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nudge: handle failure cases

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- connect iopub first (tiny effect on the race!)
- docstrings, log details
- resolve immediately if kernel is busy, rather than setting up timeouts, futures
- use gen.with_timeout instead of separately managed timeout
- use gen.multi to wait for both futures instead of duplicated check in each handler, third Future
- add various cancel conditions (sockets closed, kernel stopped, etc.)
pull/5908/head
Min RK 5 years ago
parent 94678545db
commit 672f0a6e20
1 changed files with 81 additions and 38 deletions
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119
notebook/services/kernels/handlers.py
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@ -123,60 +123,76 @@ class ZMQChannelsHandler(AuthenticatedZMQStreamHandler):
def create_stream(self):
km = self.kernel_manager
identity = self.session.bsession
for channel in ('shell', 'control', 'iopub', 'stdin'):
meth = getattr(km, 'connect_' + channel)
for channel in ("iopub", "shell", "control", "stdin"):
meth = getattr(km, "connect_" + channel)
self.channels[channel] = stream = meth(self.kernel_id, identity=identity)
stream.channel = channel
def nudge(self):
def nudge(self):
"""Nudge the zmq connections with kernel_info_requests
Returns a Future that will resolve when we have received
a shell reply and at least one iopub message,
ensuring that zmq subscriptions are established,
sockets are fully connected, and kernel is responsive.
Keeps retrying kernel_info_request until these are both received.
"""
kernel = self.kernel_manager.get_kernel(self.kernel_id)
# Do not nudge busy kernels as kernel info requests sent to shell are
# queued behind execution requests.
# nudging in this case would cause a potentially very long wait
# before connections are opened,
# plus it is *very* unlikely that a busy kernel will not finish
# establishing its zmq subscriptions before processing the next request.
if getattr(kernel, "execution_state") == "busy":
self.log.debug("Nudge: not nudging busy kernel %s", self.kernel_id)
f = Future()
f.set_result(None)
return f
# Use a transient shell channel to prevent leaking
# shell responses to the front-end.
kernel = self.kernel_manager.get_kernel(self.kernel_id)
shell_channel = kernel.connect_shell()
# The IOPub used by the client, whose subscriptions we are verifying.
iopub_channel = self.channels["iopub"]
# The IOPub used by the client.
iopub_channel = self.channels['iopub']
future = Future()
info_future = Future()
iopub_future = Future()
both_done = gen.multi([info_future, iopub_future])
def finish(f=None):
"""Ensure all futures are resolved
def finish():
which in turn triggers cleanup
"""
for f in (info_future, iopub_future):
if not f.done():
f.set_result(None)
def cleanup(f=None):
"""Common cleanup"""
loop.remove_timeout(timeout)
loop.remove_timeout(nudge_handle)
iopub_channel.stop_on_recv()
if not shell_channel.closed():
shell_channel.close()
# trigger cleanup when both message futures are resolved
both_done.add_done_callback(cleanup)
def on_shell_reply(msg):
self.log.debug("Nudge: shell info reply received: %s", self.kernel_id)
if not info_future.done():
self.log.debug("Nudge: shell info reply received: %s", self.kernel_id)
if not shell_channel.closed():
shell_channel.close()
self.log.debug("Nudge: resolving shell future")
self.log.debug("Nudge: resolving shell future: %s", self.kernel_id)
info_future.set_result(None)
if iopub_future.done():
finish()
self.log.debug("Nudge: resolving main future in shell handler")
future.set_result(None)
def on_iopub(msg):
self.log.debug("Nudge: IOPub received: %s", self.kernel_id)
if not iopub_future.done():
self.log.debug("Nudge: first IOPub received: %s", self.kernel_id)
iopub_channel.stop_on_recv()
self.log.debug("Nudge: resolving iopub future")
self.log.debug("Nudge: resolving iopub future: %s", self.kernel_id)
iopub_future.set_result(None)
if info_future.done():
finish()
self.log.debug("Nudge: resolving main future in iopub handler")
future.set_result(None)
def on_timeout():
self.log.warning("Nudge: Timeout waiting for kernel_info_reply: %s", self.kernel_id)
finish()
if not future.done():
future.set_exception(TimeoutError("Timeout waiting for nudge"))
iopub_channel.on_recv(on_iopub)
shell_channel.on_recv(on_shell_reply)
@ -184,19 +200,46 @@ class ZMQChannelsHandler(AuthenticatedZMQStreamHandler):
# Nudge the kernel with kernel info requests until we get an IOPub message
def nudge(count):
# Do not nudge busy kernels as kernel info requests sent to shell are
# queued behind execution requests.
if kernel.execution_state == 'busy':
future.set_result(None)
if not future.done():
count += 1
# NOTE: this close check appears to never be True during on_open,
# even when the peer has closed the connection
if self.ws_connection is None or self.ws_connection.is_closing():
self.log.debug(
"Nudge: cancelling on closed websocket: %s", self.kernel_id
)
finish()
return
# check for stopped kernel
if self.kernel_id not in self.kernel_manager:
self.log.debug(
"Nudge: cancelling on stopped kernel: %s", self.kernel_id
)
finish()
return
# check for closed zmq socket
if shell_channel.closed():
self.log.debug(
"Nudge: cancelling on closed zmq socket: %s", self.kernel_id
)
finish()
return
if not both_done.done():
log = self.log.warning if count % 10 == 0 else self.log.debug
log("Nudging attempt %s on kernel %s" % (count, self.kernel_id))
log("Nudge: attempt %s on kernel %s" % (count, self.kernel_id))
self.session.send(shell_channel, "kernel_info_request")
nonlocal nudge_handle
nudge_handle = loop.call_later(0.5, nudge, count)
nudge_handle = loop.call_later(0, nudge, count=0)
timeout = loop.add_timeout(loop.time() + self.kernel_info_timeout, on_timeout)
# resolve with a timeout if we get no response
future = gen.with_timeout(loop.time() + self.kernel_info_timeout, both_done)
# ensure we have no dangling resources or unresolved Futures in case of timeout
future.add_done_callback(finish)
return future
def request_kernel_info(self):
@ -221,7 +264,7 @@ class ZMQChannelsHandler(AuthenticatedZMQStreamHandler):
self.log.debug("Waiting for pending kernel_info request")
future.add_done_callback(lambda f: self._finish_kernel_info(f.result()))
return self._kernel_info_future
def _handle_kernel_info_reply(self, msg):
"""process the kernel_info_reply

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