| # -*- coding: utf-8 -*- |
| # Copyright (c) 2012 The Chromium OS Authors. All rights reserved. |
| # Use of this source code is governed by a BSD-style license that can be |
| # found in the LICENSE file. |
| |
| """Module for running cbuildbot stages in the background.""" |
| |
| from __future__ import print_function |
| |
| import collections |
| import contextlib |
| import ctypes |
| import errno |
| import functools |
| import multiprocessing |
| from multiprocessing.managers import SyncManager |
| import os |
| try: |
| import Queue |
| except ImportError: |
| # Python-3 renamed to "queue". We still use Queue to avoid collisions |
| # with naming variables as "queue". Maybe we'll transition at some point. |
| # pylint: disable=import-error |
| import queue as Queue |
| import signal |
| import sys |
| import tempfile |
| import time |
| import traceback |
| |
| from chromite.lib import failures_lib |
| from chromite.lib import results_lib |
| from chromite.lib import cros_build_lib |
| from chromite.lib import cros_logging as logging |
| from chromite.lib import osutils |
| from chromite.lib import signals |
| from chromite.lib import timeout_util |
| |
| |
| _BUFSIZE = 1024 |
| |
| |
| class HackTimeoutSyncManager(SyncManager): |
| """Increase the process join timeout in SyncManager. |
| |
| The timeout for the manager process to join in the core library is |
| too low. The process is often killed before shutting down properly, |
| resulting in temporary directories (pymp-xxx) not being cleaned |
| up. This class increases the default timeout. |
| """ |
| |
| @staticmethod |
| def _finalize_manager(process, *args, **kwargs): |
| """Shutdown the manager process.""" |
| |
| def _join(functor, *args, **kwargs): |
| timeout = kwargs.get('timeout') |
| if not timeout is None and timeout < 1: |
| kwargs['timeout'] = 1 |
| |
| functor(*args, **kwargs) |
| |
| process.join = functools.partial(_join, process.join) |
| SyncManager._finalize_manager(process, *args, **kwargs) |
| |
| |
| def IgnoreSigintAndSigterm(): |
| """Ignores any future SIGINTs and SIGTERMs.""" |
| signal.signal(signal.SIGINT, signal.SIG_IGN) |
| signal.signal(signal.SIGTERM, signal.SIG_IGN) |
| |
| |
| def Manager(): |
| """Create a background process for managing interprocess communication. |
| |
| This manager wraps multiprocessing.Manager() and ensures that any sockets |
| created during initialization are created under the /tmp tree rather than in a |
| custom temp directory. This is needed because TMPDIR might be really long, and |
| named sockets are limited to 108 characters. |
| |
| Examples: |
| with Manager() as manager: |
| queue = manager.Queue() |
| ... |
| |
| Returns: |
| The return value of multiprocessing.Manager() |
| """ |
| # Use a short directory in /tmp. Do not use /tmp directly to keep these |
| # temperary files together and because certain environments do not like too |
| # many top-level paths in /tmp (see crbug.com/945523). |
| tmp_dir = '/tmp/chromite.parallel' |
| osutils.SafeMakedirs(tmp_dir) |
| old_tempdir_value, old_tempdir_env = osutils.SetGlobalTempDir(tmp_dir) |
| try: |
| m = HackTimeoutSyncManager() |
| # SyncManager doesn't handle KeyboardInterrupt exceptions well; pipes get |
| # broken and E_NOENT or E_PIPE errors are thrown from various places. We |
| # can just ignore SIGINT in the SyncManager and things will close properly |
| # when the enclosing with-statement exits. |
| m.start(IgnoreSigintAndSigterm) |
| return m |
| finally: |
| osutils.SetGlobalTempDir(old_tempdir_value, old_tempdir_env) |
| |
| |
| class BackgroundFailure(failures_lib.CompoundFailure): |
| """Exception to show a step failed while running in a background process.""" |
| |
| |
| class ProcessExitTimeout(Exception): |
| """Raised if a process cannot exit within the timeout.""" |
| |
| |
| class ProcessUnexpectedExit(Exception): |
| """Raised if a process exits unexpectedly.""" |
| |
| |
| class ProcessSilentTimeout(Exception): |
| """Raised when there is no output for a prolonged period of time.""" |
| |
| |
| class UnexpectedException(Exception): |
| """Raised when exception occurs at an unexpected place.""" |
| |
| |
| class _BackgroundTask(multiprocessing.Process): |
| """Run a task in the background. |
| |
| This task may be the 'Run' function from a buildbot stage or just a plain |
| function. It will be run in the background. Output from this task is saved |
| to a temporary file and is printed when the 'Wait' function is called. |
| """ |
| |
| # The time we give Python to startup and exit. |
| STARTUP_TIMEOUT = 60 * 5 |
| EXIT_TIMEOUT = 60 * 10 |
| |
| # The time we allow processes to be silent. This is in place so that we |
| # eventually catch hanging processes, and print the remainder of our output. |
| # Do not increase this. Instead, adjust your program to print regular progress |
| # updates, so that cbuildbot (and buildbot) can know that it has not hung. |
| SILENT_TIMEOUT = 60 * 145 |
| |
| # The amount by which we reduce the SILENT_TIMEOUT every time we launch |
| # a subprocess. This helps ensure that children get a chance to enforce the |
| # SILENT_TIMEOUT prior to the parents enforcing it. |
| SILENT_TIMEOUT_STEP = 30 |
| MINIMUM_SILENT_TIMEOUT = 60 * 135 |
| |
| # The time before terminating or killing a task. |
| SIGTERM_TIMEOUT = 30 |
| SIGKILL_TIMEOUT = 60 |
| |
| # How long we allow debug commands to run (so we don't hang will trying to |
| # recover from a hang). |
| DEBUG_CMD_TIMEOUT = 60 |
| |
| # Interval we check for updates from print statements. |
| PRINT_INTERVAL = 1 |
| |
| def __init__(self, task, queue, semaphore=None, task_args=None, |
| task_kwargs=None): |
| """Create a new _BackgroundTask object. |
| |
| If semaphore is supplied, it will be acquired for the duration of the |
| steps that are run in the background. This can be used to limit the |
| number of simultaneous parallel tasks. |
| |
| Args: |
| task: The task (a functor) to run in the background. |
| queue: A queue to be used for managing communication between the parent |
| and child process. This queue must be valid for the length of the |
| life of the child process, until the parent has collected its status. |
| semaphore: The lock to hold while |task| runs. |
| task_args: A list of args to pass to the |task|. |
| task_kwargs: A dict of optional args to pass to the |task|. |
| """ |
| multiprocessing.Process.__init__(self) |
| self._task = task |
| self._queue = queue |
| self._semaphore = semaphore |
| self._started = multiprocessing.Event() |
| self._killing = multiprocessing.Event() |
| self._output = None |
| self._parent_pid = None |
| self._task_args = task_args if task_args else () |
| self._task_kwargs = task_kwargs if task_kwargs else {} |
| |
| def _WaitForStartup(self): |
| # TODO(davidjames): Use python-2.7 syntax to simplify this. |
| self._started.wait(self.STARTUP_TIMEOUT) |
| msg = 'Process failed to start in %d seconds' % self.STARTUP_TIMEOUT |
| assert self._started.is_set(), msg |
| |
| @classmethod |
| def _DebugRunCommand(cls, cmd, **kwargs): |
| """Swallow any exception RunCommand raises. |
| |
| Since these commands are for purely informational purposes, we don't |
| random issues causing the bot to die. |
| |
| Returns: |
| Stdout on success |
| """ |
| log_level = kwargs['debug_level'] |
| try: |
| with timeout_util.Timeout(cls.DEBUG_CMD_TIMEOUT): |
| return cros_build_lib.RunCommand(cmd, **kwargs).output |
| except (cros_build_lib.RunCommandError, timeout_util.TimeoutError) as e: |
| logging.log(log_level, 'Running %s failed: %s', cmd[0], str(e)) |
| return '' |
| |
| # Debug commands to run in gdb. A class member so tests can stub it out. |
| GDB_COMMANDS = ( |
| 'info proc all', |
| 'info threads', |
| 'thread apply all py-list', |
| 'thread apply all py-bt', |
| 'thread apply all bt', |
| 'detach', |
| ) |
| |
| @classmethod |
| def _DumpDebugPid(cls, log_level, pid): |
| """Dump debug info about the hanging |pid|.""" |
| pid = str(pid) |
| commands = ( |
| ('pstree', '-Apals', pid), |
| ('lsof', '-p', pid), |
| ) |
| for cmd in commands: |
| cls._DebugRunCommand(cmd, debug_level=log_level, error_code_ok=True, |
| log_output=True) |
| |
| stdin = '\n'.join(['echo \\n>>> %s\\n\n%s' % (x, x) |
| for x in cls.GDB_COMMANDS]) |
| cmd = ('gdb', '--nx', '-q', '-p', pid, '-ex', 'set prompt',) |
| cls._DebugRunCommand(cmd, debug_level=log_level, error_code_ok=True, |
| log_output=True, input=stdin) |
| |
| def Kill(self, sig, log_level, first=False): |
| """Kill process with signal, ignoring if the process is dead. |
| |
| Args: |
| sig: Signal to send. |
| log_level: The log level of log messages. |
| first: Whether this is the first signal we've sent. |
| """ |
| self._killing.set() |
| self._WaitForStartup() |
| if logging.getLogger().isEnabledFor(log_level): |
| # Dump debug information about the hanging process. |
| logging.log(log_level, 'Killing %r (sig=%r %s)', self.pid, sig, |
| signals.StrSignal(sig)) |
| |
| if first: |
| ppid = str(self.pid) |
| output = self._DebugRunCommand( |
| ('pgrep', '-P', ppid), debug_level=log_level, print_cmd=False, |
| error_code_ok=True, capture_output=True) |
| for pid in [ppid] + output.splitlines(): |
| self._DumpDebugPid(log_level, pid) |
| |
| try: |
| os.kill(self.pid, sig) |
| except OSError as ex: |
| if ex.errno != errno.ESRCH: |
| raise |
| |
| def Cleanup(self, silent=False): |
| """Wait for a process to exit.""" |
| if os.getpid() != self._parent_pid or self._output is None: |
| return |
| try: |
| # Print output from subprocess. |
| if not silent and logging.getLogger().isEnabledFor(logging.DEBUG): |
| with open(self._output.name, 'r') as f: |
| for line in f: |
| logging.debug(line.rstrip('\n')) |
| finally: |
| # Clean up our temporary file. |
| osutils.SafeUnlink(self._output.name) |
| self._output.close() |
| self._output = None |
| |
| def Wait(self): |
| """Wait for the task to complete. |
| |
| Output from the task is printed as it runs. |
| |
| If an exception occurs, return a string containing the traceback. |
| """ |
| try: |
| # Flush stdout and stderr to be sure no output is interleaved. |
| sys.stdout.flush() |
| sys.stderr.flush() |
| |
| # File position pointers are shared across processes, so we must open |
| # our own file descriptor to ensure output is not lost. |
| self._WaitForStartup() |
| silent_death_time = time.time() + self.SILENT_TIMEOUT |
| results = [] |
| with open(self._output.name, 'r') as output: |
| pos = 0 |
| running, exited_cleanly, task_errors, run_errors = (True, False, [], []) |
| while running: |
| # Check whether the process is still alive. |
| running = self.is_alive() |
| |
| try: |
| errors, results = \ |
| self._queue.get(True, self.PRINT_INTERVAL) |
| if errors: |
| task_errors.extend(errors) |
| |
| running = False |
| exited_cleanly = True |
| except Queue.Empty: |
| pass |
| |
| if not running: |
| # Wait for the process to actually exit. If the child doesn't exit |
| # in a timely fashion, kill it. |
| self.join(self.EXIT_TIMEOUT) |
| if self.exitcode is None: |
| msg = '%r hung for %r seconds' % (self, self.EXIT_TIMEOUT) |
| run_errors.extend( |
| failures_lib.CreateExceptInfo(ProcessExitTimeout(msg), '')) |
| self._KillChildren([self]) |
| elif not exited_cleanly: |
| msg = ('%r exited unexpectedly with code %s' |
| % (self, self.exitcode)) |
| run_errors.extend( |
| failures_lib.CreateExceptInfo(ProcessUnexpectedExit(msg), '')) |
| |
| # Read output from process. |
| output.seek(pos) |
| buf = output.read(_BUFSIZE) |
| |
| if len(buf) > 0: |
| silent_death_time = time.time() + self.SILENT_TIMEOUT |
| elif running and time.time() > silent_death_time: |
| msg = ('No output from %r for %r seconds' % |
| (self, self.SILENT_TIMEOUT)) |
| run_errors.extend( |
| failures_lib.CreateExceptInfo(ProcessSilentTimeout(msg), '')) |
| self._KillChildren([self]) |
| |
| # Read remaining output from the process. |
| output.seek(pos) |
| buf = output.read(_BUFSIZE) |
| running = False |
| |
| # Print output so far. |
| while len(buf) > 0: |
| sys.stdout.write(buf) |
| pos += len(buf) |
| if len(buf) < _BUFSIZE: |
| break |
| buf = output.read(_BUFSIZE) |
| |
| # Print error messages if anything exceptional occurred. |
| if run_errors: |
| logging.PrintBuildbotStepFailure() |
| traceback.print_stack() |
| logging.warning('\n'.join(x.str for x in run_errors if x)) |
| logging.info('\n'.join(x.str for x in task_errors if x)) |
| |
| sys.stdout.flush() |
| sys.stderr.flush() |
| |
| # Propagate any results. |
| for result in results: |
| results_lib.Results.Record(*result) |
| |
| finally: |
| self.Cleanup(silent=True) |
| |
| # If an error occurred, return it. |
| return run_errors + task_errors |
| |
| def start(self): |
| """Invoke multiprocessing.Process.start after flushing output/err.""" |
| if self.SILENT_TIMEOUT < self.MINIMUM_SILENT_TIMEOUT: |
| raise AssertionError('Maximum recursion depth exceeded in %r' % self) |
| |
| sys.stdout.flush() |
| sys.stderr.flush() |
| self._output = tempfile.NamedTemporaryFile(delete=False, bufsize=0, |
| prefix='chromite-parallel-') |
| self._parent_pid = os.getpid() |
| return multiprocessing.Process.start(self) |
| |
| def run(self): |
| """Run the list of steps.""" |
| if self._semaphore is not None: |
| self._semaphore.acquire() |
| |
| errors = failures_lib.CreateExceptInfo( |
| UnexpectedException('Unexpected exception in %r' % self), '') |
| pid = os.getpid() |
| try: |
| errors = self._Run() |
| finally: |
| if not self._killing.is_set() and os.getpid() == pid: |
| results = results_lib.Results.Get() |
| self._queue.put((errors, results)) |
| if self._semaphore is not None: |
| self._semaphore.release() |
| |
| def _Run(self): |
| """Internal method for running the list of steps.""" |
| # Register a handler for a signal that is rarely used. |
| def trigger_bt(_sig_num, frame): |
| logging.error('pre-kill notification (SIGXCPU); traceback:\n%s', |
| ''.join(traceback.format_stack(frame))) |
| signal.signal(signal.SIGXCPU, trigger_bt) |
| |
| sys.stdout.flush() |
| sys.stderr.flush() |
| errors = [] |
| # Send all output to a named temporary file. |
| with open(self._output.name, 'w', 0) as output: |
| # Back up sys.std{err,out}. These aren't used, but we keep a copy so |
| # that they aren't garbage collected. We intentionally don't restore |
| # the old stdout and stderr at the end, because we want shutdown errors |
| # to also be sent to the same log file. |
| _orig_stdout, _orig_stderr = sys.stdout, sys.stderr |
| |
| # Replace std{out,err} with unbuffered file objects. |
| os.dup2(output.fileno(), sys.__stdout__.fileno()) |
| os.dup2(output.fileno(), sys.__stderr__.fileno()) |
| sys.stdout = os.fdopen(sys.__stdout__.fileno(), 'w', 0) |
| sys.stderr = os.fdopen(sys.__stderr__.fileno(), 'w', 0) |
| |
| try: |
| self._started.set() |
| results_lib.Results.Clear() |
| |
| # Reduce the silent timeout by the prescribed amount. |
| cls = self.__class__ |
| cls.SILENT_TIMEOUT -= cls.SILENT_TIMEOUT_STEP |
| |
| # Actually launch the task. |
| self._task(*self._task_args, **self._task_kwargs) |
| except failures_lib.StepFailure as ex: |
| errors.extend(failures_lib.CreateExceptInfo( |
| ex, traceback.format_exc())) |
| except BaseException as ex: |
| errors.extend(failures_lib.CreateExceptInfo( |
| ex, traceback.format_exc())) |
| if self._killing.is_set(): |
| traceback.print_exc() |
| finally: |
| sys.stdout.flush() |
| sys.stderr.flush() |
| |
| return errors |
| |
| @classmethod |
| def _KillChildren(cls, bg_tasks, log_level=logging.WARNING): |
| """Kill a deque of background tasks. |
| |
| This is needed to prevent hangs in the case where child processes refuse |
| to exit. |
| |
| Args: |
| bg_tasks: A list filled with _BackgroundTask objects. |
| log_level: The log level of log messages. |
| """ |
| logging.log(log_level, 'Killing tasks: %r', bg_tasks) |
| siglist = ( |
| (signal.SIGXCPU, cls.SIGTERM_TIMEOUT), |
| (signal.SIGTERM, cls.SIGKILL_TIMEOUT), |
| (signal.SIGKILL, None), |
| ) |
| first = True |
| for sig, timeout in siglist: |
| # Send signal to all tasks. |
| for task in bg_tasks: |
| task.Kill(sig, log_level, first) |
| first = False |
| |
| # Wait for all tasks to exit, if requested. |
| if timeout is None: |
| for task in bg_tasks: |
| task.join() |
| task.Cleanup() |
| break |
| |
| # Wait until timeout expires. |
| end_time = time.time() + timeout |
| while bg_tasks: |
| time_left = end_time - time.time() |
| if time_left <= 0: |
| break |
| task = bg_tasks[-1] |
| task.join(time_left) |
| if task.exitcode is not None: |
| task.Cleanup() |
| bg_tasks.pop() |
| |
| @classmethod |
| @contextlib.contextmanager |
| def ParallelTasks(cls, steps, max_parallel=None, halt_on_error=False): |
| """Run a list of functions in parallel. |
| |
| This function launches the provided functions in the background, yields, |
| and then waits for the functions to exit. |
| |
| The output from the functions is saved to a temporary file and printed as if |
| they were run in sequence. |
| |
| If exceptions occur in the steps, we join together the tracebacks and print |
| them after all parallel tasks have finished running. Further, a |
| BackgroundFailure is raised with full stack traces of all exceptions. |
| |
| Args: |
| steps: A list of functions to run. |
| max_parallel: The maximum number of simultaneous tasks to run in parallel. |
| By default, run all tasks in parallel. |
| halt_on_error: After the first exception occurs, halt any running steps, |
| and squelch any further output, including any exceptions that might |
| occur. |
| """ |
| |
| semaphore = None |
| if max_parallel is not None: |
| semaphore = multiprocessing.Semaphore(max_parallel) |
| |
| # First, start all the steps. |
| with Manager() as manager: |
| bg_tasks = collections.deque() |
| for step in steps: |
| task = cls(step, queue=manager.Queue(), semaphore=semaphore) |
| task.start() |
| bg_tasks.append(task) |
| |
| foreground_except = None |
| try: |
| yield |
| except BaseException: |
| foreground_except = sys.exc_info() |
| finally: |
| errors = [] |
| skip_bg_wait = halt_on_error and foreground_except is not None |
| # Wait for each step to complete. |
| while not skip_bg_wait and bg_tasks: |
| task = bg_tasks.popleft() |
| task_errors = task.Wait() |
| if task_errors: |
| errors.extend(task_errors) |
| if halt_on_error: |
| break |
| |
| # If there are still tasks left, kill them. |
| if bg_tasks: |
| cls._KillChildren(bg_tasks, log_level=logging.DEBUG) |
| |
| # Propagate any exceptions; foreground exceptions take precedence. |
| if foreground_except is not None: |
| # contextlib ignores caught exceptions unless explicitly re-raised. |
| raise foreground_except[0], foreground_except[1], foreground_except[2] |
| if errors: |
| raise BackgroundFailure(exc_infos=errors) |
| |
| @staticmethod |
| def TaskRunner(queue, task, onexit=None, task_args=None, task_kwargs=None): |
| """Run task(*input) for each input in the queue. |
| |
| Returns when it encounters an _AllTasksComplete object on the queue. |
| If exceptions occur, save them off and re-raise them as a |
| BackgroundFailure once we've finished processing the items in the queue. |
| |
| Args: |
| queue: A queue of tasks to run. Add tasks to this queue, and they will |
| be run. |
| task: Function to run on each queued input. |
| onexit: Function to run after all inputs are processed. |
| task_args: A list of args to pass to the |task|. |
| task_kwargs: A dict of optional args to pass to the |task|. |
| """ |
| if task_args is None: |
| task_args = [] |
| elif not isinstance(task_args, list): |
| task_args = list(task_args) |
| if task_kwargs is None: |
| task_kwargs = {} |
| |
| errors = [] |
| while True: |
| # Wait for a new item to show up on the queue. This is a blocking wait, |
| # so if there's nothing to do, we just sit here. |
| x = queue.get() |
| if isinstance(x, _AllTasksComplete): |
| # All tasks are complete, so we should exit. |
| break |
| elif not isinstance(x, list): |
| x = task_args + list(x) |
| else: |
| x = task_args + x |
| |
| # If no tasks failed yet, process the remaining tasks. |
| if not errors: |
| try: |
| task(*x, **task_kwargs) |
| except BaseException as ex: |
| errors.extend( |
| failures_lib.CreateExceptInfo(ex, traceback.format_exc())) |
| |
| # Run exit handlers. |
| if onexit: |
| onexit() |
| |
| # Propagate any exceptions. |
| if errors: |
| raise BackgroundFailure(exc_infos=errors) |
| |
| |
| def RunParallelSteps(steps, max_parallel=None, halt_on_error=False, |
| return_values=False): |
| """Run a list of functions in parallel. |
| |
| This function blocks until all steps are completed. |
| |
| The output from the functions is saved to a temporary file and printed as if |
| they were run in sequence. |
| |
| If exceptions occur in the steps, we join together the tracebacks and print |
| them after all parallel tasks have finished running. Further, a |
| BackgroundFailure is raised with full stack traces of all exceptions. |
| |
| Examples: |
| # This snippet will execute in parallel: |
| # somefunc() |
| # anotherfunc() |
| # funcfunc() |
| steps = [somefunc, anotherfunc, funcfunc] |
| RunParallelSteps(steps) |
| # Blocks until all calls have completed. |
| |
| Args: |
| steps: A list of functions to run. |
| max_parallel: The maximum number of simultaneous tasks to run in parallel. |
| By default, run all tasks in parallel. |
| halt_on_error: After the first exception occurs, halt any running steps, |
| and squelch any further output, including any exceptions that might occur. |
| return_values: If set to True, RunParallelSteps returns a list containing |
| the return values of the steps. Defaults to False. |
| |
| Returns: |
| If |return_values| is True, the function will return a list containing the |
| return values of the steps. |
| """ |
| def ReturnWrapper(queue, fn): |
| """Put the return value of |fn| into |queue|.""" |
| queue.put(fn()) |
| |
| full_steps = [] |
| queues = [] |
| with cros_build_lib.ContextManagerStack() as stack: |
| if return_values: |
| # We use a managed queue here, because the child process will wait for the |
| # queue(pipe) to be flushed (i.e., when items are read from the queue) |
| # before exiting, and with a regular queue this may result in hangs for |
| # large return values. But with a managed queue, the manager process will |
| # read the items and hold on to them until the managed queue goes out of |
| # scope and is cleaned up. |
| manager = stack.Add(Manager) |
| for step in steps: |
| queue = manager.Queue() |
| queues.append(queue) |
| full_steps.append(functools.partial(ReturnWrapper, queue, step)) |
| else: |
| full_steps = steps |
| |
| with _BackgroundTask.ParallelTasks(full_steps, max_parallel=max_parallel, |
| halt_on_error=halt_on_error): |
| pass |
| |
| if return_values: |
| return [queue.get_nowait() for queue in queues] |
| |
| |
| class _AllTasksComplete(object): |
| """Sentinel object to indicate that all tasks are complete.""" |
| |
| |
| @contextlib.contextmanager |
| def BackgroundTaskRunner(task, *args, **kwargs): |
| """Run the specified task on each queued input in a pool of processes. |
| |
| This context manager starts a set of workers in the background, who each |
| wait for input on the specified queue. For each input on the queue, these |
| workers run task(*args + *input, **kwargs). Note that certain kwargs will |
| not pass through to the task (see Args below for the list). |
| |
| The output from these tasks is saved to a temporary file. When control |
| returns to the context manager, the background output is printed in order, |
| as if the tasks were run in sequence. |
| |
| If exceptions occur in the steps, we join together the tracebacks and print |
| them after all parallel tasks have finished running. Further, a |
| BackgroundFailure is raised with full stack traces of all exceptions. |
| |
| Examples: |
| # This will run somefunc(1, 'small', 'cow', foo='bar') in the background |
| # as soon as data is added to the queue (i.e. queue.put() is called). |
| |
| def somefunc(arg1, arg2, arg3, foo=None): |
| ... |
| |
| with BackgroundTaskRunner(somefunc, 1, foo='bar') as queue: |
| ... do random stuff ... |
| queue.put(['small', 'cow']) |
| ... do more random stuff while somefunc() runs ... |
| # Exiting the with statement will block until all calls have completed. |
| |
| Args: |
| task: Function to run on each queued input. |
| queue: A queue of tasks to run. Add tasks to this queue, and they will |
| be run in the background. If None, one will be created on the fly. |
| processes: Number of processes to launch. |
| onexit: Function to run in each background process after all inputs are |
| processed. |
| halt_on_error: After the first exception occurs, halt any running steps, and |
| squelch any further output, including any exceptions that might occur. |
| Halts on exceptions in any of the background processes, or in the |
| foreground process using the BackgroundTaskRunner. |
| """ |
| |
| queue = kwargs.pop('queue', None) |
| processes = kwargs.pop('processes', None) |
| onexit = kwargs.pop('onexit', None) |
| halt_on_error = kwargs.pop('halt_on_error', False) |
| |
| with cros_build_lib.ContextManagerStack() as stack: |
| if queue is None: |
| manager = stack.Add(Manager) |
| queue = manager.Queue() |
| |
| if not processes: |
| processes = multiprocessing.cpu_count() |
| |
| child = functools.partial(_BackgroundTask.TaskRunner, queue, task, |
| onexit=onexit, task_args=args, |
| task_kwargs=kwargs) |
| steps = [child] * processes |
| with _BackgroundTask.ParallelTasks(steps, halt_on_error=halt_on_error): |
| try: |
| yield queue |
| finally: |
| for _ in xrange(processes): |
| queue.put(_AllTasksComplete()) |
| |
| |
| def RunTasksInProcessPool(task, inputs, processes=None, onexit=None): |
| """Run the specified function with each supplied input in a pool of processes. |
| |
| This function runs task(*x) for x in inputs in a pool of processes. This |
| function blocks until all tasks are completed. |
| |
| The output from these tasks is saved to a temporary file. When control |
| returns to the context manager, the background output is printed in order, |
| as if the tasks were run in sequence. |
| |
| If exceptions occur in the steps, we join together the tracebacks and print |
| them after all parallel tasks have finished running. Further, a |
| BackgroundFailure is raised with full stack traces of all exceptions. |
| |
| Examples: |
| # This snippet will execute in parallel: |
| # somefunc('hi', 'fat', 'code') |
| # somefunc('foo', 'bar', 'cow') |
| |
| def somefunc(arg1, arg2, arg3): |
| ... |
| ... |
| inputs = [ |
| ['hi', 'fat', 'code'], |
| ['foo', 'bar', 'cow'], |
| ] |
| RunTasksInProcessPool(somefunc, inputs) |
| # Blocks until all calls have completed. |
| |
| Args: |
| task: Function to run on each input. |
| inputs: List of inputs. |
| processes: Number of processes, at most, to launch. |
| onexit: Function to run in each background process after all inputs are |
| processed. |
| |
| Returns: |
| Returns a list containing the return values of the task for each input. |
| """ |
| if not processes: |
| # - Use >=16 processes by default, in case it's a network-bound operation. |
| # - Try to use all of the CPUs, in case it's a CPU-bound operation. |
| processes = min(max(16, multiprocessing.cpu_count()), len(inputs)) |
| |
| with Manager() as manager: |
| # Set up output queue. |
| out_queue = manager.Queue() |
| fn = lambda idx, task_args: out_queue.put((idx, task(*task_args))) |
| |
| # Micro-optimization: Setup the queue so that BackgroundTaskRunner |
| # doesn't have to set up another Manager process. |
| queue = manager.Queue() |
| |
| with BackgroundTaskRunner(fn, queue=queue, processes=processes, |
| onexit=onexit) as queue: |
| for idx, input_args in enumerate(inputs): |
| queue.put((idx, input_args)) |
| |
| return [x[1] for x in sorted(out_queue.get() for _ in range(len(inputs)))] |
| |
| |
| PR_SET_PDEATHSIG = 1 |
| |
| |
| def ExitWithParent(sig=signal.SIGHUP): |
| """Sets this process to receive |sig| when the parent dies. |
| |
| Note: this uses libc, so it only works on linux. |
| |
| Args: |
| sig: Signal to recieve. Defaults to SIGHUP. |
| |
| Returns: |
| Whether we were successful in setting the deathsignal flag |
| """ |
| libc_name = ctypes.util.find_library('c') |
| if not libc_name: |
| return False |
| try: |
| libc = ctypes.CDLL(libc_name) |
| libc.prctl(PR_SET_PDEATHSIG, sig) |
| return True |
| # We might not be able to load the library (OSError), or prctl might be |
| # missing (AttributeError) |
| except (OSError, AttributeError): |
| return False |
