upstream/ipython Files · IPython/utils/daemonize.py

avoid race condition when deleting/starting sessions...

avoid race condition when deleting/starting sessions javascript doesn't guarantee the order of AJAX requests, so we give `Session.delete` and `Kernel.kill` a callback signature. Changing the kernel type calls `Notebook.start_kernel`, which terminates the previous session, if defined, before starting the new one. A flag is stored, to prevent multiple simultaneous attempts to start sessions, raising a SessionAlreadyStarting Error, preventing the spec_changed event from firing.

Matthias BUSSONNIER - - Load All Authors

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      """daemonize function from twisted.scripts._twistd_unix."""

      #-----------------------------------------------------------------------------

      # Copyright (c) Twisted Matrix Laboratories.

      # See Twisted's LICENSE for details.

      # http://twistedmatrix.com/

      #-----------------------------------------------------------------------------

      import os, errno

      def daemonize():

          # See http://www.erlenstar.demon.co.uk/unix/faq_toc.html#TOC16

          if os.fork():   # launch child and...

              os._exit(0) # kill off parent

          os.setsid()

          if os.fork():   # launch child and...

              os._exit(0) # kill off parent again.

          null = os.open('/dev/null', os.O_RDWR)

          for i in range(3):

              try:

                  os.dup2(null, i)

              except OSError as e:

                  if e.errno != errno.EBADF:

                      raise

          os.close(null)

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				"""daemonize function from twisted.scripts._twistd_unix."""

				#-----------------------------------------------------------------------------
				# Copyright (c) Twisted Matrix Laboratories.
				# See Twisted's LICENSE for details.
				# http://twistedmatrix.com/
				#-----------------------------------------------------------------------------

				import os, errno

				def daemonize():
				# See http://www.erlenstar.demon.co.uk/unix/faq_toc.html#TOC16
				if os.fork(): # launch child and...
				os._exit(0) # kill off parent
				os.setsid()
				if os.fork(): # launch child and...
				os._exit(0) # kill off parent again.
				null = os.open('/dev/null', os.O_RDWR)
				for i in range(3):
				try:
				os.dup2(null, i)
				except OSError as e:
				if e.errno != errno.EBADF:
				raise
				os.close(null)