API

Executors

class futurist.GreenThreadPoolExecutor(max_workers=1000, check_and_reject=None)

Executor that uses a green thread pool to execute calls asynchronously.

See: https://docs.python.org/dev/library/concurrent.futures.html and http://eventlet.net/doc/modules/greenpool.html for information on how this works.

It gathers statistics about the submissions executed for post-analysis...

__init__(max_workers=1000, check_and_reject=None)

Initializes a green thread pool executor.

Parameters:

• max_workers (int) – maximum number of workers that can be simulatenously active at the same time, further submitted work will be queued up when this limit is reached.
• check_and_reject (callback) – a callback function that will be provided two position arguments, the first argument will be this executor instance, and the second will be the number of currently queued work items in this executors backlog; the callback should raise a RejectedSubmission exception if it wants to have this submission rejected.

alive

Accessor to determine if the executor is alive/active.

statistics

ExecutorStatistics about the executors executions.

submit(fn, *args, **kwargs)

Submit some work to be executed (and gather statistics).

Parameters:

• args (list) – non-keyworded arguments
• kwargs (dictionary) – key-value arguments

class futurist.ProcessPoolExecutor(max_workers=None)

Executor that uses a process pool to execute calls asynchronously.

It gathers statistics about the submissions executed for post-analysis...

See: https://docs.python.org/dev/library/concurrent.futures.html

alive

Accessor to determine if the executor is alive/active.

statistics

ExecutorStatistics about the executors executions.

submit(fn, *args, **kwargs)

Submit some work to be executed (and gather statistics).

class futurist.SynchronousExecutor(green=False, run_work_func=<function <lambda> at 0x24428c0>)

Executor that uses the caller to execute calls synchronously.

This provides an interface to a caller that looks like an executor but will execute the calls inside the caller thread instead of executing it in a external process/thread for when this type of functionality is useful to provide...

It gathers statistics about the submissions executed for post-analysis...

__init__(green=False, run_work_func=<function <lambda> at 0x24428c0>)

Synchronous executor constructor.

Parameters:

• green (bool) – when enabled this forces the usage of greened lock classes and green futures (so that the internals of this object operate correctly under eventlet)
• run_work_func – callable that takes a single work item and runs it (typically in a blocking manner)
• run_work_func – callable

alive

Accessor to determine if the executor is alive/active.

restart()

Restarts this executor (iff previously shutoff/shutdown).

NOTE(harlowja): clears any previously gathered statistics.

statistics

ExecutorStatistics about the executors executions.

submit(fn, *args, **kwargs)

Submit some work to be executed (and gather statistics).

class futurist.ThreadPoolExecutor(max_workers=None, check_and_reject=None)

Executor that uses a thread pool to execute calls asynchronously.

It gathers statistics about the submissions executed for post-analysis...

See: https://docs.python.org/dev/library/concurrent.futures.html

__init__(max_workers=None, check_and_reject=None)

Initializes a thread pool executor.

Parameters:

• max_workers (int) – maximum number of workers that can be simultaneously active at the same time, further submitted work will be queued up when this limit is reached.
• check_and_reject (callback) – a callback function that will be provided two position arguments, the first argument will be this executor instance, and the second will be the number of currently queued work items in this executors backlog; the callback should raise a RejectedSubmission exception if it wants to have this submission rejected.

alive

Accessor to determine if the executor is alive/active.

statistics

ExecutorStatistics about the executors executions.

submit(fn, *args, **kwargs)

Submit some work to be executed (and gather statistics).

Futures

class futurist.Future

Represents the result of an asynchronous computation.

add_done_callback(fn)

Attaches a callable that will be called when the future finishes.

Args:

fn: A callable that will be called with this future as its only

argument when the future completes or is cancelled. The callable will always be called by a thread in the same process in which it was added. If the future has already completed or been cancelled then the callable will be called immediately. These callables are called in the order that they were added.

cancel()

Cancel the future if possible.

Returns True if the future was cancelled, False otherwise. A future cannot be cancelled if it is running or has already completed.

cancelled()

Return True if the future has cancelled.

done()

Return True of the future was cancelled or finished executing.

exception(timeout=None)

Return the exception raised by the call that the future represents.

Args:

timeout: The number of seconds to wait for the exception if the

future isn’t done. If None, then there is no limit on the wait time.

Returns:

The exception raised by the call that the future represents or None if the call completed without raising.

Raises:

CancelledError: If the future was cancelled. TimeoutError: If the future didn’t finish executing before the given

timeout.

exception_info(timeout=None)

Return a tuple of (exception, traceback) raised by the call that the future represents.

Args:

timeout: The number of seconds to wait for the exception if the

future isn’t done. If None, then there is no limit on the wait time.

Returns:

The exception raised by the call that the future represents or None if the call completed without raising.

Raises:

CancelledError: If the future was cancelled. TimeoutError: If the future didn’t finish executing before the given

timeout.

result(timeout=None)

Return the result of the call that the future represents.

Args:

timeout: The number of seconds to wait for the result if the future

isn’t done. If None, then there is no limit on the wait time.

Returns:

The result of the call that the future represents.

Raises:

CancelledError: If the future was cancelled. TimeoutError: If the future didn’t finish executing before the given

timeout.

Exception: If the call raised then that exception will be raised.

running()

Return True if the future is currently executing.

set_exception(exception)

Sets the result of the future as being the given exception.

Should only be used by Executor implementations and unit tests.

set_exception_info(exception, traceback)

Sets the result of the future as being the given exception and traceback.

Should only be used by Executor implementations and unit tests.

set_result(result)

Sets the return value of work associated with the future.

Should only be used by Executor implementations and unit tests.

set_running_or_notify_cancel()

Mark the future as running or process any cancel notifications.

Should only be used by Executor implementations and unit tests.

If the future has been cancelled (cancel() was called and returned True) then any threads waiting on the future completing (though calls to as_completed() or wait()) are notified and False is returned.

If the future was not cancelled then it is put in the running state (future calls to running() will return True) and True is returned.

This method should be called by Executor implementations before executing the work associated with this future. If this method returns False then the work should not be executed.

Returns:

False if the Future was cancelled, True otherwise.

Raises:

RuntimeError: if this method was already called or if set_result()

or set_exception() was called.

class futurist.GreenFuture

Represents the result of an asynchronous computation.

Periodics

Miscellaneous

class futurist.ExecutorStatistics(failures=0, executed=0, runtime=0.0, cancelled=0)

Holds immutable information about a executors executions.

average_runtime

The average runtime of all submissions executed.

Returns:average runtime of all submissions executed Return type:number Raises:ZeroDivisionError when no executions have occurred.

cancelled

How many submissions were cancelled before executing.

Returns:how many submissions were cancelled before executing Return type:number

executed

How many submissions were executed (failed or not).

Returns:how many submissions were executed Return type:number

failures

How many submissions ended up raising exceptions.

Returns:how many submissions ended up raising exceptions Return type:number

runtime

Total runtime of all submissions executed (failed or not).

Returns:total runtime of all submissions executed Return type:number

Exceptions

class futurist.RejectedSubmission

Exception raised when a submitted call is rejected (for some reason).

Waiters

futurist.waiters.wait_for_any(fs, timeout=None)

Wait for one (any) of the futures to complete.

Works correctly with both green and non-green futures (but not both together, since this can’t be guaranteed to avoid dead-lock due to how the waiting implementations are different when green threads are being used).

Returns pair (done futures, not done futures).

futurist.waiters.wait_for_all(fs, timeout=None)

Wait for all of the futures to complete.

Works correctly with both green and non-green futures (but not both together, since this can’t be guaranteed to avoid dead-lock due to how the waiting implementations are different when green threads are being used).

Returns pair (done futures, not done futures).

class futurist.waiters.DoneAndNotDoneFutures

Named tuple returned from wait_for* calls.