Readwritesplit had redundant parameter values in the
`router_diagnostics`. All module parameters with their current values are
already displayed in the `parameters` member of the resource.
The router did not take large packets into account when determining
whether the server will respond. This caused the response counts to be off
by one for all large packets.
The creation of the EOF packet is not needed as the last packet of a
result set is always guaranteed to be of the correct type. This also
allows non-resultsets to be correctly processed as the internal packet
number will be at 0 when the last result arrives.
Cleaned up some of the function names and changed the signatures to be
better suited for their use-cases.
Use angle bracket includes, combine some of the more unwieldly
conditionals into functions, added more comments.
The resultset processing for MySQL requires some extra work as it lacks
the proper SERVER_MORE_RESULTS_EXIST flag in the last EOF packet. Instead,
the first EOF packet has the SERVER_PS_OUT_PARAMS flag which needs to be
interpreted as a SERVER_MORE_RESULTS_EXIST flag for the second EOF packet.
Also corrected the EOF packet handling to do the flag checks in the code
that deals with the EOF packets.
As the modutil_state parameter is now used for more than large packet
tracking, the correct solution is to store this state object in the
readwritesplit session instead of interpreting it to a boolean value.
Added the `transaction_replay_max_size` parameter that controls the
maximum size of a transaction that can be replayed. If the limit is
exceeded, the stored statements are released thus preventing the
transaction from being replayed.
This limitation prevents accidental misuse of the transaction replaying
system when autocommit is disabled. It also allows the user to control the
amount of memory that MaxScale will use.
The transaction retrying behavior is now configurable and documented. The
`transaction_replay` parameter implicitly enables the required
functionality in the router that it needs.
As the current query was added to the transaction log before it finished,
the m_current_query contained a duplicate of the latest transaction log
entry. To correctly log only successful transactions, the statement should
be added only after it has successfully completed. This change also
removed the unnecessary cloning that took place when the statement was
added to the log before it finished.
With the fixed transaction logging, the value of m_current_query can be
stashed for later retrying while the replay process is happening. If the
replay completes successfully and the checksums match, the interrupted
query is retried.
Also added a clarifying comment to can_retry_query to explain why a query
inside a transaction cannot be retried.
Added the initial implementation of transaction replay. Transactions are
only replayed if the master fails when no statement is being executed.
The validity of the replayed transaction is done by verifying that the
checksums of the returned results are equal.
Added a close function into the Trx class to make resetting its state
easier. Also changed the return type of the pop_stmt to GWBUF* as the
places where it is used expect a raw GWBUF pointer.
The queries that make up the transaction are now stored in the router
session while the transaction is in progress. For the time being, the
queries are only used to log extra information about the transaction
contents.
Readwritesplit now calculates checksums for all successful and failed
transactions. This checksum is not of any practical use until the
transaction replaying is implemented.
Fixed string truncation warnings by reducing max parameter lengths by one
where applicable. The binlogrouter filename lengths are slightly different
so using memcpy to work around the warnings is an adequate "solution"
until the root of the problem is solved.
Removed unnecessary CMake policy settings from qc_sqlite. Adding a
self-dependency on the source file of an external project has no effect
and only caused warnings to be logged.
Large session commands weren't properly handled which caused the router to
think that the trailing end of a multi-packet query was actually a new
query.
This cannot be confidently solved in 2.2 which is why the router session
is now closed the moment a large session command is noticed.
Only commands that can contain an SQL statements should be stored for
retrying (COM_QUERY and COM_EXECUTE). Other commands are either session
commands or do not work with query retrying.
Worker is now the base class of all workers. It has a message
queue and can be run in a thread of its own, or in the calling
thread. Worker can not be used as such, but a concrete worker
class must be derived from it. Currently there is only one
concrete class RoutingWorker.
There is some overlapping in functionality between Worker and
RoutingWorker, as there is e.g. a need for broadcasting a
message to all routing workers, but not to other workers.
Currently other workers can not be created as the array for
holding the pointers to the workers is exactly as large as
there will be RoutingWorkers. That will be changed so that
the maximum number of threads is hardwired to some ridiculous
value such as 128. That's the first step in the path towards
a situation where the number of worker threads can be changed
at runtime.
The commands needs to be handled separately from the rest of the result
types.
Added a test case that reproduces the problem and verifies that the change
in code fixes it.
When a LOAD DATA LOCAL INFILE finishes, the client sends an empty
packet. The second case when the client sends an empty packet when the
previous packet was exactly 0xffffff bytes long. These two packets were
confused which caused the internal state to temporarily flip from inactive
to ending and back to inactive.
The aforementioned flip-flopping didn't have any practical differences but
it was caught by a debug assertion.
Only servers that qualify to be connected should be considered as
candidate servers. This triggered a debug assertion when a slave server
failed to execute a session command but it was chosen as a candidate
server later on.
The COM_STMT_FETCH command will create a response. This was a
readwritesplit-specific interpretation of the command and it was wrong.
Also record the currently executed command event for session commands.
Readwritesplit would not handle multiple overlapping COM_STMT_EXECUTE
commands properly if they opened cursors. This was due to the fact that
the result would not be marked as complete and COM_STMT_FETCH commands
were executed as if they did not return results.
The correct implementation is to consider a COM_STMT_EXECUTE that opens a
cursor complete only when the first EOF packet is read (that is, when the
resultset header is read). This allows subsequent COM_STMT_FETCH commands
to be handled separately.
The separate COM_STMT_FETCH handling must count the number of packets that
are being fetched. This allows correct tracking of the state of a
COM_STMT_FETCH by checking that the number of packets is correct or the
second EOF/ERR packet is read.
When a LOAD DATA LOCAL INFILE is actively rejected by the server, the
server sends an error to the client. This error was not detected and the
router was stuck in the special mode that handles LOAD DATA LOCAL INFILE.
The state could be factored out into a boolean variable as the reply
processing can be in two states: Either waiting for the response to
MASTER_GTID_WAIT or updating packet numbers.
The packet number updating can always be done as long as a buffer is
available. The discard_master_wait_gtid_result function discards the OK
packet before the packet numbers are updated so any trailing packets get
corrected properly.
