Framework for writing daemons, with API similar to threading and multiprocessing.
pandaemonium provides a framework for writing daemons in Python. The API is
based on the threading/multiprocessing model, so the primary way
of creating your own daemon is to either subclass and override the
method, or provide a function as the
target to the
Daemon there is also a locking pid file --
PidLockFile can either be used manually, or, if a complete path and file
name are provided to
Daemon, used automatically.
from pandaemonium import Daemon def DoSomethingInteresting(): "Just like it says ;)" pass daemon = Daemon(target=DoSomethingInteresting) daemon.start() # # daemon.output will contain any stdout output generated during the # daemonizing process, up to the stdin/stdout/stderr redirection # # daemon.error contains anything sent to the daemon's stderr -- which # most likely means the daemon died due to an exception # # both can be parsed, examined, ignored, etc.
from pandaemonium import Daemon class MyDaemon(Daemon): def run(): # do some interesting stuff md = MyDaemon().start()
The sequence of events that takes place when
start() is called (adapted from
The Linux Programming Interface by Michael Kerrisk) is:
- detach from the current process, creating a new session
- turn off core dumps
- set uid and gid
- set umask
- set working directory
- create pid file
- set signal handlers
- close inherited file handles
- redirect stdin/stdout/stderr
If any exceptions occur or if any feedback is generated during the
process it will be available as the
output attributes of the
daemon instance, where the parent process can analyze, print, etc before
Note: Most guides on writing daemons specify setting the umask to 0, but this creates a security hole as all files become world readable/writable by default. Pandaemonium sets the umask to 077, but that can be changed if desired.
If more control is needed than what is provided by the parameters of Daemon then one has a couple options available:
if certain set up / initialization steps need to happen somewhere in the
start()sequence, such as after setting the umask and before changing the working directory::
Daemon.stage4() # stages 1-4 have now been completed # do custom steps here Daemon.start() # stages 5-9 have now been completed, and run() called
one can also override any of the stages in a subclass (make sure and decorate with
class MyDaemon(Daemon): def run(self, ip): # do stuff @check_stage def stage7(self): # do some custom stuff with signals set up md = MyDaemon('192.168.11.1') md.start()
or, to simplify between foreground and daemon operation:
foreground = sys.argv[2:3] == ['--foreground'] pid_file = PidLockFile('/some/path/to/lock.pid') pid_file.acquire() if foreground: pid_file.seal() else: daemon = Daemon() daemon.pid_file = pid_file daemon.activate() # at this point, in either foreground or daemon mode, the pid file has # been sealed (has our correct pid written to it, and it has been # closed) run_main_program()
If one's desire is to start the daemon and automatically have any output
printed to screen, one can use
daemon.report() which prints whatever was
received from the daemon and then quits.
Daemon(target=None, args=None, kwargs=None, working_directory='/', umask=0, prevent_core=True, process_ids=None, inherit_files=None, signal_map=None, stdin=None, stdout=None, stderr=None)
target: function to call when daemonized
args: positional args to provide to target
kwargs: keyword args to provide to target
None(default) means figure it out,
Falsemeans no. Figuring it out means if the parent process is
init, or a
super server, do not detach
working_directory: directory to change to (relative to chroot, if one is in effect)
umask: mask to use when creating files
prevent_core: prevent core dump files from being created
process_ids: tuple of (uid, gid) to switch process to (use (None, None) to disable)
None(default), or a PidLockFile instance, or the string of where to create a PidLockFile
inherit_files: list of open files or file descriptors to keep open
signal_map: dictionary of signal names or numbers to method names or functions
stdin / stdout / stderr: streams to map the standard streams to. default is
Nonewhich is mapped to
Method representing the daemon's activity.
You may override this method in a subclass. The standard
method invokes the callable object passed to the object's constructor as
target argument, if any, with sequential and keyword arguments taken
kwargs arguments, respectively.
Start the daemon's activity.
This may be called at most once per daemon object. It arranges for the
run method to be invoked as a daemon process.
Collects stdout and stderr from Daemon process until stage 9 and attaches
it to the daemon instance as
error. Can be overridden
if one wants to do more interesting stuff with the daemon's output
One can override the various stages for even more customizations options.
Make sure and decorate such functions with
file_name: full path and name of file to use for locking
timeout: how long to wait before concluding that an existing held lock is not going to be released (default: -1, meaning conclude immediately)
attempt to capture the lock file; if timeout is
None use the time out
specified when PidLockFile was created.
write the current process' PID into the acquired file and close it -- should only be called by the daemon process or the stored PID will not be correct.
remove the lock file, releasing the lock.
Release history Release notifications | RSS feed
Download the file for your platform. If you're not sure which to choose, learn more about installing packages.
Hashes for pandaemonium-0.9.1-py3-none-any.whl
Hashes for pandaemonium-0.9.1-py2-none-any.whl