def lookup(key, options):
"""Look up a Datastore entity.
Gets an entity from Datastore, asynchronously. Checks the global cache,
first, if appropriate. Uses batching.
Args:
key (~datastore.Key): The key for the entity to retrieve.
options (_options.ReadOptions): The options for the request. For
example, ``{"read_consistency": EVENTUAL}``.
Returns:
:class:`~tasklets.Future`: If not an exception, future's result will be
either an entity protocol buffer or _NOT_FOUND.
"""
context = context_module.get_context()
use_datastore = context._use_datastore(key, options)
if use_datastore and options.transaction:
use_global_cache = False
else:
use_global_cache = context._use_global_cache(key, options)
if not (use_global_cache or use_datastore):
raise TypeError(
"use_global_cache and use_datastore can't both be False")
entity_pb = _NOT_FOUND
key_locked = False
if use_global_cache:
cache_key = _cache.global_cache_key(key)
result = yield _cache.global_get(cache_key)
key_locked = _cache.is_locked_value(result)
if not key_locked:
if result is not None:
entity_pb = entity_pb2.Entity()
entity_pb.MergeFromString(result)
elif use_datastore:
yield _cache.global_lock(cache_key, read=True)
yield _cache.global_watch(cache_key)
if entity_pb is _NOT_FOUND and use_datastore:
batch = _batch.get_batch(_LookupBatch, options)
entity_pb = yield batch.add(key)
# Do not cache misses
if use_global_cache and not key_locked:
if entity_pb is not _NOT_FOUND:
expires = context._global_cache_timeout(key, options)
serialized = entity_pb.SerializeToString()
yield _cache.global_compare_and_swap(cache_key,
serialized,
expires=expires)
else:
yield _cache.global_unwatch(cache_key)
raise tasklets.Return(entity_pb)
def test_global_watch(_batch, _global_cache):
batch = _batch.get_batch.return_value
future = _future_result("hi mom!")
batch.add.return_value = future
_global_cache.return_value = mock.Mock(
transient_errors=(),
strict_read=False,
spec=("transient_errors", "strict_read"),
)
assert _cache.global_watch(b"key", b"value").result() == "hi mom!"
_batch.get_batch.assert_called_once_with(_cache._GlobalCacheWatchBatch, {})
batch.add.assert_called_once_with(b"key", b"value")
def test_global_watch(_batch):
batch = _batch.get_batch.return_value
assert _cache.global_watch(b"key") is batch.add.return_value
_batch.get_batch.assert_called_once_with(_cache._GlobalCacheWatchBatch)
batch.add.assert_called_once_with(b"key")