| # Copyright 2013 The LUCI Authors. All rights reserved. |
| # Use of this source code is governed under the Apache License, Version 2.0 |
| # that can be found in the LICENSE file. |
| |
| """Classes and functions related to threading.""" |
| |
| import functools |
| import inspect |
| import logging |
| import os |
| import queue |
| import sys |
| import threading |
| import time |
| import traceback |
| |
| |
| # Priorities for tasks in AutoRetryThreadPool, particular values are important. |
| PRIORITY_HIGH = 1 << 8 |
| PRIORITY_MED = 2 << 8 |
| PRIORITY_LOW = 3 << 8 |
| |
| |
| class LockWithAssert: |
| """Wrapper around (non recursive) Lock that tracks its owner.""" |
| |
| def __init__(self): |
| self._lock = threading.Lock() |
| self._owner = None |
| |
| def __enter__(self): |
| self._lock.acquire() |
| assert self._owner is None |
| self._owner = threading.current_thread() |
| |
| def __exit__(self, _exc_type, _exec_value, _traceback): |
| self.assert_locked('Releasing unowned lock') |
| self._owner = None |
| self._lock.release() |
| return False |
| |
| def assert_locked(self, msg=None): |
| """Asserts the lock is owned by running thread.""" |
| assert self._owner == threading.current_thread(), msg |
| |
| |
| class ThreadPoolError(Exception): |
| """Base class for exceptions raised by ThreadPool.""" |
| |
| |
| class ThreadPoolEmpty(ThreadPoolError): |
| """Trying to get task result from a thread pool with no pending tasks.""" |
| |
| |
| class ThreadPoolClosed(ThreadPoolError): |
| """Trying to do something with a closed thread pool.""" |
| |
| |
| class ThreadPool: |
| """Multithreaded worker pool with priority support. |
| |
| When the priority of tasks match, it works in strict FIFO mode. |
| """ |
| QUEUE_CLASS = queue.PriorityQueue |
| # Enqueueing None causes the worker to stop. |
| # Python3 doesn't support to compare None with any integer, so putting None |
| # in priority queue will cause exception. Switch to use sys.maxsize, since |
| # lower priority takes precedence. |
| TASK_END_SENTINEL = (sys.maxsize,) |
| |
| def __init__(self, initial_threads, max_threads, queue_size, prefix=None): |
| """Immediately starts |initial_threads| threads. |
| |
| Arguments: |
| initial_threads: Number of threads to start immediately. Can be 0 if it is |
| uncertain that threads will be needed. |
| max_threads: Maximum number of threads that will be started when all the |
| threads are busy working. Often the number of CPU cores. |
| queue_size: Maximum number of tasks to buffer in the queue. 0 for |
| unlimited queue. A non-zero value may make add_task() |
| blocking. |
| prefix: Prefix to use for thread names. Pool's threads will be |
| named '<prefix>-<thread index>'. |
| """ |
| prefix = prefix or 'tp-0x%0x' % id(self) |
| logging.debug( |
| 'New ThreadPool(%d, %d, %d): %s', initial_threads, max_threads, |
| queue_size, prefix) |
| assert initial_threads <= max_threads |
| assert max_threads <= 1024 |
| |
| self.tasks = self.QUEUE_CLASS(queue_size) |
| self._max_threads = max_threads |
| self._prefix = prefix |
| |
| # Used to assign indexes to tasks. |
| self._num_of_added_tasks_lock = threading.Lock() |
| self._num_of_added_tasks = 0 |
| |
| # Lock that protected everything below (including conditional variable). |
| self._lock = threading.Lock() |
| |
| # Condition 'bool(_outputs) or bool(_exceptions) or _pending_count == 0'. |
| self._outputs_exceptions_cond = threading.Condition(self._lock) |
| self._outputs = [] |
| self._exceptions = [] |
| |
| # Number of pending tasks (queued or being processed now). |
| self._pending_count = 0 |
| |
| # List of threads. |
| self._workers = [] |
| # Number of threads that are waiting for new tasks. |
| self._ready = 0 |
| # Number of threads already added to _workers, but not yet running the loop. |
| self._starting = 0 |
| # True if close was called. Forbids adding new tasks. |
| self._is_closed = False |
| |
| for _ in range(initial_threads): |
| self._add_worker() |
| |
| def _add_worker(self): |
| """Adds one worker thread if there isn't too many. Thread-safe.""" |
| with self._lock: |
| if len(self._workers) >= self._max_threads or self._is_closed: |
| return False |
| worker = threading.Thread( |
| name='%s-%d' % (self._prefix, len(self._workers)), target=self._run) |
| self._workers.append(worker) |
| self._starting += 1 |
| logging.debug('Starting worker thread %s', worker.name) |
| worker.daemon = True |
| worker.start() |
| return True |
| |
| def add_task(self, priority, func, *args, **kwargs): |
| """Adds a task, a function to be executed by a worker. |
| |
| Arguments: |
| - priority: priority of the task versus others. Lower priority takes |
| precedence. |
| - func: function to run. Can either return a return value to be added to the |
| output list or be a generator which can emit multiple values. |
| - args and kwargs: arguments to |func|. Note that if func mutates |args| or |
| |kwargs| and that the task is retried, see |
| AutoRetryThreadPool, the retry will use the mutated |
| values. |
| |
| Returns: |
| Index of the item added, e.g. the total number of enqueued items up to |
| now. |
| """ |
| assert isinstance(priority, int) |
| assert callable(func) |
| with self._lock: |
| if self._is_closed: |
| raise ThreadPoolClosed('Can not add a task to a closed ThreadPool') |
| start_new_worker = ( |
| # Pending task count plus new task > number of available workers. |
| self.tasks.qsize() + 1 > self._ready + self._starting and |
| # Enough slots. |
| len(self._workers) < self._max_threads |
| ) |
| self._pending_count += 1 |
| with self._num_of_added_tasks_lock: |
| self._num_of_added_tasks += 1 |
| index = self._num_of_added_tasks |
| self.tasks.put((priority, index, func, args, kwargs)) |
| if start_new_worker: |
| self._add_worker() |
| return index |
| |
| def _run(self): |
| """Worker thread loop. Runs until a None task is queued.""" |
| # Thread has started, adjust counters. |
| with self._lock: |
| self._starting -= 1 |
| self._ready += 1 |
| while True: |
| try: |
| task = self.tasks.get() |
| finally: |
| with self._lock: |
| self._ready -= 1 |
| try: |
| if task == self.TASK_END_SENTINEL: |
| # We're done. |
| return |
| _priority, _index, func, args, kwargs = task |
| if inspect.isgeneratorfunction(func): |
| for out in func(*args, **kwargs): |
| self._output_append(out) |
| else: |
| out = func(*args, **kwargs) |
| self._output_append(out) |
| except Exception as e: |
| logging.warning('Caught exception: %s', e) |
| exc_info = sys.exc_info() |
| logging.info(''.join(traceback.format_tb(exc_info[2]))) |
| with self._outputs_exceptions_cond: |
| self._exceptions.append(exc_info) |
| self._outputs_exceptions_cond.notifyAll() |
| finally: |
| try: |
| # Mark thread as ready again, mark task as processed. Do it before |
| # waking up threads waiting on self.tasks.join(). Otherwise they might |
| # find ThreadPool still 'busy' and perform unnecessary wait on CV. |
| with self._outputs_exceptions_cond: |
| self._ready += 1 |
| self._pending_count -= 1 |
| if self._pending_count == 0: |
| self._outputs_exceptions_cond.notifyAll() |
| self.tasks.task_done() |
| except Exception as e: |
| # We need to catch and log this error here because this is the root |
| # function for the thread, nothing higher will catch the error. |
| logging.exception('Caught exception while marking task as done: %s', |
| e) |
| |
| def _output_append(self, out): |
| if out is not None: |
| with self._outputs_exceptions_cond: |
| self._outputs.append(out) |
| self._outputs_exceptions_cond.notifyAll() |
| |
| def join(self): |
| """Extracts all the results from each threads unordered. |
| |
| Call repeatedly to extract all the exceptions if desired. |
| |
| Note: will wait for all work items to be done before returning an exception. |
| To get an exception early, use get_one_result(). |
| """ |
| # TODO(maruel): Stop waiting as soon as an exception is caught. |
| self.tasks.join() |
| with self._outputs_exceptions_cond: |
| if self._exceptions: |
| e = self._exceptions.pop(0) |
| raise e[1] |
| out = self._outputs |
| self._outputs = [] |
| return out |
| |
| def get_one_result(self): |
| """Returns the next item that was generated or raises an exception if one |
| occurred. |
| |
| Raises: |
| ThreadPoolEmpty - no results available. |
| """ |
| # Get first available result. |
| for result in self.iter_results(): |
| return result |
| # No results -> tasks queue is empty. |
| raise ThreadPoolEmpty('Task queue is empty') |
| |
| def iter_results(self): |
| """Yields results as they appear until all tasks are processed.""" |
| while True: |
| # Check for pending results. |
| result = None |
| self._on_iter_results_step() |
| with self._outputs_exceptions_cond: |
| if self._exceptions: |
| e = self._exceptions.pop(0) |
| raise e[1] |
| if self._outputs: |
| # Remember the result to yield it outside of the lock. |
| result = self._outputs.pop(0) |
| else: |
| # No pending tasks -> all tasks are done. |
| if not self._pending_count: |
| return |
| # Some task is queued, wait for its result to appear. |
| # Use non-None timeout so that process reacts to Ctrl+C and other |
| # signals, see http://bugs.python.org/issue8844. |
| self._outputs_exceptions_cond.wait(timeout=0.1) |
| continue |
| yield result |
| |
| def close(self): |
| """Closes all the threads.""" |
| # Ensure no new threads can be started, self._workers is effectively |
| # a constant after that and can be accessed outside the lock. |
| with self._lock: |
| if self._is_closed: |
| raise ThreadPoolClosed('Can not close already closed ThreadPool') |
| self._is_closed = True |
| for _ in range(len(self._workers)): |
| self.tasks.put(self.TASK_END_SENTINEL) |
| for t in self._workers: |
| # 'join' without timeout blocks signal handlers, spin with timeout. |
| while t.is_alive(): |
| t.join(30) |
| logging.debug( |
| 'Thread pool \'%s\' closed: spawned %d threads total', |
| self._prefix, len(self._workers)) |
| |
| def abort(self): |
| """Empties the queue. |
| |
| To be used when the pool should stop early, like when Ctrl-C was detected. |
| |
| Returns: |
| Number of tasks cancelled. |
| """ |
| index = 0 |
| while True: |
| try: |
| self.tasks.get_nowait() |
| self.tasks.task_done() |
| index += 1 |
| except queue.Empty: |
| return index |
| |
| def _on_iter_results_step(self): |
| pass |
| |
| def __enter__(self): |
| """Enables 'with' statement.""" |
| return self |
| |
| def __exit__(self, _exc_type, _exc_value, _traceback): |
| """Enables 'with' statement.""" |
| self.close() |
| |
| |
| class AutoRetryThreadPool(ThreadPool): |
| """Automatically retries enqueued operations on exception.""" |
| # See also PRIORITY_* module-level constants. |
| INTERNAL_PRIORITY_BITS = (1<<8) - 1 |
| |
| def __init__(self, exceptions, retries, *args, **kwargs): |
| """ |
| Arguments: |
| exceptions: list of exception classes that can be retried on. |
| retries: maximum number of retries to do. |
| """ |
| assert exceptions and all(issubclass(e, Exception) for e in exceptions), ( |
| exceptions) |
| assert 1 <= retries <= self.INTERNAL_PRIORITY_BITS |
| super(AutoRetryThreadPool, self).__init__(*args, **kwargs) |
| self._swallowed_exceptions = tuple(exceptions) |
| self._retries = retries |
| |
| def add_task(self, priority, func, *args, **kwargs): |
| """Tasks added must not use the lower priority bits since they are reserved |
| for retries. |
| """ |
| assert (priority & self.INTERNAL_PRIORITY_BITS) == 0 |
| return super(AutoRetryThreadPool, self).add_task( |
| priority, |
| self._task_executer, |
| priority, |
| None, |
| func, |
| *args, |
| **kwargs) |
| |
| def add_task_with_channel(self, channel, priority, func, *args, **kwargs): |
| """Tasks added must not use the lower priority bits since they are reserved |
| for retries. |
| """ |
| assert (priority & self.INTERNAL_PRIORITY_BITS) == 0 |
| return super(AutoRetryThreadPool, self).add_task( |
| priority, |
| self._task_executer, |
| priority, |
| channel, |
| func, |
| *args, |
| **kwargs) |
| |
| def _task_executer(self, priority, channel, func, *args, **kwargs): |
| """Wraps the function and automatically retry on exceptions.""" |
| try: |
| result = func(*args, **kwargs) |
| if channel is None: |
| return result |
| channel.send_result(result) |
| # pylint: disable=catching-non-exception |
| except self._swallowed_exceptions as e: |
| # Retry a few times, lowering the priority. |
| actual_retries = priority & self.INTERNAL_PRIORITY_BITS |
| if actual_retries < self._retries: |
| priority += 1 |
| logging.debug( |
| 'Swallowed exception \'%s\'. Retrying at lower priority %X', |
| e, priority) |
| super(AutoRetryThreadPool, self).add_task( |
| priority, |
| self._task_executer, |
| priority, |
| channel, |
| func, |
| *args, |
| **kwargs) |
| return |
| if channel is None: |
| raise |
| channel.send_exception() |
| except Exception: |
| if channel is None: |
| raise |
| channel.send_exception() |
| |
| |
| class IOAutoRetryThreadPool(AutoRetryThreadPool): |
| """Thread pool that automatically retries on IOError. |
| |
| Supposed to be used for IO bound tasks, and thus default maximum number of |
| worker threads is independent of number of CPU cores. |
| """ |
| # Initial and maximum number of worker threads. |
| INITIAL_WORKERS = 2 |
| MAX_WORKERS = 16 if sys.maxsize > 2**32 else 8 |
| RETRIES = 5 |
| |
| def __init__(self): |
| super(IOAutoRetryThreadPool, self).__init__( |
| [IOError], |
| self.RETRIES, |
| self.INITIAL_WORKERS, |
| self.MAX_WORKERS, |
| 0, |
| 'io') |
| |
| |
| class Progress: |
| """Prints progress and accepts updates thread-safely.""" |
| def __init__(self, columns): |
| """Creates a Progress bar that will updates asynchronously from the worker |
| threads. |
| |
| Arguments: |
| columns: list of tuple(name, initialvalue), defines both the number of |
| columns and their initial values. |
| """ |
| assert all( |
| len(c) == 2 and isinstance(c[0], str) and isinstance(c[1], int) |
| for c in columns), columns |
| # Members to be used exclusively in the primary thread. |
| self.use_cr_only = True |
| self.unfinished_commands = set() |
| self.start = time.time() |
| self._last_printed_line = '' |
| self._columns = [c[1] for c in columns] |
| self._columns_lookup = dict((c[0], i) for i, c in enumerate(columns)) |
| # Setting it to True forces a print on the first print_update() call. |
| self._value_changed = True |
| |
| # To be used in all threads. |
| self._queued_updates = queue.Queue() |
| |
| def update_item(self, name, raw=False, **kwargs): |
| """Queue information to print out. |
| |
| Arguments: |
| name: string to print out to describe something that was completed. |
| raw: if True, prints the data without the header. |
| raw: if True, prints the data without the header. |
| <kwargs>: argument name is a name of a column. it's value is the increment |
| to the column, value is usually 0 or 1. |
| """ |
| assert isinstance(name, basestring), repr(name) |
| assert isinstance(raw, bool), repr(raw) |
| assert all(isinstance(v, int) for v in kwargs.values()), repr(kwargs) |
| args = [(self._columns_lookup[k], v) for k, v in kwargs.items() if v] |
| self._queued_updates.put((name, raw, args)) |
| |
| def print_update(self): |
| """Prints the current status.""" |
| # Flush all the logging output so it doesn't appear within this output. |
| for handler in logging.root.handlers: |
| handler.flush() |
| |
| got_one = False |
| while True: |
| try: |
| name, raw, args = self._queued_updates.get_nowait() |
| except queue.Empty: |
| break |
| |
| for k, v in args: |
| self._columns[k] += v |
| self._value_changed = bool(args) |
| if not name: |
| # Even if raw=True, there's nothing to print. |
| continue |
| |
| got_one = True |
| if raw: |
| # Prints the data as-is. |
| self._last_printed_line = '' |
| sys.stdout.write('\n%s\n' % name.strip('\n')) |
| else: |
| line, self._last_printed_line = self._gen_line(name) |
| sys.stdout.write(line) |
| |
| if not got_one and self._value_changed: |
| # Make sure a line is printed in that case where statistics changes. |
| line, self._last_printed_line = self._gen_line('') |
| sys.stdout.write(line) |
| got_one = True |
| self._value_changed = False |
| if got_one: |
| # Ensure that all the output is flushed to prevent it from getting mixed |
| # with other output streams (like the logging streams). |
| sys.stdout.flush() |
| |
| if self.unfinished_commands: |
| logging.debug('Waiting for the following commands to finish:\n%s', |
| '\n'.join(self.unfinished_commands)) |
| |
| def _gen_line(self, name): |
| """Generates the line to be printed.""" |
| next_line = ('[%s] %6.2fs %s') % ( |
| self._render_columns(), time.time() - self.start, name) |
| # Fill it with whitespace only if self.use_cr_only is set. |
| prefix = '' |
| if self.use_cr_only and self._last_printed_line: |
| prefix = '\r' |
| if self.use_cr_only: |
| suffix = ' ' * max(0, len(self._last_printed_line) - len(next_line)) |
| else: |
| suffix = '\n' |
| return '%s%s%s' % (prefix, next_line, suffix), next_line |
| |
| def _render_columns(self): |
| """Renders the columns.""" |
| columns_as_str = map(str, self._columns) |
| max_len = max(map(len, columns_as_str)) |
| return '/'.join(i.rjust(max_len) for i in columns_as_str) |
| |
| |
| class QueueWithProgress(queue.PriorityQueue): |
| """Implements progress support in join().""" |
| def __init__(self, progress, *args, **kwargs): |
| queue.PriorityQueue.__init__(self, *args, **kwargs) |
| self.progress = progress |
| |
| def task_done(self): |
| """Contrary to Queue.task_done(), it wakes self.all_tasks_done at each task |
| done. |
| """ |
| with self.all_tasks_done: |
| try: |
| unfinished = self.unfinished_tasks - 1 |
| if unfinished < 0: |
| raise ValueError('task_done() called too many times') |
| self.unfinished_tasks = unfinished |
| # This is less efficient, because we want the Progress to be updated. |
| self.all_tasks_done.notify_all() |
| except Exception as e: |
| logging.exception('task_done threw an exception.\n%s', e) |
| |
| def wake_up(self): |
| """Wakes up all_tasks_done. |
| |
| Unlike task_done(), do not substract one from self.unfinished_tasks. |
| """ |
| # TODO(maruel): This is highly inefficient, since the listener is awaken |
| # twice; once per output, once per task. There should be no relationship |
| # between the number of output and the number of input task. |
| with self.all_tasks_done: |
| self.all_tasks_done.notify_all() |
| |
| def join(self): |
| """Calls print_update() whenever possible.""" |
| self.progress.print_update() |
| with self.all_tasks_done: |
| while self.unfinished_tasks: |
| self.progress.print_update() |
| # Use a short wait timeout so updates are printed in a timely manner. |
| # TODO(maruel): Find a way so Progress.queue and self.all_tasks_done |
| # share the same underlying event so no polling is necessary. |
| self.all_tasks_done.wait(0.1) |
| self.progress.print_update() |
| |
| |
| class ThreadPoolWithProgress(ThreadPool): |
| QUEUE_CLASS = QueueWithProgress |
| |
| def __init__(self, progress, *args, **kwargs): |
| self.QUEUE_CLASS = functools.partial(self.QUEUE_CLASS, progress) |
| super(ThreadPoolWithProgress, self).__init__(*args, **kwargs) |
| |
| def _output_append(self, out): |
| """Also wakes up the listener on new completed test_case.""" |
| super(ThreadPoolWithProgress, self)._output_append(out) |
| self.tasks.wake_up() |
| |
| def _on_iter_results_step(self): |
| self.tasks.progress.print_update() |
| |
| |
| class DeadlockDetector: |
| """Context manager that can detect deadlocks. |
| |
| It will dump stack frames of all running threads if its 'ping' method isn't |
| called in time. |
| |
| Usage: |
| with DeadlockDetector(timeout=60) as detector: |
| for item in some_work(): |
| ... |
| detector.ping() |
| ... |
| |
| Arguments: |
| timeout - maximum allowed time between calls to 'ping'. |
| """ |
| |
| def __init__(self, timeout): |
| self.timeout = timeout |
| self._thread = None |
| # Thread stop condition. Also lock for shared variables below. |
| self._stop_cv = threading.Condition() |
| self._stop_flag = False |
| # Time when 'ping' was called last time. |
| self._last_ping = None |
| # True if pings are coming on time. |
| self._alive = True |
| |
| def __enter__(self): |
| """Starts internal watcher thread.""" |
| assert self._thread is None |
| self.ping() |
| self._thread = threading.Thread(name='deadlock-detector', target=self._run) |
| self._thread.daemon = True |
| self._thread.start() |
| return self |
| |
| def __exit__(self, *_args): |
| """Stops internal watcher thread.""" |
| assert self._thread is not None |
| with self._stop_cv: |
| self._stop_flag = True |
| self._stop_cv.notify() |
| self._thread.join() |
| self._thread = None |
| self._stop_flag = False |
| |
| def ping(self): |
| """Notify detector that main thread is still running. |
| |
| Should be called periodically to inform the detector that everything is |
| running as it should. |
| """ |
| with self._stop_cv: |
| self._last_ping = time.time() |
| self._alive = True |
| |
| def _run(self): |
| """Loop that watches for pings and dumps threads state if ping is late.""" |
| with self._stop_cv: |
| while not self._stop_flag: |
| # Skipped deadline? Dump threads and switch to 'not alive' state. |
| if self._alive and time.time() > self._last_ping + self.timeout: |
| self.dump_threads(time.time() - self._last_ping, True) |
| self._alive = False |
| |
| # Pings are on time? |
| if self._alive: |
| # Wait until the moment we need to dump stack traces. |
| # Most probably some other thread will call 'ping' to move deadline |
| # further in time. We don't bother to wake up after each 'ping', |
| # only right before initial expected deadline. |
| self._stop_cv.wait(self._last_ping + self.timeout - time.time()) |
| else: |
| # Skipped some pings previously. Just periodically silently check |
| # for new pings with some arbitrary frequency. |
| self._stop_cv.wait(self.timeout * 0.1) |
| |
| @staticmethod |
| def dump_threads(timeout=None, skip_current_thread=False): |
| """Dumps stack frames of all running threads.""" |
| all_threads = threading.enumerate() |
| current_thread_id = threading.current_thread().ident |
| |
| # Collect tracebacks: thread name -> traceback string. |
| tracebacks = {} |
| |
| # pylint: disable=W0212 |
| for thread_id, frame in sys._current_frames().items(): |
| # Don't dump deadlock detector's own thread, it's boring. |
| if thread_id == current_thread_id and skip_current_thread: |
| continue |
| |
| # Try to get more informative symbolic thread name. |
| name = 'untitled' |
| for thread in all_threads: |
| if thread.ident == thread_id: |
| name = thread.name |
| break |
| name += ' #%d' % (thread_id,) |
| tracebacks[name] = ''.join(traceback.format_stack(frame)) |
| |
| # Function to print a message. Makes it easier to change output destination. |
| def output(msg): |
| logging.warning(msg.rstrip()) |
| |
| # Print tracebacks, sorting them by thread name. That way a thread pool's |
| # threads will be printed as one group. |
| output('=============== Potential deadlock detected ===============') |
| if timeout is not None: |
| output('No pings in last %d sec.' % (timeout,)) |
| output('Dumping stack frames for all threads:') |
| for name in sorted(tracebacks): |
| output('Traceback for \'%s\':\n%s' % (name, tracebacks[name])) |
| output('===========================================================') |
| |
| |
| class TaskChannel: |
| """Queue of results of async task execution.""" |
| |
| class Timeout(Exception): |
| """Raised by 'pull' in case of timeout.""" |
| |
| _ITEM_RESULT = object() |
| _ITEM_EXCEPTION = object() |
| _ITEM_DONE = object() |
| |
| def __init__(self): |
| self._queue = queue.Queue() |
| |
| def send_result(self, result): |
| """Enqueues a result of task execution.""" |
| self._queue.put((self._ITEM_RESULT, result)) |
| |
| def send_done(self): |
| """Stops the iteration.""" |
| self._queue.put((self._ITEM_DONE, None)) |
| |
| def send_exception(self, exc_info=None): |
| """Enqueue an exception raised by a task. |
| |
| Arguments: |
| exc_info: If given, should be 3-tuple returned by sys.exc_info(), |
| default is current value of sys.exc_info(). Use default in |
| 'except' blocks to capture currently processed exception. |
| """ |
| exc_info = exc_info or sys.exc_info() |
| assert isinstance(exc_info, tuple) and len(exc_info) == 3 |
| # Transparently passing Timeout will break 'pull' contract, since a caller |
| # has no way to figure out that's an exception from the task and not from |
| # 'pull' itself. Transform Timeout into generic RuntimeError with |
| # explanation. |
| if isinstance(exc_info[1], TaskChannel.Timeout): |
| exc_info = ( |
| RuntimeError, |
| RuntimeError('Task raised Timeout exception'), |
| exc_info[2]) |
| self._queue.put((self._ITEM_EXCEPTION, exc_info)) |
| |
| def __iter__(self): |
| return self |
| |
| def next(self, timeout=None): |
| """Dequeues available result or exception. |
| |
| Args: |
| timeout: if not None will block no longer than |timeout| seconds and will |
| raise TaskChannel.Timeout exception if no results are available. |
| |
| Returns: |
| Whatever task pushes to the queue by calling 'send_result'. |
| |
| Raises: |
| TaskChannel.Timeout: waiting longer than |timeout|. |
| Whatever exception task raises. |
| """ |
| # Do not ever use timeout == None, in that case signal handlers are not |
| # being called (at least on Python 2.7, http://bugs.python.org/issue8844). |
| while True: |
| try: |
| item_type, value = self._queue.get( |
| timeout=timeout if timeout is not None else 30.0) |
| break |
| except queue.Empty: |
| if timeout is None: |
| continue |
| raise TaskChannel.Timeout() |
| if item_type == self._ITEM_RESULT: |
| return value |
| if item_type == self._ITEM_EXCEPTION: |
| # 'value' is captured sys.exc_info() 3-tuple. Use extended raise syntax |
| # to preserve stack frame of original exception (that was raised in |
| # another thread). |
| assert isinstance(value, tuple) and len(value) == 3 |
| raise value[1] |
| if item_type == self._ITEM_DONE: |
| raise StopIteration() |
| assert False, 'Impossible queue item type: %r' % item_type |
| |
| def __next__(self): |
| # For python3 compatibility |
| return self.next() |
| |
| def wrap_task(self, task): |
| """Decorator that makes a function push results into this channel.""" |
| @functools.wraps(task) |
| def wrapped(*args, **kwargs): |
| try: |
| self.send_result(task(*args, **kwargs)) |
| except Exception: |
| self.send_exception() |
| return wrapped |
| |
| |
| def num_processors(): |
| """Returns the number of processors. |
| |
| Python on OSX 10.6 raises a NotImplementedError exception. |
| """ |
| try: |
| # Multiprocessing |
| import multiprocessing |
| return multiprocessing.cpu_count() |
| except: # pylint: disable=W0702 |
| try: |
| # Mac OS 10.6 |
| return int(os.sysconf('SC_NPROCESSORS_ONLN')) # pylint: disable=E1101 |
| except: |
| # Some of the windows builders seem to get here. |
| return 4 |
