# *****************************************************************************
# * Copyright (c) 2011, 2013 Wind River Systems, Inc. and others.
# * All rights reserved. This program and the accompanying materials
# * are made available under the terms of the Eclipse Public License v1.0
# * which accompanies this distribution, and is available at
# * http://www.eclipse.org/legal/epl-v10.html
# *
# * Contributors:
# * Wind River Systems - initial API and implementation
# *****************************************************************************
"""
Module protocol provides static methods to access Target Communication
Framework root objects:
1. the framework event queue and dispatch thread
2. local instance of Locator service, which maintains a list of available
targets
3. list of open communication channels.
It also provides utility methods for posting asynchronous events,
including delayed events (timers).
"""
import sys
import threading
import time
import uuid
from . import EventQueue
_event_queue = None
_timer_dispatcher = None
def startEventQueue():
global _event_queue, _timer_dispatcher
if _event_queue and not _event_queue.isShutdown():
return
_event_queue = EventQueue.EventQueue(on_shutdown=shutdownDiscovery)
_event_queue.start()
# initialize LocatorService
from services.local.LocatorService import LocatorService
_event_queue.invokeLater(LocatorService)
# start timer dispatcher
_timer_dispatcher = threading.Thread(target=_dispatch_timers)
_timer_dispatcher.setName("TCF Timer Dispatcher")
_timer_dispatcher.setDaemon(True)
_timer_dispatcher.start()
def getEventQueue():
"""
@return instance of event queue that is used for TCF events.
"""
return _event_queue
def isDispatchThread():
"""
Returns true if the calling thread is the TCF event dispatch thread.
Use this call to ensure that a given task is being executed (or not being)
on dispatch thread.
@return true if running on the dispatch thread.
"""
return _event_queue is not None and _event_queue.isDispatchThread()
def invokeLater(c, *args, **kwargs):
"""
Causes callable to be called with given arguments
in the dispatch thread of the framework.
Events are dispatched in same order as queued.
If invokeLater is called from the dispatching thread
the callable will still be deferred until
all pending events have been processed.
This method can be invoked from any thread.
@param c - the callable to be executed asynchronously
"""
_event_queue.invokeLater(c, *args, **kwargs)
def invokeLaterWithDelay(delay, c, *args, **kwargs):
"""
Causes callable event to called in the dispatch thread of the framework.
The event is dispatched after given delay.
This method can be invoked from any thread.
@param delay milliseconds to delay event dispatch.
If delay <= 0 the event is posted into the
"ready" queue without delay.
@param c - the callable to be executed asynchronously.
"""
if delay <= 0:
_event_queue.invokeLater(c, *args, **kwargs)
else:
with _timer_queue_lock:
_timer_queue.append(Timer(time.time() + delay / 1000., c, *args,
**kwargs))
_timer_queue.sort()
_timer_queue_lock.notify()
def invokeAndWait(c, *args, **kwargs):
"""
Causes callable to be called in the dispatch thread of the framework.
Calling thread is suspended until the method is executed.
If invokeAndWait is called from the dispatching thread
the callable is executed immediately.
This method can be invoked from any thread.
@param c the callable to be executed on dispatch thread.
"""
if _event_queue.isDispatchThread():
return c(*args, **kwargs)
else:
class DoRun():
result = None
def __call__(self):
try:
self.result = c(*args, **kwargs)
finally:
with runLock:
runLock.notify()
doRun = DoRun()
runLock = threading.Condition()
with runLock:
_event_queue.invokeLater(doRun)
runLock.wait()
return doRun.result
_agentID = str(uuid.uuid4())
def getAgentID():
return _agentID
_logger = None
def setLogger(logger):
"""
Set framework logger.
By default sys.stderr is used.
@param logger - an object implementing Logger interface.
"""
global _logger
_logger = logger
def log(msg, x=None):
"""
Logs the given message.
@see #setLogger
This method can be invoked from any thread.
@param msg - log entry text
@param x - an exception associated with the log entry or None.
"""
if not _logger:
print >> sys.stderr, msg
while x:
import traceback
print >> sys.stderr, "%s: %s" % (type(x).__name__, x)
tb = getattr(x, "tb", None) or sys.exc_info()[2]
if tb:
traceback.print_tb(tb)
caused_by = getattr(x, "caused_by", None)
if caused_by:
print >> sys.stderr, "Caused by:"
x = caused_by
else:
break
else:
_logger.log(msg, x)
def startDiscovery():
"Start discovery of remote peers if not running yet"
# initialize LocatorService
from services.local.LocatorService import LocatorService
if LocatorService.locator:
invokeAndWait(LocatorService.startup)
def shutdownDiscovery():
"Shutdown discovery if running"
from .services.local.LocatorService import LocatorService
if LocatorService.locator:
invokeAndWait(LocatorService.shutdown)
def getLocator():
"""
Get instance of the framework locator service.
The service can be used to discover available remote peers.
@return instance of LocatorService.
"""
from .services.local.LocatorService import LocatorService
return LocatorService.locator
def getOpenChannels():
"""
Return an array of all open channels.
@return an array of IChannel
"""
assert isDispatchThread()
import transport
return transport.getOpenChannels()
class ChannelOpenListener(object):
"""
Interface to be implemented by clients willing to be notified when
new TCF communication channel is opened.
The interface allows a client to get pointers to channel objects that were
opened by somebody else. If a client open a channel itself, it already has
the pointer and does not need protocol.ChannelOpenListener. If a channel is
created, for example, by remote peer connecting to the client, the only way
to get the pointer is protocol.ChannelOpenListener.
"""
def onChannelOpen(self, channel):
pass
def addChannelOpenListener(listener):
"""
Add a listener that will be notified when new channel is opened.
@param listener
"""
assert isDispatchThread()
import transport
transport.addChannelOpenListener(listener)
def removeChannelOpenListener(listener):
"""
Remove channel opening listener.
@param listener
"""
assert isDispatchThread()
import transport
transport.removeChannelOpenListener(listener)
def sendEvent(service_name, event_name, data):
"""
Transmit TCF event message.
The message is sent to all open communication channels - broadcasted.
"""
assert isDispatchThread()
import transport
transport.sendEvent(service_name, event_name, data)
def sync(done):
"""
Call back after all TCF messages sent by this host up to this moment are
delivered to their intended target. This method is intended for
synchronization of messages across multiple channels.
Note: Cross channel synchronization can reduce performance and throughput.
Most clients don't need cross channel synchronization and should not call
this method.
@param done - will be executed by dispatch thread after pending
communication messages are delivered to corresponding
targets.
"""
assert isDispatchThread()
import transport
transport.sync(done)
class CongestionMonitor(object):
"""
Clients implement CongestionMonitor interface to monitor usage of local
resources, like, for example, display queue size - if the queue becomes too
big, UI response time can become too high, or it can crash all together
because of OutOfMemory errors.
TCF flow control logic prevents such conditions by throttling traffic
coming from remote peers.
Note: Local (in-bound traffic) congestion is detected by framework and
reported to remote peer without client needed to be involved. Only
clients willing to provide additional data about local congestion
should implement CongestionMonitor and register it using
protocol.addCongestionMonitor().
"""
def getCongestionLevel(self):
"""
Get current level of client resource utilization.
@return integer value in range -100..100, where -100 means all
resources are free, 0 means optimal load, and positive numbers
indicate level of congestion.
"""
raise NotImplementedError("Abstract method")
_congestion_monitors = []
def addCongestionMonitor(monitor):
"""
Register a congestion monitor.
@param monitor - client implementation of CongestionMonitor interface
"""
assert isDispatchThread()
_congestion_monitors.add(monitor)
def removeCongestionMonitor(monitor):
"""
Unregister a congestion monitor.
@param monitor - client implementation of CongestionMonitor interface
"""
assert isDispatchThread()
_congestion_monitors.remove(monitor)
def getCongestionLevel():
"""
Get current level of local traffic congestion.
@return integer value in range -100..100, where -100 means no pending
messages (no traffic), 0 means optimal load, and positive numbers
indicate level of congestion.
"""
assert isDispatchThread()
level = -100
for m in _congestion_monitors:
n = m.getCongestionLevel()
if n > level:
level = n
if _event_queue:
n = _event_queue.getCongestion()
if n > level:
level = n
if level > 100:
level = 100
return level
def addServiceProvider(provider):
"""
Register service provider.
This method can be invoked from any thread.
@param provider - ServiceProvider implementation
"""
import services
services.addServiceProvider(provider)
def removeServiceProvider(provider):
"""
Unregister service provider.
This method can be invoked from any thread.
@param provider - ServiceProvider implementation
"""
import services
services.removeServiceProvider(provider)
def addTransportProvider(provider):
"""
Register transport provider.
This method can be invoked from any thread.
@param provider - TransportProvider implementation
"""
import transport
transport.addTransportProvider(provider)
def removeTransportProvider(provider):
"""
Unregister transport provider.
This method can be invoked from any thread.
@param provider - TransportProvider implementation
"""
import transport
transport.removeTransportProvider(provider)
class Timer(object):
timer_cnt = 0
def __init__(self, time, run, *args, **kwargs):
self.id = Timer.timer_cnt
Timer.timer_cnt += 1
self.time = time
self.run = run
self.args = args
self.kwargs = kwargs
def __cmp__(self, x):
if x is self:
return 0
if self.time < x.time:
return -1
if self.time > x.time:
return +1
if self.id < x.id:
return -1
if self.id > x.id:
return +1
assert False
return 0
_timer_queue_lock = threading.Condition()
_timer_queue = []
def _dispatch_timers():
try:
with _timer_queue_lock:
while True:
if not _timer_queue:
_timer_queue_lock.wait()
else:
tm = time.time()
t = _timer_queue[0]
if t.time > tm:
_timer_queue_lock.wait(t.time - tm)
else:
_timer_queue.pop(0)
invokeLater(t.run, *t.args, **t.kwargs)
except RuntimeError:
# Event queue is shut down, exit this thread
pass
except Exception as x:
log("Exception in TCF dispatch loop", x)
