The service now uses a std::vector<SFilterDef> to store the filters it
uses. Most internal parts deal with the SFilterDef but debugcmd.cc still
moves raw pointers around (needs to be changed).
The function has use outside of the monitors as it makes execution of
worker tasks much more convenient. Currently, this change only moves the
code and takes it into use: there should be no functional changes.
Uses mostly the status functions for reading the flags. Strickly
speaking this breaks the REST API since in some cases (status combinations)
the printed string is different from what was printed before.
The signal handler no longer acquires the service list lock which removes
a number of deadlock possibilities from the shutdown process. Instead, a
global shutdown flag is set that serves the same purpose as the individual
service shutdown flags did.
The cache now enforces the defined maximum size by evicting some
entries in case the insertion of a new entry would cause the max
size to be exceeded. Currently the eviction algorithm simply
removes a random element.
The result set mechanism was ill-suited for iteration over
lists. Converting it into a class and inverting it by pushing rows into
the result set instead the result set asking for rows makes it very easy
to use with lists. It also solves some of the consistency problems that
existed with the previous implementation.
The monitor can now differentiate between slaves with a running
series of slave connections to the master from slaves with broken
links. Both still get the SERVER_SLAVE-flag if 'detect_stale_slave'
is on.
Also, relay servers must be running.
Data can now be stored on thread-local storage of the worker. By acquiring
a unique handle from the worker, a module can store a thread-local
value.
This functionality will be used to store configurations that are sometimes
updated at runtime but are largely read-only. By avoiding shared data
altogether, performance is not affected. The only synchronization that is
done is on update.
Also added a helper functions for broadcasting tasks on all routing
workers. With the old mxs_rworker_broadcast_message function, if a
function call was broadcasted it was always queued for execution. The
mxs_rworker_broadcast will immediately execute the task on the local
worker and queue it for execution of other routing workers.
Converted the internal service header to a C++ header and moved all
functions there that are for internal use only.
Added the new Service type that inherits the SERVICE struct. This is to
distinct the opaque external C interface from the C++ internals.
The filter implementation is now fully hidden. Also converted it to a C++
struct allocated with new and stored the filters in a global list instead
of embedding the list in the object itself.
When a session is closed, it releases a reference on the service and
checks if it was the last session for a destroyed service. The state of
the service was loaded after the reference count was decremented. This
behavior introduced a race condition where it was possible for a service
to be freed twice, first by the thread that marked the service as
destroyed and again by the last session for that service. By always
loading the service state before decrementing the reference count, we
avoid this race condition.
Currently, the memory ordering used for the reference counting is too
strict and could be relaxed. By default, all atomic operations use
sequentially consistent memory ordering. This guarantees correct behavior
but imposes a performance penalty. Incrementing the reference counts could
be done with a relaxed memory order as long as as we know the reference
we're incrementing is valid. Releasing a reference must use an
acquire-release order to guarantee the read-modify-write operation is
successful.
The initialization and starting of the housekeeper is now done
separately. This allows housekeeper tasks to be created when the services
are being created while still preventing the execution of the task before
the startup is complete.
Services can now be destroyed if they have no active listeners and they
are not linked to servers. When these conditions are met, the service will
be destroyed when the last session for the service is closed.
The closing of a service will close all listeners that were once assigned
to the service. This allows closing of the ports at runtime which
previously was done only on shutdown.
Exposed the command through the REST API but not through MaxAdmin as it is
deprecated.
When the query queue does not contain a complete packet
(i.e. modutil_get_next_MySQL_packet return NULL), an informative dump of
how many bytes and what is stored is logged.
By aborting the process if memory runs out when a buffer needs to be made
contiguous, we rule out other, more subtle, errors. Failing as soon as a
possible when memory allocation fails gives better error messages.
The LocalClient micro-client required a reference to the session that was
valid at construction time. This is the reason why the previous
implementation used dcb_foreach to first gather the targets and then
execute queries on them. By replacing this reference with pointers to the
raw data it requires, we lift the requirement of the orignating session
being alive at construction time.
Now that the LocalClient no longer holds a reference to the session, the
killing of the connection does not have to be done on the same thread that
started the process. This prevents the deadlock that occurred when
concurrect dcb_foreach calls were made.
Replaced the unused dcb_foreach_parallel with a version of dcb_foreach
that allows iteration of DCBs local to this worker. The dcb_foreach_local
is the basis upon which all DCB access outside of administrative tasks
should be built on.
This change will introduce a regression in functionality: The client will
no longer receive an error if no connections match the KILL query
criteria. This is done to avoid having to synchronize the workers after
they have performed the killing of their own connections.
The dcb_foreach function is not safe to use from multiple threads at the
same time. This should be asserted by checking that the function is called
only from the main worker.
The addition of this assertion also implies that only administrative
operations should use the dcb_foreach function. To accommodate this
change, the KILL command iteration needs to be adjusted.
MariaDBMonitor diagnostics printing is unsafe as some of the read
fields are arrays. To be on the safe side, the fields are now read
in the monitor worker thread.
Since diagnostics must work even for stopped monitors, a worker task
is used. In practice, it usually runs when the monitor is sleeping.
With the removal of the old session command implementation, the code that
used it can be removed or replaced with newer constructs. As a result, the
backend protocol no longer does any session command processing.
The three buffer types, GWBUF_TYPE_SESCMD_RESPONSE,
GWBUF_TYPE_RESPONSE_END and GWBUF_TYPE_SESCMD as well as their related
macros are no longer used and can be removed.
The test cases allocated servers in a way that doesn't comfortably suit
the way the servers are now allocated. Adding a helper C++ class to load
module defaults makes it easier to do explicit server initialization in
tests.
The binlogrouter was also fixed in this commit as it uses servers much
like a test would use.
The configuration system that modules use allows the SSL parameter
validation to be simplified. It should also provide more consistent error
messages for similar types of errors.
The SSL_LISTENER initialization is now done in one step. There was no good
reason to do it in two separate steps for listeners but in one step for
servers.
The `ssl` parameter now also accepts boolean values. As the parameter
behaves like a boolean and looks like a boolean, it ought to be a
boolean. It still accepts the custom `required` and `disabled` values
simply for backwards compatibility.
Also added the missing freeing functions for the SSL_LISTENER type. This
prevents failed SSL_LISTENER creations from leaking memory.
The same mechanism that is used for modules can be used for the
configuration of the core objects. This removes the need for the redundant
code that validates various values that is already present in the code
that modules use.
Relaced router_options with configuration parameters in the createInstance
router entry point. The same needs to be done for the filter API as barely
any filters use the feature.
Some routers (binlogrouter) still support router_options but using it is
deprecated. This had to be done as their use wasn't deprecated in 2.2.
The mxs::strtok function splits a string into a vector of strings based on
a set of delimiters. The function makes it easier to iterate over a set of
values given as a delimited string.
Added a new router API entry point that allows configuration changes after
the instance has been created. This makes alterations to most service
parameters at runtime possible.
An option to reconfiguration would have been the creation of a new
service and the eventual destruction of the old one. This would be a more
complicated and costly method but from an architectural point of view it
is interesting.
The actual implementation of the configuration change is left to the
router. Currently, only readwritesplit performs reconfiguration as
implementing it with versioned configurations is very easy.
Versioned configurations can be considered an adequate first step but it
is not an optimal solution as it causes a bottleneck in the reference
counting of the shared configuration. Thread-specific configuration
definitions would make for a more efficient solution but the
implementation is more complex.
With the global configuration parameter 'query_classifier_cache'
the query classification cache can be turned on. At the moment it
does not matter what value it has; its presence simply enables the
caching.
Eventually you will be able to specify how much memory the cache
is allowed to consume.
