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#         http://www.apache.org/licenses/LICENSE-2.0
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from oslo_service import service

from neutron_lib.callbacks import events
from neutron_lib.callbacks import registry
from neutron_lib.callbacks import resources


class BaseWorker(service.ServiceBase):
    """Partial implementation of the ServiceBase ABC.

    Subclasses will still need to add the other abstract methods defined in
    service.ServiceBase. See oslo_service for more details.

    If a plugin needs to handle synchronization with the Neutron database and
    do this only once instead of in every API worker, for instance, it would
    define a BaseWorker class and the plugin would have get_workers return
    an array of BaseWorker instances. For example:

    .. code-block:: python

        class MyPlugin(...):
            def get_workers(self):
                return [MyPluginWorker()]

        class MyPluginWorker(BaseWorker):
            def start(self):
                super(MyPluginWorker, self).start()
                do_sync()
    """

    # default class value for case when super().__init__ is not called
    _default_process_count = 1

    def __init__(self, worker_process_count=_default_process_count):
        """Initialize a worker instance.

        :param worker_process_count: Defines how many processes to spawn for
            worker:
                0 - spawn 1 new worker thread,
                1..N - spawn N new worker processes
        """
        self._worker_process_count = worker_process_count

    @property
    def worker_process_count(self):
        """The worker's process count.

        :returns: The number of processes to spawn for this worker.
        """
        return self._worker_process_count

    def start(self):
        """Start the worker.

        If worker_process_count is greater than 0, a callback notification
        is sent. Subclasses should call this method before doing their
        own start() work.
        :returns: None
        """
        if self.worker_process_count > 0:
            registry.notify(resources.PROCESS, events.AFTER_INIT, self.start)