Signal handling API

class SignalHandler1(pid_file, sigint=None, sigterm=None, sigabrt=None)

New in version 0.1.

Handles signals for the daemonized process.

Parameters:
  • pid_file (str) – The path to the PID file.
  • sigint – A callable handler for the SIGINT signal. May also be daemoniker.IGNORE_SIGNAL to explicitly ignore the signal. Passing the default value of None will assign the default SIGINT handler, which will simply raise daemoniker.SIGINT within the main thread.
  • sigterm – A callable handler for the SIGTERM signal. May also be daemoniker.IGNORE_SIGNAL to explicitly ignore the signal. Passing the default value of None will assign the default SIGTERM handler, which will simply raise daemoniker.SIGTERM within the main thread.
  • sigabrt – A callable handler for the SIGABRT signal. May also be daemoniker.IGNORE_SIGNAL to explicitly ignore the signal. Passing the default value of None will assign the default SIGABRT handler, which will simply raise daemoniker.SIGABRT within the main thread.

Warning

There is a slight difference in handler calling between Windows and Unix systems. In every case, the default handler will always raise from within the main thread. However, if you define a custom signal handler, on Windows systems it will be called from within a daughter thread devoted to signal handling. This has two consequences:

  1. All signal handlers must be threadsafe
  2. On Windows, future signals will be silently dropped until the callback completes

On Unix systems, the handler will be called from within the main thread.

Note

On Windows, CTRL_C_EVENT and CTRL_BREAK_EVENT signals are both converted to SIGINT signals internally. This also applies to custom signal handlers.

>>> from daemoniker import SignalHandler1
>>> sighandler = SignalHandler1('pid.pid')
sigint

The current handler for SIGINT signals. This must be a callable. It will be invoked with a single argument: the signal number. It may be re-assigned, even after calling start(). Deleting it will restore the default Daemoniker signal handler; to ignore it, instead assign daemoniker.IGNORE_SIGNAL as the handler.

sigterm

The current handler for SIGTERM signals. This must be a callable. It will be invoked with a single argument: the signal number. It may be re-assigned, even after calling start(). Deleting it will restore the default Daemoniker signal handler; to ignore it, instead assign daemoniker.IGNORE_SIGNAL as the handler.

sigabrt

The current handler for SIGABRT signals. This must be a callable. It will be invoked with a single argument: the signal number. It may be re-assigned, even after calling start(). Deleting it will restore the default Daemoniker signal handler; to ignore it, instead assign daemoniker.IGNORE_SIGNAL as the handler.

start()

Starts signal handling. Must be called to receive signals with the SignalHandler.

stop()

Stops signal handling. Must be called to stop receive signals. stop will be automatically called:

  1. at the interpreter exit, and
  2. when the main thread exits.

stop is idempotent. On Unix systems, it will also restore the previous signal handlers.

IGNORE_SIGNAL

A constant used to explicitly declare that a SignalHandler1 should ignore a particular signal.

send(pid_file, signal)

New in version 0.1.

Send a signal to the process at pid_file.

Parameters:
  • pid_file (str) – The path to the PID file.
  • signal –

    The signal to send. This may be either:

    1. an instance of one of the ReceivedSignal exceptions, for example: daemoniker.SIGINT() (see SIGINT)
    2. the class for one of the ReceivedSignal exceptions, for example: daemoniker.SIGINT (see SIGINT)
    3. an integer-like value, corresponding to the signal number, for example: signal.SIGINT
 
>>> from daemoniker import send
>>> from daemoniker import SIGINT
>>> send('pid.pid', SIGINT)