Library for running OpenStack services
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# Copyright 2012 Red Hat, Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
import logging
import threading
import warnings
from debtcollector import removals
import eventlet
from eventlet import greenpool
from oslo_service import loopingcall
from oslo_utils import timeutils
LOG = logging.getLogger(__name__)
def _on_thread_done(_greenthread, group, thread):
"""Callback function to be passed to GreenThread.link() when we spawn().
Calls the :class:`ThreadGroup` to notify it to remove this thread from
the associated group.
"""
group.thread_done(thread)
class Thread(object):
"""Wrapper around a greenthread.
Holds a reference to the :class:`ThreadGroup`. The Thread will notify
the :class:`ThreadGroup` when it has done so it can be removed from
the threads list.
"""
def __init__(self, thread, group, link=True):
self.thread = thread
if link:
self.thread.link(_on_thread_done, group, self)
self._ident = id(thread)
@property
def ident(self):
return self._ident
def stop(self):
"""Kill the thread by raising GreenletExit within it."""
self.thread.kill()
def wait(self):
"""Block until the thread completes and return the result."""
return self.thread.wait()
def link(self, func, *args, **kwargs):
"""Schedule a function to be run upon completion of the thread."""
self.thread.link(func, *args, **kwargs)
def cancel(self, *throw_args):
"""Prevent the thread from starting if it has not already done so.
:param throw_args: the `exc_info` data to raise from :func:`wait`.
"""
self.thread.cancel(*throw_args)
class ThreadGroup(object):
"""A group of greenthreads and timers.
The point of the ThreadGroup class is to:
* keep track of timers and greenthreads (making it easier to stop them
when need be).
* provide an easy API to add timers.
.. note::
The API is inconsistent, confusing, and not orthogonal. The same verbs
often mean different things when applied to timers and threads,
respectively. Read the documentation carefully.
"""
def __init__(self, thread_pool_size=10):
"""Create a ThreadGroup with a pool of greenthreads.
:param thread_pool_size: the maximum number of threads allowed to run
concurrently.
"""
self.pool = greenpool.GreenPool(thread_pool_size)
self.threads = []
self.timers = []
def add_dynamic_timer(self, callback, initial_delay=None,
periodic_interval_max=None, *args, **kwargs):
"""Add a timer that controls its own period dynamically.
The period of each iteration of the timer is controlled by the return
value of the callback function on the previous iteration.
.. warning::
Passing arguments to the callback function is deprecated. Use the
:func:`add_dynamic_timer_args` method to pass arguments for the
callback function.
:param callback: The callback function to run when the timer is
triggered.
:param initial_delay: The delay in seconds before first triggering the
timer. If not set, the timer is liable to be
scheduled immediately.
:param periodic_interval_max: The maximum interval in seconds to allow
the callback function to request. If
provided, this is also used as the
default delay if None is returned by the
callback function.
:returns: an :class:`oslo_service.loopingcall.DynamicLoopingCall`
instance
"""
if args or kwargs:
warnings.warn("Calling add_dynamic_timer() with arguments to the "
"callback function is deprecated. Use "
"add_dynamic_timer_args() instead.",
DeprecationWarning)
return self.add_dynamic_timer_args(
callback, args, kwargs,
initial_delay=initial_delay,
periodic_interval_max=periodic_interval_max)
def add_dynamic_timer_args(self, callback, args=None, kwargs=None,
initial_delay=None, periodic_interval_max=None,
stop_on_exception=True):
"""Add a timer that controls its own period dynamically.
The period of each iteration of the timer is controlled by the return
value of the callback function on the previous iteration.
:param callback: The callback function to run when the timer is
triggered.
:param args: A list of positional args to the callback function.
:param kwargs: A dict of keyword args to the callback function.
:param initial_delay: The delay in seconds before first triggering the
timer. If not set, the timer is liable to be
scheduled immediately.
:param periodic_interval_max: The maximum interval in seconds to allow
the callback function to request. If
provided, this is also used as the
default delay if None is returned by the
callback function.
:param stop_on_exception: Pass ``False`` to have the timer continue
running even if the callback function raises
an exception.
:returns: an :class:`oslo_service.loopingcall.DynamicLoopingCall`
instance
"""
args = args or []
kwargs = kwargs or {}
timer = loopingcall.DynamicLoopingCall(callback, *args, **kwargs)
timer.start(initial_delay=initial_delay,
periodic_interval_max=periodic_interval_max,
stop_on_exception=stop_on_exception)
self.timers.append(timer)
return timer
def add_timer(self, interval, callback, initial_delay=None,
*args, **kwargs):
"""Add a timer with a fixed period.
.. warning::
Passing arguments to the callback function is deprecated. Use the
:func:`add_timer_args` method to pass arguments for the callback
function.
:param interval: The minimum period in seconds between calls to the
callback function.
:param callback: The callback function to run when the timer is
triggered.
:param initial_delay: The delay in seconds before first triggering the
timer. If not set, the timer is liable to be
scheduled immediately.
:returns: an :class:`oslo_service.loopingcall.FixedIntervalLoopingCall`
instance
"""
if args or kwargs:
warnings.warn("Calling add_timer() with arguments to the callback "
"function is deprecated. Use add_timer_args() "
"instead.",
DeprecationWarning)
return self.add_timer_args(interval, callback, args, kwargs,
initial_delay=initial_delay)
def add_timer_args(self, interval, callback, args=None, kwargs=None,
initial_delay=None, stop_on_exception=True):
"""Add a timer with a fixed period.
:param interval: The minimum period in seconds between calls to the
callback function.
:param callback: The callback function to run when the timer is
triggered.
:param args: A list of positional args to the callback function.
:param kwargs: A dict of keyword args to the callback function.
:param initial_delay: The delay in seconds before first triggering the
timer. If not set, the timer is liable to be
scheduled immediately.
:param stop_on_exception: Pass ``False`` to have the timer continue
running even if the callback function raises
an exception.
:returns: an :class:`oslo_service.loopingcall.FixedIntervalLoopingCall`
instance
"""
args = args or []
kwargs = kwargs or {}
pulse = loopingcall.FixedIntervalLoopingCall(callback, *args, **kwargs)
pulse.start(interval=interval,
initial_delay=initial_delay,
stop_on_exception=stop_on_exception)
self.timers.append(pulse)
return pulse
def add_thread(self, callback, *args, **kwargs):
"""Spawn a new thread.
This call will block until capacity is available in the thread pool.
After that, it returns immediately (i.e. *before* the new thread is
scheduled).
:param callback: the function to run in the new thread.
:param args: positional arguments to the callback function.
:param kwargs: keyword arguments to the callback function.
:returns: a :class:`Thread` object
"""
gt = self.pool.spawn(callback, *args, **kwargs)
th = Thread(gt, self, link=False)
self.threads.append(th)
gt.link(_on_thread_done, self, th)
return th
def thread_done(self, thread):
"""Remove a completed thread from the group.
This method is automatically called on completion of a thread in the
group, and should not be called explicitly.
"""
self.threads.remove(thread)
def timer_done(self, timer):
"""Remove a timer from the group.
:param timer: The timer object returned from :func:`add_timer` or its
analogues.
"""
self.timers.remove(timer)
def _perform_action_on_threads(self, action_func, on_error_func):
current = threading.current_thread()
# Iterate over a copy of self.threads so thread_done doesn't
# modify the list while we're iterating
for x in self.threads[:]:
if x.ident == current.ident:
# Don't perform actions on the current thread.
continue
try:
action_func(x)
except eventlet.greenlet.GreenletExit: # nosec
# greenlet exited successfully
pass
except Exception:
on_error_func(x)
def _stop_threads(self):
self._perform_action_on_threads(
lambda x: x.stop(),
lambda x: LOG.exception('Error stopping thread.'))
def stop_timers(self, wait=False):
"""Stop all timers in the group and remove them from the group.
No new invocations of timers will be triggered after they are stopped,
but calls that are in progress will not be interrupted.
To wait for in-progress calls to complete, pass ``wait=True`` - calling
:func:`wait` will not have the desired effect as the timers will have
already been removed from the group.
:param wait: If true, block until all timers have been stopped before
returning.
"""
for timer in self.timers:
timer.stop()
if wait:
self._wait_timers()
self.timers = []
def stop(self, graceful=False):
"""Stop all timers and threads in the group.
No new invocations of timers will be triggered after they are stopped,
but calls that are in progress will not be interrupted.
If ``graceful`` is false, kill all threads immediately by raising
GreenletExit. Note that in this case, this method will **not** block
until all threads and running timer callbacks have actually exited. To
guarantee that all threads have exited, call :func:`wait`.
If ``graceful`` is true, do not kill threads. Block until all threads
and running timer callbacks have completed. This is equivalent to
calling :func:`stop_timers` with ``wait=True`` followed by
:func:`wait`.
:param graceful: If true, block until all timers have stopped and all
threads completed; never kill threads. Otherwise,
kill threads immediately and return immediately even
if there are timer callbacks still running.
"""
self.stop_timers(wait=graceful)
if graceful:
# In case of graceful=True, wait for all threads to be
# finished, never kill threads
self._wait_threads()
else:
# In case of graceful=False(Default), kill threads
# immediately
self._stop_threads()
def _wait_timers(self):
for x in self.timers:
try:
x.wait()
except eventlet.greenlet.GreenletExit: # nosec
# greenlet exited successfully
pass
except Exception:
LOG.exception('Error waiting on timer.')
def _wait_threads(self):
self._perform_action_on_threads(
lambda x: x.wait(),
lambda x: LOG.exception('Error waiting on thread.'))
def wait(self):
"""Block until all timers and threads in the group are complete.
.. note::
Before calling this method, any timers should be stopped first by
calling :func:`stop_timers`, :func:`stop`, or :func:`cancel` with a
``timeout`` argument. Otherwise this will block forever.
.. note::
Calling :func:`stop_timers` removes the timers from the group, so a
subsequent call to this method will not wait for any in-progress
timer calls to complete.
Any exceptions raised by the threads will be logged but suppressed.
.. note::
This call guarantees only that the threads themselves have
completed, **not** that any cleanup functions added via
:func:`Thread.link` have completed.
"""
self._wait_timers()
self._wait_threads()
def _any_threads_alive(self):
current = threading.current_thread()
for x in self.threads[:]:
if x.ident == current.ident:
# Don't check current thread.
continue
if not x.thread.dead:
return True
return False
@removals.remove(removal_version='?')
def cancel(self, *throw_args, **kwargs):
"""Cancel unstarted threads in the group, and optionally stop the rest.
.. warning::
This method is deprecated and should not be used. It will be
removed in a future release.
If called without the ``timeout`` argument, this does **not** stop any
running threads, but prevents any threads in the group that have not
yet started from running, then returns immediately. Timers are not
affected.
If the 'timeout' argument is supplied, then it serves as a grace period
to allow running threads to finish. After the timeout, any threads in
the group that are still running will be killed by raising GreenletExit
in them, and all timers will be stopped (so that they are not
retriggered - timer calls that are in progress will not be
interrupted). This method will **not** block until all threads have
actually exited, nor that all in-progress timer calls have completed.
To guarantee that all threads have exited, call :func:`wait`. If all
threads complete before the timeout expires, timers will be left
running; there is no way to then stop those timers, so for consistent
behaviour :func`stop_timers` should be called before calling this
method.
:param throw_args: the `exc_info` data to raise from
:func:`Thread.wait` for any of the unstarted
threads. (Though note that :func:`ThreadGroup.wait`
suppresses exceptions.)
:param timeout: time to wait for running threads to complete before
calling stop(). If not supplied, threads that are
already running continue to completion.
:param wait_time: length of time in seconds to sleep between checks of
whether any threads are still alive. (Default 1s.)
"""
self._perform_action_on_threads(
lambda x: x.cancel(*throw_args),
lambda x: LOG.exception('Error canceling thread.'))
timeout = kwargs.get('timeout', None)
if timeout is None:
return
wait_time = kwargs.get('wait_time', 1)
watch = timeutils.StopWatch(duration=timeout)
watch.start()
while self._any_threads_alive():
if not watch.expired():
eventlet.sleep(wait_time)
continue
LOG.debug("Cancel timeout reached, stopping threads.")
self.stop()