Add server maintenance mode.

Maintenance mode prevents a server from having new connections made
to it and stops MaxScale from monitoring a server. It is designed
to allow a server to be taken out of an active cluster for maintenance.
It prevents new connections and allowsg existing connections to
drain away prior to performaing maintenance on the server.

server/core/server.c

@@ -344,6 +344,8 @@ char	*status = NULL;
 	if ((status = (char *)malloc(200)) == NULL)
 		return NULL;
 	status[0] = 0;
+	if (server->status & SERVER_MAINT)
+		strcat(status, "Maintenance, ");
 	if (server->status & SERVER_MASTER)
 		strcat(status, "Master, ");
 	if (server->status & SERVER_SLAVE)

server/include/server.h

@@ -35,6 +35,7 @@
  * 20/05/14	Massimiliano Pinto	Addition of server_string field
  * 20/05/14	Massimiliano Pinto	Addition of node_id field
  * 23/05/14	Massimiliano Pinto	Addition of rlag and node_ts fields
+ * 03/06/14	Mark Riddoch		Addition of maintainance mode
  *
  * @endverbatim
  */
@@ -80,12 +81,13 @@ typedef struct server {
 #define SERVER_MASTER	0x0002		/**<< The server is a master, i.e. can handle writes */
 #define SERVER_SLAVE	0x0004		/**<< The server is a slave, i.e. can handle reads */
 #define SERVER_JOINED	0x0008		/**<< The server is joined in a Galera cluster */
+#define SERVER_MAINT	0x1000		/**<< Server is in maintenance mode */
 
 /**
  * Is the server running - the macro returns true if the server is marked as running
  * regardless of it's state as a master or slave
  */
-#define	SERVER_IS_RUNNING(server)	((server)->status & SERVER_RUNNING)
+#define	SERVER_IS_RUNNING(server)	(((server)->status & (SERVER_RUNNING|SERVER_MAINT)) == SERVER_RUNNING)
 /**
  * Is the server marked as down - the macro returns true if the server is beleived
  * to be inoperable.
@@ -96,19 +98,24 @@ typedef struct server {
  * in order for the macro to return true
  */
 #define	SERVER_IS_MASTER(server) \
-			(((server)->status & (SERVER_RUNNING|SERVER_MASTER|SERVER_SLAVE)) == (SERVER_RUNNING|SERVER_MASTER))
+			(((server)->status & (SERVER_RUNNING|SERVER_MASTER|SERVER_SLAVE|SERVER_MAINT)) == (SERVER_RUNNING|SERVER_MASTER))
 /**
  * Is the server a slave? The server must be both running and marked as a slave
  * in order for the macro to return true
  */
 #define	SERVER_IS_SLAVE(server)	\
-			(((server)->status & (SERVER_RUNNING|SERVER_MASTER|SERVER_SLAVE)) == (SERVER_RUNNING|SERVER_SLAVE))
+			(((server)->status & (SERVER_RUNNING|SERVER_MASTER|SERVER_SLAVE|SERVER_MAINT)) == (SERVER_RUNNING|SERVER_SLAVE))
 
 /**
  * Is the server joined Galera node? The server must be running and joined. 
  */
 #define SERVER_IS_JOINED(server) \
-	(((server)->status & (SERVER_RUNNING|SERVER_JOINED)) == (SERVER_RUNNING|SERVER_JOINED))
+	(((server)->status & (SERVER_RUNNING|SERVER_JOINED|SERVER_MAINT)) == (SERVER_RUNNING|SERVER_JOINED))
+
+/**
+ * Is the server in maintenance mode. 
+ */
+#define SERVER_IN_MAINT(server)		((server)->status & SERVER_MAINT)
 
 extern SERVER	*server_alloc(char *, char *, unsigned short);
 extern int	server_free(SERVER *);

server/modules/monitor/galera_mon.c

@@ -28,6 +28,7 @@
  *					that has the lowest value of wsrep_local_index
  * 23/05/14	Massimiliano Pinto	Added 1 configuration option (setInterval).
  * 					Interval is printed in diagnostics.
+ * 03/06/14	Mark Riddoch		Add support for maintenance mode
  *
  * @endverbatim
  */
@@ -309,6 +310,10 @@ char 			*server_string;
 	if (uname == NULL)
 		return;
 
+	/* Don't even probe server flagged as in maintenance */
+	if (SERVER_IN_MAINT(database->server))
+		return;
+
 	if (database->con == NULL || mysql_ping(database->con) != 0)
 	{
 		char *dpwd = decryptPassword(passwd);
@@ -415,7 +420,7 @@ long master_id;
 
 			/* set master_id to the lowest value of ptr->server->node_id */
 
-			if (ptr->server->node_id >= 0 && SERVER_IS_JOINED(ptr->server)) {
+			if ((! SERVER_IN_MAINT(ptr->server))  && ptr->server->node_id >= 0 && SERVER_IS_JOINED(ptr->server)) {
 				if (ptr->server->node_id < master_id && master_id >= 0) {
 					master_id = ptr->server->node_id;
 				} else {
@@ -423,7 +428,7 @@ long master_id;
 						master_id = ptr->server->node_id;
 					}
 				}
-			} else {
+			} else if (!SERVER_IN_MAINT(ptr->server)) {
 				/* clear M/S status */
 				server_clear_status(ptr->server, SERVER_SLAVE);
                 		server_clear_status(ptr->server, SERVER_MASTER);
@@ -436,7 +441,7 @@ long master_id;
 		/* this server loop sets Master and Slave roles */
 		while (ptr)
 		{
-			if (ptr->server->node_id >= 0 && master_id >= 0) {
+			if ((! SERVER_IN_MAINT(ptr->server)) && ptr->server->node_id >= 0 && master_id >= 0) {
 				/* set the Master role */
 				if (SERVER_IS_JOINED(ptr->server) && (ptr->server->node_id == master_id)) {
                 			server_set_status(ptr->server, SERVER_MASTER);

server/modules/monitor/mysql_mon.c

@@ -32,6 +32,7 @@
  *					New server field version_string is updated.
  * 28/05/14	Massimiliano Pinto	Added set Id and configuration options (setInverval)
  *					Parameters are now printed in diagnostics
+ * 03/06/14	Mark Ridoch		Add support for maintenance mode
  *
  * @endverbatim
  */
@@ -323,6 +324,11 @@ int			replication_heartbeat = handle->replicationHeartbeat;
 	}
 	if (uname == NULL)
 		return;
+
+	/* Don't probe servers in maintenance mode */
+	if (SERVER_IN_MAINT(database->server))
+		return;
+
 	if (database->con == NULL || mysql_ping(database->con) != 0)
 	{
 		char *dpwd = decryptPassword(passwd);

server/modules/routing/debugcmd.c

@@ -754,11 +754,13 @@ static struct {
 	char		*str;
 	unsigned int	bit;
 } ServerBits[] = {
-	{ "running", 	SERVER_RUNNING },
-	{ "master",	SERVER_MASTER },
-	{ "slave",	SERVER_SLAVE },
-	{ "synced",	SERVER_JOINED },
-	{ NULL,		0 }
+	{ "running", 		SERVER_RUNNING },
+	{ "master",		SERVER_MASTER },
+	{ "slave",		SERVER_SLAVE },
+	{ "synced",		SERVER_JOINED },
+	{ "maintenance",	SERVER_MAINT },
+	{ "maint",		SERVER_MAINT },
+	{ NULL,			0 }
 };
 /**
  * Map the server status bit

server/modules/routing/readconnroute.c

@@ -352,6 +352,9 @@ int			master_host = -1;
 				inst->bitmask)));
 		}
 
+		if (SERVER_IN_MAINT(inst->server))
+			continue;
+
 		/*
 		 * If router_options=slave, get the running master
  		 * It will be used if there are no running slaves at all