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.
To be able to do that, we need to get hold of the MXS_MONITORED_SERVER
corresponding to the SERVER specified as the new master.
So, instead of just return a boolean indicating whether the server was
found or not we return the MXS_MONITORED_SERVER pointer.
If the client sends data before authentication is complete, it must not be
discarded and it needs to be processed like as if it was sent in a
separate network packet.
Switchover expects one or two servers as argument, one (the new
master) if there is no master and two (the new master, and the
current master) if there currently is a master.
The procedure is as follows:
- Stop monitor
- Check that provided arguments are reasonable.
- If there is no master currently, then only one argument is
accepted.
- If there is a master, then it must also be specified.
This is to prevent pathological cases where the situation has
changed after the admin has issued the switchover command.
- Check the failover mode and disable it.
- Perform the failover.
- If succeeded, enable failover if it was.
- If it failed, if failover was enabled, do not enable it and log
an alert. If failover was not enabled, just log an error.
If a module command returns a json object, it will always be
returned to the caller, irrespective of whether the command
itself succeeded or not.
Otherwise, if the command failed and if the module command has
set an error message, that error message will be returned as a
json object containing the error message.
If a module command returns a json object, it will always be
returned to the caller, irrespective of whether the command
itself succeeded or not.
Otherwise, if the command failed and if the module command has
set an error message, that error message will be returned as a
json object containing the error message.
Since the module command interface was expanded to include a JSON output
parameter, there is no longer a need for an output DCB. As the JSON can be
printed by both maxadmin and the REST API, this allows the removal of
explicit output formatting in module commands.
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.
The yargs framework combined with the pkg packaging causes the executable
name to be mangled on installation. For this reason, the usage should be
explicitly added to each command.
The `failover` and `failover_timeout` parameters are now declared as a
part of the mysqlmon module. Changed the implementation of the failover
function so that the dependencies on the monitor struct can be removed or
moved into parameters.
Split the state change processing and failover handling into two separate
functions and added a call to the failover function into mysqlmon. This
prevents unintended behavior when failover is enabled for non-mysqlmon
monitors. The parameter itself still needs to be moved into mysqlmon.
Moved the failover documentation to the mysqlmon documentation as it is
specific to this monitor.
As the monitor event is now stored in the server, it can be re-used when
the event is converted to string form. This also fixes the problem of
state calculation taking place when the event happened in the past.
The failover command is simulated by executing a call to /usr/bin/echo
with all possible monitor parameters. This allows testing of the failover
mechanism without actually using the failover command.
The timestamp of the last change from passive to active is now
tracked. This, with the timestamps of the last master_down and master_up
events, allows detection of cases when MaxScale was failed over but the
failover was not done.
Currently, only a warning is logged if no new master has appeared within
90 seconds of a master_down event and MaxScale was set to active from
passive.
The last event and when the event was triggered is now shown for all
servers. The latest change from passive to active is also shown.
When an event occurs on a server, it is now stored so that the last event
for each server is known. This allows a state change to trigger an event
even if, at the time of the event, no action was taken.
This change is only cosmetic as no functionality is implemented.
The `passive` parameter can be given in the configuration file or on the
command line. It is displayed in the diagnostic output and changes to it
are persisted.
The variable itself does nothing.
The `script_timeout` and `journal_max_age` parameters weren't handled in
the monitor alteration code.
Also added missing documentation to maxadmin help output for
`alter monitor`.
When the database firewall filter is used in white-list mode,
'USE <db>' should be allowed. When connecting, it is always
possible to specify the database anyway so restricting
'USE <db>' serves no purpose.
