""" The multiprocessing server core is a reimplementation of the
:mod:`Bcfg2.Server.BuiltinCore` that uses the Python
:mod:`multiprocessing` library to offload work to multiple child
processes. As such, it requires Python 2.6+.
The parent communicates with the children over
:class:`multiprocessing.Queue` objects via a
:class:`Bcfg2.Server.MultiprocessingCore.RPCQueue` object.
A method being called via the RPCQueue must be exposed by the child by
decorating it with :func:`Bcfg2.Server.Core.exposed`.
"""
import time
import threading
import lxml.etree
import multiprocessing
import Bcfg2.Options
import Bcfg2.Server.Cache
import Bcfg2.Server.Plugin
from itertools import cycle
from Bcfg2.Compat import Queue, Empty, wraps
from Bcfg2.Server.Core import Core, exposed
from Bcfg2.Server.BuiltinCore import BuiltinCore
from multiprocessing.connection import Listener, Client
[docs]class RPCQueue(Bcfg2.Server.Plugin.Debuggable):
""" An implementation of a :class:`multiprocessing.Queue` designed
for several additional use patterns:
* Random-access reads, based on a key that identifies the data;
* Publish-subscribe, where a datum is sent to all hosts.
The subscribers can deal with this as a normal Queue with no
special handling.
"""
poll_wait = 3.0
def __init__(self):
Bcfg2.Server.Plugin.Debuggable.__init__(self)
self._terminate = threading.Event()
self._queues = dict()
self._listeners = []
[docs] def add_subscriber(self, name):
""" Add a subscriber to the queue. This returns the
:class:`multiprocessing.Queue` object that the subscriber
should read from. """
self._queues[name] = multiprocessing.Queue()
return self._queues[name]
[docs] def publish(self, method, args=None, kwargs=None):
""" Publish an RPC call to the queue for consumption by all
subscribers. """
for queue in self._queues.values():
queue.put((None, (method, args or [], kwargs or dict())))
[docs] def rpc(self, dest, method, args=None, kwargs=None):
""" Make an RPC call to the named subscriber, expecting a
response. This opens a
:class:`multiprocessing.connection.Listener` and passes the
Listener address to the child as part of the RPC call, so that
the child can connect to the Listener to submit its results.
"""
listener = Listener()
self.logger.debug("Created new RPC listener at %s" % listener.address)
self._listeners.append(listener)
try:
self._queues[dest].put((listener.address,
(method, args or [], kwargs or dict())))
conn = listener.accept()
try:
while not self._terminate.is_set():
if conn.poll(self.poll_wait):
return conn.recv()
finally:
conn.close()
finally:
listener.close()
self._listeners.remove(listener)
[docs] def close(self):
""" Close queues and connections. """
self._terminate.set()
self.logger.debug("Closing RPC queues")
for name, queue in self._queues.items():
self.logger.debug("Closing RPC queue to %s" % name)
queue.close()
# close any listeners that are waiting for connections
self.logger.debug("Closing RPC connections")
for listener in self._listeners:
self.logger.debug("Closing RPC connection at %s" %
listener.address)
listener.close()
[docs]class DualEvent(object):
""" DualEvent is a clone of :class:`threading.Event` that
internally implements both :class:`threading.Event` and
:class:`multiprocessing.Event`. """
def __init__(self, threading_event=None, multiprocessing_event=None):
self._threading_event = threading_event or threading.Event()
self._multiproc_event = multiprocessing_event or \
multiprocessing.Event()
if threading_event or multiprocessing_event:
# initialize internal flag to false, regardless of the
# state of either object passed in
self.clear()
[docs] def is_set(self):
""" Return true if and only if the internal flag is true. """
return self._threading_event.is_set()
isSet = is_set
[docs] def set(self):
""" Set the internal flag to true. """
self._threading_event.set()
self._multiproc_event.set()
[docs] def clear(self):
""" Reset the internal flag to false. """
self._threading_event.clear()
self._multiproc_event.clear()
[docs] def wait(self, timeout=None):
""" Block until the internal flag is true, or until the
optional timeout occurs. """
return self._threading_event.wait(timeout=timeout)
[docs]class ChildCore(Core):
""" A child process for :class:`Bcfg2.MultiprocessingCore.Core`.
This core builds configurations from a given
:class:`multiprocessing.Pipe`. Note that this is a full-fledged
server core; the only input it gets from the parent process is the
hostnames of clients to render. All other state comes from the
FAM. However, this core only is used to render configs; it doesn't
handle anything else (authentication, probes, etc.) because those
are all much faster. There's no reason that it couldn't handle
those, though, if the pipe communication "protocol" were made more
robust. """
#: How long to wait while polling for new RPC commands. This
#: doesn't affect the speed with which a command is processed, but
#: setting it too high will result in longer shutdown times, since
#: we only check for the termination event from the main process
#: every ``poll_wait`` seconds.
poll_wait = 3.0
def __init__(self, name, rpc_q, terminate):
"""
:param name: The name of this child
:type name: string
:param read_q: The queue the child will read from for RPC
communications from the parent process.
:type read_q: multiprocessing.Queue
:param write_q: The queue the child will write the results of
RPC calls to.
:type write_q: multiprocessing.Queue
:param terminate: An event that flags ChildCore objects to shut
themselves down.
:type terminate: multiprocessing.Event
"""
Core.__init__(self)
#: The name of this child
self.name = name
#: The :class:`multiprocessing.Event` that will be monitored
#: to determine when this child should shut down.
self.terminate = terminate
#: The queue used for RPC communication
self.rpc_q = rpc_q
# override this setting so that the child doesn't try to write
# the pidfile
Bcfg2.Options.setup.daemon = False
# ensure that the child doesn't start a perflog thread
self.perflog_thread = None
self._rmi = dict()
def _run(self):
return True
def _dispatch(self, address, data):
""" Method dispatcher used for commands received from
the RPC queue. """
if address is not None:
# if the key is None, then no response is expected. we
# make the return connection before dispatching the actual
# RPC call so that the parent is blocking for a connection
# as briefly as possible
self.logger.debug("Connecting to parent via %s" % address)
client = Client(address)
method, args, kwargs = data
func = None
rv = None
if "." in method:
if method in self._rmi:
func = self._rmi[method]
else:
self.logger.error("%s: Method %s does not exist" % (self.name,
method))
elif not hasattr(self, method):
self.logger.error("%s: Method %s does not exist" % (self.name,
method))
else: # method is not a plugin RMI, and exists
func = getattr(self, method)
if not func.exposed:
self.logger.error("%s: Method %s is not exposed" % (self.name,
method))
func = None
if func is not None:
self.logger.debug("%s: Calling RPC method %s" % (self.name,
method))
rv = func(*args, **kwargs)
if address is not None:
# if the key is None, then no response is expected
self.logger.debug("Returning data to parent via %s" % address)
client.send(rv)
def _block(self):
self._rmi = self._get_rmi()
while not self.terminate.is_set():
try:
address, data = self.rpc_q.get(timeout=self.poll_wait)
threadname = "-".join(str(i) for i in data)
rpc_thread = threading.Thread(name=threadname,
target=self._dispatch,
args=[address, data])
rpc_thread.start()
except Empty:
pass
except KeyboardInterrupt:
break
self.shutdown()
[docs] def shutdown(self):
Core.shutdown(self)
self.logger.info("%s: Closing RPC command queue" % self.name)
self.rpc_q.close()
while len(threading.enumerate()) > 1:
threads = [t for t in threading.enumerate()
if t != threading.current_thread()]
self.logger.info("%s: Waiting for %d thread(s): %s" %
(self.name, len(threads),
[t.name for t in threads]))
time.sleep(1)
self.logger.info("%s: All threads stopped" % self.name)
def _get_rmi(self):
rmi = dict()
for pname, pinst in self._get_rmi_objects().items():
for crmi in pinst.__child_rmi__:
if isinstance(crmi, tuple):
mname = crmi[1]
else:
mname = crmi
rmi["%s.%s" % (pname, mname)] = getattr(pinst, mname)
return rmi
[docs] @exposed
def expire_cache(self, *tags, **kwargs):
""" Expire cached data """
Bcfg2.Server.Cache.expire(*tags, exact=kwargs.pop("exact", False))
[docs] @exposed
def GetConfig(self, client):
""" Render the configuration for a client """
self.metadata.update_client_list()
self.logger.debug("%s: Building configuration for %s" %
(self.name, client))
return lxml.etree.tostring(self.BuildConfiguration(client))
[docs]class MultiprocessingCore(BuiltinCore):
""" A multiprocessing core that delegates building the actual
client configurations to
:class:`Bcfg2.Server.MultiprocessingCore.ChildCore` objects. The
parent process doesn't build any children itself; all calls to
:func:`GetConfig` are delegated to children. All other calls are
handled by the parent process. """
options = BuiltinCore.options + [
Bcfg2.Options.Option(
'--children', dest="core_children",
cf=('server', 'children'), type=int,
default=multiprocessing.cpu_count(),
help='Spawn this number of children for the multiprocessing core')]
#: How long to wait for a child process to shut down cleanly
#: before it is terminated.
shutdown_timeout = 10.0
def __init__(self):
BuiltinCore.__init__(self)
#: A dict of child name -> one end of the
#: :class:`multiprocessing.Pipe` object used to communicate
#: with that child. (The child is given the other end of the
#: Pipe.)
self.pipes = dict()
#: A queue that keeps track of which children are available to
#: render a configuration. A child is popped from the queue
#: when it starts to render a config, then it's pushed back on
#: when it's done. This lets us use a blocking call to
#: :func:`Queue.Queue.get` when waiting for an available
#: child.
self.available_children = \
Queue(maxsize=Bcfg2.Options.setup.core_children)
#: The flag that indicates when to stop child threads and
#: processes
self.terminate = DualEvent(threading_event=self.terminate)
#: A :class:`Bcfg2.Server.MultiprocessingCore.RPCQueue` object
#: used to send or publish commands to children.
self.rpc_q = RPCQueue()
#: A list of children that will be cycled through
self._all_children = []
#: An iterator that each child will be taken from in sequence,
#: to provide a round-robin distribution of render requests
self.children = None
def __str__(self):
if hasattr(Bcfg2.Options.setup, "server"):
return "%s(%s; %s children)" % (self.__class__.__name__,
Bcfg2.Options.setup.server,
len(self._all_children))
else:
return "%s(%s children)" % (self.__class__.__name__,
len(self._all_children))
def _run(self):
for cnum in range(Bcfg2.Options.setup.core_children):
name = "Child-%s" % cnum
self.logger.debug("Starting child %s" % name)
child_q = self.rpc_q.add_subscriber(name)
childcore = ChildCore(name, child_q, self.terminate)
child = multiprocessing.Process(target=childcore.run, name=name)
child.start()
self.logger.debug("Child %s started with PID %s" % (name,
child.pid))
self._all_children.append(name)
self.logger.debug("Started %s children: %s" % (len(self._all_children),
self._all_children))
self.children = cycle(self._all_children)
Bcfg2.Server.Cache.add_expire_hook(self.cache_dispatch)
return BuiltinCore._run(self)
[docs] def shutdown(self):
BuiltinCore.shutdown(self)
self.logger.info("Closing RPC command queues")
self.rpc_q.close()
def term_children():
""" Terminate all remaining multiprocessing children. """
for child in multiprocessing.active_children():
self.logger.error("Waited %s seconds to shut down %s, "
"terminating" % (self.shutdown_timeout,
child.name))
child.terminate()
timer = threading.Timer(self.shutdown_timeout, term_children)
timer.start()
while len(multiprocessing.active_children()):
self.logger.info("Waiting for %s child(ren): %s" %
(len(multiprocessing.active_children()),
[c.name
for c in multiprocessing.active_children()]))
time.sleep(1)
timer.cancel()
self.logger.info("All children shut down")
while len(threading.enumerate()) > 1:
threads = [t for t in threading.enumerate()
if t != threading.current_thread()]
self.logger.info("Waiting for %s thread(s): %s" %
(len(threads), [t.name for t in threads]))
time.sleep(1)
self.logger.info("Shutdown complete")
def _get_rmi(self):
child_rmi = dict()
for pname, pinst in self._get_rmi_objects().items():
for crmi in pinst.__child_rmi__:
if isinstance(crmi, tuple):
parentname, childname = crmi
else:
parentname = childname = crmi
child_rmi["%s.%s" % (pname, parentname)] = \
"%s.%s" % (pname, childname)
rmi = BuiltinCore._get_rmi(self)
for method in rmi.keys():
if method in child_rmi:
rmi[method] = self._child_rmi_wrapper(method,
rmi[method],
child_rmi[method])
return rmi
def _child_rmi_wrapper(self, method, parent_rmi, child_rmi):
""" Returns a callable that dispatches a call to the given
child RMI to child processes, and calls the parent RMI locally
(i.e., in the parent process). """
@wraps(parent_rmi)
def inner(*args, **kwargs):
""" Function that dispatches an RMI call to child
processes and to the (original) parent function. """
self.logger.debug("Dispatching RMI call to %s to children: %s" %
(method, child_rmi))
self.rpc_q.publish(child_rmi, args=args, kwargs=kwargs)
return parent_rmi(*args, **kwargs)
return inner
[docs] @exposed
def set_debug(self, address, debug):
self.rpc_q.set_debug(debug)
self.rpc_q.publish("set_debug", args=[address, debug])
return BuiltinCore.set_debug(self, address, debug)
[docs] def cache_dispatch(self, tags, exact, _):
""" Publish cache expiration events to child nodes. """
self.rpc_q.publish("expire_cache", args=tags, kwargs=dict(exact=exact))
[docs] @exposed
def GetConfig(self, address):
client = self.resolve_client(address)[0]
childname = self.children.next()
self.logger.debug("Building configuration for %s on %s" % (client,
childname))
return self.rpc_q.rpc(childname, "GetConfig", args=[client])
[docs] @exposed
def get_statistics(self, address):
stats = dict()
def _aggregate_statistics(newstats, prefix=None):
""" Aggregate a set of statistics from a child or parent
server core. This adds the statistics to the overall
statistics dict (optionally prepending a prefix, such as
"Child-1", to uniquely identify this set of statistics),
and aggregates it with the set of running totals that are
kept from all cores. """
for statname, vals in newstats.items():
if statname.startswith("ChildCore:"):
statname = statname[5:]
if prefix:
prettyname = "%s:%s" % (prefix, statname)
else:
prettyname = statname
stats[prettyname] = vals
totalname = "Total:%s" % statname
if totalname not in stats:
stats[totalname] = vals
else:
newmin = min(stats[totalname][0], vals[0])
newmax = max(stats[totalname][1], vals[1])
newcount = stats[totalname][3] + vals[3]
newmean = ((stats[totalname][2] * stats[totalname][3]) +
(vals[2] * vals[3])) / newcount
stats[totalname] = (newmin, newmax, newmean, newcount)
stats = dict()
for childname in self._all_children:
_aggregate_statistics(
self.rpc_q.rpc(childname, "get_statistics", args=[address]),
prefix=childname)
_aggregate_statistics(BuiltinCore.get_statistics(self, address))
return stats
