Function daemonizing

src/borg/helpers/process.py:66–147

Like daemonize(), but as a context manager. The with-body is executed in the background process, while the foreground process survives until the body is left or the given timeout is exceeded. In the latter case a warning is reported by the foreground. Context variable is (old_id

(*, timeout=5, show_rc=False)

@contextlib.contextmanager
def daemonizing(*, timeout=5, show_rc=False):
    """Like daemonize(), but as a context manager.

    The with-body is executed in the background process,
    while the foreground process survives until the body is left
    or the given timeout is exceeded. In the latter case a warning is
    reported by the foreground.
    Context variable is (old_id, new_id) get_process_id tuples.
    An exception raised in the body is reported by the foreground
    as a warning as well as propagated outside the body in the background.
    In case of a warning, the foreground exits with exit code EXIT_WARNING
    instead of EXIT_SUCCESS.
    """
    with _daemonize() as (old_id, new_id):
        if new_id is None:
            # The original / parent process, waiting for a signal to die.
            logger.debug("Daemonizing: Foreground process (%s, %s, %s) is waiting for background process..." % old_id)
            exit_code = EXIT_SUCCESS
            # Indeed, SIGHUP and SIGTERM handlers should have been set on archiver.run(). Just in case...
            with (
                signal_handler("SIGINT", raising_signal_handler(KeyboardInterrupt)),
                signal_handler("SIGHUP", raising_signal_handler(SigHup)),
                signal_handler("SIGTERM", raising_signal_handler(SigTerm)),
            ):
                try:
                    if timeout > 0:
                        time.sleep(timeout)
                except SigTerm:
                    # Normal termination; expected from grandchild, see 'os.kill()' below
                    pass
                except SigHup:
                    # Background wants to indicate a problem; see 'os.kill()' below,
                    # log message will come from grandchild.
                    exit_code = EXIT_WARNING
                except KeyboardInterrupt:
                    # Manual termination.
                    logger.debug("Daemonizing: Foreground process (%s, %s, %s) received SIGINT." % old_id)
                    exit_code = EXIT_SIGNAL_BASE + 2
                except BaseException as e:
                    # Just in case...
                    logger.warning(
                        "Daemonizing: Foreground process received an exception while waiting:\n"
                        + "".join(traceback.format_exception(e.__class__, e, e.__traceback__))
                    )
                    exit_code = EXIT_WARNING
                else:
                    logger.warning("Daemonizing: Background process did not respond (timeout). Is it alive?")
                    exit_code = EXIT_WARNING
                finally:
                    # Before terminating the foreground process, honor --show-rc by logging the rc here as well.
                    # This is mostly a consistency fix and not very useful considering that the main action
                    # happens in the daemon process.
                    if show_rc:
                        from ..helpers import do_show_rc

                        do_show_rc(exit_code)
                    # Don't call with-body, but die immediately!
                    # return would be sufficient, but we want to pass the exit code.