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MXS-860: Detect whether replication is configured

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The `detect_stale_slave` functionality used to only work when MaxScale had
the knowledge that a master server has existed and that replication was
working at some point in time. This might be a "safe" way to do it in
regards to staleness of the data but in practice it is preferrable to
always allow slave to be used for reads.

This change adds the missing functionality to the monitor by assigning
slave status to all servers which are configured as replication slaves
when no master can be found.

The new member variable that was added to the SERVER should be removed in
2.1 where the server_info offers the same functionalty without "polluting"
the SERVER type.
This commit is contained in:
Markus Makela 2016-09-12 05:06:42 +03:00
parent 8be833640f
commit 6dc75d4b9c
5 changed files with 18 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
Documentation/Monitors/MySQL-Monitor.md
View File

@ -78,10 +78,6 @@ With this parameter, slaves that have lost their master but have been slaves of
a master server can retain their slave status even without a master. This means
that when a slave loses its master, it can still be used for reads.
If MaxScale loses the connection to the slave, the slave will lose the stale
slave state because MaxScale doesn't know if the slave has had recent contact
with the master server.
If this feature is disabled, a server is considered a valid slave if and only if
it has a running master server monitored by this monitor.

1
Documentation/Release-Notes/MaxScale-2.0.1-Release-Notes.md
View File

@ -120,6 +120,7 @@ Please consult
* [MXS-845](https://jira.mariadb.org/browse/MXS-845): "Server down" event is re-triggered after maintenance mode is repeated
* [MXS-842](https://jira.mariadb.org/browse/MXS-842): Unexpected / undocumented behaviour when multiple available masters from mmmon monitor
* [MXS-846](https://jira.mariadb.org/browse/MXS-846): MMMon: Maintenance mode on slave logs error message every second
* [MXS-860](https://jira.mariadb.org/browse/MXS-860): I want to access the web site if master server is down.
## Known Issues and Limitations

1
server/core/server.c
View File

@ -88,6 +88,7 @@ server_alloc(char *servname, char *protocol, unsigned short port)
server->persistmax = 0;
server->persistmaxtime = 0;
server->persistpoolmax = 0;
server->slave_configured = false;
spinlock_init(&server->persistlock);
spinlock_acquire(&server_spin);

2
server/include/server.h
View File

@ -102,6 +102,8 @@ typedef struct server
int depth; /**< Replication level in the tree */
long slaves[MAX_NUM_SLAVES]; /**< Slaves of this node */
bool master_err_is_logged; /*< If node failed, this indicates whether it is logged */
bool slave_configured; /**< Server is configured as a replication slave
* TODO: Remove this for 2.1 */
DCB *persistent; /**< List of unused persistent connections to the server */
SPINLOCK persistlock; /**< Lock for adjusting the persistent connections list */
long persistpoolmax; /**< Maximum size of persistent connections pool */

14
server/modules/monitor/mysql_mon.c
View File

@ -323,8 +323,11 @@ static inline void monitor_mysql100_db(MONITOR_SERVERS* database)
return;
}
database->server->slave_configured = false;
while ((row = mysql_fetch_row(result)))
{
database->server->slave_configured = true;
/* get Slave_IO_Running and Slave_SQL_Running values*/
if (strncmp(row[12], "Yes", 3) == 0
&& strncmp(row[13], "Yes", 3) == 0)
@ -407,8 +410,11 @@ static inline void monitor_mysql55_db(MONITOR_SERVERS* database)
return;
}
database->server->slave_configured = false;
while ((row = mysql_fetch_row(result)))
{
database->server->slave_configured = true;
/* get Slave_IO_Running and Slave_SQL_Running values*/
if (strncmp(row[10], "Yes", 3) == 0
&& strncmp(row[11], "Yes", 3) == 0)
@ -479,8 +485,11 @@ static inline void monitor_mysql51_db(MONITOR_SERVERS* database)
return;
}
database->server->slave_configured = false;
while ((row = mysql_fetch_row(result)))
{
database->server->slave_configured = true;
/* get Slave_IO_Running and Slave_SQL_Running values*/
if (strncmp(row[10], "Yes", 3) == 0
&& strncmp(row[11], "Yes", 3) == 0)
@ -994,6 +1003,11 @@ monitorMain(void *arg)
{
ptr->pending_status |= SERVER_SLAVE;
}
else if (root_master == NULL && ptr->server->slave_configured)
{
/** TODO: Change this in 2.1 to use the server_info mechanism */
ptr->pending_status |= SERVER_SLAVE;
}
}
ptr->server->status = ptr->pending_status;