This makes the code clearer and reduces race conditions, as the monitor
could be writing SERVER->status while a router is reading it. Also,
the time during which the SERVER struct is locked drops to a fraction.
Since monitors are now freed at MaxScale exit, the server data should be freed. Also,
gtid domain variables are now initialized with a common constant.
StartMonitor() now takes a MXS_MONITOR_INSTANCE and returns
true, if the monitor could be started and false otherwise.
So, the setup is such that in createInstance(), the instance
data is created and then using startMonitor() and stopMonitor()
the monitor is started/stopped. Finally in destroyInstance(),
the actual instance data is deleted.
CreateInstance() (renamed from initMonitor()) and destroyInstance()
(renamed from finishMonitor()) have now tentatively been
implemented for all monitors.
Next step is to
1) change the prototype of startMonitor() to
bool (*startMonitor)(MXS_SPECIFIC_MONITOR*,
const MXS_MONITOR_PARAMETER*);
and assume that mon->handle will always contain the
instance,
2) not delete any data in stopMonitor(),
3) add monitorCreateAll() that calls createInstance() for all
monitors (and call that in main()), and
4) add monitorDestroyAll() that calls destroyInstance() for
all monitors (and call that in main()).
The master down verification through slaves won't work with this commit. It needs to be
redesigned to handle multiple slave connections or removed. Also, only the first row of
slave status data is used by the monitor, so multiple slave connections are still
incorrectly handled.
Autoselection is allowed for current master only, or both current and new master.
Autoselection is not allowed for just the new master.
Also, do_switchover() writes to its parameters when autoselecting for
better error messages.
The old hkheartbeat variable was changed to the mxs_clock() function that
simply wraps an atomic load of the variable. This allows it to be
correctly read by MaxScale as well as opening up the possibility of
converting the value load to a relaxed memory order read.
Renamed the header and associated macros. Removed inclusion of the
heartbeat header from the housekeeper header and added it to the files
that were missing it.
MASTER_GTID_WAIT uses gtid_slave_pos when comparing to the target gtid. This creates
problems with multi-domain gtids. It's simpler to just query the server for its
gtids repeatedly. Also, the method is now in MariaDBServer.
Renamed the two gtid-classes to better match MariaDB documentation. One
domain-server-sequence-combination is now a "Gtid", as these identify
a transaction. A "GtidList" contains a list of Gtid:s for handling multi-domain
server variables composed of multiple comma separated Gtid:s.
Removed unused methods and renamed some existing ones. Moved the Gtid-code
to its own file.
The operations between Gtid:s are now more complicated so the class implements
them instead of the monitor. The Old Gtid-container has been renamed
GtidTriplet, and only stores the values for one triplet.
Also, the QueryResult integer reading method now only reads non-negative integers
since the server rarely returns negative values. This frees negative values for
indicating parsing error(s).
Gtid-class was moved back to utility.hh/.cc because the QueryResult-class requires it.
Renamed to MariaDBServer. The objects have a pointer to the underlying
MXS_MONITORED_SERVER. The purpose is to have the monitor mainly use
MariaDBServer instead of the current mix of MXS_MONITORED_SERVER* and
MySqlServerInfo and to simplify the mapping between the two. Also,
many methods can be moved to the MariaDBServer class later on.
Some functions have been converted from MXS_MONITORED_SERVER* to
MariaDBServer.
In theory, the value of m_master could change between reading it to
local variable and stopping monitor. To be on the safe side, stop the
monitor first.
1. Move some remaining class data private.
2. Linebreak long lines.
3. Move current master autoselection inside class method.
4. Remove single-use constant #defines.
5. Monitor status is only written inside loop.
