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@minrk
Forked from jasongrout/testfork.py
Created May 30, 2012 01:05
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"""
A test forking server
To start a single kernel by forking, do::
python -i testfork.py
The kernel object will be in the ``a`` variable. When you close the
python session, the forked kernel will be killed.
"""
import sys
from multiprocessing import Process
from IPython.config.loader import Config
from IPython.utils.traitlets import Any
from IPython.zmq.kernelmanager import KernelManager
from IPython.zmq.ipkernel import IPKernelApp
from IPython.zmq.blockingkernelmanager import BlockingKernelManager
# only using BlockingKernelManager in this case so that it's usable at the bottom.
# The KernelManager is an incomplete base class, but appropriate for building
# various subclasses.
def kernel_target_f(config):
"""launch a kernel, for use with multiprocessing.Process(target=this)"""
app = IPKernelApp.instance(config=config)
app.initialize([])
app.start()
class ForkingKernelManager(BlockingKernelManager):
# the KernelManager insists that `kernel` is a Popen instance
# but we want to *only* fork and embed, not exec a new process
kernel = Any()
def __init__(self, *args, **kwargs):
super(ForkingKernelManager, self ).__init__(*args, **kwargs)
# later on, we can override the _bind_socket function
# to support UDS sockets
def kill_kernel(self):
""" Kill the running kernel. """
if self.has_kernel:
# Pause the heart beat channel if it exists.
if self._hb_channel is not None:
self._hb_channel.pause()
# Attempt to kill the kernel.
try:
import os
print "Killing kernel process %d . . ."%self.kernel.pid,
os.kill(self.kernel.pid,15)
self.kernel.join()
except OSError, e:
# In Windows, we will get an Access Denied error if the process
# has already terminated. Ignore it.
if sys.platform == 'win32':
if e.winerror != 5:
raise
# On Unix, we may get an ESRCH error if the process has already
# terminated. Ignore it.
else:
from errno import ESRCH
if e.errno != ESRCH:
raise
self.kernel = None
else:
raise RuntimeError("Cannot kill kernel. No kernel is running!")
def start_kernel(self, **kw):
cfg = Config()
cfg.IPKernelApp.ip = self.ip
cfg.IPKernelApp.shell_port = self.shell_port
cfg.IPKernelApp.iopub_port = self.iopub_port
cfg.IPKernelApp.stdin_port = self.stdin_port
cfg.IPKernelApp.hb_port = self.hb_port
cfg.Session.key = self.session.key
p = Process(target=kernel_target_f, args=(cfg,))
p.start()
# make sure p is killed when we leave the program
def killpid(p):
"""p is the Process object"""
import os
print "Killing kernel process %d . . ."%p.pid,
os.kill(p.pid,15)
p.join()
print "done"
import atexit
from functools import partial
atexit.register(partial(killpid,p))
self.kernel = p
start_port = 5021
a=ForkingKernelManager()
# set the key *before* launching, so it will be in the file
a.session.key = 'abracadabra'
a.shell_port,a.iopub_port,a.stdin_port,a.hb_port = range(start_port,start_port+4)
a.start_kernel()
a.start_channels()
# now try to use it:
s=a.shell_channel
s.execute('print "hello"')
s.execute('print "world"')
# get replies:
s.get_msg()
s.get_msg()
# display output
iopub = a.sub_channel
for msg in iopub.get_msgs():
if msg['msg_type'] == 'stream':
content = msg['content']
print "received %s:" % content['name']
print content['data']
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