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s3transfer
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futures.py
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# Copyright 2016 Amazon.com, Inc. or its affiliates. All Rights Reserved. # # Licensed under the Apache License, Version 2.0 (the "License"). You # may not use this file except in compliance with the License. A copy of # the License is located at # # http://aws.amazon.com/apache2.0/ # # or in the "license" file accompanying this file. This file is # distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF # ANY KIND, either express or implied. See the License for the specific # language governing permissions and limitations under the License. import copy import logging import sys import threading from collections import namedtuple from concurrent import futures from s3transfer.compat import MAXINT from s3transfer.exceptions import CancelledError, TransferNotDoneError from s3transfer.utils import FunctionContainer, TaskSemaphore logger = logging.getLogger(__name__) class BaseTransferFuture: @property def meta(self): """The metadata associated to the TransferFuture""" raise NotImplementedError('meta') def done(self): """Determines if a TransferFuture has completed :returns: True if completed. False, otherwise. """ raise NotImplementedError('done()') def result(self): """Waits until TransferFuture is done and returns the result If the TransferFuture succeeded, it will return the result. If the TransferFuture failed, it will raise the exception associated to the failure. """ raise NotImplementedError('result()') def cancel(self): """Cancels the request associated with the TransferFuture""" raise NotImplementedError('cancel()') class BaseTransferMeta: @property def call_args(self): """The call args used in the transfer request""" raise NotImplementedError('call_args') @property def transfer_id(self): """The unique id of the transfer""" raise NotImplementedError('transfer_id') @property def user_context(self): """A dictionary that requesters can store data in""" raise NotImplementedError('user_context') class TransferFuture(BaseTransferFuture): def __init__(self, meta=None, coordinator=None): """The future associated to a submitted transfer request :type meta: TransferMeta :param meta: The metadata associated to the request. This object is visible to the requester. :type coordinator: TransferCoordinator :param coordinator: The coordinator associated to the request. This object is not visible to the requester. """ self._meta = meta if meta is None: self._meta = TransferMeta() self._coordinator = coordinator if coordinator is None: self._coordinator = TransferCoordinator() @property def meta(self): return self._meta def done(self): return self._coordinator.done() def result(self): try: # Usually the result() method blocks until the transfer is done, # however if a KeyboardInterrupt is raised we want want to exit # out of this and propagate the exception. return self._coordinator.result() except KeyboardInterrupt as e: self.cancel() raise e def cancel(self): self._coordinator.cancel() def set_exception(self, exception): """Sets the exception on the future.""" if not self.done(): raise TransferNotDoneError( 'set_exception can only be called once the transfer is ' 'complete.' ) self._coordinator.set_exception(exception, override=True) class TransferMeta(BaseTransferMeta): """Holds metadata about the TransferFuture""" def __init__(self, call_args=None, transfer_id=None): self._call_args = call_args self._transfer_id = transfer_id self._size = None self._user_context = {} @property def call_args(self): """The call args used in the transfer request""" return self._call_args @property def transfer_id(self): """The unique id of the transfer""" return self._transfer_id @property def size(self): """The size of the transfer request if known""" return self._size @property def user_context(self): """A dictionary that requesters can store data in""" return self._user_context def provide_transfer_size(self, size): """A method to provide the size of a transfer request By providing this value, the TransferManager will not try to call HeadObject or use the use OS to determine the size of the transfer. """ self._size = size class TransferCoordinator: """A helper class for managing TransferFuture""" def __init__(self, transfer_id=None): self.transfer_id = transfer_id self._status = 'not-started' self._result = None self._exception = None self._associated_futures = set() self._failure_cleanups = [] self._done_callbacks = [] self._done_event = threading.Event() self._lock = threading.Lock() self._associated_futures_lock = threading.Lock() self._done_callbacks_lock = threading.Lock() self._failure_cleanups_lock = threading.Lock() def __repr__(self): return '{}(transfer_id={})'.format( self.__class__.__name__, self.transfer_id ) @property def exception(self): return self._exception @property def associated_futures(self): """The list of futures associated to the inprogress TransferFuture Once the transfer finishes this list becomes empty as the transfer is considered done and there should be no running futures left. """ with self._associated_futures_lock: # We return a copy of the list because we do not want to # processing the returned list while another thread is adding # more futures to the actual list. return copy.copy(self._associated_futures) @property def failure_cleanups(self): """The list of callbacks to call when the TransferFuture fails""" return self._failure_cleanups @property def status(self): """The status of the TransferFuture The currently supported states are: * not-started - Has yet to start. If in this state, a transfer can be canceled immediately and nothing will happen. * queued - SubmissionTask is about to submit tasks * running - Is inprogress. In-progress as of now means that the SubmissionTask that runs the transfer is being executed. So there is no guarantee any transfer requests had been made to S3 if this state is reached. * cancelled - Was cancelled * failed - An exception other than CancelledError was thrown * success - No exceptions were thrown and is done. """ return self._status def set_result(self, result): """Set a result for the TransferFuture Implies that the TransferFuture succeeded. This will always set a result because it is invoked on the final task where there is only ever one final task and it is ran at the very end of a transfer process. So if a result is being set for this final task, the transfer succeeded even if something came a long and canceled the transfer on the final task. """ with self._lock: self._exception = None self._result = result self._status = 'success' def set_exception(self, exception, override=False): """Set an exception for the TransferFuture Implies the TransferFuture failed. :param exception: The exception that cause the transfer to fail. :param override: If True, override any existing state. """ with self._lock: if not self.done() or override: self._exception = exception self._status = 'failed' def result(self): """Waits until TransferFuture is done and returns the result If the TransferFuture succeeded, it will return the result. If the TransferFuture failed, it will raise the exception associated to the failure. """ # Doing a wait() with no timeout cannot be interrupted in python2 but # can be interrupted in python3 so we just wait with the largest # possible value integer value, which is on the scale of billions of # years... self._done_event.wait(MAXINT) # Once done waiting, raise an exception if present or return the # final result. if self._exception: raise self._exception return self._result def cancel(self, msg='', exc_type=CancelledError): """Cancels the TransferFuture :param msg: The message to attach to the cancellation :param exc_type: The type of exception to set for the cancellation """ with self._lock: if not self.done(): should_announce_done = False logger.debug('%s cancel(%s) called', self, msg) self._exception = exc_type(msg) if self._status == 'not-started': should_announce_done = True self._status = 'cancelled' if should_announce_done: self.announce_done() def set_status_to_queued(self): """Sets the TransferFutrue's status to running""" self._transition_to_non_done_state('queued') def set_status_to_running(self): """Sets the TransferFuture's status to running""" self._transition_to_non_done_state('running') def _transition_to_non_done_state(self, desired_state): with self._lock: if self.done(): raise RuntimeError( 'Unable to transition from done state %s to non-done ' 'state %s.' % (self.status, desired_state) ) self._status = desired_state def submit(self, executor, task, tag=None): """Submits a task to a provided executor :type executor: s3transfer.futures.BoundedExecutor :param executor: The executor to submit the callable to :type task: s3transfer.tasks.Task :param task: The task to submit to the executor :type tag: s3transfer.futures.TaskTag :param tag: A tag to associate to the submitted task :rtype: concurrent.futures.Future :returns: A future representing the submitted task """ logger.debug( "Submitting task {} to executor {} for transfer request: {}.".format( task, executor, self.transfer_id ) ) future = executor.submit(task, tag=tag) # Add this created future to the list of associated future just # in case it is needed during cleanups. self.add_associated_future(future) future.add_done_callback( FunctionContainer(self.remove_associated_future, future) ) return future def done(self): """Determines if a TransferFuture has completed :returns: False if status is equal to 'failed', 'cancelled', or 'success'. True, otherwise """ return self.status in ['failed', 'cancelled', 'success'] def add_associated_future(self, future): """Adds a future to be associated with the TransferFuture""" with self._associated_futures_lock: self._associated_futures.add(future) def remove_associated_future(self, future): """Removes a future's association to the TransferFuture""" with self._associated_futures_lock: self._associated_futures.remove(future) def add_done_callback(self, function, *args, **kwargs): """Add a done callback to be invoked when transfer is done""" with self._done_callbacks_lock: self._done_callbacks.append( FunctionContainer(function, *args, **kwargs) ) def add_failure_cleanup(self, function, *args, **kwargs): """Adds a callback to call upon failure""" with self._failure_cleanups_lock: self._failure_cleanups.append( FunctionContainer(function, *args, **kwargs) ) def announce_done(self): """Announce that future is done running and run associated callbacks This will run any failure cleanups if the transfer failed if not they have not been run, allows the result() to be unblocked, and will run any done callbacks associated to the TransferFuture if they have not already been ran. """ if self.status != 'success': self._run_failure_cleanups() self._done_event.set() self._run_done_callbacks() def _run_done_callbacks(self): # Run the callbacks and remove the callbacks from the internal # list so they do not get ran again if done is announced more than # once. with self._done_callbacks_lock: self._run_callbacks(self._done_callbacks) self._done_callbacks = [] def _run_failure_cleanups(self): # Run the cleanup callbacks and remove the callbacks from the internal # list so they do not get ran again if done is announced more than # once. with self._failure_cleanups_lock: self._run_callbacks(self.failure_cleanups) self._failure_cleanups = [] def _run_callbacks(self, callbacks): for callback in callbacks: self._run_callback(callback) def _run_callback(self, callback): try: callback() # We do not want a callback interrupting the process, especially # in the failure cleanups. So log and catch, the exception. except Exception: logger.debug("Exception raised in %s." % callback, exc_info=True) class BoundedExecutor: EXECUTOR_CLS = futures.ThreadPoolExecutor def __init__( self, max_size, max_num_threads, tag_semaphores=None, executor_cls=None ): """An executor implementation that has a maximum queued up tasks The executor will block if the number of tasks that have been submitted and is currently working on is past its maximum. :params max_size: The maximum number of inflight futures. An inflight future means that the task is either queued up or is currently being executed. A size of None or 0 means that the executor will have no bound in terms of the number of inflight futures. :params max_num_threads: The maximum number of threads the executor uses. :type tag_semaphores: dict :params tag_semaphores: A dictionary where the key is the name of the tag and the value is the semaphore to use when limiting the number of tasks the executor is processing at a time. :type executor_cls: BaseExecutor :param underlying_executor_cls: The executor class that get bounded by this executor. If None is provided, the concurrent.futures.ThreadPoolExecutor class is used. """ self._max_num_threads = max_num_threads if executor_cls is None: executor_cls = self.EXECUTOR_CLS self._executor = executor_cls(max_workers=self._max_num_threads) self._semaphore = TaskSemaphore(max_size) self._tag_semaphores = tag_semaphores def submit(self, task, tag=None, block=True): """Submit a task to complete :type task: s3transfer.tasks.Task :param task: The task to run __call__ on :type tag: s3transfer.futures.TaskTag :param tag: An optional tag to associate to the task. This is used to override which semaphore to use. :type block: boolean :param block: True if to wait till it is possible to submit a task. False, if not to wait and raise an error if not able to submit a task. :returns: The future associated to the submitted task """ semaphore = self._semaphore # If a tag was provided, use the semaphore associated to that # tag. if tag: semaphore = self._tag_semaphores[tag] # Call acquire on the semaphore. acquire_token = semaphore.acquire(task.transfer_id, block) # Create a callback to invoke when task is done in order to call # release on the semaphore. release_callback = FunctionContainer( semaphore.release, task.transfer_id, acquire_token ) # Submit the task to the underlying executor. future = ExecutorFuture(self._executor.submit(task)) # Add the Semaphore.release() callback to the future such that # it is invoked once the future completes. future.add_done_callback(release_callback) return future def shutdown(self, wait=True): self._executor.shutdown(wait) class ExecutorFuture: def __init__(self, future): """A future returned from the executor Currently, it is just a wrapper around a concurrent.futures.Future. However, this can eventually grow to implement the needed functionality of concurrent.futures.Future if we move off of the library and not affect the rest of the codebase. :type future: concurrent.futures.Future :param future: The underlying future """ self._future = future def result(self): return self._future.result() def add_done_callback(self, fn): """Adds a callback to be completed once future is done :param fn: A callable that takes no arguments. Note that is different than concurrent.futures.Future.add_done_callback that requires a single argument for the future. """ # The done callback for concurrent.futures.Future will always pass a # the future in as the only argument. So we need to create the # proper signature wrapper that will invoke the callback provided. def done_callback(future_passed_to_callback): return fn() self._future.add_done_callback(done_callback) def done(self): return self._future.done() class BaseExecutor: """Base Executor class implementation needed to work with s3transfer""" def __init__(self, max_workers=None): pass def submit(self, fn, *args, **kwargs): raise NotImplementedError('submit()') def shutdown(self, wait=True): raise NotImplementedError('shutdown()') class NonThreadedExecutor(BaseExecutor): """A drop-in replacement non-threaded version of ThreadPoolExecutor""" def submit(self, fn, *args, **kwargs): future = NonThreadedExecutorFuture() try: result = fn(*args, **kwargs) future.set_result(result) except Exception: e, tb = sys.exc_info()[1:] logger.debug( 'Setting exception for %s to %s with traceback %s', future, e, tb, ) future.set_exception_info(e, tb) return future def shutdown(self, wait=True): pass class NonThreadedExecutorFuture: """The Future returned from NonThreadedExecutor Note that this future is **not** thread-safe as it is being used from the context of a non-threaded environment. """ def __init__(self): self._result = None self._exception = None self._traceback = None self._done = False self._done_callbacks = [] def set_result(self, result): self._result = result self._set_done() def set_exception_info(self, exception, traceback): self._exception = exception self._traceback = traceback self._set_done() def result(self, timeout=None): if self._exception: raise self._exception.with_traceback(self._traceback) return self._result def _set_done(self): self._done = True for done_callback in self._done_callbacks: self._invoke_done_callback(done_callback) self._done_callbacks = [] def _invoke_done_callback(self, done_callback): return done_callback(self) def done(self): return self._done def add_done_callback(self, fn): if self._done: self._invoke_done_callback(fn) else: self._done_callbacks.append(fn) TaskTag = namedtuple('TaskTag', ['name']) IN_MEMORY_UPLOAD_TAG = TaskTag('in_memory_upload') IN_MEMORY_DOWNLOAD_TAG = TaskTag('in_memory_download')