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https://git.anonymousland.org/anonymousland/synapse.git
synced 2025-05-06 11:34:59 -04:00
Speed up @cachedList (#13591)
This speeds things up by ~2x. The vast majority of the time is now spent in `LruCache` moving things around the linked lists. We do this via two things: 1. Don't create a deferred per-key during bulk set operations in `DeferredCache`. Instead, only create them if a subsequent caller asks for the key. 2. Add a bulk lookup API to `DeferredCache` rather than use a loop.
This commit is contained in:
Erik Johnston
GitHub
parent
05c9c7363b
commit
f7ddfe17a3
4 changed files with 298 additions and 141 deletions
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@ -14,15 +14,19 @@
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import abc
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import enum
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import threading
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from typing import (
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Callable,
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Collection,
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Dict,
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Generic,
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Iterable,
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MutableMapping,
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Optional,
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Set,
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Sized,
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Tuple,
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TypeVar,
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Union,
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cast,
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@ -31,7 +35,6 @@ from typing import (
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from prometheus_client import Gauge
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from twisted.internet import defer
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from twisted.python import failure
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from twisted.python.failure import Failure
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from synapse.util.async_helpers import ObservableDeferred
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@ -94,7 +97,7 @@ class DeferredCache(Generic[KT, VT]):
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# _pending_deferred_cache maps from the key value to a `CacheEntry` object.
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self._pending_deferred_cache: Union[
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TreeCache, "MutableMapping[KT, CacheEntry]"
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TreeCache, "MutableMapping[KT, CacheEntry[KT, VT]]"
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] = cache_type()
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def metrics_cb() -> None:
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@ -159,15 +162,16 @@ class DeferredCache(Generic[KT, VT]):
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Raises:
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KeyError if the key is not found in the cache
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"""
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callbacks = [callback] if callback else []
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val = self._pending_deferred_cache.get(key, _Sentinel.sentinel)
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if val is not _Sentinel.sentinel:
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val.callbacks.update(callbacks)
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val.add_invalidation_callback(key, callback)
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if update_metrics:
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m = self.cache.metrics
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assert m # we always have a name, so should always have metrics
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m.inc_hits()
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return val.deferred.observe()
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return val.deferred(key)
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callbacks = (callback,) if callback else ()
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val2 = self.cache.get(
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key, _Sentinel.sentinel, callbacks=callbacks, update_metrics=update_metrics
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@ -177,6 +181,73 @@ class DeferredCache(Generic[KT, VT]):
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else:
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return defer.succeed(val2)
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def get_bulk(
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self,
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keys: Collection[KT],
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callback: Optional[Callable[[], None]] = None,
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) -> Tuple[Dict[KT, VT], Optional["defer.Deferred[Dict[KT, VT]]"], Collection[KT]]:
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"""Bulk lookup of items in the cache.
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Returns:
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A 3-tuple of:
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1. a dict of key/value of items already cached;
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2. a deferred that resolves to a dict of key/value of items
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we're already fetching; and
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3. a collection of keys that don't appear in the previous two.
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"""
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# The cached results
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cached = {}
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# List of pending deferreds
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pending = []
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# Dict that gets filled out when the pending deferreds complete
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pending_results = {}
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# List of keys that aren't in either cache
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missing = []
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callbacks = (callback,) if callback else ()
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for key in keys:
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# Check if its in the main cache.
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immediate_value = self.cache.get(
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key,
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_Sentinel.sentinel,
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callbacks=callbacks,
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)
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if immediate_value is not _Sentinel.sentinel:
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cached[key] = immediate_value
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continue
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# Check if its in the pending cache
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pending_value = self._pending_deferred_cache.get(key, _Sentinel.sentinel)
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if pending_value is not _Sentinel.sentinel:
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pending_value.add_invalidation_callback(key, callback)
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def completed_cb(value: VT, key: KT) -> VT:
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pending_results[key] = value
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return value
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# Add a callback to fill out `pending_results` when that completes
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d = pending_value.deferred(key).addCallback(completed_cb, key)
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pending.append(d)
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continue
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# Not in either cache
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missing.append(key)
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# If we've got pending deferreds, squash them into a single one that
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# returns `pending_results`.
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pending_deferred = None
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if pending:
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pending_deferred = defer.gatherResults(
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pending, consumeErrors=True
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).addCallback(lambda _: pending_results)
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return (cached, pending_deferred, missing)
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def get_immediate(
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self, key: KT, default: T, update_metrics: bool = True
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) -> Union[VT, T]:
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@ -218,84 +289,89 @@ class DeferredCache(Generic[KT, VT]):
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value: a deferred which will complete with a result to add to the cache
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callback: An optional callback to be called when the entry is invalidated
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"""
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if not isinstance(value, defer.Deferred):
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raise TypeError("not a Deferred")
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callbacks = [callback] if callback else []
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self.check_thread()
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existing_entry = self._pending_deferred_cache.pop(key, None)
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if existing_entry:
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existing_entry.invalidate()
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self._pending_deferred_cache.pop(key, None)
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# XXX: why don't we invalidate the entry in `self.cache` yet?
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# we can save a whole load of effort if the deferred is ready.
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if value.called:
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result = value.result
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if not isinstance(result, failure.Failure):
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self.cache.set(key, cast(VT, result), callbacks)
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return value
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# otherwise, we'll add an entry to the _pending_deferred_cache for now,
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# and add callbacks to add it to the cache properly later.
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observable = ObservableDeferred(value, consumeErrors=True)
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observer = observable.observe()
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entry = CacheEntry(deferred=observable, callbacks=callbacks)
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entry = CacheEntrySingle[KT, VT](value)
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entry.add_invalidation_callback(key, callback)
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self._pending_deferred_cache[key] = entry
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def compare_and_pop() -> bool:
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"""Check if our entry is still the one in _pending_deferred_cache, and
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if so, pop it.
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Returns true if the entries matched.
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"""
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existing_entry = self._pending_deferred_cache.pop(key, None)
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if existing_entry is entry:
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return True
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# oops, the _pending_deferred_cache has been updated since
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# we started our query, so we are out of date.
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#
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# Better put back whatever we took out. (We do it this way
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# round, rather than peeking into the _pending_deferred_cache
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# and then removing on a match, to make the common case faster)
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if existing_entry is not None:
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self._pending_deferred_cache[key] = existing_entry
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return False
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def cb(result: VT) -> None:
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if compare_and_pop():
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self.cache.set(key, result, entry.callbacks)
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else:
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# we're not going to put this entry into the cache, so need
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# to make sure that the invalidation callbacks are called.
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# That was probably done when _pending_deferred_cache was
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# updated, but it's possible that `set` was called without
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# `invalidate` being previously called, in which case it may
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# not have been. Either way, let's double-check now.
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entry.invalidate()
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def eb(_fail: Failure) -> None:
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compare_and_pop()
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entry.invalidate()
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# once the deferred completes, we can move the entry from the
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# _pending_deferred_cache to the real cache.
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#
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observer.addCallbacks(cb, eb)
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deferred = entry.deferred(key).addCallbacks(
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self._completed_callback,
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self._error_callback,
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callbackArgs=(entry, key),
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errbackArgs=(entry, key),
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)
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# we return a new Deferred which will be called before any subsequent observers.
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return observable.observe()
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return deferred
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def start_bulk_input(
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self,
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keys: Collection[KT],
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callback: Optional[Callable[[], None]] = None,
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) -> "CacheMultipleEntries[KT, VT]":
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"""Bulk set API for use when fetching multiple keys at once from the DB.
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Called *before* starting the fetch from the DB, and the caller *must*
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call either `complete_bulk(..)` or `error_bulk(..)` on the return value.
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"""
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entry = CacheMultipleEntries[KT, VT]()
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entry.add_global_invalidation_callback(callback)
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for key in keys:
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self._pending_deferred_cache[key] = entry
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return entry
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def _completed_callback(
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self, value: VT, entry: "CacheEntry[KT, VT]", key: KT
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) -> VT:
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"""Called when a deferred is completed."""
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# We check if the current entry matches the entry associated with the
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# deferred. If they don't match then it got invalidated.
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current_entry = self._pending_deferred_cache.pop(key, None)
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if current_entry is not entry:
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if current_entry:
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self._pending_deferred_cache[key] = current_entry
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return value
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self.cache.set(key, value, entry.get_invalidation_callbacks(key))
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return value
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def _error_callback(
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self,
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failure: Failure,
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entry: "CacheEntry[KT, VT]",
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key: KT,
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) -> Failure:
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"""Called when a deferred errors."""
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# We check if the current entry matches the entry associated with the
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# deferred. If they don't match then it got invalidated.
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current_entry = self._pending_deferred_cache.pop(key, None)
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if current_entry is not entry:
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if current_entry:
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self._pending_deferred_cache[key] = current_entry
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return failure
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for cb in entry.get_invalidation_callbacks(key):
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cb()
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return failure
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def prefill(
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self, key: KT, value: VT, callback: Optional[Callable[[], None]] = None
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) -> None:
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callbacks = [callback] if callback else []
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callbacks = (callback,) if callback else ()
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self.cache.set(key, value, callbacks=callbacks)
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self._pending_deferred_cache.pop(key, None)
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def invalidate(self, key: KT) -> None:
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"""Delete a key, or tree of entries
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@ -311,41 +387,129 @@ class DeferredCache(Generic[KT, VT]):
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self.cache.del_multi(key)
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# if we have a pending lookup for this key, remove it from the
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# _pending_deferred_cache, which will (a) stop it being returned
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# for future queries and (b) stop it being persisted as a proper entry
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# _pending_deferred_cache, which will (a) stop it being returned for
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# future queries and (b) stop it being persisted as a proper entry
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# in self.cache.
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entry = self._pending_deferred_cache.pop(key, None)
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# run the invalidation callbacks now, rather than waiting for the
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# deferred to resolve.
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if entry:
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# _pending_deferred_cache.pop should either return a CacheEntry, or, in the
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# case of a TreeCache, a dict of keys to cache entries. Either way calling
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# iterate_tree_cache_entry on it will do the right thing.
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for entry in iterate_tree_cache_entry(entry):
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entry.invalidate()
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for cb in entry.get_invalidation_callbacks(key):
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cb()
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def invalidate_all(self) -> None:
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self.check_thread()
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self.cache.clear()
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for entry in self._pending_deferred_cache.values():
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entry.invalidate()
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for key, entry in self._pending_deferred_cache.items():
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for cb in entry.get_invalidation_callbacks(key):
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cb()
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self._pending_deferred_cache.clear()
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class CacheEntry:
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__slots__ = ["deferred", "callbacks", "invalidated"]
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class CacheEntry(Generic[KT, VT], metaclass=abc.ABCMeta):
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"""Abstract class for entries in `DeferredCache[KT, VT]`"""
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def __init__(
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self, deferred: ObservableDeferred, callbacks: Iterable[Callable[[], None]]
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):
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self.deferred = deferred
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self.callbacks = set(callbacks)
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self.invalidated = False
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@abc.abstractmethod
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def deferred(self, key: KT) -> "defer.Deferred[VT]":
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"""Get a deferred that a caller can wait on to get the value at the
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given key"""
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...
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def invalidate(self) -> None:
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if not self.invalidated:
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self.invalidated = True
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for callback in self.callbacks:
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callback()
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self.callbacks.clear()
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@abc.abstractmethod
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def add_invalidation_callback(
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self, key: KT, callback: Optional[Callable[[], None]]
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) -> None:
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"""Add an invalidation callback"""
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...
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@abc.abstractmethod
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def get_invalidation_callbacks(self, key: KT) -> Collection[Callable[[], None]]:
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"""Get all invalidation callbacks"""
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...
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class CacheEntrySingle(CacheEntry[KT, VT]):
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"""An implementation of `CacheEntry` wrapping a deferred that results in a
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single cache entry.
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"""
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__slots__ = ["_deferred", "_callbacks"]
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def __init__(self, deferred: "defer.Deferred[VT]") -> None:
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self._deferred = ObservableDeferred(deferred, consumeErrors=True)
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self._callbacks: Set[Callable[[], None]] = set()
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def deferred(self, key: KT) -> "defer.Deferred[VT]":
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return self._deferred.observe()
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def add_invalidation_callback(
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self, key: KT, callback: Optional[Callable[[], None]]
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) -> None:
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if callback is None:
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return
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self._callbacks.add(callback)
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def get_invalidation_callbacks(self, key: KT) -> Collection[Callable[[], None]]:
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return self._callbacks
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class CacheMultipleEntries(CacheEntry[KT, VT]):
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"""Cache entry that is used for bulk lookups and insertions."""
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__slots__ = ["_deferred", "_callbacks", "_global_callbacks"]
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def __init__(self) -> None:
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self._deferred: Optional[ObservableDeferred[Dict[KT, VT]]] = None
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self._callbacks: Dict[KT, Set[Callable[[], None]]] = {}
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self._global_callbacks: Set[Callable[[], None]] = set()
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def deferred(self, key: KT) -> "defer.Deferred[VT]":
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if not self._deferred:
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self._deferred = ObservableDeferred(defer.Deferred(), consumeErrors=True)
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return self._deferred.observe().addCallback(lambda res: res.get(key))
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def add_invalidation_callback(
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self, key: KT, callback: Optional[Callable[[], None]]
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) -> None:
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if callback is None:
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return
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self._callbacks.setdefault(key, set()).add(callback)
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def get_invalidation_callbacks(self, key: KT) -> Collection[Callable[[], None]]:
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return self._callbacks.get(key, set()) | self._global_callbacks
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def add_global_invalidation_callback(
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self, callback: Optional[Callable[[], None]]
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) -> None:
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"""Add a callback for when any keys get invalidated."""
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if callback is None:
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return
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self._global_callbacks.add(callback)
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def complete_bulk(
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self,
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cache: DeferredCache[KT, VT],
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result: Dict[KT, VT],
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) -> None:
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"""Called when there is a result"""
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for key, value in result.items():
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cache._completed_callback(value, self, key)
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if self._deferred:
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self._deferred.callback(result)
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def error_bulk(
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self, cache: DeferredCache[KT, VT], keys: Collection[KT], failure: Failure
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) -> None:
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"""Called when bulk lookup failed."""
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for key in keys:
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cache._error_callback(failure, self, key)
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if self._deferred:
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self._deferred.errback(failure)
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