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"""The Python scheduler for rich scheduling.
The Pure ZMQ scheduler does not allow routing schemes other than LRU,
nor does it check msg_id DAG dependencies. For those, a slightly slower
Python Scheduler exists.
* Min RK
# Copyright (C) 2010-2011 The IPython Development Team
# Distributed under the terms of the BSD License. The full license is in
# the file COPYING, distributed as part of this software.
# Imports
from __future__ import print_function
import logging
import sys
from datetime import datetime, timedelta
from random import randint, random
from types import FunctionType
import numpy
except ImportError:
numpy = None
import zmq
from zmq.eventloop import ioloop, zmqstream
# local imports
from IPython.external.decorator import decorator
from IPython.config.loader import Config
from IPython.utils.traitlets import Instance, Dict, List, Set, Int, Enum
from IPython.parallel import error
from IPython.parallel.factory import SessionFactory
from IPython.parallel.util import connect_logger, local_logger
from .dependency import Dependency
def logged(f,self,*args,**kwargs):
# print ("#--------------------")
self.log.debug("scheduler::%s(*%s,**%s)"%(f.func_name, args, kwargs))
# print ("#--")
return f(self,*args, **kwargs)
# Chooser functions
def plainrandom(loads):
"""Plain random pick."""
n = len(loads)
return randint(0,n-1)
def lru(loads):
"""Always pick the front of the line.
The content of `loads` is ignored.
Assumes LRU ordering of loads, with oldest first.
return 0
def twobin(loads):
"""Pick two at random, use the LRU of the two.
The content of loads is ignored.
Assumes LRU ordering of loads, with oldest first.
n = len(loads)
a = randint(0,n-1)
b = randint(0,n-1)
return min(a,b)
def weighted(loads):
"""Pick two at random using inverse load as weight.
Return the less loaded of the two.
# weight 0 a million times more than 1:
weights = 1./(1e-6+numpy.array(loads))
sums = weights.cumsum()
t = sums[-1]
x = random()*t
y = random()*t
idx = 0
idy = 0
while sums[idx] < x:
idx += 1
while sums[idy] < y:
idy += 1
if weights[idy] > weights[idx]:
return idy
return idx
def leastload(loads):
"""Always choose the lowest load.
If the lowest load occurs more than once, the first
occurance will be used. If loads has LRU ordering, this means
the LRU of those with the lowest load is chosen.
return loads.index(min(loads))
# Classes
# store empty default dependency:
MET = Dependency([])
class TaskScheduler(SessionFactory):
"""Python TaskScheduler object.
This is the simplest object that supports msg_id based
DAG dependencies. *Only* task msg_ids are checked, not
msg_ids of jobs submitted via the MUX queue.
hwm = Int(0, config=True, shortname='hwm',
help="""specify the High Water Mark (HWM) for the downstream
socket in the Task scheduler. This is the maximum number
of allowed outstanding tasks on each engine."""
scheme_name = Enum(('leastload', 'pure', 'lru', 'plainrandom', 'weighted', 'twobin'),
'leastload', config=True, shortname='scheme', allow_none=False,
help="""select the task scheduler scheme [default: Python LRU]
Options are: 'pure', 'lru', 'plainrandom', 'weighted', 'twobin','leastload'"""
def _scheme_name_changed(self, old, new):
self.log.debug("Using scheme %r"%new)
self.scheme = globals()[new]
# input arguments:
scheme = Instance(FunctionType) # function for determining the destination
def _scheme_default(self):
return leastload
client_stream = Instance(zmqstream.ZMQStream) # client-facing stream
engine_stream = Instance(zmqstream.ZMQStream) # engine-facing stream
notifier_stream = Instance(zmqstream.ZMQStream) # hub-facing sub stream
mon_stream = Instance(zmqstream.ZMQStream) # hub-facing pub stream
# internals:
graph = Dict() # dict by msg_id of [ msg_ids that depend on key ]
retries = Dict() # dict by msg_id of retries remaining (non-neg ints)
# waiting = List() # list of msg_ids ready to run, but haven't due to HWM
depending = Dict() # dict by msg_id of (msg_id, raw_msg, after, follow)
pending = Dict() # dict by engine_uuid of submitted tasks
completed = Dict() # dict by engine_uuid of completed tasks
failed = Dict() # dict by engine_uuid of failed tasks
destinations = Dict() # dict by msg_id of engine_uuids where jobs ran (reverse of completed+failed)
clients = Dict() # dict by msg_id for who submitted the task
targets = List() # list of target IDENTs
loads = List() # list of engine loads
# full = Set() # set of IDENTs that have HWM outstanding tasks
all_completed = Set() # set of all completed tasks
all_failed = Set() # set of all failed tasks
all_done = Set() # set of all finished tasks=union(completed,failed)
all_ids = Set() # set of all submitted task IDs
blacklist = Dict() # dict by msg_id of locations where a job has encountered UnmetDependency
auditor = Instance('zmq.eventloop.ioloop.PeriodicCallback')
def start(self):
self.engine_stream.on_recv(self.dispatch_result, copy=False)
self._notification_handlers = dict(
registration_notification = self._register_engine,
unregistration_notification = self._unregister_engine
self.auditor = ioloop.PeriodicCallback(self.audit_timeouts, 2e3, self.loop) # 1 Hz
self.auditor.start()"Scheduler started [%s]"%self.scheme_name)
def resume_receiving(self):
"""Resume accepting jobs."""
self.client_stream.on_recv(self.dispatch_submission, copy=False)
def stop_receiving(self):
"""Stop accepting jobs while there are no engines.
Leave them in the ZMQ queue."""
# [Un]Registration Handling
def dispatch_notification(self, msg):
"""dispatch register/unregister events."""
idents,msg = self.session.feed_identities(msg)
except ValueError:
self.log.warn("task::Invalid Message: %r"%msg)
msg = self.session.unpack_message(msg)
except ValueError:
self.log.warn("task::Unauthorized message from: %r"%idents)
msg_type = msg['msg_type']
handler = self._notification_handlers.get(msg_type, None)
if handler is None:
self.log.error("Unhandled message type: %r"%msg_type)
except KeyError:
self.log.error("task::Invalid notification msg: %r"%msg)
def _register_engine(self, uid):
"""New engine with ident `uid` became available."""
# head of the line:
# initialize sets
self.completed[uid] = set()
self.failed[uid] = set()
self.pending[uid] = {}
if len(self.targets) == 1:
# rescan the graph:
def _unregister_engine(self, uid):
"""Existing engine with ident `uid` became unavailable."""
if len(self.targets) == 1:
# this was our only engine
# handle any potentially finished tasks:
# don't pop destinations, because they might be used later
# map(self.destinations.pop, self.completed.pop(uid))
# map(self.destinations.pop, self.failed.pop(uid))
# prevent this engine from receiving work
idx = self.targets.index(uid)
# wait 5 seconds before cleaning up pending jobs, since the results might
# still be incoming
if self.pending[uid]:
dc = ioloop.DelayedCallback(lambda : self.handle_stranded_tasks(uid), 5000, self.loop)
def handle_stranded_tasks(self, engine):
"""Deal with jobs resident in an engine that died."""
lost = self.pending[engine]
for msg_id in lost.keys():
if msg_id not in self.pending[engine]:
# prevent double-handling of messages
raw_msg = lost[msg_id][0]
idents,msg = self.session.feed_identities(raw_msg, copy=False)
parent = self.session.unpack(msg[1].bytes)
idents = [engine, idents[0]]
# build fake error reply
raise error.EngineError("Engine %r died while running task %r"%(engine, msg_id))
content = error.wrap_exception()
msg = self.session.msg('apply_reply', content, parent=parent, subheader={'status':'error'})
raw_reply = map(zmq.Message, self.session.serialize(msg, ident=idents))
# and dispatch it
# finally scrub completed/failed lists
# Job Submission
def dispatch_submission(self, raw_msg):
"""Dispatch job submission to appropriate handlers."""
# ensure targets up to date:
idents, msg = self.session.feed_identities(raw_msg, copy=False)
msg = self.session.unpack_message(msg, content=False, copy=False)
except Exception:
self.log.error("task::Invaid task msg: %r"%raw_msg, exc_info=True)
# send to monitor
self.mon_stream.send_multipart(['intask']+raw_msg, copy=False)
header = msg['header']
msg_id = header['msg_id']
# targets
targets = set(header.get('targets', []))
retries = header.get('retries', 0)
self.retries[msg_id] = retries
# time dependencies
after = Dependency(header.get('after', []))
if after.all:
if after.success:
if after.failure:
if after.check(self.all_completed, self.all_failed):
# recast as empty set, if `after` already met,
# to prevent unnecessary set comparisons
after = MET
# location dependencies
follow = Dependency(header.get('follow', []))
# turn timeouts into datetime objects:
timeout = header.get('timeout', None)
if timeout:
timeout = + timedelta(0,timeout,0)
args = [raw_msg, targets, after, follow, timeout]
# validate and reduce dependencies:
for dep in after,follow:
# check valid:
if msg_id in dep or dep.difference(self.all_ids):
self.depending[msg_id] = args
return self.fail_unreachable(msg_id, error.InvalidDependency)
# check if unreachable:
if dep.unreachable(self.all_completed, self.all_failed):
self.depending[msg_id] = args
return self.fail_unreachable(msg_id)
if after.check(self.all_completed, self.all_failed):
# time deps already met, try to run
if not self.maybe_run(msg_id, *args):
# can't run yet
if msg_id not in self.all_failed:
# could have failed as unreachable
self.save_unmet(msg_id, *args)
self.save_unmet(msg_id, *args)
# @logged
def audit_timeouts(self):
"""Audit all waiting tasks for expired timeouts."""
now =
for msg_id in self.depending.keys():
# must recheck, in case one failure cascaded to another:
if msg_id in self.depending:
raw,after,targets,follow,timeout = self.depending[msg_id]
if timeout and timeout < now:
self.fail_unreachable(msg_id, error.TaskTimeout)
def fail_unreachable(self, msg_id, why=error.ImpossibleDependency):
"""a task has become unreachable, send a reply with an ImpossibleDependency
if msg_id not in self.depending:
self.log.error("msg %r already failed!"%msg_id)
raw_msg,targets,after,follow,timeout = self.depending.pop(msg_id)
for mid in follow.union(after):
if mid in self.graph:
# FIXME: unpacking a message I've already unpacked, but didn't save:
idents,msg = self.session.feed_identities(raw_msg, copy=False)
header = self.session.unpack(msg[1].bytes)
raise why()
content = error.wrap_exception()
msg = self.session.send(self.client_stream, 'apply_reply', content,
parent=header, ident=idents)
self.session.send(self.mon_stream, msg, ident=['outtask']+idents)
self.update_graph(msg_id, success=False)
def maybe_run(self, msg_id, raw_msg, targets, after, follow, timeout):
"""check location dependencies, and run if they are met."""
blacklist = self.blacklist.setdefault(msg_id, set())
if follow or targets or blacklist or self.hwm:
# we need a can_run filter
def can_run(idx):
# check hwm
if self.hwm and self.loads[idx] == self.hwm:
return False
target = self.targets[idx]
# check blacklist
if target in blacklist:
return False
# check targets
if targets and target not in targets:
return False
# check follow
return follow.check(self.completed[target], self.failed[target])
indices = filter(can_run, range(len(self.targets)))
if not indices:
# couldn't run
if follow.all:
# check follow for impossibility
dests = set()
relevant = set()
if follow.success:
relevant = self.all_completed
if follow.failure:
relevant = relevant.union(self.all_failed)
for m in follow.intersection(relevant):
if len(dests) > 1:
self.depending[msg_id] = (raw_msg, targets, after, follow, timeout)
return False
if targets:
# check blacklist+targets for impossibility
if not targets or not targets.intersection(self.targets):
self.depending[msg_id] = (raw_msg, targets, after, follow, timeout)
return False
return False
indices = None
self.submit_task(msg_id, raw_msg, targets, follow, timeout, indices)
return True
def save_unmet(self, msg_id, raw_msg, targets, after, follow, timeout):
"""Save a message for later submission when its dependencies are met."""
self.depending[msg_id] = [raw_msg,targets,after,follow,timeout]
# track the ids in follow or after, but not those already finished
for dep_id in after.union(follow).difference(self.all_done):
if dep_id not in self.graph:
self.graph[dep_id] = set()
def submit_task(self, msg_id, raw_msg, targets, follow, timeout, indices=None):
"""Submit a task to any of a subset of our targets."""
if indices:
loads = [self.loads[i] for i in indices]
loads = self.loads
idx = self.scheme(loads)
if indices:
idx = indices[idx]
target = self.targets[idx]
# print (target, map(str, msg[:3]))
# send job to the engine
self.engine_stream.send(target, flags=zmq.SNDMORE, copy=False)
self.engine_stream.send_multipart(raw_msg, copy=False)
# update load
self.pending[target][msg_id] = (raw_msg, targets, MET, follow, timeout)
# notify Hub
content = dict(msg_id=msg_id, engine_id=target)
self.session.send(self.mon_stream, 'task_destination', content=content,
# Result Handling
def dispatch_result(self, raw_msg):
"""dispatch method for result replies"""
idents,msg = self.session.feed_identities(raw_msg, copy=False)
msg = self.session.unpack_message(msg, content=False, copy=False)
engine = idents[0]
idx = self.targets.index(engine)
except ValueError:
pass # skip load-update for dead engines
except Exception:
self.log.error("task::Invaid result: %r"%raw_msg, exc_info=True)
header = msg['header']
parent = msg['parent_header']
if header.get('dependencies_met', True):
success = (header['status'] == 'ok')
msg_id = parent['msg_id']
retries = self.retries[msg_id]
if not success and retries > 0:
# failed
self.retries[msg_id] = retries - 1
self.handle_unmet_dependency(idents, parent)
del self.retries[msg_id]
# relay to client and update graph
self.handle_result(idents, parent, raw_msg, success)
# send to Hub monitor
self.mon_stream.send_multipart(['outtask']+raw_msg, copy=False)
self.handle_unmet_dependency(idents, parent)
def handle_result(self, idents, parent, raw_msg, success=True):
"""handle a real task result, either success or failure"""
# first, relay result to client
engine = idents[0]
client = idents[1]
# swap_ids for XREP-XREP mirror
raw_msg[:2] = [client,engine]
# print (map(str, raw_msg[:4]))
self.client_stream.send_multipart(raw_msg, copy=False)
# now, update our data structures
msg_id = parent['msg_id']
self.blacklist.pop(msg_id, None)
if success:
self.destinations[msg_id] = engine
self.update_graph(msg_id, success)
def handle_unmet_dependency(self, idents, parent):
"""handle an unmet dependency"""
engine = idents[0]
msg_id = parent['msg_id']
if msg_id not in self.blacklist:
self.blacklist[msg_id] = set()
args = self.pending[engine].pop(msg_id)
raw,targets,after,follow,timeout = args
if self.blacklist[msg_id] == targets:
self.depending[msg_id] = args
elif not self.maybe_run(msg_id, *args):
# resubmit failed
if msg_id not in self.all_failed:
# put it back in our dependency tree
self.save_unmet(msg_id, *args)
if self.hwm:
idx = self.targets.index(engine)
except ValueError:
pass # skip load-update for dead engines
if self.loads[idx] == self.hwm-1:
def update_graph(self, dep_id=None, success=True):
"""dep_id just finished. Update our dependency
graph and submit any jobs that just became runable.
Called with dep_id=None to update entire graph for hwm, but without finishing
a task.
# print ("\n\n***********")
# pprint (dep_id)
# pprint (self.graph)
# pprint (self.depending)
# pprint (self.all_completed)
# pprint (self.all_failed)
# print ("\n\n***********\n\n")
# update any jobs that depended on the dependency
jobs = self.graph.pop(dep_id, [])
# recheck *all* jobs if
# a) we have HWM and an engine just become no longer full
# or b) dep_id was given as None
if dep_id is None or self.hwm and any( [ load==self.hwm-1 for load in self.loads ]):
jobs = self.depending.keys()
for msg_id in jobs:
raw_msg, targets, after, follow, timeout = self.depending[msg_id]
if after.unreachable(self.all_completed, self.all_failed)\
or follow.unreachable(self.all_completed, self.all_failed):
elif after.check(self.all_completed, self.all_failed): # time deps met, maybe run
if self.maybe_run(msg_id, raw_msg, targets, MET, follow, timeout):
for mid in follow.union(after):
if mid in self.graph:
# methods to be overridden by subclasses
def add_job(self, idx):
"""Called after self.targets[idx] just got the job with header.
Override with subclasses. The default ordering is simple LRU.
The default loads are the number of outstanding jobs."""
self.loads[idx] += 1
for lis in (self.targets, self.loads):
def finish_job(self, idx):
"""Called after self.targets[idx] just finished a job.
Override with subclasses."""
self.loads[idx] -= 1
def launch_scheduler(in_addr, out_addr, mon_addr, not_addr, config=None,
logname='root', log_url=None, loglevel=logging.DEBUG,
from zmq.eventloop import ioloop
from zmq.eventloop.zmqstream import ZMQStream
if config:
# unwrap dict back into Config
config = Config(config)
ctx = zmq.Context()
loop = ioloop.IOLoop()
ins = ZMQStream(ctx.socket(zmq.XREP),loop)
ins.setsockopt(zmq.IDENTITY, identity)
outs = ZMQStream(ctx.socket(zmq.XREP),loop)
outs.setsockopt(zmq.IDENTITY, identity)
mons = ZMQStream(ctx.socket(zmq.PUB),loop)
nots = ZMQStream(ctx.socket(zmq.SUB),loop)
nots.setsockopt(zmq.SUBSCRIBE, '')
# setup logging. Note that these will not work in-process, because they clobber
# existing loggers.
if log_url:
log = connect_logger(logname, ctx, log_url, root="scheduler", loglevel=loglevel)
log = local_logger(logname, loglevel)
scheduler = TaskScheduler(client_stream=ins, engine_stream=outs,
mon_stream=mons, notifier_stream=nots,
loop=loop, log=log,
except KeyboardInterrupt:
print ("interrupted, exiting...", file=sys.__stderr__)
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