Preparation for adding KILL syntax support.
Session id changed to uint32 everywhere. Added atomic op.
Session id can be acquired before session_alloc().
Added session_alloc_with_id(), which is given a session id number.
Worker object has a session_id->SESSION* mapping, not used yet.
Adds a server-specific parameter, "use_proxy_protocol". If enabled,
a header string is sent to the backend when a routing session connection
changes state to MXS_AUTH_STATE_CONNECTED. The string contains the real
client IP and port.
As 'client' is the fake DCB that emulates a client session,
poll.thread.id for the "dummy client" must be set to the current
thread_id that calls blr_start_master()
This affects both startup and START SLAVE (via mysql client)
When a prepared statement preparation is being routed to the master, the
response is now collected into one buffer before being sent back. This
allows proper processing of pipelined prepared statements.
The same operations of protocol state and inspections of the buffer were
done in multiple places. Combining these into one function removes the
duplicated code.
The backend MySQL protocol can now collect prepared statement preparation
responses as well as result sets. This removes the need to parse and
collect the preparation responses at the router level.
Removed pthread_self calls from the backend modules. This makes the debug
logging easier to parse when the messages aren't prefixed with the verbose
thread ID.
When responses are being tracked, the execution of a LOAD DATA LOCAL
INFILE requires special handling. The readwritesplit now has a simple
state machine for the handling of the LOAD DATA LOCAL INFILE command. This
should also make the code a bit more readable.
The readwritesplit didn't correctly process the response packets that
contained more than one part of a multi-result response. By processing the
packets in a loop, this problem is avoided.
Removed some of the more "unique" ways of sending error messages in favor
of simply writing the error to the client DCB. This removes the need for
extra logic in the clientReply response handling.
The functions used to track the resultset EOF packets now expose the
position of the end of the result set. This allows the modules that use
them to check if more results exist in the same buffer.
Added the status bits for OK and EOF packets to the mysql.h protocol
header. This can be used to check for various state changes that happen in
the session. Currently the status bits are only used to detect if more
results are expected.
When statement based routing was used, it was possible that the current
statement being executed wasn't properly updated. Readwritesplit requires
it to track whether a command will create a response.
When batched queries are done through readwritesplit, it will now handle
them one by one. This allows batched queries to be used with
readwritesplit but it does impose a performance penalty when compared to
direct execution on the backend.
Now possible to send a function and arguments to a specific worker
thread for execution.
In particular, this will be used for transferring the injection of
fake hangup events into DCBs, related to a particular server, from
the monitor thread to the worker threads, thus removing the need
for locks.
MXS_WORKER is an abstraction of a worker aka worker thread.
It has a pipe whose read descriptor is added to the worker/thread
specific poll set and a write descriptor used for sending messages
to the worker.
The worker exposes a function mxs_worker_post_message using which
messages can be sent to the worker. These messages can be sent from
any thread but will be delivered on the thread dedicated for the
worker.
To illustrate how it works, maxadmin has been provided with a new
command "ping workers" that sends a message to every worker, which
then logs a message to the log.
Additional refactoring are needed, since there currently are overlaps
and undesirable interactions between the poll mechanism, the thread
mechanism and the worker mechanism.
This is visible currently, for instance, by it not being possible to
shut down MaxScale. The reason is that the workers should be shut down
first, then the poll mechanism and finally the threads. The shutdown
need to be arranged so that a shutdown message is sent to the workers
who then cause the polling loop to exit, which will cause the threads
to exit.
That can be arranged cleanly by making poll_waitevents() a "method"
of the worker, which implies that the poll set becomes a "member
variable" of the worker.
To be continued.
A module can now declare a path parameter for a directory that does not
yet exist. If the directory does not exist, MaxScale will create the
directory with the requested permissions.
If a complete response is delivered in many buffers, then calling
gwbuf_length() whenever you need the complete size starts to hurt.
By caching the length of the data received sofar and by updating
the length in clientReply(), gwbuf_length() will be called exactly
once for each buffer(chain) delivered to routeQuery().
