Currently the state change explanations are only added to mariadbmon. They
are less relevant for Galera clusters as they themselves explain why they
change their states but should still be added to make them easier to
analyze.
The event that isn't explained and is most often encountered is the loss
of a Slave status. Most often the loss of a Slave status happens because
either the IO thread or the SQL thread has stopped. Printing the states of
the threads as well as the latest error should hint at what caused the
outage.
The information can be added to the REST API in 2.5 where the monitors can
add extra information to the server JSON.
During switchover/failover, server events are altered. The ALTER
EVENT command automatically modifies the event charset and collation
to the values of the connetion running the query. This may cause
the event to become invalid.
Fixed this by changing connection charset and collation to the ones
in the event description just before altering it.
The mon_ping_or_connect_to_db resets the MYSQL handle which caused the
loss of the error message. Returning a new enumeration value for
authentication errors solves this problem.
Now properly checks if configuration and diagnostics functions are ran in either
main() or in the admin worker. This is useful for debugging and enforcing
thread safety.
Also, monitors are now started and stopped in the admin worker.
By having a separate FINISHED state and a STOPPED state, it is possible to
know at which point in the worker's lifetime an event is done. Posting of
messages before a worker is started is allowed but posting them after the
worker has stopped is not.
This fixes avrorouter related failures and all other failures that stem
from worker messages being ignored at startup.
The command script is now stored in string form. Substitution is performed
using normal string methods instead of regular expressions, since all used
substitutions are simple string replacements. Tokenization is performed after
substitution.
