Source code for dramatiq.middleware.current_message

# This file is a part of Dramatiq.
#
# Copyright (C) 2019 CLEARTYPE SRL <[email protected]>
#
# Dramatiq is free software; you can redistribute it and/or modify it
# under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation, either version 3 of the License, or (at
# your option) any later version.
#
# Dramatiq is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
# FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
# License for more details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

from threading import local

from .middleware import Middleware


class CurrentMessage(Middleware):
    """Middleware that exposes the current message via a thread-local
    variable.

    Example:
      >>> import dramatiq
      >>> from dramatiq.middleware import CurrentMessage

      >>> @dramatiq.actor
      ... def example(x):
      ...     print(CurrentMessage.get_current_message())
      ...
      >>> example.send(1)

    """

    STATE = local()

    @classmethod
    def get_current_message(cls):
        """Get the message that triggered the current actor.  Messages
        are thread local so this returns ``None`` when called outside
        of actor code.
        """
        return getattr(cls.STATE, "message", None)

    def before_process_message(self, broker, message):
        setattr(self.STATE, "message", message)

    def after_process_message(self, broker, message, *, result=None, exception=None):
        delattr(self.STATE, "message")