The check for rotate event conditions was wrong which led to false error
message about unexpected binlog file and position combinations.
The position of the last event was reset every time a file was opened which
caused problems when the binlog file was rotated. The slave's current positions
were compared to the position where the last event started and because the
last_event_pos variable didn't point to the rotate event of the previous binlog,
the slave's never got the rotate event.
The name of the binlog file was added to the log message where a slave
is behind the master but the same file is used. This makes debugging the problem
a bit easier.
The decision to send an event to a slave can now only be made in one place.
This will force all events to pass the same checks before they are sent to
the slaves.
The position of the next event to be written was used as the position
of the current event. This caused the checks for the position of the current
safe event to fail and the non-transaction safe version was used.
This only happened with events that are not done inside a transaction i.e.
DDL statements.
The message is logged when a DDL statement is executed. It should not be
logged if trx_safe is on since the current_safe_event should always point
at the event we are sending. The current_safe_event is set to the wrong value
which causes this message to be logged.
Due to the false positives caused by this, the message is removed.
The message now states the location where it was called from and the amount
of events received from the master. In addition to this, new logging was
added when unsafe events are sent to slaves when transaction safety is enabled.
The duplicate event error message now logs the length of the slave's
write queue. This will tell how much data is still buffered inside MaxScale
when duplicate events are detected.
If a duplicate event is detected the state of the slave is set
to BLRS_ERRORED and the connection is closed. That way the
duplicate event will not break the slave, and it will pick
up its state when it reconnects.
When an event is sent to a slave, we store information about the
event and who sent it, so that we can detect if the same event is
sent twice. If a duplicate event is detected, we log information
about it.
If transaction safety was disabled and a large event sent in multiple SQL
packets was received, the distribution of that event to the slaves would fail.
The empty packet sent after a large event which fits into exactly one packet
was written to disk and the writing of no bytes caused it to be treated as
an error.
The router->last_written is used to store the position where the last event was
written. The replication header is also stored in a separate structure in
the router which is used later when the last packet of a multi-packet event
arrives.
In blr_slave_callback the bits of slave->cstate are reset and
set as one transaction. Earlier they were reset in one and
set in another, leading to a situation where slave->cstate did
not contain a sensible value for a short period of time.
Further, it is now explicitly checked in blr_distribute_binlog_record
that slave->cstate indeed contains a meaningful value.
The unsafe slave position is no longer an error and will be treated the
same way if no events are available i.e. the slaves are no longer disconnected.
The log messages now have more information such as the current committed
transaction event being processed and the number of events sent by the
current thread.
Changed burst_size to long instead of unsigned long.
This way check burst_size > 0 is now effective.
Setting "burstsize" option in router_options may be required.
i.e.: burstsize=10M
Slave request for a log_pos behind binlog file size may result in a
disconnection or replication error:
if binlog file is latest one slave get disconnected otherwise an error
message is returned and replication stops
The binlog file is now always opened when it is needed and closed
when we are finished with it. That will remove any potential
file concurrency issues between different threads dealing with
the same slave.
