IPython/zmq/kernel.py

#!/usr/bin/env python
"""A simple interactive kernel that talks to a frontend over 0MQ.

Things to do:

* Finish implementing `raw_input`.
* Implement `set_parent` logic. Right before doing exec, the Kernel should
  call set_parent on all the PUB objects with the message about to be executed.
* Implement random port and security key logic.
* Implement control messages.
* Implement event loop and poll version.
"""

#-----------------------------------------------------------------------------
# Imports
#-----------------------------------------------------------------------------

# Standard library imports.
import __builtin__
from code import CommandCompiler
import os
import sys
from threading import Thread
import time
import traceback

# System library imports.
import zmq

# Local imports.
from IPython.external.argparse import ArgumentParser
from session import Session, Message, extract_header
from completer import KernelCompleter

#-----------------------------------------------------------------------------
# Kernel and stream classes
#-----------------------------------------------------------------------------

class InStream(object):
    """ A file like object that reads from a 0MQ XREQ socket."""

    def __init__(self, session, socket):
        self.session = session
        self.socket = socket

    def close(self):
        self.socket = None

    def flush(self):
        if self.socket is None:
            raise ValueError('I/O operation on closed file')
        
    def isatty(self):
        return False

    def next(self):
        raise IOError('Seek not supported.')

    def read(self, size=-1):
        # FIXME: Do we want another request for this?
        string = '\n'.join(self.readlines())
        return self._truncate(string, size)

    def readline(self, size=-1):
        if self.socket is None:
            raise ValueError('I/O operation on closed file')
        else:
            content = dict(size=size)
            msg = self.session.msg('readline_request', content=content) 
            reply = self._request(msg)
            line = reply['content']['line']
            return self._truncate(line, size)

    def readlines(self, sizehint=-1):
        # Sizehint is ignored, as is permitted.
        if self.socket is None:
            raise ValueError('I/O operation on closed file')
        else:
            lines = []
            while True:
                line = self.readline()
                if line:
                    lines.append(line)
                else:
                    break
            return lines

    def seek(self, offset, whence=None):
        raise IOError('Seek not supported.')

    def write(self, string):
        raise IOError('Write not supported on a read only stream.')

    def writelines(self, sequence):
        raise IOError('Write not supported on a read only stream.')
    
    def _request(self, msg):
        # Flush output before making the request. This ensures, for example,
        # that raw_input(prompt) actually gets a prompt written.
        sys.stderr.flush()
        sys.stdout.flush()

        self.socket.send_json(msg)
        while True:
            try:
                reply = self.socket.recv_json(zmq.NOBLOCK)
            except zmq.ZMQError, e:
                if e.errno == zmq.EAGAIN:
                    pass
                else:
                    raise
            else:
                break
        return reply

    def _truncate(self, string, size):
        if size >= 0:
            if isinstance(string, str):
                return string[:size]
            elif isinstance(string, unicode):
                encoded = string.encode('utf-8')[:size]
                return encoded.decode('utf-8', 'ignore')
        return string


class OutStream(object):
    """A file like object that publishes the stream to a 0MQ PUB socket."""

    def __init__(self, session, pub_socket, name, max_buffer=200):
        self.session = session
        self.pub_socket = pub_socket
        self.name = name
        self._buffer = []
        self._buffer_len = 0
        self.max_buffer = max_buffer
        self.parent_header = {}

    def set_parent(self, parent):
        self.parent_header = extract_header(parent)

    def close(self):
        self.pub_socket = None

    def flush(self):
        if self.pub_socket is None:
            raise ValueError(u'I/O operation on closed file')
        else:
            if self._buffer:
                data = ''.join(self._buffer)
                content = {u'name':self.name, u'data':data}
                msg = self.session.msg(u'stream', content=content,
                                       parent=self.parent_header)
                print>>sys.__stdout__, Message(msg)
                self.pub_socket.send_json(msg)
                self._buffer_len = 0
                self._buffer = []

    def isatty(self):
        return False

    def next(self):
        raise IOError('Read not supported on a write only stream.')

    def read(self, size=None):
        raise IOError('Read not supported on a write only stream.')

    readline=read

    def write(self, s):
        if self.pub_socket is None:
            raise ValueError('I/O operation on closed file')
        else:
            self._buffer.append(s)
            self._buffer_len += len(s)
            self._maybe_send()

    def _maybe_send(self):
        if '\n' in self._buffer[-1]:
            self.flush()
        if self._buffer_len > self.max_buffer:
            self.flush()

    def writelines(self, sequence):
        if self.pub_socket is None:
            raise ValueError('I/O operation on closed file')
        else:
            for s in sequence:
                self.write(s)


class DisplayHook(object):

    def __init__(self, session, pub_socket):
        self.session = session
        self.pub_socket = pub_socket
        self.parent_header = {}

    def __call__(self, obj):
        if obj is None:
            return

        __builtin__._ = obj
        msg = self.session.msg(u'pyout', {u'data':repr(obj)},
                               parent=self.parent_header)
        self.pub_socket.send_json(msg)

    def set_parent(self, parent):
        self.parent_header = extract_header(parent)


class Kernel(object):

    def __init__(self, session, reply_socket, pub_socket):
        self.session = session
        self.reply_socket = reply_socket
        self.pub_socket = pub_socket
        self.user_ns = {}
        self.history = []
        self.compiler = CommandCompiler()
        self.completer = KernelCompleter(self.user_ns)
        
        # Build dict of handlers for message types
        msg_types = [ 'execute_request', 'complete_request', 
                      'object_info_request' ]
        self.handlers = {}
        for msg_type in msg_types:
            self.handlers[msg_type] = getattr(self, msg_type)

    def abort_queue(self):
        while True:
            try:
                ident = self.reply_socket.recv(zmq.NOBLOCK)
            except zmq.ZMQError, e:
                if e.errno == zmq.EAGAIN:
                    break
            else:
                assert self.reply_socket.rcvmore(), "Unexpected missing message part."
                msg = self.reply_socket.recv_json()
            print>>sys.__stdout__, "Aborting:"
            print>>sys.__stdout__, Message(msg)
            msg_type = msg['msg_type']
            reply_type = msg_type.split('_')[0] + '_reply'
            reply_msg = self.session.msg(reply_type, {'status' : 'aborted'}, msg)
            print>>sys.__stdout__, Message(reply_msg)
            self.reply_socket.send(ident,zmq.SNDMORE)
            self.reply_socket.send_json(reply_msg)
            # We need to wait a bit for requests to come in. This can probably
            # be set shorter for true asynchronous clients.
            time.sleep(0.1)

    def execute_request(self, ident, parent):
        try:
            code = parent[u'content'][u'code']
        except:
            print>>sys.__stderr__, "Got bad msg: "
            print>>sys.__stderr__, Message(parent)
            return
        pyin_msg = self.session.msg(u'pyin',{u'code':code}, parent=parent)
        self.pub_socket.send_json(pyin_msg)
        try:
            comp_code = self.compiler(code, '<zmq-kernel>')
            sys.displayhook.set_parent(parent)
            exec comp_code in self.user_ns, self.user_ns
        except:
            result = u'error'
            etype, evalue, tb = sys.exc_info()
            tb = traceback.format_exception(etype, evalue, tb)
            exc_content = {
                u'status' : u'error',
                u'traceback' : tb,
                u'ename' : unicode(etype.__name__),
                u'evalue' : unicode(evalue)
            }
            exc_msg = self.session.msg(u'pyerr', exc_content, parent)
            self.pub_socket.send_json(exc_msg)
            reply_content = exc_content
        else:
            reply_content = {'status' : 'ok'}
        reply_msg = self.session.msg(u'execute_reply', reply_content, parent)
        print>>sys.__stdout__, Message(reply_msg)
        self.reply_socket.send(ident, zmq.SNDMORE)
        self.reply_socket.send_json(reply_msg)
        if reply_msg['content']['status'] == u'error':
            self.abort_queue()

    def complete_request(self, ident, parent):
        matches = {'matches' : self.complete(parent),
                   'status' : 'ok'}
        completion_msg = self.session.send(self.reply_socket, 'complete_reply',
                                           matches, parent, ident)
        print >> sys.__stdout__, completion_msg

    def complete(self, msg):
        return self.completer.complete(msg.content.line, msg.content.text)

    def object_info_request(self, ident, parent):
        context = parent['content']['oname'].split('.')
        object_info = self.object_info(context)
        msg = self.session.send(self.reply_socket, 'object_info_reply',
                                object_info, parent, ident)
        print >> sys.__stdout__, msg

    def object_info(self, context):
        symbol, leftover = self.symbol_from_context(context)
        if symbol is not None and not leftover:
            doc = getattr(symbol, '__doc__', '')
        else:
            doc = ''
        object_info = dict(docstring = doc)
        return object_info

    def symbol_from_context(self, context):
        if not context:
            return None, context

        base_symbol_string = context[0]
        symbol = self.user_ns.get(base_symbol_string, None)
        if symbol is None:
            symbol = __builtin__.__dict__.get(base_symbol_string, None)
        if symbol is None:
            return None, context

        context = context[1:]
        for i, name in enumerate(context):
            new_symbol = getattr(symbol, name, None)
            if new_symbol is None:
                return symbol, context[i:]
            else:
                symbol = new_symbol

        return symbol, []

    def start(self):
        while True:
            ident = self.reply_socket.recv()
            assert self.reply_socket.rcvmore(), "Unexpected missing message part."
            msg = self.reply_socket.recv_json()
            omsg = Message(msg)
            print>>sys.__stdout__
            print>>sys.__stdout__, omsg
            handler = self.handlers.get(omsg.msg_type, None)
            if handler is None:
                print >> sys.__stderr__, "UNKNOWN MESSAGE TYPE:", omsg
            else:
                handler(ident, omsg)

#-----------------------------------------------------------------------------
# Kernel main and launch functions
#-----------------------------------------------------------------------------

class ExitPollerUnix(Thread):
    """ A Unix-specific daemon thread that terminates the program immediately 
    when this process' parent process no longer exists.
    """

    def __init__(self):
        super(ExitPollerUnix, self).__init__()
        self.daemon = True
    
    def run(self):
        # We cannot use os.waitpid because it works only for child processes.
        from errno import EINTR
        while True:
            try:
                if os.getppid() == 1:
                    os._exit(1)
                time.sleep(1.0)
            except OSError, e:
                if e.errno == EINTR:
                    continue
                raise

class ExitPollerWindows(Thread):
    """ A Windows-specific daemon thread that terminates the program immediately
    when a Win32 handle is signaled.
    """ 
    
    def __init__(self, handle):
        super(ExitPollerWindows, self).__init__()
        self.daemon = True
        self.handle = handle

    def run(self):
        from _subprocess import WaitForSingleObject, WAIT_OBJECT_0, INFINITE
        result = WaitForSingleObject(self.handle, INFINITE)
        if result == WAIT_OBJECT_0:
            os._exit(1)


def bind_port(socket, ip, port):
    """ Binds the specified ZMQ socket. If the port is less than zero, a random
    port is chosen. Returns the port that was bound.
    """
    connection = 'tcp://%s' % ip
    if port <= 0:
        port = socket.bind_to_random_port(connection)
    else:
        connection += ':%i' % port
        socket.bind(connection)
    return port


def main():
    """ Main entry point for launching a kernel.
    """
    # Parse command line arguments.
    parser = ArgumentParser()
    parser.add_argument('--ip', type=str, default='127.0.0.1',
                        help='set the kernel\'s IP address [default: local]')
    parser.add_argument('--xrep', type=int, metavar='PORT', default=0,
                        help='set the XREP channel port [default: random]')
    parser.add_argument('--pub', type=int, metavar='PORT', default=0,
                        help='set the PUB channel port [default: random]')
    parser.add_argument('--req', type=int, metavar='PORT', default=0,
                        help='set the REQ channel port [default: random]')
    if sys.platform == 'win32':
        parser.add_argument('--parent', type=int, metavar='HANDLE', 
                            default=0, help='kill this process if the process '
                            'with HANDLE dies')
    else:
        parser.add_argument('--parent', action='store_true', 
                            help='kill this process if its parent dies')
    namespace = parser.parse_args()

    # Create a context, a session, and the kernel sockets.
    print >>sys.__stdout__, "Starting the kernel..."
    context = zmq.Context()
    session = Session(username=u'kernel')

    reply_socket = context.socket(zmq.XREP)
    xrep_port = bind_port(reply_socket, namespace.ip, namespace.xrep)
    print >>sys.__stdout__, "XREP Channel on port", xrep_port

    pub_socket = context.socket(zmq.PUB)
    pub_port = bind_port(pub_socket, namespace.ip, namespace.pub)
    print >>sys.__stdout__, "PUB Channel on port", pub_port

    req_socket = context.socket(zmq.XREQ)
    req_port = bind_port(req_socket, namespace.ip, namespace.req)
    print >>sys.__stdout__, "REQ Channel on port", req_port

    # Redirect input streams and set a display hook.
    sys.stdin = InStream(session, req_socket)
    sys.stdout = OutStream(session, pub_socket, u'stdout')
    sys.stderr = OutStream(session, pub_socket, u'stderr')
    sys.displayhook = DisplayHook(session, pub_socket)

    # Create the kernel.
    kernel = Kernel(session, reply_socket, pub_socket)

    # Configure this kernel/process to die on parent termination, if necessary.
    if namespace.parent:
        if sys.platform == 'win32':
            poller = ExitPollerWindows(namespace.parent)
        else:
            poller = ExitPollerUnix()
        poller.start()

    # Start the kernel mainloop.
    kernel.start()


def launch_kernel(xrep_port=0, pub_port=0, req_port=0, independent=False):
    """ Launches a localhost kernel, binding to the specified ports.

    Parameters
    ----------
    xrep_port : int, optional
        The port to use for XREP channel.

    pub_port : int, optional
        The port to use for the SUB channel.

    req_port : int, optional
        The port to use for the REQ (raw input) channel.

    independent : bool, optional (default False) 
        If set, the kernel process is guaranteed to survive if this process
        dies. If not set, an effort is made to ensure that the kernel is killed
        when this process dies. Note that in this case it is still good practice
        to kill kernels manually before exiting.

    Returns
    -------
    A tuple of form:
        (kernel_process, xrep_port, pub_port, req_port)
    where kernel_process is a Popen object and the ports are integers.
    """
    import socket
    from subprocess import Popen

    # Find open ports as necessary.
    ports = []
    ports_needed = int(xrep_port <= 0) + int(pub_port <= 0) + int(req_port <= 0)
    for i in xrange(ports_needed):
        sock = socket.socket()
        sock.bind(('', 0))
        ports.append(sock)
    for i, sock in enumerate(ports):
        port = sock.getsockname()[1]
        sock.close()
        ports[i] = port
    if xrep_port <= 0:
        xrep_port = ports.pop(0)
    if pub_port <= 0:
        pub_port = ports.pop(0)
    if req_port <= 0:
        req_port = ports.pop(0)
        
    # Spawn a kernel.
    command = 'from IPython.zmq.kernel import main; main()'
    arguments = [ sys.executable, '-c', command, '--xrep', str(xrep_port), 
                  '--pub', str(pub_port), '--req', str(req_port) ]
    if independent:
        if sys.platform == 'win32':
            proc = Popen(['start', '/b'] + arguments, shell=True)
        else:
            proc = Popen(arguments, preexec_fn=lambda: os.setsid())
    else:
        if sys.platform == 'win32':
            from _subprocess import DuplicateHandle, GetCurrentProcess, \
                DUPLICATE_SAME_ACCESS
            pid = GetCurrentProcess()
            handle = DuplicateHandle(pid, pid, pid, 0, 
                                     True, # Inheritable by new  processes.
                                     DUPLICATE_SAME_ACCESS)
            proc = Popen(arguments + ['--parent', str(int(handle))])
        else:
            proc = Popen(arguments + ['--parent'])

    return proc, xrep_port, pub_port, req_port
    

if __name__ == '__main__':
    main()