Add support for Galera xtrabackup donor availability

Documentation/Getting-Started/Configuration-Guide.md

@@ -435,6 +435,7 @@ backend_write_timeout=2
 
 # galeramon specific options
 disable_master_failback=0
+available_when_donor=0
 ```
 
 #### `module`
@@ -499,6 +500,12 @@ The server status field may have the `SERVER_MASTER_STICKINESS` bit, meaning the
 
 Anyway, a new master will be selected in case of current master failure, regardless the option value.
 
+#### `available_when_donor`
+
+This option if set to 1 will allow Galera monitor to keep a node in `Donor` status in the server pool if it is using any xtrabackup method for SST, e.g. `wsrep_sst_method` equal to `xtrabackup` or `xtrabackup-v2`.
+
+As xtrabackup is a non-locking SST method, a node in `Donor` status can still be considered in sync. This option is not enabled by default and should be used as the administrator's discretion.
+
 #### `backend_connect_timeout`
 
 This option, with default value of `3` sets the monitor connect timeout to backends.

server/core/config.c

@@ -42,6 +42,7 @@
  * 07/11/14	Massimiliano Pinto	Addition of monitor timeouts for connect/read/write
  * 20/02/15	Markus Mäkelä		Added connection_timeout parameter for services
  * 05/03/15	Massimiliano	Pinto	Added notification_feedback support
+ * 20/04/15	Guillaume Lefranc	Added available_when_donor parameter
  *
  * @endverbatim
  */
@@ -1893,6 +1894,7 @@ static char *monitor_params[] =
 		"backend_connect_timeout",
 		"backend_read_timeout",
 		"backend_write_timeout",
+		"available_when_donor",
                 NULL
         };
 /**
@@ -2278,4 +2280,4 @@ void config_add_param(CONFIG_CONTEXT* obj, char* key,char* value)
     nptr->value = strdup(value);
     nptr->next = obj->parameters;
     obj->parameters = nptr;
-}
+}

server/modules/monitor/galera_mon.c

@@ -32,6 +32,7 @@
  * 24/06/14	Massimiliano Pinto	Added depth level 0 for each node
  * 30/10/14	Massimiliano Pinto	Added disableMasterFailback feature
  * 10/11/14	Massimiliano Pinto	Added setNetworkTimeout for connect,read,write
+ * 20/05/15	Guillaume Lefranc	Added availableWhenDonor feature
  *
  * @endverbatim
  */
@@ -158,6 +159,7 @@ CONFIG_PARAMETER* params = (CONFIG_PARAMETER*)opt;
 		handle->id = MONITOR_DEFAULT_ID;
 		handle->interval = MONITOR_INTERVAL;
 		handle->disableMasterFailback = 0;
+		handle->availableWhenDonor = 0;
 		handle->master = NULL;
 		handle->connect_timeout=DEFAULT_CONNECT_TIMEOUT;
 		handle->read_timeout=DEFAULT_READ_TIMEOUT;
@@ -170,6 +172,8 @@ CONFIG_PARAMETER* params = (CONFIG_PARAMETER*)opt;
 	{
 	    if(!strcmp(params->name,"disable_master_failback"))
 		handle->disableMasterFailback = config_truth_value(params->value);
+	    if(!strcmp(params->name,"available_when_donor"))
+		handle->availableWhenDonor = config_truth_value(params->value);
 	    params = params->next;
 	}
 
@@ -289,6 +293,7 @@ char		*sep;
 
 	dcb_printf(dcb,"\tSampling interval:\t%lu milliseconds\n", handle->interval);
 	dcb_printf(dcb,"\tMaster Failback:\t%s\n", (handle->disableMasterFailback == 1) ? "off" : "on");
+	dcb_printf(dcb,"\tAvailable when Donor:\t%s\n", (handle->availableWhenDonor == 1) ? "on" : "off");
 	dcb_printf(dcb,"\tConnect Timeout:\t%i seconds\n", handle->connect_timeout);
 	dcb_printf(dcb,"\tRead Timeout:\t\t%i seconds\n", handle->read_timeout);
 	dcb_printf(dcb,"\tWrite Timeout:\t\t%i seconds\n", handle->write_timeout);
@@ -428,14 +433,28 @@ char 			*server_string;
 	}	
 
 	/* Check if the the Galera FSM shows this node is joined to the cluster */
-	if (mysql_query(database->con, "SHOW STATUS LIKE 'wsrep_local_state_comment'") == 0
+	if (mysql_query(database->con, "SHOW STATUS LIKE 'wsrep_local_state'") == 0
 		&& (result = mysql_store_result(database->con)) != NULL)
 	{
 		num_fields = mysql_num_fields(result);
 		while ((row = mysql_fetch_row(result)))
 		{
-			if (strncasecmp(row[1], "SYNCED", 3) == 0)
+			if (strcmp(row[1], "4") == 0) 
 				isjoined = 1;
+	
+			/* Check if the node is a donor and is using xtrabackup, in this case it can stay alive */
+			else if (strcmp(row[1], "2") == 0 && handle->availableWhenDonor == 1) {
+				if (mysql_query(database->con, "SHOW VARIABLES LIKE 'wsrep_sst_method'") == 0
+					&& (result = mysql_store_result(database->con)) != NULL)
+				{
+					num_fields = mysql_num_fields(result);
+					while ((row = mysql_fetch_row(result)))
+					{
+						if (strncmp(row[1], "xtrabackup", 10) == 0)
+							isjoined = 1;
+					}
+				}
+			}
 		}
 		mysql_free_result(result);
 	}
@@ -732,6 +751,22 @@ MYSQL_MONITOR   *handle = (MYSQL_MONITOR *)arg;
         memcpy(&handle->disableMasterFailback, &disable, sizeof(int));
 }
 
+/**
+ * Allow a Galera node to be in sync when Donor.
+ *
+ * When enabled, the monitor will check if the node is using xtrabackup or xtrabackup-v2
+ * as SST method. In that case, node will stay as synced.
+ *
+ * @param arg		The handle allocated by startMonitor
+ * @param disable	To allow sync status use 1, 0 for traditional behavior
+ */
+static void
+availableWhenDonor(void *arg, int disable)
+{
+MYSQL_MONITOR   *handle = (MYSQL_MONITOR *)arg;
+        memcpy(&handle->availableWhenDonor, &disable, sizeof(int));
+}
+
 /**
  * Set the timeouts to use in the monitor.
  *

server/modules/monitor/mysqlmon.h

@@ -35,6 +35,7 @@
  * 28/08/14	Massimiliano	Pinto	Addition of detectStaleMaster
  * 30/10/14	Massimiliano	Pinto	Addition of disableMasterFailback
  * 07/11/14	Massimiliano	Pinto	Addition of NetworkTimeout: connect, read, write
+ * 20/05/15	Guillaume Lefranc	Addition of availableWhenDonor
  *
  * @endverbatim
  */
@@ -68,6 +69,7 @@ typedef struct {
 	int	replicationHeartbeat;	/**< Monitor flag for MySQL replication heartbeat */
 	int	detectStaleMaster;	/**< Monitor flag for MySQL replication Stale Master detection */
 	int	disableMasterFailback;	/**< Monitor flag for Galera Cluster Master failback */
+	int	availableWhenDonor;	/**< Monitor flag for Galera Cluster Donor availability */
 	MONITOR_SERVERS *master;	/**< Master server for MySQL Master/Slave replication */
 	MONITOR_SERVERS	*databases;     /**< Linked list of servers to monitor */
 	int	connect_timeout;	/**< Connect timeout in seconds for mysql_real_connect */