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.
"""

import __builtin__
import sys
import time
import traceback

from code import CommandCompiler

import zmq

from session import Session, Message, extract_header
from completer import KernelCompleter

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 isattr(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 RawInput(object):

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

    def __call__(self, prompt=None):
        msg = self.session.msg(u'raw_input')
        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[u'content'][u'data']


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
        self.handlers = {}
        for msg_type in ['execute_request', 'complete_request']:
            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'etype' : unicode(etype),
                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 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__, omsg
            handler = self.handlers.get(omsg.msg_type, None)
            if handler is None:
                print >> sys.__stderr__, "UNKNOWN MESSAGE TYPE:", omsg
            else:
                handler(ident, omsg)


def main():
    c = zmq.Context()

    ip = '127.0.0.1'
    port_base = 5555
    connection = ('tcp://%s' % ip) + ':%i'
    rep_conn = connection % port_base
    pub_conn = connection % (port_base+1)

    print >>sys.__stdout__, "Starting the kernel..."
    print >>sys.__stdout__, "On:",rep_conn, pub_conn

    session = Session(username=u'kernel')

    reply_socket = c.socket(zmq.ROUTER)
    reply_socket.bind(rep_conn)

    pub_socket = c.socket(zmq.PUB)
    pub_socket.bind(pub_conn)

    stdout = OutStream(session, pub_socket, u'stdout')
    stderr = OutStream(session, pub_socket, u'stderr')
    sys.stdout = stdout
    sys.stderr = stderr

    display_hook = DisplayHook(session, pub_socket)
    sys.displayhook = display_hook

    kernel = Kernel(session, reply_socket, pub_socket)

    # For debugging convenience, put sleep and a string in the namespace, so we
    # have them every time we start.
    kernel.user_ns['sleep'] = time.sleep
    kernel.user_ns['s'] = 'Test string'
    
    print >>sys.__stdout__, "Use Ctrl-\\ (NOT Ctrl-C!) to terminate."
    kernel.start()


if __name__ == '__main__':
    main()