There is a race condition between the addition of the DCB into epoll and
the execution of the event that initiates the protocol pointer for the DCB
and sends the handshake to the client. If a hangup event would occur
before the handshake would be sent, it would be possible that the DCB
would get freed before the code that sends the handshake is executed.
By picking the worker who owns the DCB before the DCB is placed into the
owner's epoll instance, we make sure no events arrive on the DCB while the
control is transferred from the accepting worker to the owning
worker.
When poll_add_dcb was called for a DCB that once was polling system but
was subsequently removed, the DCB would appear twice in the worker's list
of DCBs. This caused a hang when the DCB was the last one in the worker's
list and dcb_foreach_local would be called.
To prevent the aforementioned problem, the DCBs are now added and removed
directly to and from the workers instead of indirectly via poll_add_dcb
and poll_remove_dcb.
If the connection to the master is lost, knowing what type of an error
caused the call to handleError helps deduce what was the real reason for
it. Logging the idle time of the connection helps detect when the
wait_timeout of a connection is exceeded.
If the session doesn't match the required username or remote address, the
match data is not allocated. This also doubles as a replacement of the
active member variable.
The code used a rather questionable method for parsing SQL statements
instead of using the query classifier for detecting transaction start and
stop events.
The previous main routing worker is now run in a separate thread.
Next step is to treat all routing workers in an identical fashion.
MainWorker is not yet used for anything, but in a subsequent change
the old housekeeper functionality will be moved in top of MainWorker.
First step in the introduction of a MainWorker. When finished, all
routing workers will run in separate threads (currently one runs in
the main thread), and the main worker run in the main thread.
Housekeeper will disappear and to the extent housekeeping tasks are
needed (where applicable they will be changed into delayed calls)
they will be run by the main worker.
Most of the ones still remaining outside are special cases.
Also, removed locking from status manipulation functions as it
has not been required for quite some time.
