如何实现支持命名空间的 FIFO 队列

I'm using the following approach to handle a FIFO queue based on Google App Engine db.Model (see this question).

from google.appengine.ext import db
from google.appengine.ext import webapp
from google.appengine.ext.webapp import run_wsgi_app

class QueueItem(db.Model):
  created = db.DateTimeProperty(required=True, auto_now_add=True)
  data = db.BlobProperty(required=True)

  @staticmethod
  def push(data):
    """Add a new queue item."""
    return QueueItem(data=data).put()

  @staticmethod
  def pop():
    """Pop the oldest item off the queue."""
    def _tx_pop(candidate_key):
      # Try and grab the candidate key for ourselves. This will fail if
      # another task beat us to it.
      task = QueueItem.get(candidate_key)
      if task:
        task.delete()
      return task
    # Grab some tasks and try getting them until we find one that hasn't been
    # taken by someone else ahead of us
    while True:
      candidate_keys = QueueItem.all(keys_only=True).order('created').fetch(10)
      if not candidate_keys:
        # No tasks in queue
        return None
      for candidate_key in candidate_keys:
        task = db.run_in_transaction(_tx_pop, candidate_key)
        if task:
          return task

此队列按预期工作(非常好).

def deferred_worker():
        data= QueueItem.pop()
        do_something_with(data)

def deferred_worker(client_ID):
        data= QueueItem_of_this_client_ID.pop() # I need to implement this
        do_something_with(data)

QueueItem.all(keys_only=True).filter(client_ID=an_ID).order('created').fetch(10)

from google.appengine.api import users
from google.appengine.api.namespace_manager import set_namespace

class ClientClass(webapp.RequestHandler):
  def get(self):
    # For this example let's assume the user_id is your unique id.
    # You could just as easily use a parameter you are passed.
    user = users.get_current_user()
    if user:
       # If there is a user, use their queue.  Otherwise the global queue.
       set_namespace(user.user_id())

    item = QueueItem.pop()
    self.response.out.write(str(item))

    QueueItem.push('The next task.')