lib-master: Hide connect(stats-writer) errors when running via CLI

Only hide errors that occur if the stats process isn't running, i.e. when
socket isn't found or there's no listener. This way e.g. permission errors
are still logged, which points to a wrong configuration.

src/lib-master/master-service-settings.c

@@ -589,7 +589,13 @@ int master_service_settings_read(struct master_service *service,
 		const char *path = t_strdup_printf("%s/%s",
 			service->set->base_dir,
 			service->set->stats_writer_socket_path);
-		service->stats_client = stats_client_init(path);
+		/* When running standalone (e.g. doveadm) try to connect to the
+		   stats socket, but don't log an error if it's not running.
+		   It may be intentional. */
+		bool silent_notfound_errors =
+			(service->flags & MASTER_SERVICE_FLAG_STANDALONE) != 0;
+		service->stats_client =
+			stats_client_init(path, silent_notfound_errors);
 	} T_END;
 
 	if (service->set->shutdown_clients)

src/lib-master/stats-client.c

@@ -19,6 +19,7 @@ struct stats_client {
 	struct timeout *to_reconnect;
 	bool handshaked;
 	bool handshake_received_at_least_once;
+	bool silent_notfound_errors;
 };
 
 static struct connection_list *stats_clients;
@@ -307,24 +308,27 @@ static void stats_client_send_registered_categories(struct stats_client *client)
 
 static void stats_client_connect(struct stats_client *client)
 {
-	if (connection_client_connect(&client->conn) < 0)
-		i_error("net_connect_unix(%s) failed: %m", client->conn.name);
-	else {
+	if (connection_client_connect(&client->conn) == 0) {
 		/* read the handshake so the global debug filter is updated */
 		stats_client_send_registered_categories(client);
 		if (!client->handshake_received_at_least_once)
 			stats_client_wait_handshake(client);
+	} else if (!client->silent_notfound_errors ||
+		   (errno != ENOENT && errno != ECONNREFUSED)) {
+		i_error("net_connect_unix(%s) failed: %m", client->conn.name);
 	}
 }
 
-struct stats_client *stats_client_init(const char *path)
+struct stats_client *
+stats_client_init(const char *path, bool silent_notfound_errors)
 {
 	struct stats_client *client;
 
 	if (stats_clients == NULL)
 		stats_global_init();
 
 	client = i_new(struct stats_client, 1);
+	client->silent_notfound_errors = silent_notfound_errors;
 	connection_init_client_unix(stats_clients, &client->conn, path);
 	stats_client_connect(client);
 	return client;

src/lib-master/stats-client.h

@@ -1,7 +1,8 @@
 #ifndef STATS_CLIENT_H
 #define STATS_CLIENT_H
 
-struct stats_client *stats_client_init(const char *path);
+struct stats_client *
+stats_client_init(const char *path, bool silent_notfound_errors);
 void stats_client_deinit(struct stats_client **client);
 
 #endif