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.
When servers were added to monitors that were created at runtime, the
server list serialization overwrote the original persisted configuration
of the monitor. To solve this problem, the serialization of the server
list and the monitor parameters were combined.
When binary data was processed, it was possible that the values were
misinterpreted as OK packets which caused debug assertions to trigger.
In addition to this, readwritesplit did not handle the case when all
packets were routed individually.
The authentication phase expects full packets. If the packets aren't
complete a debug assertion would get hit. To detect this, the result of
the extracted buffer needs to be checked.
If multiple queries that only generate OK packets were executed, the
result returned by the server would consist of a chain of OK packets. This
special case needs to be handled by the modutil_count_signal_packets.
The current implementation is very ugly as it simulates a result with at
least one resultset in it. A better implementation would hide it behind a
simple boolean return value and an internal state object.
A multi-statements can return multiple resultsets in one response. To
accommodate for this, both the readwritesplit and modutil code must be
altered.
By ignoring complete resultsets in readwritesplit, the code can deduce
whether a result is complete or not.
The original offset needs to be separately tracked to assert that an OK
packet is not the first packet in the buffer. The functional offset into
the buffer is modified to reduce the need to iterate over buffers that
have already been processed.
When LEAST_BEHIND_MASTER routing criteria was used, the info level logging
function would fall through to the default case. In debug builds, this
would trigger a debug assertion.
Returning the results of a query as a set of packets is currently more
efficient. This is mainly due to the fact that each individual packet for
single packet routing is allocated from the heap which causes a
significant loss in performance.
Took the new capability into use in readwritesplit and modified the
reply_is_complete function to work with non-contiguous results.
The GLIBC backtrace functionality doesn't generate file names and line
numbers in the generated stacktrace. This can to be done manually by
executing a set of system commands.
Conceptually doing non-signal-safe operations in a signal handler is very
wrong but as stacktraces are only printed when something has gone horribly
wrong, there is no real need to worry about making things worse.
As a safeguard for fatal errors while the stacktrace is being generated,
it is first dumped into the standard error output of the process. This
will function even if malloc is corrupted.
When the router requires statement based output, the gathering of complete
packets can be skipped as the process of splitting the complete packets
into individual packets implies that only complete packets are handled.
Also added a quicker check for stored protocol commands than a call to
protocol_get_srv_command.
The backend protocol command tracking didn't check whether the session was
the dummy session. The DCB's session is always set to this value when it
is put into the persistent pool.
If a query was processed in the client protocol module when a prepared
statement was being executed by the backend module, the current command
would get overwritten. This caused a debug assertion in readwritesplit to
trigger as the result was neither a single packet nor a collected result.
The RCAP_TYPE_STMT_INPUT capability guarantees that a buffer contains a
complete packet. This information can be used to track the currently
executed command based on the buffer contents which allows asynchronicity
betweent the client and backend protocol. In practice this only comes in
play when routers queue queries for later execution.
