dragon.mpbridge.pool

Dragon’s replacement for Multiprocessing Pool.

By default this uses the dragon native pool and sets DRAGON_BASEPOOL="NATIVE". The private api for this class is still under development. To revert to the version based on the multiprocessing.Pool class with a patched terminate_pool method, set DRAGON_BASEPOOL="PATCHED" in the environment.

Functions

`Pool`([processes, initializer, initargs, ...])
`dragon_terminate_pool`(cls, taskqueue, ...)
`starmapstar`(args)

Classes

`BaseImplPool`
`DragonPool`	Dragon's replacement for Multiprocessing Pool.
`DragonPoolPatched`	Dragon's patched implementation of Multiprocessing Pool.
`WrappedDragonProcess`
`WrappedResult`	Returned by all functions that return a result.

class DragonPoolPatched

Dragon’s patched implementation of Multiprocessing Pool.

__init__(*args, **kwargs)

class WrappedResult

Returned by all functions that return a result. Wraps ApplyResult and MapResult so that correct timeout error can be raised.

__init__(result: Optional[ApplyResult] = None)

Initializes wrapped result by saving input result

Parameters: result (ApplyResult or MapResult, optional) – returned result from native pool, defaults to None

get(timeout: Optional[float] = None) → Any

Retrieves returned values of work submitted to pool

Parameters: timeout (float, optional) – timeout for getting result, defaults to None
Raises: multiprocessing.TimeoutError – raised if result is not ready in specified timeout
Returns: value returned by func(*args, **kwargs)
Return type: Any

ready() → bool

Checks whether the result is ready.

Returns: returns True if the result is ready or False if it isn’t
Return type: bool

successful() → bool

Checks if the result is ready and returns whether the function call was successful.

Raises: ValueError – raised if result is not ready
Returns: returns True if function call was successful
Return type: bool

wait(timeout: Optional[float] = None) → None

Waits on event for result to be ready

Parameters: timeout (float, optional) – timeout indicating how long to wait for result to be ready, defaults to None

class DragonPool

Dragon’s replacement for Multiprocessing Pool.

__init__(*args, context=None, **kwargs)

Init method

Parameters

processes (int, optional) – number of worker processes, defaults to None
initializer (callable, optional) – initializer function, defaults to None
initargs (tuple, optional) – arguments for initializer function, defaults to ()
maxtasksperchild (int, optional) – maximum tasks each worker will perform, defaults to None
policy (dragon.infrastructure.policy.Policy) – determines the placement of the processes

Raises

ValueError – raised if number of worker processes is less than 1

apply_async(func: callable, args: tuple = (), kwargs: dict = {}, callback: Optional[callable] = None, error_callback: Optional[callable] = None) → WrappedResult

Equivalent to calling func(*args, **kwargs) in a non-blocking way. A result is immediately returned and then updated when func(*args, **kwargs) has completed.

Parameters

func (callable) – user function to be called by worker function
args (tuple, optional) – input args to func, defaults to ()
kwargs (dict, optional) – input kwargs to func, defaults to {}
callback (callable, optional) – user provided callback function, defaults to None
error_callback (callable, optional) – user provided error callback function, defaults to None

Raises

ValueError – raised if pool has already been closed or terminated

Returns

A result that has a get method to retrieve result of func(*args, **kwargs)

Return type

WrappedResult

map_async(func: callable, iterable: Iterable, chunksize: Optional[int] = None, callback: Optional[callable] = None, error_callback: Optional[callable] = None) → WrappedResult

Apply func to each element in iterable. The results are collected in a list that is returned immediately. It is equivalent to map if the get method is called immediately on the returned result.

Parameters

func (callable) – user provided function to call on elements of iterable
iterable (iterable) – input args to func
chunksize (int, optional) – size of work elements to be submitted to input work queue, defaults to None
callback (callable, optional) – user provided callback function, defaults to None
error_callback (callable, optional) – user provided error callback function, defaults to None

Returns

A result that has a get method that returns an iterable of the output from applying func to each element of iterable.

Return type

WrappedResult

apply(func: callable, args: tuple = (), kwds: dict = {}) → Any

Equivalent to calling func(*args, **kwargs) in a blocking way. The function returns when func(*args, **kwargs) has completed and the result has been updated with the output

Parameters

func (callable) – user function to be called by worker
args (tuple, optional) – input args to func, defaults to ()
kwds (dict, optional) – input kwargs to func, defaults to {}

Returns

The result of func(*args, **kwargs)

Return type

map(func: callable, iterable: Iterable, chunksize: Optional[int] = None) → Iterable[Any]

Apply func to each element in iterable, collecting the results in a list that is returned.

Parameters

func (callable) – user provided function to call on elements of iterable
iterable (Iterable) – input args to func
chunksize (int, optional) – size of work elements to be submitted to input work queue, defaults to None

Returns

list of results from applying func to each element of input iterable

Return type

Iterable[Any]

starmap(func: callable, iterable: Iterable[Iterable], chunksize: Optional[int] = None) → Iterable[Any]

Like map() method but the elements of the iterable are expected to be iterables as well and will be unpacked as arguments. Hence func and (a, b) becomes func(a, b).

Parameters

func (callable) – user provided function to call on elements of iterable
iterable (Iterable[Iterable]) – input iterable args to func
chunksize (int, optional) – size of work elements to be submitted to input work queue, defaults to None

Returns

results of applying func to input iterable args

Return type

Iterable[Any]

starmap_async(func: callable, iterable: Iterable[Iterable], chunksize: Optional[int] = None, callback: Optional[callable] = None, error_callback: Optional[callable] = None) → WrappedResult

Asynchronous version of starmap() method.

Parameters

func (callable) – user provided function to call on elements of iterable
iterable (Iterable[Iterable]) – input iterable args to func
chunksize (int, optional) – size of work elements to be submitted to input work queue, defaults to None
callback (callable, optional) – user provided callback function, defaults to None
error_callback (callable, optional) – user provided error callback function, defaults to None

Returns

A result that has a get method that returns an iterable of the output from applying func to each element of iterable.

Return type

WrappedResult

imap_unordered(func: callable, iterable: Iterable, chunksize: int = 1) → IMapUnorderedIterator

Like imap() method but ordering of results is arbitrary.

Parameters

func (callable) – user provided function to call on elements of iterable
iterable (Iterable) – input args to func
chunksize (int, optional) – size of work elements to be submitted to input work queue, defaults to 1

Raises

ValueError – raised if chunksize is less than one

Returns

results of calling func on iterable elements

Return type

IMapUnorderedIterator or Any

imap(func: callable, iterable: Iterable, chunksize: int = 1) → IMapIterator

Equivalent of map() – can be MUCH slower than Pool.map(). Unlike map(), the iterable isn’t immediately turned into a list. Rather, it is iterated over and items are put into the queue one at a time if chunksize=1. Unlike the non-imap variants of map, the returned object can then be iterated over and individual results will be returned as soon as they are available rather than when all work submitted via the iterable is done.

Parameters

func (callable) – user provided function to call on elements of iterable
iterable (Iterable) – input args to func
chunksize (int, optional) – size of work elements to be submitted to input work queue, defaults to 1

Raises

ValueError – raised if chunksize is less than one

Returns

results of calling func on iterable elements

Return type

IMapIterator or Any

class BaseImplPool

__init__(*args, **kwargs)