Given the assumption that queries are rarely 16MB long and that
realistically the only time that happens is during a large dump of data,
we can limit the size of a single read to at most one MariaDB/MySQL packet
at a time. This change allows the network throttling to engage a lot
sooner and reduces the maximum overshoot of throtting to 16MB.
Some SQL clients may default to a different authentication plugin than
"mysql_native_password". Since this is the only one supported by MySQL-
authenticator, the client is instructed to swap its plugin.
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.
The prefix was always added even when the original version would've been
acceptable. For example, a version string of 5.5.40 would get converted to
5.5.5-5.5.40 which is quite confusing for older client applications.
Minor renaming of the session state enum values. Also exposed the session
state stringification function in the public header and removed the
stringification macro.
Allocating the session before a DCB guarantees that at no point will a DCB
have a null session. This further clarifies the concept of the session and
also allows the listener reference to be moved there.
Ideally, the session itself would allocate and assign the client DCB but
since the Listener is the only one who does it, it's acceptable for now.
As each connection now immediately gets a session the dummy session is no
longer required. The next step would be to combine parts of the session
and the client DCB into one entity. This would prevent the possibility of
a client DCB with no associated session. Backend DCBs are different as
they can move from one session to another when the persistent connection
pool is in use.
Whenever a client DCB is accepted, a session for it is allocated. This
simplifies the handling of shared data between DCBs by allowing it to be
placed inside the session object. Currently, the data is stashed away in
the client DCB.
By doing the actual accepting of the new DCB in the core, the protocol
modules can only do the actual protocol level work. This removes some of
the redundant code that was in the protocol modules.
Allocating DCB with new allows the use of C++ objects in the DCB
struct. Also the explicit poll field can be replaced by inheriting from
MXB_POLL_DATA.
Modified the functions to use a listener instead of a DCB in the accepting
process. This removes some of the dependenices that the listeners have on
the DCB system.
If the client sends two different sets of capability bits during the
authentication phase of an SSL enabled connection, both sets need to be
combined. This prevents capabilities from degrading mid-connection which
is the case when Oracle Connector/J drops the SSL capability bit
mid-authentication.
If the service doesn't require collection of complete packets, the user
reauthentication done with COM_CHANGE_USER would be skipped. This caused
the change_user test to fail.
By temporarily switching to full packet collection mode for the duration
of the COM_CHANGE_USER, we avoid duplicating the code for the streaming
router types.
If the initial handshake that is sent by the accepting thread is buffered,
the subsequent flushing of it is done by the owning thread. As
cross-thread buffer usage is not allowed, the initial handshake must be
sent by the owning thread.
