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mitogen/ansible_mitogen/strategy.py

358 lines
14 KiB
Python

# Copyright 2019, David Wilson
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
#
# 1. Redistributions of source code must retain the above copyright notice,
# this list of conditions and the following disclaimer.
#
# 2. Redistributions in binary form must reproduce the above copyright notice,
# this list of conditions and the following disclaimer in the documentation
# and/or other materials provided with the distribution.
#
# 3. Neither the name of the copyright holder nor the names of its contributors
# may be used to endorse or promote products derived from this software without
# specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
# POSSIBILITY OF SUCH DAMAGE.
from __future__ import absolute_import
import os
import signal
import threading
try:
import setproctitle
except ImportError:
setproctitle = None
import mitogen.core
import ansible_mitogen.affinity
import ansible_mitogen.loaders
import ansible_mitogen.mixins
import ansible_mitogen.process
import ansible
import ansible.executor.process.worker
try:
# 2.8+ has a standardized "unset" object.
from ansible.utils.sentinel import Sentinel
except ImportError:
Sentinel = None
ANSIBLE_VERSION_MIN = '2.3'
ANSIBLE_VERSION_MAX = '2.8'
NEW_VERSION_MSG = (
"Your Ansible version (%s) is too recent. The most recent version\n"
"supported by Mitogen for Ansible is %s.x. Please check the Mitogen\n"
"release notes to see if a new version is available, otherwise\n"
"subscribe to the corresponding GitHub issue to be notified when\n"
"support becomes available.\n"
"\n"
" https://mitogen.rtfd.io/en/latest/changelog.html\n"
" https://github.com/dw/mitogen/issues/\n"
)
OLD_VERSION_MSG = (
"Your version of Ansible (%s) is too old. The oldest version supported by "
"Mitogen for Ansible is %s."
)
def _assert_supported_release():
"""
Throw AnsibleError with a descriptive message in case of being loaded into
an unsupported Ansible release.
"""
v = ansible.__version__
if v[:len(ANSIBLE_VERSION_MIN)] < ANSIBLE_VERSION_MIN:
raise ansible.errors.AnsibleError(
OLD_VERSION_MSG % (v, ANSIBLE_VERSION_MIN)
)
if v[:len(ANSIBLE_VERSION_MAX)] > ANSIBLE_VERSION_MAX:
raise ansible.errors.AnsibleError(
NEW_VERSION_MSG % (ansible.__version__, ANSIBLE_VERSION_MAX)
)
def _patch_awx_callback():
"""
issue #400: AWX loads a display callback that suffers from thread-safety
issues. Detect the presence of older AWX versions and patch the bug.
"""
# AWX uses sitecustomize.py to force-load this package. If it exists, we're
# running under AWX.
try:
from awx_display_callback.events import EventContext
from awx_display_callback.events import event_context
except ImportError:
return
if hasattr(EventContext(), '_local'):
# Patched version.
return
def patch_add_local(self, **kwargs):
tls = vars(self._local)
ctx = tls.setdefault('_ctx', {})
ctx.update(kwargs)
EventContext._local = threading.local()
EventContext.add_local = patch_add_local
_patch_awx_callback()
def wrap_action_loader__get(name, *args, **kwargs):
"""
While the mitogen strategy is active, trap action_loader.get() calls,
augmenting any fetched class with ActionModuleMixin, which replaces various
helper methods inherited from ActionBase with implementations that avoid
the use of shell fragments wherever possible.
This is used instead of static subclassing as it generalizes to third party
action plugins outside the Ansible tree.
"""
get_kwargs = {'class_only': True}
if name in ('fetch',):
name = 'mitogen_' + name
if ansible.__version__ >= '2.8':
get_kwargs['collection_list'] = kwargs.pop('collection_list', None)
klass = action_loader__get(name, **get_kwargs)
if klass:
bases = (ansible_mitogen.mixins.ActionModuleMixin, klass)
adorned_klass = type(str(name), bases, {})
if kwargs.get('class_only'):
return adorned_klass
return adorned_klass(*args, **kwargs)
def wrap_connection_loader__get(name, *args, **kwargs):
"""
While a Mitogen strategy is active, rewrite connection_loader.get() calls
for some transports into requests for a compatible Mitogen transport.
"""
if name in ('buildah', 'docker', 'kubectl', 'jail', 'local',
'lxc', 'lxd', 'machinectl', 'setns', 'ssh'):
name = 'mitogen_' + name
return connection_loader__get(name, *args, **kwargs)
def wrap_worker__run(self):
"""
While a Mitogen strategy is active, trap WorkerProcess.run() calls and use
the opportunity to set the worker's name in the process list and log
output, activate profiling if requested, and bind the worker to a specific
CPU.
"""
if setproctitle:
setproctitle.setproctitle('worker:%s task:%s' % (
self._host.name,
self._task.action,
))
# Ignore parent's attempts to murder us when we still need to write
# profiling output.
if mitogen.core._profile_hook.__name__ != '_profile_hook':
signal.signal(signal.SIGTERM, signal.SIG_IGN)
ansible_mitogen.logging.set_process_name('task')
ansible_mitogen.affinity.policy.assign_worker()
return mitogen.core._profile_hook('WorkerProcess',
lambda: worker__run(self)
)
class AnsibleWrappers(object):
"""
Manage add/removal of various Ansible runtime hooks.
"""
def _add_plugin_paths(self):
"""
Add the Mitogen plug-in directories to the ModuleLoader path, avoiding
the need for manual configuration.
"""
base_dir = os.path.join(os.path.dirname(__file__), 'plugins')
ansible_mitogen.loaders.connection_loader.add_directory(
os.path.join(base_dir, 'connection')
)
ansible_mitogen.loaders.action_loader.add_directory(
os.path.join(base_dir, 'action')
)
def _install_wrappers(self):
"""
Install our PluginLoader monkey patches and update global variables
with references to the real functions.
"""
global action_loader__get
action_loader__get = ansible_mitogen.loaders.action_loader.get
ansible_mitogen.loaders.action_loader.get = wrap_action_loader__get
global connection_loader__get
connection_loader__get = ansible_mitogen.loaders.connection_loader.get
ansible_mitogen.loaders.connection_loader.get = wrap_connection_loader__get
global worker__run
worker__run = ansible.executor.process.worker.WorkerProcess.run
ansible.executor.process.worker.WorkerProcess.run = wrap_worker__run
def _remove_wrappers(self):
"""
Uninstall the PluginLoader monkey patches.
"""
ansible_mitogen.loaders.action_loader.get = action_loader__get
ansible_mitogen.loaders.connection_loader.get = connection_loader__get
ansible.executor.process.worker.WorkerProcess.run = worker__run
def install(self):
self._add_plugin_paths()
self._install_wrappers()
def remove(self):
self._remove_wrappers()
class StrategyMixin(object):
"""
This mix-in enhances any built-in strategy by arranging for an appropriate
WorkerModel instance to be constructed as necessary, or for the existing
one to be reused.
The WorkerModel in turn arranges for a connection multiplexer to be started
somewhere (by default in an external process), and for WorkerProcesses to
grow support for using those top-level services to communicate with remote
hosts.
Mitogen:
A private Broker IO multiplexer thread is created to dispatch IO
between the local Router and any connected streams, including streams
connected to Ansible WorkerProcesses, and SSH commands implementing
connections to remote machines.
A Router is created that implements message dispatch to any locally
registered handlers, and message routing for remote streams. Router is
the junction point through which WorkerProceses and remote SSH contexts
can communicate.
Router additionally adds message handlers for a variety of base
services, review the Standard Handles section of the How It Works guide
in the documentation.
A ContextService is installed as a message handler in the connection
mutliplexer subprocess and run on a private thread. It is responsible
for accepting requests to establish new SSH connections from worker
processes, and ensuring precisely one connection exists and is reused
for subsequent playbook steps. The service presently runs in a single
thread, so to begin with, new SSH connections are serialized.
Finally a mitogen.unix listener is created through which WorkerProcess
can establish a connection back into the connection multiplexer, in
order to avail of ContextService. A UNIX listener socket is necessary
as there is no more sane mechanism to arrange for IPC between the
Router in the connection multiplexer, and the corresponding Router in
the worker process.
Ansible:
PluginLoader monkey patches are installed to catch attempts to create
connection and action plug-ins.
For connection plug-ins, if the desired method is "local" or "ssh", it
is redirected to one of the "mitogen_*" connection plug-ins. That
plug-in implements communication via a UNIX socket connection to the
connection multiplexer process, and uses ContextService running there
to establish a persistent connection to the target.
For action plug-ins, the original class is looked up as usual, but a
new subclass is created dynamically in order to mix-in
ansible_mitogen.target.ActionModuleMixin, which overrides many of the
methods usually inherited from ActionBase in order to replace them with
pure-Python equivalents that avoid the use of shell.
In particular, _execute_module() is overridden with an implementation
that uses ansible_mitogen.target.run_module() executed in the target
Context. run_module() implements module execution by importing the
module as if it were a normal Python module, and capturing its output
in the remote process. Since the Mitogen module loader is active in the
remote process, all the heavy lifting of transferring the action module
and its dependencies are automatically handled by Mitogen.
"""
def _queue_task(self, host, task, task_vars, play_context):
"""
Many PluginLoader caches are defective as they are only populated in
the ephemeral WorkerProcess. Touch each plug-in path before forking to
ensure all workers receive a hot cache.
"""
ansible_mitogen.loaders.module_loader.find_plugin(
name=task.action,
mod_type='',
)
ansible_mitogen.loaders.action_loader.get(
name=task.action,
class_only=True,
)
if play_context.connection is not Sentinel:
# 2.8 appears to defer computing this until inside the worker.
# TODO: figure out where it has moved.
ansible_mitogen.loaders.connection_loader.get(
name=play_context.connection,
class_only=True,
)
return super(StrategyMixin, self)._queue_task(
host=host,
task=task,
task_vars=task_vars,
play_context=play_context,
)
def _get_worker_model(self):
"""
In classic mode a single :class:`WorkerModel` exists, which manages
references and configuration of the associated connection multiplexer
process.
"""
return ansible_mitogen.process.get_classic_worker_model()
def run(self, iterator, play_context, result=0):
"""
Wrap :meth:`run` to ensure requisite infrastructure and modifications
are configured for the duration of the call.
"""
_assert_supported_release()
wrappers = AnsibleWrappers()
self._worker_model = self._get_worker_model()
ansible_mitogen.process.set_worker_model(self._worker_model)
try:
self._worker_model.on_strategy_start()
try:
wrappers.install()
try:
run = super(StrategyMixin, self).run
return mitogen.core._profile_hook('Strategy',
lambda: run(iterator, play_context)
)
finally:
wrappers.remove()
finally:
self._worker_model.on_strategy_complete()
finally:
ansible_mitogen.process.set_worker_model(None)