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""" Defines helper functions for creating kernel entry points and process
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launchers.
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"""
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# Standard library imports.
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import atexit
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import os
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import socket
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from subprocess import Popen, PIPE
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import sys
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# Local imports.
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from parentpoller import ParentPollerWindows
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def base_launch_kernel(code, shell_port=0, iopub_port=0, stdin_port=0, hb_port=0,
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ip=None, stdin=None, stdout=None, stderr=None,
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executable=None, independent=False, extra_arguments=[]):
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""" Launches a localhost kernel, binding to the specified ports.
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Parameters
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----------
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code : str,
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A string of Python code that imports and executes a kernel entry point.
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shell_port : int, optional
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The port to use for XREP channel.
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iopub_port : int, optional
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The port to use for the SUB channel.
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stdin_port : int, optional
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The port to use for the REQ (raw input) channel.
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hb_port : int, optional
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The port to use for the hearbeat REP channel.
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ip : str, optional
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The ip address the kernel will bind to.
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stdin, stdout, stderr : optional (default None)
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Standards streams, as defined in subprocess.Popen.
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executable : str, optional (default sys.executable)
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The Python executable to use for the kernel process.
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independent : bool, optional (default False)
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If set, the kernel process is guaranteed to survive if this process
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dies. If not set, an effort is made to ensure that the kernel is killed
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when this process dies. Note that in this case it is still good practice
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to kill kernels manually before exiting.
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extra_arguments = list, optional
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A list of extra arguments to pass when executing the launch code.
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Returns
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-------
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A tuple of form:
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(kernel_process, shell_port, iopub_port, stdin_port, hb_port)
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where kernel_process is a Popen object and the ports are integers.
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"""
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# Find open ports as necessary.
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ports = []
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ports_needed = int(shell_port <= 0) + int(iopub_port <= 0) + \
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int(stdin_port <= 0) + int(hb_port <= 0)
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for i in xrange(ports_needed):
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sock = socket.socket()
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sock.bind(('', 0))
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ports.append(sock)
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for i, sock in enumerate(ports):
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port = sock.getsockname()[1]
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sock.close()
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ports[i] = port
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if shell_port <= 0:
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shell_port = ports.pop(0)
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if iopub_port <= 0:
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iopub_port = ports.pop(0)
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if stdin_port <= 0:
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stdin_port = ports.pop(0)
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if hb_port <= 0:
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hb_port = ports.pop(0)
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# Build the kernel launch command.
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if executable is None:
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executable = sys.executable
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arguments = [ executable, '-c', code, '--shell=%i'%shell_port,
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'--iopub=%i'%iopub_port, '--stdin=%i'%stdin_port,
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'--hb=%i'%hb_port ]
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if ip is not None:
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arguments.append('--ip=%s'%ip)
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arguments.extend(extra_arguments)
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# Popen will fail (sometimes with a deadlock) if stdin, stdout, and stderr
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# are invalid. Unfortunately, there is in general no way to detect whether
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# they are valid. The following two blocks redirect them to (temporary)
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# pipes in certain important cases.
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# If this process has been backgrounded, our stdin is invalid. Since there
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# is no compelling reason for the kernel to inherit our stdin anyway, we'll
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# place this one safe and always redirect.
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redirect_in = True
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_stdin = PIPE if stdin is None else stdin
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# If this process in running on pythonw, we know that stdin, stdout, and
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# stderr are all invalid.
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redirect_out = sys.executable.endswith('pythonw.exe')
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if redirect_out:
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_stdout = PIPE if stdout is None else stdout
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_stderr = PIPE if stderr is None else stderr
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else:
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_stdout, _stderr = stdout, stderr
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# Spawn a kernel.
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if sys.platform == 'win32':
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# Create a Win32 event for interrupting the kernel.
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interrupt_event = ParentPollerWindows.create_interrupt_event()
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arguments += [ '--interrupt=%i'%interrupt_event ]
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# If the kernel is running on pythonw and stdout/stderr are not been
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# re-directed, it will crash when more than 4KB of data is written to
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# stdout or stderr. This is a bug that has been with Python for a very
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# long time; see http://bugs.python.org/issue706263.
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# A cleaner solution to this problem would be to pass os.devnull to
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# Popen directly. Unfortunately, that does not work.
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if executable.endswith('pythonw.exe'):
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if stdout is None:
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arguments.append('--no-stdout')
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if stderr is None:
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arguments.append('--no-stderr')
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# Launch the kernel process.
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if independent:
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proc = Popen(arguments,
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creationflags=512, # CREATE_NEW_PROCESS_GROUP
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stdin=_stdin, stdout=_stdout, stderr=_stderr)
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else:
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from _subprocess import DuplicateHandle, GetCurrentProcess, \
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DUPLICATE_SAME_ACCESS
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pid = GetCurrentProcess()
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handle = DuplicateHandle(pid, pid, pid, 0,
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True, # Inheritable by new processes.
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DUPLICATE_SAME_ACCESS)
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proc = Popen(arguments + ['--parent=%i'%int(handle)],
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stdin=_stdin, stdout=_stdout, stderr=_stderr)
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# Attach the interrupt event to the Popen objet so it can be used later.
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proc.win32_interrupt_event = interrupt_event
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else:
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if independent:
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proc = Popen(arguments, preexec_fn=lambda: os.setsid(),
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stdin=_stdin, stdout=_stdout, stderr=_stderr)
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else:
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proc = Popen(arguments + ['--parent=1'],
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stdin=_stdin, stdout=_stdout, stderr=_stderr)
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# Clean up pipes created to work around Popen bug.
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if redirect_in:
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if stdin is None:
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proc.stdin.close()
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if redirect_out:
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if stdout is None:
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proc.stdout.close()
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if stderr is None:
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proc.stderr.close()
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return proc, shell_port, iopub_port, stdin_port, hb_port
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