GLib.ThreadPool¶
record (struct)
The GThreadPool struct represents a thread pool.
A thread pool is useful when you wish to asynchronously fork out the execution of work and continue working in your own thread. If that will happen often, the overhead of starting and destroying a thread each time might be too high. In such cases reusing already started threads seems like a good idea. And it indeed is, but implementing this can be tedious and error-prone.
Therefore GLib provides thread pools for your convenience. An added advantage is, that the threads can be shared between the different subsystems of your program, when they are using GLib.
To create a new thread pool, you use ThreadPool.new.
It is destroyed by ThreadPool.free.
If you want to execute a certain task within a thread pool, use ThreadPool.push.
To get the current number of running threads you call ThreadPool.get_num_threads.
To get the number of still unprocessed tasks you call ThreadPool.unprocessed.
To control the maximum number of threads for a thread pool, you use
ThreadPool.get_max_threads. and ThreadPool.set_max_threads.
Finally you can control the number of unused threads, that are kept alive by GLib for future use.
The current number can be fetched with ThreadPool.get_num_unused_threads.
The maximum number can be controlled by ThreadPool.get_max_unused_threads and
ThreadPool.set_max_unused_threads. All currently unused threads
can be stopped by calling ThreadPool.stop_unused_threads.
Methods¶
free¶
Frees all resources allocated for pool.
If immediate is True, no new task is processed for pool.
Otherwise pool is not freed before the last task is processed.
Note however, that no thread of this pool is interrupted while
processing a task. Instead at least all still running threads
can finish their tasks before the pool is freed.
If wait_ is True, this function does not return before all
tasks to be processed (dependent on immediate, whether all
or only the currently running) are ready.
Otherwise this function returns immediately.
After calling this function pool must not be used anymore.
Parameters:
immediate— shouldpoolshut down immediately?wait_— should the function wait for all tasks to be finished?
get_max_threads¶
Returns the maximal number of threads for pool.
get_num_threads¶
Returns the number of threads currently running in pool.
move_to_front¶
Moves the item to the front of the queue of unprocessed items, so that it will be processed next.
Parameters:
data— an unprocessed item in the pool
push¶
Inserts data into the list of tasks to be executed by pool.
When the number of currently running threads is lower than the
maximal allowed number of threads, a new thread is started (or
reused) with the properties given to g_thread_pool_new().
Otherwise, data stays in the queue until a thread in this pool
finishes its previous task and processes data.
error can be None to ignore errors, or non-None to report
errors. An error can only occur when a new thread couldn't be
created. In that case data is simply appended to the queue of
work to do.
Before version 2.32, this function did not return a success status.
Parameters:
data— a new task forpool
set_max_threads¶
Sets the maximal allowed number of threads for pool.
A value of -1 means that the maximal number of threads
is unlimited. If pool is an exclusive thread pool, setting
the maximal number of threads to -1 is not allowed.
Setting max_threads to 0 means stopping all work for pool.
It is effectively frozen until max_threads is set to a non-zero
value again.
A thread is never terminated while calling func, as supplied by
g_thread_pool_new(). Instead the maximal number of threads only
has effect for the allocation of new threads in ThreadPool.push.
A new thread is allocated, whenever the number of currently
running threads in pool is smaller than the maximal number.
error can be None to ignore errors, or non-None to report
errors. An error can only occur when a new thread couldn't be
created.
Before version 2.32, this function did not return a success status.
Parameters:
max_threads— a new maximal number of threads forpool, or -1 for unlimited
unprocessed¶
Returns the number of tasks still unprocessed in pool.
Static functions¶
get_max_idle_time¶
This function will return the maximum interval that a
thread will wait in the thread pool for new tasks before
being stopped.
If this function returns 0, threads waiting in the thread pool for new work are not stopped.
get_max_unused_threads¶
Returns the maximal allowed number of unused threads.
get_num_unused_threads¶
Returns the number of currently unused threads.
set_max_idle_time¶
This function will set the maximum interval that a thread
waiting in the pool for new tasks can be idle for before
being stopped. This function is similar to calling
ThreadPool.stop_unused_threads on a regular timeout,
except this is done on a per thread basis.
By setting interval to 0, idle threads will not be stopped.
The default value is 15000 (15 seconds).
Parameters:
interval— the maximuminterval(in milliseconds) a thread can be idle
set_max_unused_threads¶
Sets the maximal number of unused threads to max_threads.
If max_threads is -1, no limit is imposed on the number
of unused threads.
The default value is 8 since GLib 2.84. Previously the default value was 2.
Parameters:
max_threads— maximal number of unused threads
stop_unused_threads¶
Stops all currently unused threads. This does not change the maximal number of unused threads. This function can be used to regularly stop all unused threads e.g. from g_timeout_add().