IPython/parallel/heartmonitor.py

#!/usr/bin/env python
"""
A multi-heart Heartbeat system using PUB and XREP sockets. pings are sent out on the PUB,
and hearts are tracked based on their XREQ identities.
"""
#-----------------------------------------------------------------------------
#  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.
#-----------------------------------------------------------------------------

from __future__ import print_function
import time
import logging
import uuid

import zmq
from zmq.devices import ProcessDevice,ThreadDevice
from zmq.eventloop import ioloop, zmqstream

from IPython.utils.traitlets import Set, Instance, CFloat, Bool
from .factory import LoggingFactory

class Heart(object):
    """A basic heart object for responding to a HeartMonitor.
    This is a simple wrapper with defaults for the most common
    Device model for responding to heartbeats.
    
    It simply builds a threadsafe zmq.FORWARDER Device, defaulting to using 
    SUB/XREQ for in/out.
    
    You can specify the XREQ's IDENTITY via the optional heart_id argument."""
    device=None
    id=None
    def __init__(self, in_addr, out_addr, in_type=zmq.SUB, out_type=zmq.XREQ, heart_id=None):
        self.device = ThreadDevice(zmq.FORWARDER, in_type, out_type)
        self.device.daemon=True
        self.device.connect_in(in_addr)
        self.device.connect_out(out_addr)
        if in_type == zmq.SUB:
            self.device.setsockopt_in(zmq.SUBSCRIBE, "")
        if heart_id is None:
            heart_id = str(uuid.uuid4())
        self.device.setsockopt_out(zmq.IDENTITY, heart_id)
        self.id = heart_id
    
    def start(self):
        return self.device.start()
        
class HeartMonitor(LoggingFactory):
    """A basic HeartMonitor class
    pingstream: a PUB stream
    pongstream: an XREP stream
    period: the period of the heartbeat in milliseconds"""
    
    period=CFloat(1000, config=True) # in milliseconds
    
    pingstream=Instance('zmq.eventloop.zmqstream.ZMQStream')
    pongstream=Instance('zmq.eventloop.zmqstream.ZMQStream')
    loop = Instance('zmq.eventloop.ioloop.IOLoop')
    def _loop_default(self):
        return ioloop.IOLoop.instance()
    debug=Bool(False)
    
    # not settable:
    hearts=Set()
    responses=Set()
    on_probation=Set()
    last_ping=CFloat(0)
    _new_handlers = Set()
    _failure_handlers = Set()
    lifetime = CFloat(0)
    tic = CFloat(0)
    
    def __init__(self, **kwargs):
        super(HeartMonitor, self).__init__(**kwargs)
        
        self.pongstream.on_recv(self.handle_pong)
    
    def start(self):
        self.caller = ioloop.PeriodicCallback(self.beat, self.period, self.loop)
        self.caller.start()
    
    def add_new_heart_handler(self, handler):
        """add a new handler for new hearts"""
        self.log.debug("heartbeat::new_heart_handler: %s"%handler)
        self._new_handlers.add(handler)
        
    def add_heart_failure_handler(self, handler):
        """add a new handler for heart failure"""
        self.log.debug("heartbeat::new heart failure handler: %s"%handler)
        self._failure_handlers.add(handler)
            
    def beat(self):
        self.pongstream.flush() 
        self.last_ping = self.lifetime
        
        toc = time.time()
        self.lifetime += toc-self.tic
        self.tic = toc
        # self.log.debug("heartbeat::%s"%self.lifetime)
        goodhearts = self.hearts.intersection(self.responses)
        missed_beats = self.hearts.difference(goodhearts)
        heartfailures = self.on_probation.intersection(missed_beats)
        newhearts = self.responses.difference(goodhearts)
        map(self.handle_new_heart, newhearts)
        map(self.handle_heart_failure, heartfailures)
        self.on_probation = missed_beats.intersection(self.hearts)
        self.responses = set()
        # print self.on_probation, self.hearts
        # self.log.debug("heartbeat::beat %.3f, %i beating hearts"%(self.lifetime, len(self.hearts)))
        self.pingstream.send(str(self.lifetime))
    
    def handle_new_heart(self, heart):
        if self._new_handlers:
            for handler in self._new_handlers:
                handler(heart)
        else:
            self.log.info("heartbeat::yay, got new heart %s!"%heart)
        self.hearts.add(heart)
    
    def handle_heart_failure(self, heart):
        if self._failure_handlers:
            for handler in self._failure_handlers:
                try:
                    handler(heart)
                except Exception as e:
                    self.log.error("heartbeat::Bad Handler! %s"%handler, exc_info=True)
                    pass
        else:
            self.log.info("heartbeat::Heart %s failed :("%heart)
        self.hearts.remove(heart)
        
    
    def handle_pong(self, msg):
        "a heart just beat"
        if msg[1] == str(self.lifetime):
            delta = time.time()-self.tic
            # self.log.debug("heartbeat::heart %r took %.2f ms to respond"%(msg[0], 1000*delta))
            self.responses.add(msg[0])
        elif msg[1] == str(self.last_ping):
            delta = time.time()-self.tic + (self.lifetime-self.last_ping)
            self.log.warn("heartbeat::heart %r missed a beat, and took %.2f ms to respond"%(msg[0], 1000*delta))
            self.responses.add(msg[0])
        else:
            self.log.warn("heartbeat::got bad heartbeat (possibly old?): %s (current=%.3f)"%
            (msg[1],self.lifetime))


if __name__ == '__main__':
    loop = ioloop.IOLoop.instance()
    context = zmq.Context()
    pub = context.socket(zmq.PUB)
    pub.bind('tcp://127.0.0.1:5555')
    xrep = context.socket(zmq.XREP)
    xrep.bind('tcp://127.0.0.1:5556')
    
    outstream = zmqstream.ZMQStream(pub, loop)
    instream = zmqstream.ZMQStream(xrep, loop)
    
    hb = HeartMonitor(loop, outstream, instream)
    
    loop.start()