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MXS-1441 Add switchover and switchover_timeout config vars

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Tentative documentation.

With the 'switchover' config variable the switchover functionality
can be enabled. If enabled a REST API endpoint will appear, using
which that switchover can be initiated.

Switchover can only be performed when MaxScale is in active mode
and failover will be disabled for the duration of the switchover.
Only if the switchover succeeds, will failover be enabled again.

Might be easier to expose that REST API always and only change
the behaviour when calling it, instead of making it appear and
re-appear.
This commit is contained in:
Johan Wikman 2017-09-28 11:30:20 +03:00
parent d4fd34cecd
commit ff467e218a
3 changed files with 49 additions and 2 deletions
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33
Documentation/Monitors/MySQL-Monitor.md
View File

@ -243,6 +243,39 @@ from passive to active will wait for a failover to take place after an apparent
loss of a master server. If no new master server is detected within the
configured time period, the failover will be initiated again.
### `switchover`
Enable switchover via MaxScale. This parameter expects a boolean value and
the default value is false.
When the switchover functionality is enabled, a REST API endpoint will be
made available, using which switchover may be performed. The endpoint will
be available irrespective of whether MaxScale is in active or passive mode,
but switchover will only be attempted if MaxScale is in active mode and an
error logged if an attempt is made when MaxScale is in passive mode.
Switchover may also be triggered from MaxAdmin and the same rules regarding
active/passive holds.
It is safe to perform switchover even with the failover functionality
enabled, as MaxScale will disable the failover behaviour for the duration
of the switchover.
Only if the switchover succeeds, will the failover functionality be re-enabled.
Otherwise it will remain disabled and must be turned on manually via the REST
API or MaxAdmin.
TODO: Document the URL path. Probably will include the monitor section name
from the configuration.
### `switchover_timeout`
The timeout for the cluster switchover in seconds. The default value is 90
seconds.
If no successful switchover takes place within the configured time period,
a message is logged and the failover (not switchover) functionality will not
be enabled, even if it was enabled before the switchover attempt.
## Using the MySQL Monitor With Binlogrouter
Since MaxScale 2.2 it's possible to detect a replication setup

2
server/modules/monitor/mysqlmon.h
View File

@ -65,6 +65,8 @@ typedef struct
bool allow_external_slaves; /**< Whether to allow usage of external slave servers */
bool failover; /**< If master failover is enabled */
uint32_t failover_timeout; /**< Timeout in seconds for the master failover */
bool switchover; /**< If master switchover is enabled */
uint32_t switchover_timeout; /**< Timeout in seconds for the master switchover */
MXS_MONITOR* monitor;
} MYSQL_MONITOR;

16
server/modules/monitor/mysqlmon/mysql_mon.c
View File

@ -60,11 +60,15 @@ void check_maxscale_schema_replication(MXS_MONITOR *monitor);
static bool report_version_err = true;
static const char* hb_table_name = "maxscale_schema.replication_heartbeat";
static const char CN_FAILOVER[] = "failover";
static const char CN_FAILOVER_TIMEOUT[] = "failover_timeout";
static const char CN_FAILOVER[] = "failover";
static const char CN_FAILOVER_TIMEOUT[] = "failover_timeout";
static const char CN_SWITCHOVER[] = "switchover";
static const char CN_SWITCHOVER_TIMEOUT[] = "switchover_timeout";
/** Default failover timeout */
#define DEFAULT_FAILOVER_TIMEOUT "90"
/** Default switchover timeout */
#define DEFAULT_SWITCHOVER_TIMEOUT "90"
/**
* The module entry point routine. It is this routine that
@ -124,6 +128,8 @@ MXS_MODULE* MXS_CREATE_MODULE()
},
{CN_FAILOVER, MXS_MODULE_PARAM_BOOL, "false"},
{CN_FAILOVER_TIMEOUT, MXS_MODULE_PARAM_COUNT, DEFAULT_FAILOVER_TIMEOUT},
{CN_SWITCHOVER, MXS_MODULE_PARAM_BOOL, "false"},
{CN_SWITCHOVER_TIMEOUT, MXS_MODULE_PARAM_COUNT, DEFAULT_SWITCHOVER_TIMEOUT},
{MXS_END_MODULE_PARAMS}
}
};
@ -272,6 +278,8 @@ startMonitor(MXS_MONITOR *monitor, const MXS_CONFIG_PARAMETER* params)
handle->allow_external_slaves = config_get_bool(params, "allow_external_slaves");
handle->failover = config_get_bool(params, CN_FAILOVER);
handle->failover_timeout = config_get_integer(params, CN_FAILOVER_TIMEOUT);
handle->switchover = config_get_bool(params, CN_SWITCHOVER);
handle->switchover_timeout = config_get_integer(params, CN_SWITCHOVER_TIMEOUT);
bool error = false;
@ -331,6 +339,8 @@ static void diagnostics(DCB *dcb, const MXS_MONITOR *mon)
dcb_printf(dcb, "Failover:\t%s\n", handle->failover ? "Enabled" : "Disabled");
dcb_printf(dcb, "Failover Timeout:\t%u\n", handle->failover_timeout);
dcb_printf(dcb, "Switchover:\t%s\n", handle->switchover ? "Enabled" : "Disabled");
dcb_printf(dcb, "Switchover Timeout:\t%u\n", handle->switchover_timeout);
dcb_printf(dcb, "MaxScale MonitorId:\t%lu\n", handle->id);
dcb_printf(dcb, "Replication lag:\t%s\n", (handle->replicationHeartbeat == 1) ? "enabled" : "disabled");
dcb_printf(dcb, "Detect Stale Master:\t%s\n", (handle->detectStaleMaster == 1) ? "enabled" : "disabled");
@ -379,6 +389,8 @@ static json_t* diagnostics_json(const MXS_MONITOR *mon)
json_object_set_new(rval, "mysql51_replication", json_boolean(handle->mysql51_replication));
json_object_set_new(rval, CN_FAILOVER, json_boolean(handle->failover));
json_object_set_new(rval, CN_FAILOVER_TIMEOUT, json_integer(handle->failover_timeout));
json_object_set_new(rval, CN_SWITCHOVER, json_boolean(handle->switchover));
json_object_set_new(rval, CN_SWITCHOVER_TIMEOUT, json_integer(handle->switchover_timeout));
if (handle->script)
{