GLib.ThreadPool

Fields

Name	Type	Access	Description
exclusive	bool	r/w	are all threads exclusive to this pool
func	GLib.Func	r/w	the function to execute in the threads of this pool
user_data	object	r/w	the user data for the threads of this pool

Methods

class	get_max_idle_time ()
class	get_max_unused_threads ()
class	get_num_unused_threads ()
class	set_max_idle_time (interval)
class	set_max_unused_threads (max_threads)
class	stop_unused_threads ()
	free (immediate, wait_)
	get_max_threads ()
	get_num_threads ()
	move_to_front (data)
	push (data)
	set_max_threads (max_threads)
	unprocessed ()

Details

class GLib.ThreadPool

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 [func`GLib`.ThreadPool.new]. It is destroyed by [method`GLib`.ThreadPool.free].

If you want to execute a certain task within a thread pool, use [method`GLib`.ThreadPool.push].

To get the current number of running threads you call [method`GLib`.ThreadPool.get_num_threads]. To get the number of still unprocessed tasks you call [method`GLib`.ThreadPool.unprocessed]. To control the maximum number of threads for a thread pool, you use [method`GLib`.ThreadPool.get_max_threads]. and [method`GLib`.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 [func`GLib`.ThreadPool.get_num_unused_threads]. The maximum number can be controlled by [func`GLib`.ThreadPool.get_max_unused_threads] and [func`GLib`.ThreadPool.set_max_unused_threads]. All currently unused threads can be stopped by calling [func`GLib`.ThreadPool.stop_unused_threads].

classmethod get_max_idle_time()

Returns:

the maximum interval (milliseconds) to wait for new tasks in the thread pool before stopping the thread

Return type:

int

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.

New in version 2.10.

classmethod get_max_unused_threads()

Returns:

the maximal number of unused threads

Return type:

int

Returns the maximal allowed number of unused threads.

classmethod get_num_unused_threads()

Returns:

the number of currently unused threads

Return type:

int

Returns the number of currently unused threads.

classmethod set_max_idle_time(interval)

Parameters:

interval (int) – the maximum interval (in milliseconds) a thread can be idle

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 GLib.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).

New in version 2.10.

classmethod set_max_unused_threads(max_threads)

Parameters:

max_threads (int) – maximal number of 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 2.

classmethod 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 GLib.timeout_add().

free(immediate, wait_)

Parameters:

• immediate (bool) – should self shut down immediately?

• wait (bool) – should the function wait for all tasks to be finished?

Frees all resources allocated for self.

If immediate is True, no new task is processed for self. Otherwise self 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 self 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 self must not be used anymore.

get_max_threads()

Returns:

the maximal number of threads

Return type:

int

Returns the maximal number of threads for self.

get_num_threads()

Returns:

the number of threads currently running

Return type:

int

Returns the number of threads currently running in self.

move_to_front(data)

Parameters:

data (object or None) – an unprocessed item in the pool

Returns:

True if the item was found and moved

Return type:

bool

Moves the item to the front of the queue of unprocessed items, so that it will be processed next.

New in version 2.46.

push(data)

Parameters:

data (object or None) – a new task for self

Raises:

GLib.Error

Returns:

True on success, False if an error occurred

Return type:

bool

Inserts data into the list of tasks to be executed by self.

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.

set_max_threads(max_threads)

Parameters:

max_threads (int) – a new maximal number of threads for self, or -1 for unlimited

Raises:

GLib.Error

Returns:

True on success, False if an error occurred

Return type:

bool

Sets the maximal allowed number of threads for self. A value of -1 means that the maximal number of threads is unlimited. If self 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 self. 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 GLib.ThreadPool.push(). A new thread is allocated, whenever the number of currently running threads in self 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.

unprocessed()

Returns:

the number of unprocessed tasks

Return type:

int

Returns the number of tasks still unprocessed in self.