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MXS-1441 Add switchover_script parameter

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If a switchover_script parameter is given, its value will be used as
the switchover script. Otherwise the default will be used. Currently
just echo.

The MySQL Monitor now introduces two script variables, CURRENT_MASTER
and NEW_MASTER, that contain information about the current and new
master respectively.

Switchover is performed only if switchover has been enabled and MaxScale
is *not* in passive mode.
This commit is contained in:
Johan Wikman
2017-10-03 11:57:58 +03:00
parent 17c3d1e612
commit 267a45ad63
3 changed files with 168 additions and 54 deletions
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51
Documentation/Monitors/MySQL-Monitor.md
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@ -264,8 +264,55 @@ 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.
When switchover is iniated via the REST-API, the URL path looks as follows:
```
/v1/maxscale/mysqlmon/switchover?<monitor-instance>&<new-master>&<current-master>
```
where `<monitor-instance>` is the monitor section mame from the MaxScale
configuration file, `<new-master>` the name of the server that should be
made into the new master and `<current-master>` the server that currently
is the master. If there is no master currently, then `<current-master>`
need not be specified.
So, given a MaxScale configuration file like
```
[Cluster1]
type=monitor
module=mysqlmon
servers=server1, server2, server3, server 4
...
```
with the assumption that `server2` is the current master, then the URL
path for making `server4` the new master would be:
```
/v1/maxscale/mysqlmon/switchover?Cluster1&server4&server2
```
### `switchover_script`
*NOTE* By default, MariaDB MaxScale uses the MariaDB provided switchover
script, so `switchover_script` need not be specified.
This command will be executed when MaxScale has been told to perform a
switchover, either via MaxAdmin or the REST-API. The parameter should be an
absolute path to a command or the command should be in the executable path.
The user which is used to run MaxScale should have execution rights to the
file itself and the directory it resides in.
```
script=/home/user/myswitchover.sh current_master=$CURRENT_MASTER new_master=$NEW_MASTER
```
In addition to the substitutions documented in
[Common Monitor Parameters](./Monitor-Common.md)
the following substitutions will be made to the parameter value:
* `$CURRENT_MASTER` will be replaced with the IP and port of the current
master. If the is no current master, the value will be `none`.
* `$NEW_MASTER` will be replaced with the IP and port of the server that
should be made into the new master.
The script should return 0 for success and a non-zero value for failure.
### `switchover_timeout`