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438 lines
16 KiB
Python
438 lines
16 KiB
Python
# Copyright 2017, David Wilson
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#
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# Redistribution and use in source and binary forms, with or without
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# modification, are permitted provided that the following conditions are met:
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#
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# 1. Redistributions of source code must retain the above copyright notice,
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# this list of conditions and the following disclaimer.
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#
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# 2. Redistributions in binary form must reproduce the above copyright notice,
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# this list of conditions and the following disclaimer in the documentation
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# and/or other materials provided with the distribution.
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#
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# 3. Neither the name of the copyright holder nor the names of its contributors
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# may be used to endorse or promote products derived from this software without
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# specific prior written permission.
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#
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# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
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# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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# POSSIBILITY OF SUCH DAMAGE.
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"""
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Classes in this file define Mitogen 'services' that run (initially) within the
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connection multiplexer process that is forked off the top-level controller
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process.
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Once a worker process connects to a multiplexer process
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(Connection._connect()), it communicates with these services to establish new
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connections, grant access to files by children, and register for notification
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when a child has completed a job.
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"""
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from __future__ import absolute_import
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import logging
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import os
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import os.path
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import pprint
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import sys
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import threading
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import zlib
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import mitogen
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import mitogen.service
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import ansible_mitogen.target
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LOG = logging.getLogger(__name__)
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class Error(Exception):
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pass
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class ContextService(mitogen.service.Service):
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"""
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Used by workers to fetch the single Context instance corresponding to a
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connection configuration, creating the matching connection if it does not
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exist.
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For connection methods and their parameters, see:
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https://mitogen.readthedocs.io/en/latest/api.html#context-factories
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This concentrates connections in the top-level process, which may become a
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bottleneck. The bottleneck can be removed using per-CPU connection
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processes and arranging for the worker to select one according to a hash of
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the connection parameters (sharding).
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"""
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handle = 500
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max_message_size = 1000
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max_interpreters = int(os.getenv('MITOGEN_MAX_INTERPRETERS', '20'))
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def __init__(self, *args, **kwargs):
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super(ContextService, self).__init__(*args, **kwargs)
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self._lock = threading.Lock()
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#: Records the :meth:`get` result dict for successful calls, returned
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#: for identical subsequent calls. Keyed by :meth:`key_from_kwargs`.
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self._response_by_key = {}
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#: List of :class:`mitogen.core.Message` waiting for the result dict
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#: for a particular connection config. Keyed as sbove.
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self._waiters_by_key = {}
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#: Mapping of :class:`mitogen.core.Context` -> reference count. Each
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#: call to :meth:`get` increases this by one. Calls to :meth:`put`
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#: decrease it by one.
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self._refs_by_context = {}
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#: List of contexts in creation order by via= parameter. When
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#: :attr:`max_interpreters` is reached, the most recently used context
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#: is destroyed to make room for any additional context.
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self._update_lru_by_via = {}
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#: :meth:`key_from_kwargs` result by Context.
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self._key_by_context = {}
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@mitogen.service.expose(mitogen.service.AllowParents())
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@mitogen.service.arg_spec({
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'context': mitogen.core.Context
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})
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def put(self, context):
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"""
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Return a reference, making it eligable for recycling once its reference
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count reaches zero.
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"""
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LOG.debug('%r.put(%r)', self, context)
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assert self._refs_by_context[context] > 0
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self._refs_by_context[context] -= 1
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def key_from_kwargs(self, **kwargs):
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"""
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Generate a deduplication key from the request. The default
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implementation returns a string based on a stable representation of the
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input dictionary generated by :py:func:`pprint.pformat`.
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"""
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return pprint.pformat(kwargs)
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def _produce_response(self, key, response):
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"""
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Reply to every waiting request matching a configuration key with a
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response dictionary, deleting the list of waiters when done.
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:param str key:
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Result of :meth:`key_from_kwargs`
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:param dict response:
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Response dictionary
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:returns:
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Number of waiters that were replied to.
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"""
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self._lock.acquire()
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try:
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waiters = self._waiters_by_key.pop(key)
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count = len(waiters)
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for msg in waiters:
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msg.reply(response)
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finally:
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self._lock.release()
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return count
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def _update_lru(self, new_context, **kwargs):
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"""
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Update the LRU ("MRU"?) list associated with the connection described
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by `kwargs`, destroying the most recently created context if the list
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is full. Finally add `new_context` to the list.
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"""
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via = kwargs.get('via')
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if via is None:
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# We don't have a limit on the number of directly connections.
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return
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lru = self._update_lru_by_via.setdefault(via, [])
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if len(lru) < self.max_interpreters:
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lru.append(new_context)
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return
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for context in reversed(lru):
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if self._refs_by_context[context] == 0:
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break
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else:
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LOG.warning('via=%r reached maximum number of interpreters, '
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'but they are all marked as in-use.', via)
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return
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LOG.info('%r._discard_one(): shutting down %r', self, context)
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context.shutdown()
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key = self._key_by_context[context]
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self._lock.acquire()
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try:
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del self._response_by_key[key]
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del self._refs_by_context[context]
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del self._key_by_context[context]
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lru.remove(context)
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lru.append(new_context)
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finally:
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self._lock.release()
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def _connect(self, key, method_name, **kwargs):
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"""
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Actual connect implementation. Arranges for the Mitogen connection to
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be created and enqueues an asynchronous call to start the forked task
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parent in the remote context.
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:param key:
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Deduplication key representing the connection configuration.
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:param method_name:
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:class:`mitogen.parent.Router` method implementing the connection
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type.
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:param kwargs:
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Keyword arguments passed to the router method.
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:returns:
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Dict like::
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{
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'context': mitogen.core.Context or None,
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'home_dir': str or None,
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'msg': str or None
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}
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Where either `msg` is an error message and the remaining fields are
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:data:`None`, or `msg` is :data:`None` and the remaining fields are
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set.
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"""
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method = getattr(self.router, method_name, None)
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if method is None:
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raise Error('no such Router method: %s' % (method_name,))
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try:
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context = method(**kwargs)
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except mitogen.core.StreamError as e:
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return {
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'context': None,
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'home_dir': None,
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'msg': str(e),
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}
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if kwargs.get('via'):
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self._update_lru(context, method_name=method_name, **kwargs)
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home_dir = context.call(os.path.expanduser, '~')
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# We don't need to wait for the result of this. Ideally we'd check its
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# return value somewhere, but logs will catch a failure anyway.
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context.call_async(ansible_mitogen.target.start_fork_parent)
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self._key_by_context[context] = key
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self._refs_by_context[context] = 0
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return {
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'context': context,
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'home_dir': home_dir,
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'msg': None,
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}
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@mitogen.service.expose(mitogen.service.AllowParents())
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@mitogen.service.arg_spec({
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'method_name': str
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})
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def get(self, msg, **kwargs):
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"""
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Return a Context referring to an established connection with the given
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configuration, establishing a new connection as necessary.
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:param str method_name:
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The :class:`mitogen.parent.Router` connection method to use.
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:param dict kwargs:
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Keyword arguments passed to `mitogen.master.Router.[method_name]()`.
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:returns tuple:
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Tuple of `(context, home_dir)`, where:
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* `context` is the mitogen.master.Context referring to the
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target context.
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* `home_dir` is a cached copy of the remote directory.
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"""
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key = self.key_from_kwargs(**kwargs)
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self._lock.acquire()
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try:
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response = self._response_by_key.get(key)
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if response is not None:
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self._refs_by_context[response['context']] += 1
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return response
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waiters = self._waiters_by_key.get(key)
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if waiters is not None:
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waiters.append(msg)
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return self.NO_REPLY
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self._waiters_by_key[key] = [msg]
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finally:
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self._lock.release()
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# I'm the first thread to wait, so I will create the connection.
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try:
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response = self._connect(key, **kwargs)
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count = self._produce_response(key, response)
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if response['msg'] is None:
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# Only record the response for non-error results.
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self._response_by_key[key] = response
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# Set the reference count to the number of waiters.
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self._refs_by_context[response['context']] += count
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except mitogen.core.CallError:
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e = sys.exc_info()[1]
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self._produce_response(key, e)
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except Exception:
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e = sys.exc_info()[1]
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self._produce_response(key, mitogen.core.CallError(e))
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return self.NO_REPLY
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class FileService(mitogen.service.Service):
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"""
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Primitive latency-inducing file server for old-style incantations of the
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module runner. This is to be replaced later with a scheme that forwards
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files known to be missing without the target having to ask for them,
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avoiding a corresponding roundtrip per file.
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Paths must be explicitly added to the service by a trusted context before
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they will be served to an untrusted context.
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"""
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handle = 501
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max_message_size = 1000
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unregistered_msg = 'Path is not registered with FileService.'
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def __init__(self, router):
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super(FileService, self).__init__(router)
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self._paths = {}
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@mitogen.service.expose(policy=mitogen.service.AllowParents())
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@mitogen.service.arg_spec({
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'path': basestring
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})
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def register(self, path):
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"""
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Authorize a path for access by child contexts. Calling this repeatedly
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with the same path is harmless.
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:param str path:
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File path.
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"""
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if path not in self._paths:
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LOG.debug('%r: registering %r', self, path)
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with open(path, 'rb') as fp:
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self._paths[path] = zlib.compress(fp.read())
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@mitogen.service.expose(policy=mitogen.service.AllowAny())
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@mitogen.service.arg_spec({
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'path': basestring
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})
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def fetch(self, path):
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"""
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Fetch a file's data.
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:param str path:
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File path.
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:returns:
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The file data.
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:raises mitogen.core.CallError:
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The path was not registered.
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"""
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if path not in self._paths:
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raise mitogen.core.CallError(self.unregistered_msg)
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LOG.debug('Serving %r', path)
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return self._paths[path]
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class JobResultService(mitogen.service.Service):
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"""
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Receive the result of a task from a child and forward it to interested
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listeners. If no listener exists, store the result until it is requested.
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Storing results in an intermediary service allows:
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* the lifetime of the worker to be decoupled from the lifetime of the job,
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* for new and unrelated workers to request the job result after the original
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worker that spawned it has exitted,
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* for synchronous and asynchronous jobs to be treated identically,
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* for latency-free polling and waiting on job results, and
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* for Ansible job IDs to be be used to refer to a job in preference to
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Mitogen-internal identifiers such as Sender and Context.
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Results are keyed by job ID.
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"""
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handle = 502
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max_message_size = 1048576 * 64
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def __init__(self, router):
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super(JobResultService, self).__init__(router)
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self._lock = threading.Lock()
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self._result_by_job_id = {}
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self._sender_by_job_id = {}
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@mitogen.service.expose(mitogen.service.AllowParents())
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@mitogen.service.arg_spec({
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'job_id': str,
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'sender': mitogen.core.Sender,
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})
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def listen(self, job_id, sender):
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"""
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Register to receive the result of a job when it becomes available.
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:param str job_id:
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Job ID to listen for.
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:param mitogen.core.Sender sender:
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Sender on which to deliver the job result.
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"""
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LOG.debug('%r.listen(job_id=%r, sender=%r)', self, job_id, sender)
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with self._lock:
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if job_id in self._sender_by_job_id:
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raise Error('Listener already exists for job: %s' % (job_id,))
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self._sender_by_job_id[job_id] = sender
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@mitogen.service.expose(mitogen.service.AllowParents())
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@mitogen.service.arg_spec({
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'job_id': basestring,
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})
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def get(self, job_id):
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"""
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Return a job's result if it is available, otherwise return immediately.
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The job result is forgotten once it has been returned by this method.
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:param str job_id:
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Job ID to return.
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:returns:
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Job result dictionary, or :data:`None`.
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"""
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LOG.debug('%r.get(job_id=%r)', self, job_id)
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with self._lock:
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return self._result_by_job_id.pop(job_id, None)
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@mitogen.service.expose(mitogen.service.AllowAny())
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@mitogen.service.arg_spec({
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'job_id': basestring,
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'result': dict
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})
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def push(self, job_id, result):
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"""
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Deliver a job's result from a child context, notifying any listener
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registred via :meth:`listen` of the result.
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:param str job_id:
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Job ID whose result is being pushed.
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:param dict result:
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Job result dictionary.
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"""
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LOG.debug('%r.push(job_id=%r, result=%r)', self, job_id, result)
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with self._lock:
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if job_id in self._result_by_job_id:
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raise Error('Result already exists for job: %s' % (job_id,))
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sender = self._sender_by_job_id.pop(job_id, None)
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if sender:
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sender.send(result)
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else:
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self._result_by_job_id[job_id] = result
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