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Don't hold onto full state in state cache (#13324)
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2 changed files with 55 additions and 16 deletions
1
changelog.d/13324.misc
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1
changelog.d/13324.misc
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@ -0,0 +1 @@
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Reduce the amount of state we store in the `state_cache`.
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@ -14,7 +14,7 @@
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# limitations under the License.
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import heapq
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import logging
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from collections import defaultdict
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from collections import ChainMap, defaultdict
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from typing import (
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TYPE_CHECKING,
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Any,
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@ -92,8 +92,11 @@ class _StateCacheEntry:
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prev_group: Optional[int] = None,
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delta_ids: Optional[StateMap[str]] = None,
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):
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if state is None and state_group is None:
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raise Exception("Either state or state group must be not None")
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if state is None and state_group is None and prev_group is None:
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raise Exception("One of state, state_group or prev_group must be not None")
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if prev_group is not None and delta_ids is None:
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raise Exception("If prev_group is set so must delta_ids")
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# A map from (type, state_key) to event_id.
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#
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@ -120,18 +123,48 @@ class _StateCacheEntry:
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if self._state is not None:
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return self._state
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assert self.state_group is not None
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if self.state_group is not None:
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return await state_storage.get_state_ids_for_group(
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self.state_group, state_filter
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)
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return await state_storage.get_state_ids_for_group(
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self.state_group, state_filter
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assert self.prev_group is not None and self.delta_ids is not None
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prev_state = await state_storage.get_state_ids_for_group(
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self.prev_group, state_filter
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)
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def __len__(self) -> int:
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# The len should is used to estimate how large this cache entry is, for
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# cache eviction purposes. This is why if `self.state` is None it's fine
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# to return 1.
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# ChainMap expects MutableMapping, but since we're using it immutably
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# its safe to give it immutable maps.
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return ChainMap(self.delta_ids, prev_state) # type: ignore[arg-type]
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return len(self._state) if self._state else 1
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def set_state_group(self, state_group: int) -> None:
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"""Update the state group assigned to this state (e.g. after we've
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persisted it).
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Note: this will cause the cache entry to drop any stored state.
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"""
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self.state_group = state_group
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# We clear out the state as we know longer need to explicitly keep it in
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# the `state_cache` (as the store state group cache will do that).
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self._state = None
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def __len__(self) -> int:
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# The len should be used to estimate how large this cache entry is, for
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# cache eviction purposes. This is why it's fine to return 1 if we're
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# not storing any state.
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length = 0
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if self._state:
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length += len(self._state)
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if self.delta_ids:
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length += len(self.delta_ids)
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return length or 1 # Make sure its not 0.
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class StateHandler:
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@ -320,7 +353,7 @@ class StateHandler:
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current_state_ids=state_ids_before_event,
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)
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)
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entry.state_group = state_group_before_event
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entry.set_state_group(state_group_before_event)
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else:
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state_group_before_event = entry.state_group
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@ -747,7 +780,7 @@ def _make_state_cache_entry(
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old_state_event_ids = set(state.values())
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if new_state_event_ids == old_state_event_ids:
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# got an exact match.
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return _StateCacheEntry(state=new_state, state_group=sg)
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return _StateCacheEntry(state=None, state_group=sg)
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# TODO: We want to create a state group for this set of events, to
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# increase cache hits, but we need to make sure that it doesn't
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@ -769,9 +802,14 @@ def _make_state_cache_entry(
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prev_group = old_group
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delta_ids = n_delta_ids
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return _StateCacheEntry(
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state=new_state, state_group=None, prev_group=prev_group, delta_ids=delta_ids
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)
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if prev_group is not None:
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# If we have a prev group and deltas then we can drop the new state from
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# the cache (to reduce memory usage).
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return _StateCacheEntry(
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state=None, state_group=None, prev_group=prev_group, delta_ids=delta_ids
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)
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else:
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return _StateCacheEntry(state=new_state, state_group=None)
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@attr.s(slots=True, auto_attribs=True)
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