freezer.lib.pep3143daemon.daemon module¶
Implementation of PEP 3143 DaemonContext
-
class
freezer.lib.pep3143daemon.daemon.
DaemonContext
(chroot_directory=None, working_directory='/', umask=0, uid=None, gid=None, prevent_core=True, detach_process=None, files_preserve=None, pidfile=None, stdin=None, stdout=None, stderr=None, signal_map=None)¶ Bases:
object
Implementation of PEP 3143 DaemonContext class
This class should be instantiated only once in every program that has to become a Unix Daemon. Typically you should call its open method after you have done everything that may require root privileges. For example opening port <= 1024.
Each option can be passed as a keyword argument to the constructor, but can also be changed by assigning a new value to the corresponding attribute on the instance.
Altering attributes after open() is called, will have no effect. In future versions, trying to do so, will may raise a DaemonError.
- Parameters
chroot_directory (str) – Full path to the directory that should be set as effective root directory. If None, the root directory is not changed.
working_directory (str.) – Full Path to the working directory to which to change to. If chroot_directory is not None, and working_directory is not starting with chroot_directory, working directory is prefixed with chroot_directory.
umask (int.) – File access creation mask for this daemon after start
uid (int.) – Effective user id after daemon start.
gid (int.) – Effective group id after daemon start.
prevent_core (bool.) – Prevent core file generation.
detach_process (bool.) – If True, do the double fork magic. If the process was started by inet or an init like program, you may don´t need to detach. If not set, we try to figure out if forking is needed.
files_preserve (list) – List of integers, or objects with a fileno method, that represent files that should not be closed while daemonizing.
pidfile (Instance of Class that implements a pidfile behaviour) – Instance that implements a pidfile, while daemonizing its acquire method will be called.
stdin (file object.) – Redirect stdin to this file, if None, redirect to /dev/null.
stdout (file object.) – Redirect stdout to this file, if None, redirect to /dev/null.
stderr (file object.) – Redirect stderr to this file, if None, redirect to /dev/null.
signal_map (instance of dict) – Mapping from operating system signal to callback actions.
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close
()¶ Dummy function
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property
is_open
¶ True when this instances open method was called
- Returns
bool
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open
()¶ Daemonize this process
Do everything that is needed to become a Unix daemon.
- Returns
None
- Raise
DaemonError
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terminate
(signal_number, stack_frame)¶ Terminate this process
Simply terminate this process by raising SystemExit. This method is called if signal.SIGTERM was received.
Check carefully if this really is what you want!
Most likely it is not!
You should implement a function/method that is able to cleanly shutdown you daemon. Like gracefully terminating child processes, threads. or closing files.
You can create a custom handler by overriding this method, ot setting a custom handler via the signal_map. It is also possible to set the signal handlers directly via signal.signal().
- Returns
None
- Raise
SystemExit
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property
working_directory
¶ The working_directory property
- Returns
str
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exception
freezer.lib.pep3143daemon.daemon.
DaemonError
¶ Bases:
Exception
Exception raised by DaemonContext
-
freezer.lib.pep3143daemon.daemon.
close_filenos
(preserve)¶ Close unprotected file descriptors
Close all open file descriptors that are not in preserve.
If ulimit -nofile is “unlimited”, all is defined filenos <= 4096, else all is <= the output of resource.getrlimit().
- Parameters
preserve (set) – set with protected files
- Returns
None
-
freezer.lib.pep3143daemon.daemon.
default_signal_map
()¶ Create the default signal map for this system.
- Returns
dict
-
freezer.lib.pep3143daemon.daemon.
detach_required
()¶ Check if detaching is required
This is done by collecting the results of parent_is_inet and parent_is_init. If one of them is True, detaching, aka the daemonizing, aka the double fork magic, is not required, and can be skipped.
- Returns
bool
-
freezer.lib.pep3143daemon.daemon.
parent_is_inet
()¶ Check if parent is inet
Check if our parent seems ot be a superserver, aka inetd/xinetd.
This is done by checking if sys.__stdin__ is a network socket.
- Returns
bool
-
freezer.lib.pep3143daemon.daemon.
parent_is_init
()¶ Check if parent is Init
Check if the parent process is init, or something else that owns PID 1.
- Returns
bool
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freezer.lib.pep3143daemon.daemon.
redirect_stream
(system, target)¶ Redirect Unix streams
If None, redirect Stream to /dev/null, else redirect to target.
- Parameters
system (file object) – ether sys.stdin, sys.stdout, or sys.stderr
target (None, File Object) – File like object, or None
- Returns
None
- Raise
DaemonError