#
# 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 .
#
# Authors:
# Tristan Van Berkom
# Jürg Billeter
# Tristan Maat
# 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))
utils._kill_process_tree(self._process.pid)
# 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 {}
#######################################################
# 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