mirror of
https://github.com/clearml/clearml-agent
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75 lines
2.9 KiB
Python
75 lines
2.9 KiB
Python
import os
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def daemonize_process(redirect_fd=None):
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"""
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Detach a process from the controlling terminal and run it in the background as a daemon.
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"""
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assert redirect_fd is None or isinstance(redirect_fd, int)
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# re-spawn in the same directory
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WORKDIR = os.getcwd()
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# The standard I/O file descriptors are redirected to /dev/null by default.
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if hasattr(os, "devnull"):
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devnull = os.devnull
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else:
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devnull = "/dev/null"
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try:
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# Fork a child process so the parent can exit. This returns control to
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# the command-line or shell. It also guarantees that the child will not
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# be a process group leader, since the child receives a new process ID
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# and inherits the parent's process group ID. This step is required
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# to insure that the next call to os.setsid is successful.
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pid = os.fork()
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except OSError as e:
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raise Exception("%s [%d]" % (e.strerror, e.errno))
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if pid == 0: # The first child.
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# To become the session leader of this new session and the process group
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# leader of the new process group, we call os.setsid().
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# The process is also guaranteed not to have a controlling terminal.
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os.setsid()
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# Is ignoring SIGHUP necessary? (Set handlers for asynchronous events.)
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# import signal
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# signal.signal(signal.SIGHUP, signal.SIG_IGN)
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try:
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# Fork a second child and exit immediately to prevent zombies. This
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# causes the second child process to be orphaned, making the init
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# process responsible for its cleanup.
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pid = os.fork() # Fork a second child.
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except OSError as e:
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raise Exception("%s [%d]" % (e.strerror, e.errno))
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if pid == 0: # The second child.
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# Since the current working directory may be a mounted filesystem, we
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# avoid the issue of not being able to unmount the filesystem at
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# shutdown time by changing it to the root directory.
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os.chdir(WORKDIR)
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# We probably don't want the file mode creation mask inherited from
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# the parent, so we give the child complete control over permissions.
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os.umask(0)
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else:
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# Exit parent (the first child) of the second child.
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os._exit(0)
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else:
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# Exit parent of the first child.
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os._exit(0)
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# notice we count on the fact that we keep all file descriptors open,
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# since we opened then in the parent process, but the daemon process will use them
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# Redirect the standard I/O file descriptors to the specified file /dev/null.
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if redirect_fd is None:
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redirect_fd = os.open(devnull, os.O_RDWR)
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# Duplicate standard input to standard output and standard error.
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# standard output (1), standard error (2)
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os.dup2(redirect_fd, 1)
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os.dup2(redirect_fd, 2)
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return 0
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