */
 
 static void
@@ -5592,6 +5578,8 @@ do_standby_switchover(void)
 
 	/* Check for entry in the new master's pg_stat_replication */
 
+	local_conn = establish_db_connection(options.conninfo, true);
+
 	{
 		int			i,
 			replication_check_timeout  = 60,
@@ -5601,8 +5589,6 @@ do_standby_switchover(void)
 
 		initPQExpBuffer(&event_details);
 
-		local_conn = establish_db_connection(options.conninfo, true);
-
 		i = 0;
 		for (;;)
 		{