I want to embed a ZMQ kernel in my Python app to be able to debug it remotely, mostly to get a remote REPL shell into it.
I cannot just use
because that has many side effects, such as messing around with sys.stdout, sys.stderr, sys.excepthook, signal.signal, etc and I don't want these side effects. Also, embed_kernel() is blocking and doesn't really work out-of-the-box in a separate thread (see here).
So, I came up with this code, which is far too complicated in my opinion.
def initIPythonKernel():
# You can remotely connect to this kernel. See the output on stdout.
try:
import IPython.kernel.zmq.ipkernel
from IPython.kernel.zmq.ipkernel import Kernel
from IPython.kernel.zmq.heartbeat import Heartbeat
from IPython.kernel.zmq.session import Session
from IPython.kernel import write_connection_file
import zmq
from zmq.eventloop import ioloop
from zmq.eventloop.zmqstream import ZMQStream
IPython.kernel.zmq.ipkernel.signal = lambda sig, f: None # Overwrite.
except ImportError, e:
print "IPython import error, cannot start IPython kernel. %s" % e
return
import atexit
import socket
import logging
import threading
# Do in mainthread to avoid history sqlite DB errors at exit.
# https://github.com/ipython/ipython/issues/680
assert isinstance(threading.currentThread(), threading._MainThread)
try:
connection_file = "kernel-%s.json" % os.getpid()
def cleanup_connection_file():
try:
os.remove(connection_file)
except (IOError, OSError):
pass
atexit.register(cleanup_connection_file)
logger = logging.Logger("IPython")
logger.addHandler(logging.NullHandler())
session = Session(username=u'kernel')
context = zmq.Context.instance()
ip = socket.gethostbyname(socket.gethostname())
transport = "tcp"
addr = "%s://%s" % (transport, ip)
shell_socket = context.socket(zmq.ROUTER)
shell_port = shell_socket.bind_to_random_port(addr)
iopub_socket = context.socket(zmq.PUB)
iopub_port = iopub_socket.bind_to_random_port(addr)
control_socket = context.socket(zmq.ROUTER)
control_port = control_socket.bind_to_random_port(addr)
hb_ctx = zmq.Context()
heartbeat = Heartbeat(hb_ctx, (transport, ip, 0))
hb_port = heartbeat.port
heartbeat.start()
shell_stream = ZMQStream(shell_socket)
control_stream = ZMQStream(control_socket)
kernel = Kernel(session=session,
shell_streams=[shell_stream, control_stream],
iopub_socket=iopub_socket,
log=logger)
write_connection_file(connection_file,
shell_port=shell_port, iopub_port=iopub_port, control_port=control_port, hb_port=hb_port,
ip=ip)
print "To connect another client to this IPython kernel, use:", \
"ipython console --existing %s" % connection_file
except Exception, e:
print "Exception while initializing IPython ZMQ kernel. %s" % e
return
def ipython_thread():
kernel.start()
try:
ioloop.IOLoop.instance().start()
except KeyboardInterrupt:
pass
thread = threading.Thread(target=ipython_thread, name="IPython kernel")
thread.daemon = True
thread.start()
Is there an easier method? If not, I guess this is a feature request.
(Related StackOverflow question. Updated code, as a PIP package, background_zmq_ipython.)
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