celery/celery/backends/tyrant.py

"""celery.backends.tyrant"""
from django.core.exceptions import ImproperlyConfigured

try:
    import pytyrant
except ImportError:
    raise ImproperlyConfigured(
            "The Tokyo Tyrant backend requires the pytyrant library.")

from celery.backends.base import KeyValueStoreBackend
from django.conf import settings


class Backend(KeyValueStoreBackend):
    """Tokyo Cabinet based task backend store.

    .. attribute:: tyrant_host

        The hostname to the Tokyo Tyrant server.

    .. attribute:: tyrant_port

        The port to the Tokyo Tyrant server.

    """
    tyrant_host = None
    tyrant_port = None

    def __init__(self, tyrant_host=None, tyrant_port=None):
        """Initialize Tokyo Tyrant backend instance.

        Raises :class:`django.core.exceptions.ImproperlyConfigured` if
        :setting:`TT_HOST` or :setting:`TT_PORT` is not set.

        """
        self.tyrant_host = tyrant_host or \
                            getattr(settings, "TT_HOST", self.tyrant_host)
        self.tyrant_port = tyrant_port or \
                            getattr(settings, "TT_PORT", self.tyrant_port)
        if self.tyrant_port:
            self.tyrant_port = int(self.tyrant_port)
        if not self.tyrant_host or not self.tyrant_port:
            raise ImproperlyConfigured(
                "To use the Tokyo Tyrant backend, you have to "
                "set the TT_HOST and TT_PORT settings in your settings.py")
        super(Backend, self).__init__()
        self._connection = None

    def open(self):
        """Get :class:`pytyrant.PyTyrant`` instance with the current
        server configuration.

        The connection is then cached until you do an
        explicit :meth:`close`.

        """
        # connection overrides bool()
        if self._connection is None:
            self._connection = pytyrant.PyTyrant.open(self.tyrant_host,
                                                      self.tyrant_port)
        return self._connection

    def close(self):
        """Close the tyrant connection and remove the cache."""
        # connection overrides bool()
        if self._connection is not None:
            self._connection.close()
            self._connection = None

    def process_cleanup(self):
        self.close()

    def get(self, key):
        return self.open().get(key)

    def set(self, key, value):
        self.open()[key] = value