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.
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.
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.
When log messages are written with both address and port information, IPv6
addresses can cause confusion if the normal address:port formatting is
used. The RFC 3986 suggests that all IPv6 addresses are expressed as a
bracket enclosed address optionally followed by the port that is separate
from the address by a colon.
In practice, the "all interfaces" address and port number 3306 can be
written in IPv4 numbers-and-dots notation as 0.0.0.0:3306 and in IPv6
notation as [::]:3306. Using the latter format in log messages keeps the
output consistent with all types of addresses.
The details of the standard can be found at the following addresses:
https://www.ietf.org/rfc/rfc3986.txthttps://www.rfc-editor.org/std/std66.txt
The readwritesplit now sends COM_PING queries to backend servers that have
been idle for too long. The option is configured with the
`connection_keepalive` parameter.
The static module capabilities are now used to query the capabilities of
filters and routers. The new RCAP_TYPE_NOAUTH capability is also taken
into use. These changes removes the need for the `is_internal_service`
function.
The static capabilities declared in getCapabilities allows certain
capabilities to be queried before instances are created. The intended use
of this capability is to remove the need for the `is_internal_service`
function.
The routers no longer need to track the number of errors each DCB
receives. This is now done by the protocol modules.
The type of the DCB no longer needs to be checked in the handleError
implementation as the function is only called when a backend DCB fails.
Altered the function to assert that the DCB is a backend DCB in addition
to the existing assertions for non-NULL backend reference on function
return.
Move the fetching of the backend reference after the type of the DCB is
inspected in handleError. This removes the need to handle the case where
the returned bref is NULL and the DCB is a client DCB.
The highwater and lowwater callbacks were never registered for the client
DCBs in the binlogrouter.
The DCB hangup callbacks were never called by the core and were replaced
with fake hangup events in an earlier version.
Removed unused spinlocks from DCBs, sessions and the MySQL protocol
structs. They were used in a context where only one thread has access to
the structure.
Removed unused member variables from DCBs.
The combination of the default values of `disable_sescmd_history=false`
and `max_slave_connections=100%` does not make sense as it is not possible
to find a replacement slave in case an active one fails.
Moved some typedefs to router.h and server.h, changed a few
constants to these enums. Renamed some types in config.h to
remove "Gateway".
There are still some functions in the public header which are
only used in core, but they seem to fit the theme of public functions
so were not moved.
handleError can detect READ ONLY transaction set when problem_dcb ==
rses->forced_node->bref_dcb.
Session will be closed and rses->forced_node set to NULL
All modules now declare a name for the module. This is name is added as a
prefix to all messages logged by a module. The prefix should help
determine which part of the system logs a message.
The parameters that readwritesplit uses now use the new system. This
removes the need for the qualified parameter processing found in config.c.
All values for router_options are now also accepted as parameters. The
router_options is deprecated and support for it will be removed in a
future version.
The MXS_MODULDE object now contains optinal pointers for functions
to be called att process and thread startup and shutdown. Since the
functions were added to the end, strictly speaking, all structures
would not have needed to have been modified, but better to be
explicit. In a subsequent change, these will be called.
C++ does not support flexible arrays, so for the time being C++
modules are restricted to 10 parameters. Better approach is to
factor out the parameters to a separate array and then just store
a pointer to that array in MXS_MODULE.
The variables now use the actual option and parameter names. This should
help make the code more readable and easier to understand in relation to
the used options.
The MODULE_INFO is now the main object which is used by modules to convey
information to the MaxScale core. The MXS_MODULE name is more apt as it
now contains the actual module definition.
The old MODULES structure was moved into load_utils.c as an internal
implementation and was renamed so that it is not confused with the new
MODULE structure.
The modules are now declared with a common macro. This allows future
additions to the module loading process while also making the loaded
symbol name a constant.
This allows modules to only expose one entry point with a consistent
signature. In the future, this could be used to implement declarations of
module parameters.
If a slave fails while a non-critical read is being executed, the read is
retried on a different server. This is controlled by the new
`retry_failed_reads` option.
Only selects done that are done outside of a transaction and with
autocommit enabled are retried.
When a DCB error occurs, the handleError entry point of the routers is
called. The caller of this entry point expects that the error handler
marks the DCB as handled. The aforementioned behavior is wrong as the
error handler should not keep track of whether the handler was already
called.
Closing the DCB and the backend reference that uses it at the same time
makes the error handling code clearer and removes some of the assumptions
that the code made. It will cause the DCB to be closed in multiple places
but the logic of why a DCB is being closed is more visible from the code.
This change should remove all cases where a DCB is closed without a
tightly coupled backend reference.
If the `error_on_write` mode is used when a master loses the master state,
the backend would not get closed. This would allow masters that appear
back to be used which is not intended.
Added a check for the validity of the backend DCBs before they are
closed. This should guarantee that only valid DCBs are closed by
readwritesplit.
However, this is not the correct solution for the problem. The DCB should
not be in an invalid state in the first place and this fix just removes
the bad side effects of the double closing.
With the added logging in the readwritesplit error handler, more detailed
information should become available.
If a DCB is passed to the error handler for which we cannot find the
corresponding backend reference, it should not be closed.
Added extra logging for situations where the backend reference can't be
found or it is in the wrong state.
