handlers.py 文件源码

def _try_free_lease(self, shard_state, slice_retry=False):
    """Try to free lease.

    A lightweight transaction to update shard_state and unset
    slice_start_time to allow the next retry to happen without blocking.
    We don't care if this fails or not because the lease will expire
    anyway.

    Under normal execution, _save_state_and_schedule_next is the exit point.
    It updates/saves shard state and schedules the next slice or returns.
    Other exit points are:
    1. _are_states_consistent: at the beginning of handle, checks
      if datastore states and the task are in sync.
      If not, raise or return.
    2. _attempt_slice_retry: may raise exception to taskqueue.
    3. _save_state_and_schedule_next: may raise exception when taskqueue/db
       unreachable.

    This handler should try to free the lease on every exceptional exit point.

    Args:
      shard_state: model.ShardState.
      slice_retry: whether to count this as a failed slice execution.
    """
    @db.transactional
    def _tx():
      fresh_state = model.ShardState.get_by_shard_id(shard_state.shard_id)
      if fresh_state and fresh_state.active:

        fresh_state.slice_start_time = None
        fresh_state.slice_request_id = None
        if slice_retry:
          fresh_state.slice_retries += 1
        fresh_state.put()
    try:
      _tx()

    except Exception, e:
      logging.warning(e)
      logging.warning(
          "Release lock for shard %s failed. Wait for lease to expire.",
          shard_state.shard_id)