from remoteproxy import RemoteEventHandler, ExitError, NoResultError, LocalObjectProxy, ObjectProxy import subprocess, atexit, os, sys, time, random, socket, signal import cPickle as pickle import multiprocessing.connection __all__ = ['Process', 'QtProcess', 'ForkedProcess', 'ExitError', 'NoResultError'] class Process(RemoteEventHandler): """ Bases: RemoteEventHandler This class is used to spawn and control a new python interpreter. It uses subprocess.Popen to start the new process and communicates with it using multiprocessing.Connection objects over a network socket. By default, the remote process will immediately enter an event-processing loop that carries out requests send from the parent process. Remote control works mainly through proxy objects:: proc = Process() ## starts process, returns handle rsys = proc._import('sys') ## asks remote process to import 'sys', returns ## a proxy which references the imported module rsys.stdout.write('hello\n') ## This message will be printed from the remote ## process. Proxy objects can usually be used ## exactly as regular objects are. proc.close() ## Request the remote process shut down Requests made via proxy objects may be synchronous or asynchronous and may return objects either by proxy or by value (if they are picklable). See ProxyObject for more information. """ def __init__(self, name=None, target=None, copySysPath=True): """ ============ ============================================================= Arguments: name Optional name for this process used when printing messages from the remote process. target Optional function to call after starting remote process. By default, this is startEventLoop(), which causes the remote process to process requests from the parent process until it is asked to quit. If you wish to specify a different target, it must be picklable (bound methods are not). copySysPath If true, copy the contents of sys.path to the remote process ============ ============================================================= """ if target is None: target = startEventLoop if name is None: name = str(self) ## random authentication key authkey = ''.join([chr(random.getrandbits(7)) for i in range(20)]) ## Listen for connection from remote process (and find free port number) port = 10000 while True: try: l = multiprocessing.connection.Listener(('localhost', int(port)), authkey=authkey) break except socket.error as ex: if ex.errno != 98: raise port += 1 ## start remote process, instruct it to run target function sysPath = sys.path if copySysPath else None bootstrap = os.path.abspath(os.path.join(os.path.dirname(__file__), 'bootstrap.py')) self.proc = subprocess.Popen((sys.executable, bootstrap), stdin=subprocess.PIPE) targetStr = pickle.dumps(target) ## double-pickle target so that child has a chance to ## set its sys.path properly before unpickling the target pickle.dump((name+'_child', port, authkey, targetStr, sysPath), self.proc.stdin) self.proc.stdin.close() ## open connection for remote process conn = l.accept() RemoteEventHandler.__init__(self, conn, name+'_parent', pid=self.proc.pid) atexit.register(self.join) def join(self, timeout=10): if self.proc.poll() is None: self.close() start = time.time() while self.proc.poll() is None: if timeout is not None and time.time() - start > timeout: raise Exception('Timed out waiting for remote process to end.') time.sleep(0.05) def startEventLoop(name, port, authkey): conn = multiprocessing.connection.Client(('localhost', int(port)), authkey=authkey) global HANDLER HANDLER = RemoteEventHandler(conn, name, os.getppid()) while True: try: HANDLER.processRequests() # exception raised when the loop should exit time.sleep(0.01) except ExitError: break class ForkedProcess(RemoteEventHandler): """ ForkedProcess is a substitute for Process that uses os.fork() to generate a new process. This is much faster than starting a completely new interpreter and child processes automatically have a copy of the entire program state from before the fork. This makes it an appealing approach when parallelizing expensive computations. (see also Parallelizer) However, fork() comes with some caveats and limitations: - fork() is not available on Windows. - It is not possible to have a QApplication in both parent and child process (unless both QApplications are created _after_ the call to fork()) Attempts by the forked process to access Qt GUI elements created by the parent will most likely cause the child to crash. - Likewise, database connections are unlikely to function correctly in a forked child. - Threads are not copied by fork(); the new process will have only one thread that starts wherever fork() was called in the parent process. - Forked processes are unceremoniously terminated when join() is called; they are not given any opportunity to clean up. (This prevents them calling any cleanup code that was only intended to be used by the parent process) - Normally when fork()ing, open file handles are shared with the parent process, which is potentially dangerous. ForkedProcess is careful to close all file handles that are not explicitly needed--stdout, stderr, and a single pipe to the parent process. """ def __init__(self, name=None, target=0, preProxy=None, randomReseed=True): """ When initializing, an optional target may be given. If no target is specified, self.eventLoop will be used. If None is given, no target will be called (and it will be up to the caller to properly shut down the forked process) preProxy may be a dict of values that will appear as ObjectProxy in the remote process (but do not need to be sent explicitly since they are available immediately before the call to fork(). Proxies will be availabe as self.proxies[name]. If randomReseed is True, the built-in random and numpy.random generators will be reseeded in the child process. """ self.hasJoined = False if target == 0: target = self.eventLoop if name is None: name = str(self) conn, remoteConn = multiprocessing.Pipe() proxyIDs = {} if preProxy is not None: for k, v in preProxy.iteritems(): proxyId = LocalObjectProxy.registerObject(v) proxyIDs[k] = proxyId pid = os.fork() if pid == 0: self.isParent = False ## We are now in the forked process; need to be extra careful what we touch while here. ## - no reading/writing file handles/sockets owned by parent process (stdout is ok) ## - don't touch QtGui or QApplication at all; these are landmines. ## - don't let the process call exit handlers ## - ## close all file handles we do not want shared with parent conn.close() sys.stdin.close() ## otherwise we screw with interactive prompts. fid = remoteConn.fileno() os.closerange(3, fid) os.closerange(fid+1, 4096) ## just guessing on the maximum descriptor count.. ## Override any custom exception hooks def excepthook(*args): import traceback traceback.print_exception(*args) sys.excepthook = excepthook ## Make it harder to access QApplication instance if 'PyQt4.QtGui' in sys.modules: sys.modules['PyQt4.QtGui'].QApplication = None sys.modules.pop('PyQt4.QtGui', None) sys.modules.pop('PyQt4.QtCore', None) ## sabotage atexit callbacks atexit._exithandlers = [] atexit.register(lambda: os._exit(0)) if randomReseed: if 'numpy.random' in sys.modules: sys.modules['numpy.random'].seed(os.getpid() ^ int(time.time()*10000%10000)) if 'random' in sys.modules: sys.modules['random'].seed(os.getpid() ^ int(time.time()*10000%10000)) RemoteEventHandler.__init__(self, remoteConn, name+'_child', pid=os.getppid()) ppid = os.getppid() self.forkedProxies = {} for name, proxyId in proxyIDs.iteritems(): self.forkedProxies[name] = ObjectProxy(ppid, proxyId=proxyId, typeStr=repr(preProxy[name])) if target is not None: target() else: self.isParent = True self.childPid = pid remoteConn.close() RemoteEventHandler.handlers = {} ## don't want to inherit any of this from the parent. RemoteEventHandler.__init__(self, conn, name+'_parent', pid=pid) atexit.register(self.join) def eventLoop(self): while True: try: self.processRequests() # exception raised when the loop should exit time.sleep(0.01) except ExitError: break except: print "Error occurred in forked event loop:" sys.excepthook(*sys.exc_info()) sys.exit(0) def join(self, timeout=10): if self.hasJoined: return #os.kill(pid, 9) try: self.close(callSync='sync', timeout=timeout, noCleanup=True) ## ask the child process to exit and require that it return a confirmation. os.waitpid(self.childPid, 0) except IOError: ## probably remote process has already quit pass self.hasJoined = True def kill(self): """Immediately kill the forked remote process. This is generally safe because forked processes are already expected to _avoid_ any cleanup at exit.""" os.kill(self.childPid, signal.SIGKILL) self.hasJoined = True ##Special set of subclasses that implement a Qt event loop instead. class RemoteQtEventHandler(RemoteEventHandler): def __init__(self, *args, **kwds): RemoteEventHandler.__init__(self, *args, **kwds) def startEventTimer(self): from pyqtgraph.Qt import QtGui, QtCore self.timer = QtCore.QTimer() self.timer.timeout.connect(self.processRequests) self.timer.start(10) def processRequests(self): try: RemoteEventHandler.processRequests(self) except ExitError: from pyqtgraph.Qt import QtGui, QtCore QtGui.QApplication.instance().quit() self.timer.stop() #raise class QtProcess(Process): """ QtProcess is essentially the same as Process, with two major differences: - The remote process starts by running startQtEventLoop() which creates a QApplication in the remote process and uses a QTimer to trigger remote event processing. This allows the remote process to have its own GUI. - A QTimer is also started on the parent process which polls for requests from the child process. This allows Qt signals emitted within the child process to invoke slots on the parent process and vice-versa. Example:: proc = QtProcess() rQtGui = proc._import('PyQt4.QtGui') btn = rQtGui.QPushButton('button on child process') btn.show() def slot(): print 'slot invoked on parent process' btn.clicked.connect(proxy(slot)) # be sure to send a proxy of the slot """ def __init__(self, **kwds): if 'target' not in kwds: kwds['target'] = startQtEventLoop Process.__init__(self, **kwds) self.startEventTimer() def startEventTimer(self): from pyqtgraph.Qt import QtGui, QtCore ## avoid module-level import to keep bootstrap snappy. self.timer = QtCore.QTimer() app = QtGui.QApplication.instance() if app is None: raise Exception("Must create QApplication before starting QtProcess") self.timer.timeout.connect(self.processRequests) self.timer.start(10) def processRequests(self): try: Process.processRequests(self) except ExitError: self.timer.stop() def startQtEventLoop(name, port, authkey): conn = multiprocessing.connection.Client(('localhost', int(port)), authkey=authkey) from pyqtgraph.Qt import QtGui, QtCore #from PyQt4 import QtGui, QtCore app = QtGui.QApplication.instance() #print app if app is None: app = QtGui.QApplication([]) app.setQuitOnLastWindowClosed(False) ## generally we want the event loop to stay open ## until it is explicitly closed by the parent process. global HANDLER HANDLER = RemoteQtEventHandler(conn, name, os.getppid()) HANDLER.startEventTimer() app.exec_()