If the session command could not be routed, the log message should contain
the actual command that was routed. This makes failure analysis much
easier.
If a limit on the replication lag is configured, servers with unmeasured
replication lag should not be used. The code in question did use them even
when a limit was set as the value used for undefined lag was -1 which
always measured lower than the limit.
The charset sent in the handshake is now done with the following
priorities:
* First Master server
* Last Slave server
* First Running server or Down server whose charset is known
The change is that server in the Down state to which we've successfully
connected to can also be used as the charset source. This, in addition
with an "empty" default charset, helps avoid the use of the default latin1
charset unless absolutely necessary.
By logging the password hash when user authentication fails due to a
password mismatch, we can be certain what the client sent and what is the
currently stored value in MaxScale. This should not be on by default which
is why a new parameter is required.
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.
The code relied on last_read for the idle time calculation which caused
the pings that were written to not reset the idle time. This increased the
chance of multiple COM_PING packets being sent to a backend before a reply
was received.
The use of the server state is not transactional across multiple uses of
the function. This means that any assertions on the target state can fail
if the monitor updates the state between target selection and the
assertion.
The backend didn't expect AuthSwitchRequest packets in response to the
handshake response packets. This is allowed by the protocol and appears to
happen with at least MySQL 8.0.
The Connector-C was changed to always return only the client's charset,
not the actual charset that the connection ends up using. To cope with
this, the code has to use SQL to join the default character set name to
the default collation for it which can be used to extract the numeric ID
of the charset.
The slave backend would be closed twice if it would both respond with a
different result and be closed due to a hangup before the master
responded.
Added a test case that reproduced the problem.
If the client DCB of the session was passed into the function, it was
possible that the session pointer for it was already set to null. The
session pointer of an open DCB is never null but a client DCB's session
pointer can be null if accessed via the MXS_SESSION object.
By incrementing the counters when the session is created, we know that the
counter will always be decremented correctly. This does cause the listener
session to be counted as an actual session but this is already present in
the statistics calculations and is something we have to live with in 2.3
This change also makes it possible to overshoot the connection count
limitation as the session creation is delayed until authentication
fails. Both of these problems are fixed in 2.4.
The default database was not exposed in the warning that was logged when
authentication failed. The authentication uses the username, host and the
default database to find the user entry and the lack of the default
database made it hard to know for sure which user entry a client should've
matched against.
