The custom random number generator can now be replaced with a C++11
RNG. This greatly improves the reliability and trustworthiness of it.
In addition to this, the conversion of the RNG to a thread-local object
removes the race condition that was present in the previous
implementation. It also theoretically improves performance by a tiny bit.
It does not save much in characters compared to std::function<void ()>
and it's a bit misleading as not just any callable object will do, but
only one that takes no argument and returns void.
In preparation for Worker::post() to be renamed to Worker:execute().
The concept of _posting_ will be reserved to mean the transfer of
something over the message queue to the worker for processing and
nothing else.
This is the first step in some cleanup of the Worker interface.
The execution mode must now be explicitly specified, but that is
just a temporary step. Further down the road, _posting_ will
*always* mean via the message loop while _executing_ will optionally
and by default mean direct execution if the calling thread is that
of the worker.
The 'events' and 'script' config values were defined for every monitor.
Removed the extra definitions and moved the variables to MXS_MONITOR.
MariaDBMonitor was printing config values a second time, they are
already printed by the caller.
Moved the events enum definition to the internal header since it's no longer
required by modules.
Added a default config setting "all" to 'events' to clarify that it enables
all events.
The ssl parameters were defined as strings even thought they were actually
enums. The events parameter was also a string even though it was an enum.
Also added the missing "all" value to the events enum. This fixes the
regression of scripts not being launched on all events by default.
Moved the definition of the default version string where it should be and
removed the empty value check.
The get_suffixed_size function is now exposed in the internal config
header and it also checks for the validity of the size types.
Took the new function into use and added the appropriate error messages.
In principle it would be better if the qc information were
obtained via a specific query_classifier resource. However,
there are multiple problems with that (e.g. the qc has no way
of safely accessing information of another thread) and hence
the worker specific qc cache statistics is reported as part of
the worker statistics.
The Session class now contains all of the C++ objects that were previously
in the MXS_SESSION struct. It is also allocated with new but all
initialization is still done outside of the Session in session_alloc_body.
This commit will not compile as it is a part of a set of commits that make
parts of the session private.
The most relevant string variables of a service are now duplicated as C++
strings. This should ease the eventual transition to a fully C++ internal
representation of the service. The array of refresh rates was also wrapped
inside a std::vector to remove the need to manually manage memory.
Separated the SERVICE_USER struct into its individual components as there
was no real need to have them inside a struct.
The service now has a private std::mutex that is used for
synchronization.
Renamed the vector of services to use snake_case.
Use lock guards with mutexes to make usage easier and safer. This makes
the code smaller as well as slightly easier to read.
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.