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channels.py
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channels.py
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"""Base classes to manage a Client's interaction with a running kernel"""
# Copyright (c) IPython Development Team.
# Distributed under the terms of the Modified BSD License.
from __future__ import absolute_import
import atexit
import errno
from threading import Thread
import time
import zmq
# import ZMQError in top-level namespace, to avoid ugly attribute-error messages
# during garbage collection of threads at exit:
from zmq import ZMQError
from zmq.eventloop import ioloop, zmqstream
from IPython.core.release import kernel_protocol_version_info
from .channelsabc import (
ShellChannelABC, IOPubChannelABC,
HBChannelABC, StdInChannelABC,
)
from IPython.utils.py3compat import string_types, iteritems
#-----------------------------------------------------------------------------
# Constants and exceptions
#-----------------------------------------------------------------------------
major_protocol_version = kernel_protocol_version_info[0]
class InvalidPortNumber(Exception):
pass
#-----------------------------------------------------------------------------
# Utility functions
#-----------------------------------------------------------------------------
# some utilities to validate message structure, these might get moved elsewhere
# if they prove to have more generic utility
def validate_string_list(lst):
"""Validate that the input is a list of strings.
Raises ValueError if not."""
if not isinstance(lst, list):
raise ValueError('input %r must be a list' % lst)
for x in lst:
if not isinstance(x, string_types):
raise ValueError('element %r in list must be a string' % x)
def validate_string_dict(dct):
"""Validate that the input is a dict with string keys and values.
Raises ValueError if not."""
for k, v in iteritems(dct):
if not isinstance(k, string_types):
raise ValueError('key %r in dict must be a string' % k)
if not isinstance(v, string_types):
raise ValueError('value %r in dict must be a string' % v)
#-----------------------------------------------------------------------------
# ZMQ Socket Channel classes
#-----------------------------------------------------------------------------
class ZMQSocketChannel(Thread):
"""The base class for the channels that use ZMQ sockets."""
context = None
session = None
socket = None
ioloop = None
stream = None
_address = None
_exiting = False
proxy_methods = []
def __init__(self, context, session, address):
"""Create a channel.
Parameters
----------
context : :class:`zmq.Context`
The ZMQ context to use.
session : :class:`session.Session`
The session to use.
address : zmq url
Standard (ip, port) tuple that the kernel is listening on.
"""
super(ZMQSocketChannel, self).__init__()
self.daemon = True
self.context = context
self.session = session
if isinstance(address, tuple):
if address[1] == 0:
message = 'The port number for a channel cannot be 0.'
raise InvalidPortNumber(message)
address = "tcp://%s:%i" % address
self._address = address
atexit.register(self._notice_exit)
def _notice_exit(self):
self._exiting = True
def _run_loop(self):
"""Run my loop, ignoring EINTR events in the poller"""
while True:
try:
self.ioloop.start()
except ZMQError as e:
if e.errno == errno.EINTR:
continue
else:
raise
except Exception:
if self._exiting:
break
else:
raise
else:
break
def stop(self):
"""Stop the channel's event loop and join its thread.
This calls :meth:`~threading.Thread.join` and returns when the thread
terminates. :class:`RuntimeError` will be raised if
:meth:`~threading.Thread.start` is called again.
"""
if self.ioloop is not None:
self.ioloop.stop()
self.join()
self.close()
def close(self):
if self.ioloop is not None:
try:
self.ioloop.close(all_fds=True)
except Exception:
pass
if self.socket is not None:
try:
self.socket.close(linger=0)
except Exception:
pass
self.socket = None
@property
def address(self):
"""Get the channel's address as a zmq url string.
These URLS have the form: 'tcp://127.0.0.1:5555'.
"""
return self._address
def _queue_send(self, msg):
"""Queue a message to be sent from the IOLoop's thread.
Parameters
----------
msg : message to send
This is threadsafe, as it uses IOLoop.add_callback to give the loop's
thread control of the action.
"""
def thread_send():
self.session.send(self.stream, msg)
self.ioloop.add_callback(thread_send)
def _handle_recv(self, msg):
"""Callback for stream.on_recv.
Unpacks message, and calls handlers with it.
"""
ident, smsg = self.session.feed_identities(msg)
msg = self.session.deserialize(smsg)
self.call_handlers(msg)
class ShellChannel(ZMQSocketChannel):
"""The shell channel for issuing request/replies to the kernel."""
command_queue = None
# flag for whether execute requests should be allowed to call raw_input:
allow_stdin = True
proxy_methods = [
'execute',
'complete',
'inspect',
'history',
'kernel_info',
'shutdown',
'is_complete',
]
def __init__(self, context, session, address):
super(ShellChannel, self).__init__(context, session, address)
self.ioloop = ioloop.IOLoop()
def run(self):
"""The thread's main activity. Call start() instead."""
self.socket = self.context.socket(zmq.DEALER)
self.socket.linger = 1000
self.socket.setsockopt(zmq.IDENTITY, self.session.bsession)
self.socket.connect(self.address)
self.stream = zmqstream.ZMQStream(self.socket, self.ioloop)
self.stream.on_recv(self._handle_recv)
self._run_loop()
def call_handlers(self, msg):
"""This method is called in the ioloop thread when a message arrives.
Subclasses should override this method to handle incoming messages.
It is important to remember that this method is called in the thread
so that some logic must be done to ensure that the application level
handlers are called in the application thread.
"""
raise NotImplementedError(
'call_handlers must be defined in a subclass.')
def execute(self, code, silent=False, store_history=True,
user_expressions=None, allow_stdin=None):
"""Execute code in the kernel.
Parameters
----------
code : str
A string of Python code.
silent : bool, optional (default False)
If set, the kernel will execute the code as quietly possible, and
will force store_history to be False.
store_history : bool, optional (default True)
If set, the kernel will store command history. This is forced
to be False if silent is True.
user_expressions : dict, optional
A dict mapping names to expressions to be evaluated in the user's
dict. The expression values are returned as strings formatted using
:func:`repr`.
allow_stdin : bool, optional (default self.allow_stdin)
Flag for whether the kernel can send stdin requests to frontends.
Some frontends (e.g. the Notebook) do not support stdin requests.
If raw_input is called from code executed from such a frontend, a
StdinNotImplementedError will be raised.
Returns
-------
The msg_id of the message sent.
"""
if user_expressions is None:
user_expressions = {}
if allow_stdin is None:
allow_stdin = self.allow_stdin
# Don't waste network traffic if inputs are invalid
if not isinstance(code, string_types):
raise ValueError('code %r must be a string' % code)
validate_string_dict(user_expressions)
# Create class for content/msg creation. Related to, but possibly
# not in Session.
content = dict(code=code, silent=silent, store_history=store_history,
user_expressions=user_expressions,
allow_stdin=allow_stdin,
)
msg = self.session.msg('execute_request', content)
self._queue_send(msg)
return msg['header']['msg_id']
def complete(self, code, cursor_pos=None):
"""Tab complete text in the kernel's namespace.
Parameters
----------
code : str
The context in which completion is requested.
Can be anything between a variable name and an entire cell.
cursor_pos : int, optional
The position of the cursor in the block of code where the completion was requested.
Default: ``len(code)``
Returns
-------
The msg_id of the message sent.
"""
if cursor_pos is None:
cursor_pos = len(code)
content = dict(code=code, cursor_pos=cursor_pos)
msg = self.session.msg('complete_request', content)
self._queue_send(msg)
return msg['header']['msg_id']
def inspect(self, code, cursor_pos=None, detail_level=0):
"""Get metadata information about an object in the kernel's namespace.
It is up to the kernel to determine the appropriate object to inspect.
Parameters
----------
code : str
The context in which info is requested.
Can be anything between a variable name and an entire cell.
cursor_pos : int, optional
The position of the cursor in the block of code where the info was requested.
Default: ``len(code)``
detail_level : int, optional
The level of detail for the introspection (0-2)
Returns
-------
The msg_id of the message sent.
"""
if cursor_pos is None:
cursor_pos = len(code)
content = dict(code=code, cursor_pos=cursor_pos,
detail_level=detail_level,
)
msg = self.session.msg('inspect_request', content)
self._queue_send(msg)
return msg['header']['msg_id']
def history(self, raw=True, output=False, hist_access_type='range', **kwargs):
"""Get entries from the kernel's history list.
Parameters
----------
raw : bool
If True, return the raw input.
output : bool
If True, then return the output as well.
hist_access_type : str
'range' (fill in session, start and stop params), 'tail' (fill in n)
or 'search' (fill in pattern param).
session : int
For a range request, the session from which to get lines. Session
numbers are positive integers; negative ones count back from the
current session.
start : int
The first line number of a history range.
stop : int
The final (excluded) line number of a history range.
n : int
The number of lines of history to get for a tail request.
pattern : str
The glob-syntax pattern for a search request.
Returns
-------
The msg_id of the message sent.
"""
content = dict(raw=raw, output=output, hist_access_type=hist_access_type,
**kwargs)
msg = self.session.msg('history_request', content)
self._queue_send(msg)
return msg['header']['msg_id']
def kernel_info(self):
"""Request kernel info."""
msg = self.session.msg('kernel_info_request')
self._queue_send(msg)
return msg['header']['msg_id']
def _handle_kernel_info_reply(self, msg):
"""handle kernel info reply
sets protocol adaptation version
"""
adapt_version = int(msg['content']['protocol_version'].split('.')[0])
if adapt_version != major_protocol_version:
self.session.adapt_version = adapt_version
def shutdown(self, restart=False):
"""Request an immediate kernel shutdown.
Upon receipt of the (empty) reply, client code can safely assume that
the kernel has shut down and it's safe to forcefully terminate it if
it's still alive.
The kernel will send the reply via a function registered with Python's
atexit module, ensuring it's truly done as the kernel is done with all
normal operation.
"""
# Send quit message to kernel. Once we implement kernel-side setattr,
# this should probably be done that way, but for now this will do.
msg = self.session.msg('shutdown_request', {'restart': restart})
self._queue_send(msg)
return msg['header']['msg_id']
def is_complete(self, code):
msg = self.session.msg('is_complete_request', {'code': code})
self._queue_send(msg)
return msg['header']['msg_id']
class IOPubChannel(ZMQSocketChannel):
"""The iopub channel which listens for messages that the kernel publishes.
This channel is where all output is published to frontends.
"""
def __init__(self, context, session, address):
super(IOPubChannel, self).__init__(context, session, address)
self.ioloop = ioloop.IOLoop()
def run(self):
"""The thread's main activity. Call start() instead."""
self.socket = self.context.socket(zmq.SUB)
self.socket.linger = 1000
self.socket.setsockopt(zmq.SUBSCRIBE, b'')
self.socket.setsockopt(zmq.IDENTITY, self.session.bsession)
self.socket.connect(self.address)
self.stream = zmqstream.ZMQStream(self.socket, self.ioloop)
self.stream.on_recv(self._handle_recv)
self._run_loop()
def call_handlers(self, msg):
"""This method is called in the ioloop thread when a message arrives.
Subclasses should override this method to handle incoming messages.
It is important to remember that this method is called in the thread
so that some logic must be done to ensure that the application leve
handlers are called in the application thread.
"""
raise NotImplementedError(
'call_handlers must be defined in a subclass.')
def flush(self, timeout=1.0):
"""Immediately processes all pending messages on the iopub channel.
Callers should use this method to ensure that :meth:`call_handlers`
has been called for all messages that have been received on the
0MQ SUB socket of this channel.
This method is thread safe.
Parameters
----------
timeout : float, optional
The maximum amount of time to spend flushing, in seconds. The
default is one second.
"""
# We do the IOLoop callback process twice to ensure that the IOLoop
# gets to perform at least one full poll.
stop_time = time.time() + timeout
for i in range(2):
self._flushed = False
self.ioloop.add_callback(self._flush)
while not self._flushed and time.time() < stop_time:
time.sleep(0.01)
def _flush(self):
"""Callback for :method:`self.flush`."""
self.stream.flush()
self._flushed = True
class StdInChannel(ZMQSocketChannel):
"""The stdin channel to handle raw_input requests that the kernel makes."""
msg_queue = None
proxy_methods = ['input']
def __init__(self, context, session, address):
super(StdInChannel, self).__init__(context, session, address)
self.ioloop = ioloop.IOLoop()
def run(self):
"""The thread's main activity. Call start() instead."""
self.socket = self.context.socket(zmq.DEALER)
self.socket.linger = 1000
self.socket.setsockopt(zmq.IDENTITY, self.session.bsession)
self.socket.connect(self.address)
self.stream = zmqstream.ZMQStream(self.socket, self.ioloop)
self.stream.on_recv(self._handle_recv)
self._run_loop()
def call_handlers(self, msg):
"""This method is called in the ioloop thread when a message arrives.
Subclasses should override this method to handle incoming messages.
It is important to remember that this method is called in the thread
so that some logic must be done to ensure that the application leve
handlers are called in the application thread.
"""
raise NotImplementedError(
'call_handlers must be defined in a subclass.')
def input(self, string):
"""Send a string of raw input to the kernel."""
content = dict(value=string)
msg = self.session.msg('input_reply', content)
self._queue_send(msg)
class HBChannel(ZMQSocketChannel):
"""The heartbeat channel which monitors the kernel heartbeat.
Note that the heartbeat channel is paused by default. As long as you start
this channel, the kernel manager will ensure that it is paused and un-paused
as appropriate.
"""
time_to_dead = 3.0
socket = None
poller = None
_running = None
_pause = None
_beating = None
def __init__(self, context, session, address):
super(HBChannel, self).__init__(context, session, address)
self._running = False
self._pause = True
self.poller = zmq.Poller()
def _create_socket(self):
if self.socket is not None:
# close previous socket, before opening a new one
self.poller.unregister(self.socket)
self.socket.close()
self.socket = self.context.socket(zmq.REQ)
self.socket.linger = 1000
self.socket.connect(self.address)
self.poller.register(self.socket, zmq.POLLIN)
def _poll(self, start_time):
"""poll for heartbeat replies until we reach self.time_to_dead.
Ignores interrupts, and returns the result of poll(), which
will be an empty list if no messages arrived before the timeout,
or the event tuple if there is a message to receive.
"""
until_dead = self.time_to_dead - (time.time() - start_time)
# ensure poll at least once
until_dead = max(until_dead, 1e-3)
events = []
while True:
try:
events = self.poller.poll(1000 * until_dead)
except ZMQError as e:
if e.errno == errno.EINTR:
# ignore interrupts during heartbeat
# this may never actually happen
until_dead = self.time_to_dead - (time.time() - start_time)
until_dead = max(until_dead, 1e-3)
pass
else:
raise
except Exception:
if self._exiting:
break
else:
raise
else:
break
return events
def run(self):
"""The thread's main activity. Call start() instead."""
self._create_socket()
self._running = True
self._beating = True
while self._running:
if self._pause:
# just sleep, and skip the rest of the loop
time.sleep(self.time_to_dead)
continue
since_last_heartbeat = 0.0
# io.rprint('Ping from HB channel') # dbg
# no need to catch EFSM here, because the previous event was
# either a recv or connect, which cannot be followed by EFSM
self.socket.send(b'ping')
request_time = time.time()
ready = self._poll(request_time)
if ready:
self._beating = True
# the poll above guarantees we have something to recv
self.socket.recv()
# sleep the remainder of the cycle
remainder = self.time_to_dead - (time.time() - request_time)
if remainder > 0:
time.sleep(remainder)
continue
else:
# nothing was received within the time limit, signal heart
# failure
self._beating = False
since_last_heartbeat = time.time() - request_time
self.call_handlers(since_last_heartbeat)
# and close/reopen the socket, because the REQ/REP cycle has
# been broken
self._create_socket()
continue
def pause(self):
"""Pause the heartbeat."""
self._pause = True
def unpause(self):
"""Unpause the heartbeat."""
self._pause = False
def is_beating(self):
"""Is the heartbeat running and responsive (and not paused)."""
if self.is_alive() and not self._pause and self._beating:
return True
else:
return False
def stop(self):
"""Stop the channel's event loop and join its thread."""
self._running = False
super(HBChannel, self).stop()
def call_handlers(self, since_last_heartbeat):
"""This method is called in the ioloop thread when a message arrives.
Subclasses should override this method to handle incoming messages.
It is important to remember that this method is called in the thread
so that some logic must be done to ensure that the application level
handlers are called in the application thread.
"""
raise NotImplementedError(
'call_handlers must be defined in a subclass.')
#---------------------------------------------------------------------#---
# ABC Registration
#-----------------------------------------------------------------------------
ShellChannelABC.register(ShellChannel)
IOPubChannelABC.register(IOPubChannel)
HBChannelABC.register(HBChannel)
StdInChannelABC.register(StdInChannel)