| # |
| # Copyright (C) 2018 Codethink Limited |
| # |
| # This program is free software; you can redistribute it and/or |
| # modify it under the terms of the GNU Lesser General Public |
| # License as published by the Free Software Foundation; either |
| # version 2 of the License, or (at your option) any later version. |
| # |
| # This library is distributed in the hope that it will be useful, |
| # but WITHOUT ANY WARRANTY; without even the implied warranty of |
| # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| # Lesser General Public License for more details. |
| # |
| # You should have received a copy of the GNU Lesser General Public |
| # License along with this library. If not, see <http://www.gnu.org/licenses/>. |
| # |
| # Authors: |
| # Tristan Van Berkom <tristan.vanberkom@codethink.co.uk> |
| # Jürg Billeter <juerg.billeter@codethink.co.uk> |
| # Tristan Maat <tristan.maat@codethink.co.uk> |
| |
| # System imports |
| import os |
| import sys |
| import signal |
| import datetime |
| import traceback |
| import asyncio |
| import multiprocessing |
| |
| import psutil |
| |
| # BuildStream toplevel imports |
| from ..._exceptions import ImplError, BstError, set_last_task_error, SkipJob |
| from ..._message import Message, MessageType, unconditional_messages |
| from ... import _signals, utils |
| |
| # Return code values shutdown of job handling child processes |
| # |
| RC_OK = 0 |
| RC_FAIL = 1 |
| RC_PERM_FAIL = 2 |
| RC_SKIPPED = 3 |
| |
| |
| # Used to distinguish between status messages and return values |
| class Envelope(): |
| def __init__(self, message_type, message): |
| self._message_type = message_type |
| self._message = message |
| |
| |
| # Process class that doesn't call waitpid on its own. |
| # This prevents conflicts with the asyncio child watcher. |
| class Process(multiprocessing.Process): |
| # pylint: disable=attribute-defined-outside-init |
| def start(self): |
| self._popen = self._Popen(self) |
| self._sentinel = self._popen.sentinel |
| |
| |
| # Job() |
| # |
| # The Job object represents a parallel task, when calling Job.spawn(), |
| # the given `Job.child_process()` will be called in parallel to the |
| # calling process, and `Job.parent_complete()` will be called with the |
| # action result in the calling process when the job completes. |
| # |
| # Args: |
| # scheduler (Scheduler): The scheduler |
| # action_name (str): The queue action name |
| # logfile (str): A template string that points to the logfile |
| # that should be used - should contain {pid}. |
| # resources (iter(ResourceType)) - A set of resources this job |
| # wants to use. |
| # exclusive_resources (iter(ResourceType)) - A set of resources |
| # this job wants to use |
| # exclusively. |
| # max_retries (int): The maximum number of retries |
| # |
| class Job(): |
| |
| def __init__(self, scheduler, action_name, logfile, *, |
| resources=None, exclusive_resources=None, max_retries=0): |
| |
| if resources is None: |
| resources = set() |
| else: |
| resources = set(resources) |
| if exclusive_resources is None: |
| exclusive_resources = set() |
| else: |
| exclusive_resources = set(resources) |
| |
| assert exclusive_resources <= resources, "All exclusive resources must also be resources!" |
| |
| # |
| # Public members |
| # |
| self.action_name = action_name # The action name for the Queue |
| self.child_data = None # Data to be sent to the main process |
| |
| # The resources this job wants to access |
| self.resources = resources |
| # Resources this job needs to access exclusively, i.e., no |
| # other job should be allowed to access them |
| self.exclusive_resources = exclusive_resources |
| |
| # |
| # Private members |
| # |
| self._scheduler = scheduler # The scheduler |
| self._queue = None # A message passing queue |
| self._process = None # The Process object |
| self._watcher = None # Child process watcher |
| self._listening = False # Whether the parent is currently listening |
| self._suspended = False # Whether this job is currently suspended |
| self._max_retries = max_retries # Maximum number of automatic retries |
| self._result = None # Return value of child action in the parent |
| self._tries = 0 # Try count, for retryable jobs |
| self._skipped_flag = False # Indicate whether the job was skipped. |
| self._terminated = False # Whether this job has been explicitly terminated |
| |
| # If False, a retry will not be attempted regardless of whether _tries is less than _max_retries. |
| # |
| self._retry_flag = True |
| self._logfile = logfile |
| self._task_id = None |
| |
| # spawn() |
| # |
| # Spawns the job. |
| # |
| def spawn(self): |
| |
| self._queue = multiprocessing.Queue() |
| |
| self._tries += 1 |
| self._parent_start_listening() |
| |
| # Spawn the process |
| self._process = Process(target=self._child_action, args=[self._queue]) |
| |
| # Block signals which are handled in the main process such that |
| # the child process does not inherit the parent's state, but the main |
| # process will be notified of any signal after we launch the child. |
| # |
| with _signals.blocked([signal.SIGINT, signal.SIGTSTP, signal.SIGTERM], ignore=False): |
| self._process.start() |
| |
| # Wait for the child task to complete. |
| # |
| # This is a tricky part of python which doesnt seem to |
| # make it to the online docs: |
| # |
| # o asyncio.get_child_watcher() will return a SafeChildWatcher() instance |
| # which is the default type of watcher, and the instance belongs to the |
| # "event loop policy" in use (so there is only one in the main process). |
| # |
| # o SafeChildWatcher() will register a SIGCHLD handler with the asyncio |
| # loop, and will selectively reap any child pids which have been |
| # terminated. |
| # |
| # o At registration time, the process will immediately be checked with |
| # `os.waitpid()` and will be reaped immediately, before add_child_handler() |
| # returns. |
| # |
| # The self._parent_child_completed callback passed here will normally |
| # be called after the child task has been reaped with `os.waitpid()`, in |
| # an event loop callback. Otherwise, if the job completes too fast, then |
| # the callback is called immediately. |
| # |
| self._watcher = asyncio.get_child_watcher() |
| self._watcher.add_child_handler(self._process.pid, self._parent_child_completed) |
| |
| # terminate() |
| # |
| # Politely request that an ongoing job terminate soon. |
| # |
| # This will send a SIGTERM signal to the Job process. |
| # |
| def terminate(self): |
| |
| # First resume the job if it's suspended |
| self.resume(silent=True) |
| |
| self.message(MessageType.STATUS, "{} terminating".format(self.action_name)) |
| |
| # Make sure there is no garbage on the queue |
| self._parent_stop_listening() |
| |
| # Terminate the process using multiprocessing API pathway |
| self._process.terminate() |
| |
| self._terminated = True |
| |
| # terminate_wait() |
| # |
| # Wait for terminated jobs to complete |
| # |
| # Args: |
| # timeout (float): Seconds to wait |
| # |
| # Returns: |
| # (bool): True if the process terminated cleanly, otherwise False |
| # |
| def terminate_wait(self, timeout): |
| |
| # Join the child process after sending SIGTERM |
| self._process.join(timeout) |
| return self._process.exitcode is not None |
| |
| # kill() |
| # |
| # Forcefully kill the process, and any children it might have. |
| # |
| def kill(self): |
| |
| # Force kill |
| self.message(MessageType.WARN, |
| "{} did not terminate gracefully, killing".format(self.action_name)) |
| |
| try: |
| utils._kill_process_tree(self._process.pid) |
| # This can happen if the process died of its own accord before |
| # we try to kill it |
| except psutil.NoSuchProcess: |
| return |
| |
| # suspend() |
| # |
| # Suspend this job. |
| # |
| def suspend(self): |
| if not self._suspended: |
| self.message(MessageType.STATUS, |
| "{} suspending".format(self.action_name)) |
| |
| try: |
| # Use SIGTSTP so that child processes may handle and propagate |
| # it to processes they spawn that become session leaders |
| os.kill(self._process.pid, signal.SIGTSTP) |
| |
| # For some reason we receive exactly one suspend event for every |
| # SIGTSTP we send to the child fork(), even though the child forks |
| # are setsid(). We keep a count of these so we can ignore them |
| # in our event loop suspend_event() |
| self._scheduler.internal_stops += 1 |
| self._suspended = True |
| except ProcessLookupError: |
| # ignore, process has already exited |
| pass |
| |
| # resume() |
| # |
| # Resume this suspended job. |
| # |
| def resume(self, silent=False): |
| if self._suspended: |
| if not silent and not self._scheduler.terminated: |
| self.message(MessageType.STATUS, |
| "{} resuming".format(self.action_name)) |
| |
| os.kill(self._process.pid, signal.SIGCONT) |
| self._suspended = False |
| |
| # set_task_id() |
| # |
| # This is called by Job subclasses to set a plugin ID |
| # associated with the task at large (if any element is related |
| # to the task). |
| # |
| # The task ID helps keep messages in the frontend coherent |
| # in the case that multiple plugins log in the context of |
| # a single task (e.g. running integration commands should appear |
| # in the frontend for the element being built, not the element |
| # running the integration commands). |
| # |
| # Args: |
| # task_id (int): The plugin identifier for this task |
| # |
| def set_task_id(self, task_id): |
| self._task_id = task_id |
| |
| # skipped |
| # |
| # This will evaluate to True if the job was skipped |
| # during processing, or if it was forcefully terminated. |
| # |
| # Returns: |
| # (bool): Whether the job should appear as skipped |
| # |
| @property |
| def skipped(self): |
| return self._skipped_flag or self._terminated |
| |
| ####################################################### |
| # Abstract Methods # |
| ####################################################### |
| |
| # parent_complete() |
| # |
| # This will be executed after the job finishes, and is expected to |
| # pass the result to the main thread. |
| # |
| # Args: |
| # success (bool): Whether the job was successful. |
| # result (any): The result returned by child_process(). |
| # |
| def parent_complete(self, success, result): |
| raise ImplError("Job '{kind}' does not implement parent_complete()" |
| .format(kind=type(self).__name__)) |
| |
| # child_process() |
| # |
| # This will be executed after fork(), and is intended to perform |
| # the job's task. |
| # |
| # Returns: |
| # (any): A (simple!) object to be returned to the main thread |
| # as the result. |
| # |
| def child_process(self): |
| raise ImplError("Job '{kind}' does not implement child_process()" |
| .format(kind=type(self).__name__)) |
| |
| # message(): |
| # |
| # Logs a message, this will be logged in the task's logfile and |
| # conditionally also be sent to the frontend. |
| # |
| # Args: |
| # message_type (MessageType): The type of message to send |
| # message (str): The message |
| # kwargs: Remaining Message() constructor arguments |
| # |
| def message(self, message_type, message, **kwargs): |
| args = dict(kwargs) |
| args['scheduler'] = True |
| self._scheduler.context.message(Message(None, message_type, message, **args)) |
| |
| # child_process_data() |
| # |
| # Abstract method to retrieve additional data that should be |
| # returned to the parent process. Note that the job result is |
| # retrieved independently. |
| # |
| # Values can later be retrieved in Job.child_data. |
| # |
| # Returns: |
| # (dict) A dict containing values to be reported to the main process |
| # |
| def child_process_data(self): |
| return {} |
| |
| def key(self): |
| raise ImplError("Job '{kind}' does not implement key()" |
| .format(kind=type(self).__name__)) |
| |
| ####################################################### |
| # Local Private Methods # |
| ####################################################### |
| # |
| # Methods prefixed with the word 'child' take place in the child process |
| # |
| # Methods prefixed with the word 'parent' take place in the parent process |
| # |
| # Other methods can be called in both child or parent processes |
| # |
| ####################################################### |
| |
| # _child_action() |
| # |
| # Perform the action in the child process, this calls the action_cb. |
| # |
| # Args: |
| # queue (multiprocessing.Queue): The message queue for IPC |
| # |
| def _child_action(self, queue): |
| |
| # This avoids some SIGTSTP signals from grandchildren |
| # getting propagated up to the master process |
| os.setsid() |
| |
| # First set back to the default signal handlers for the signals |
| # we handle, and then clear their blocked state. |
| # |
| signal_list = [signal.SIGTSTP, signal.SIGTERM] |
| for sig in signal_list: |
| signal.signal(sig, signal.SIG_DFL) |
| signal.pthread_sigmask(signal.SIG_UNBLOCK, signal_list) |
| |
| # Assign the queue we passed across the process boundaries |
| # |
| # Set the global message handler in this child |
| # process to forward messages to the parent process |
| self._queue = queue |
| self._scheduler.context.set_message_handler(self._child_message_handler) |
| |
| starttime = datetime.datetime.now() |
| stopped_time = None |
| |
| def stop_time(): |
| nonlocal stopped_time |
| stopped_time = datetime.datetime.now() |
| |
| def resume_time(): |
| nonlocal stopped_time |
| nonlocal starttime |
| starttime += (datetime.datetime.now() - stopped_time) |
| |
| # Time, log and and run the action function |
| # |
| with _signals.suspendable(stop_time, resume_time), \ |
| self._scheduler.context.recorded_messages(self._logfile) as filename: |
| |
| self.message(MessageType.START, self.action_name, logfile=filename) |
| |
| try: |
| # Try the task action |
| result = self.child_process() # pylint: disable=assignment-from-no-return |
| except SkipJob as e: |
| elapsed = datetime.datetime.now() - starttime |
| self.message(MessageType.SKIPPED, str(e), |
| elapsed=elapsed, logfile=filename) |
| |
| # Alert parent of skip by return code |
| self._child_shutdown(RC_SKIPPED) |
| except BstError as e: |
| elapsed = datetime.datetime.now() - starttime |
| self._retry_flag = e.temporary |
| |
| if self._retry_flag and (self._tries <= self._max_retries): |
| self.message(MessageType.FAIL, |
| "Try #{} failed, retrying".format(self._tries), |
| elapsed=elapsed, logfile=filename) |
| else: |
| self.message(MessageType.FAIL, str(e), |
| elapsed=elapsed, detail=e.detail, |
| logfile=filename, sandbox=e.sandbox) |
| |
| self._queue.put(Envelope('child_data', self.child_process_data())) |
| |
| # Report the exception to the parent (for internal testing purposes) |
| self._child_send_error(e) |
| |
| # Set return code based on whether or not the error was temporary. |
| # |
| self._child_shutdown(RC_FAIL if self._retry_flag else RC_PERM_FAIL) |
| |
| except Exception as e: # pylint: disable=broad-except |
| |
| # If an unhandled (not normalized to BstError) occurs, that's a bug, |
| # send the traceback and formatted exception back to the frontend |
| # and print it to the log file. |
| # |
| elapsed = datetime.datetime.now() - starttime |
| detail = "An unhandled exception occured:\n\n{}".format(traceback.format_exc()) |
| |
| self.message(MessageType.BUG, self.action_name, |
| elapsed=elapsed, detail=detail, |
| logfile=filename) |
| # Unhandled exceptions should permenantly fail |
| self._child_shutdown(RC_PERM_FAIL) |
| |
| else: |
| # No exception occurred in the action |
| self._queue.put(Envelope('child_data', self.child_process_data())) |
| self._child_send_result(result) |
| |
| elapsed = datetime.datetime.now() - starttime |
| self.message(MessageType.SUCCESS, self.action_name, elapsed=elapsed, |
| logfile=filename) |
| |
| # Shutdown needs to stay outside of the above context manager, |
| # make sure we dont try to handle SIGTERM while the process |
| # is already busy in sys.exit() |
| self._child_shutdown(RC_OK) |
| |
| # _child_send_error() |
| # |
| # Sends an error to the main process through the message queue |
| # |
| # Args: |
| # e (Exception): The error to send |
| # |
| def _child_send_error(self, e): |
| domain = None |
| reason = None |
| |
| if isinstance(e, BstError): |
| domain = e.domain |
| reason = e.reason |
| |
| envelope = Envelope('error', { |
| 'domain': domain, |
| 'reason': reason |
| }) |
| self._queue.put(envelope) |
| |
| # _child_send_result() |
| # |
| # Sends the serialized result to the main process through the message queue |
| # |
| # Args: |
| # result (object): A simple serializable object, or None |
| # |
| # Note: If None is passed here, nothing needs to be sent, the |
| # result member in the parent process will simply remain None. |
| # |
| def _child_send_result(self, result): |
| if result is not None: |
| envelope = Envelope('result', result) |
| self._queue.put(envelope) |
| |
| # _child_shutdown() |
| # |
| # Shuts down the child process by cleaning up and exiting the process |
| # |
| # Args: |
| # exit_code (int): The exit code to exit with |
| # |
| def _child_shutdown(self, exit_code): |
| self._queue.close() |
| sys.exit(exit_code) |
| |
| # _child_message_handler() |
| # |
| # A Context delegate for handling messages, this replaces the |
| # frontend's main message handler in the context of a child task |
| # and performs local logging to the local log file before sending |
| # the message back to the parent process for further propagation. |
| # |
| # Args: |
| # message (Message): The message to log |
| # context (Context): The context object delegating this message |
| # |
| def _child_message_handler(self, message, context): |
| |
| message.action_name = self.action_name |
| message.task_id = self._task_id |
| |
| # Send to frontend if appropriate |
| if context.silent_messages() and (message.message_type not in unconditional_messages): |
| return |
| |
| if message.message_type == MessageType.LOG: |
| return |
| |
| self._queue.put(Envelope('message', message)) |
| |
| # _parent_shutdown() |
| # |
| # Shuts down the Job on the parent side by reading any remaining |
| # messages on the message queue and cleaning up any resources. |
| # |
| def _parent_shutdown(self): |
| # Make sure we've read everything we need and then stop listening |
| self._parent_process_queue() |
| self._parent_stop_listening() |
| |
| # _parent_child_completed() |
| # |
| # Called in the main process courtesy of asyncio's ChildWatcher.add_child_handler() |
| # |
| # Args: |
| # pid (int): The PID of the child which completed |
| # returncode (int): The return code of the child process |
| # |
| def _parent_child_completed(self, pid, returncode): |
| self._parent_shutdown() |
| |
| # We don't want to retry if we got OK or a permanent fail. |
| # This is set in _child_action but must also be set for the parent. |
| # |
| self._retry_flag = returncode == RC_FAIL |
| |
| # Set the flag to alert Queue that this job skipped. |
| self._skipped_flag = returncode == RC_SKIPPED |
| |
| if self._retry_flag and (self._tries <= self._max_retries) and not self._scheduler.terminated: |
| self.spawn() |
| return |
| |
| success = returncode in (RC_OK, RC_SKIPPED) |
| self.parent_complete(success, self._result) |
| self._scheduler.job_completed(self, success) |
| |
| # Force the deletion of the queue and process objects to try and clean up FDs |
| self._queue = self._process = None |
| |
| # _parent_process_envelope() |
| # |
| # Processes a message Envelope deserialized form the message queue. |
| # |
| # this will have the side effect of assigning some local state |
| # on the Job in the parent process for later inspection when the |
| # child process completes. |
| # |
| # Args: |
| # envelope (Envelope): The message envelope |
| # |
| def _parent_process_envelope(self, envelope): |
| if not self._listening: |
| return |
| |
| if envelope._message_type == 'message': |
| # Propagate received messages from children |
| # back through the context. |
| self._scheduler.context.message(envelope._message) |
| elif envelope._message_type == 'error': |
| # For regression tests only, save the last error domain / reason |
| # reported from a child task in the main process, this global state |
| # is currently managed in _exceptions.py |
| set_last_task_error(envelope._message['domain'], |
| envelope._message['reason']) |
| elif envelope._message_type == 'result': |
| assert self._result is None |
| self._result = envelope._message |
| elif envelope._message_type == 'child_data': |
| # If we retry a job, we assign a new value to this |
| self.child_data = envelope._message |
| else: |
| raise Exception() |
| |
| # _parent_process_queue() |
| # |
| # Reads back message envelopes from the message queue |
| # in the parent process. |
| # |
| def _parent_process_queue(self): |
| while not self._queue.empty(): |
| envelope = self._queue.get_nowait() |
| self._parent_process_envelope(envelope) |
| |
| # _parent_recv() |
| # |
| # A callback to handle I/O events from the message |
| # queue file descriptor in the main process message loop |
| # |
| def _parent_recv(self, *args): |
| self._parent_process_queue() |
| |
| # _parent_start_listening() |
| # |
| # Starts listening on the message queue |
| # |
| def _parent_start_listening(self): |
| # Warning: Platform specific code up ahead |
| # |
| # The multiprocessing.Queue object does not tell us how |
| # to receive io events in the receiving process, so we |
| # need to sneak in and get its file descriptor. |
| # |
| # The _reader member of the Queue is currently private |
| # but well known, perhaps it will become public: |
| # |
| # http://bugs.python.org/issue3831 |
| # |
| if not self._listening: |
| self._scheduler.loop.add_reader( |
| self._queue._reader.fileno(), self._parent_recv) |
| self._listening = True |
| |
| # _parent_stop_listening() |
| # |
| # Stops listening on the message queue |
| # |
| def _parent_stop_listening(self): |
| if self._listening: |
| self._scheduler.loop.remove_reader(self._queue._reader.fileno()) |
| self._listening = False |
