repository.py

#
# Repository abstraction for queuing
#

import weakref
from scheduler import QueueThread, QueuedEvent

class FIFOEvent(QueuedEvent):
    def __init__(self, cond, name=None):
        self._goodtogo=False
        super().__init__(cond, name=name)

    def __lt__(self, other):
        return True

class FIFO(QueueThread):
    def __init__(self, **kwargs):
        super().__init__(target = self._fifo_thread, **kwargs)

    def _fifo_thread(self):
        with self._cond:
            while not self._terminate:
                ev=self._list
                if ev:
                    # We can only remove ev from the list when ev.cond allows
                    with ev.cond:
                        ev._goodtogo=True
                        ev.cond.notifyAll()
                self._cond.wait()

            # Termination cleanup
            ev=self._list
            while ev:
                # We can only remove ev from the list when ev.cond allows
                with ev.cond:
                    ev.cond.notifyAll()
                    ev=ev.next

    # cond has to be acquired on entry!
    def queue_action(self, cond, action=lambda: (), name=None):
        ev=FIFOEvent(cond, name=name)

        with self._cond:
            self._insert(ev)

        goodtogo=False
        terminate_=False
        while not goodtogo and not terminate_:
            # This will release the lock on cond, allowing queue manager (scheduler)
            # thread to notify us if we are already to be released
            ev.cond.wait()
            with ev.cond:
                goodtogo=ev._goodtogo
            with self._cond:
                terminate_=self._terminate

        try:
            if not terminate_:
                action()
        finally:
            with self._cond:
                self._unlink(ev)
                # Let _fifo_thread proceed to next action
                self._cond.notify()

class Repository(FIFO):
    def __init__(self, name):
        super().__init__(name = 'RepositoryThread %s' % name)
        self.repository_name=name


# TODO: Should use weak references but they give KeyError
repositories=weakref.WeakValueDictionary()

def get_controller(name):
    if name in repositories:
        repo = repositories[name]
    else:
        repo = Repository(name)
        repo.start()
        repositories[name] = repo
    return repo