airflow/listeners/listener.py

#
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# to you under the Apache License, Version 2.0 (the
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from __future__ import annotations

import logging
from typing import TYPE_CHECKING

import pluggy

from airflow.plugins_manager import integrate_listener_plugins

if TYPE_CHECKING:
    from pluggy._hooks import _HookRelay

log = logging.getLogger(__name__)


_listener_manager: ListenerManager | None = None


class ListenerManager:
    """Manage listener registration and provides hook property for calling them."""

    def __init__(self):
        from airflow.listeners.spec import dagrun, lifecycle, taskinstance

        self.pm = pluggy.PluginManager("airflow")
        self.pm.add_hookspecs(lifecycle)
        self.pm.add_hookspecs(dagrun)
        self.pm.add_hookspecs(taskinstance)

    @property
    def has_listeners(self) -> bool:
        return len(self.pm.get_plugins()) > 0

    @property
    def hook(self) -> _HookRelay:
        """Return hook, on which plugin methods specified in spec can be called."""
        return self.pm.hook

    def add_listener(self, listener):
        if self.pm.is_registered(listener):
            return
        self.pm.register(listener)

    def clear(self):
        """Remove registered plugins."""
        for plugin in self.pm.get_plugins():
            self.pm.unregister(plugin)


def get_listener_manager() -> ListenerManager:
    """Get singleton listener manager."""
    global _listener_manager
    if not _listener_manager:
        _listener_manager = ListenerManager()
        integrate_listener_plugins(_listener_manager)
    return _listener_manager