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.
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.
If a query is interrupted that was sent to the master, it is now
retried. This allows all autocommit queries to be transparently retried if
the server in question fails.
Now that the readwritesplit uses the same mechanism for both
retry_failed_reads and delayed query retries, the re-routing function
should accept a delay of 0 seconds. This makes the mechanism more suitable
for other uses e.g. delaying of queries in filters.
This is a proof-of-concept that validates the query retrying method. The
actual implementation of the query retrying mechanism needs more thought
as using the housekeeper is not very efficient.
A member variable and local variable had the same names which caused the
member variable to not be used. With the change in the member variable,
this went unnoticed.
Keeping track of the closed state of the session inside the router session
itself is not needed as the MaxScale core should already do that.
The skygw_chk_t variables are rather meaningless and are obsoleted by
Valgrind/ASAN.
Most of the funtionality is now a member function of either the RWSplit or
RWSplitSession class. This removes the need to pass the router and session
parameters to all functions.
Moved the RWBackend class implementation into its own file. Made some of
the command type functions a part of the <maxscale/protocol/mysql.h>
header to make it reusable.
The `master_reconnection` parameter now controls both the reconnection of
the master server as well as the migration of the master server to another
server. Although these two cases appear to be different, the end result
from readwritesplit's point of view is the same and are thus controlled
with the same parameter.
The RWBackend class now resets its internal state when it is closed. This
allows readwritesplit to handle the case when a result was expected from
the master but the master died before the result was returned. The same
code should also handle slave connection failures mid-result, allowing
Backend reuse.
Added a test case that verifies the new functionality when combined with
`master_failure_mode=error_on_write`.
Provides a clearer separation between what deals with query
classification and what deals with query routing.
Functions have only been moved. No other cleanup has been
done.
The result collection did not reset properly when a non-resultset was
returned for a request. As collected result need to be distinguishable
from single packet responses, a new buffer type was added.
The new buffer type is used by readwritesplit which uses result collection
for preparation of prepared statements.
Moved the current command tracking to the RWBackend class as the command
tracked by the protocol is can change before a response to the executed
command is received.
Removed a false debug assertion in the mxs_mysql_extract_ps_response
function that was triggered when a very large prepared statement response
was processed in multiple parts.
Inlined the getter/setter type functions that are often used. Profiling
shows that inlining the RWBackend get/set functions for the reply state
manipulation reduces the relative cost of the function to acceptable
levels. Inlining the Backend state function did not have as large an
effect but it appears contribute a slight performance boost.
The result processing code did unnecessary work to confirm that the result
buffers are contiguous. The code also assumed that multiple packets can be
routed at the same time when in fact only one contiguous result packet is
returned at a time.
By assuming that the buffers are contiguous and contain only one packet,
most of the copying and buffer manipulation can be avoided.
If a prepared statement sends large amounts of data, the target server
where the data is sent will be tracked. The tracked target was not reset
after a multi-packet query was completed and the target itself was used to
check whether the session was processing a multi-packet query.
Changed the check to use the boolean variable instead of the target and
added a reset of the tracked target after a multi-packet query was
completed.
The EOF packet calculation function in modutil.cc didn't handle the case
where the payload exceeded maximum packet size and could mistake binary
data for a ERR packet.
The state of a multi-packet payload is now exposed by the
modutil_count_signal_packets function. This allows proper handling of
large multi-packet payloads.
Added minor improvements to mxs1110_16mb to handle testing of this change.
