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checkpoint: mostly what I wanted here

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This commit is contained in:
Olivier Wilkinson (reivilibre)
2021-08-23 18:52:56 +01:00
parent eda19443ab
commit 42da29594f
2 changed files with 392 additions and 26 deletions
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208
synapse/storage/databases/state/store.py
View File

@@ -14,9 +14,14 @@
import logging
from collections import namedtuple
from typing import Dict, Iterable, List, Optional, Set, Tuple
from typing import Any, Dict, FrozenSet, Iterable, List, Optional, Set, Tuple, Union
import attr
from twisted.internet.defer import Deferred
from synapse.api.constants import EventTypes
from synapse.logging.context import make_deferred_yieldable
from synapse.storage._base import SQLBaseStore
from synapse.storage.database import DatabasePool
from synapse.storage.databases.state.bg_updates import StateBackgroundUpdateStore
@@ -26,9 +31,12 @@ from synapse.storage.util.sequence import build_sequence_generator
from synapse.types import MutableStateMap, StateMap
from synapse.util.caches.descriptors import cached
from synapse.util.caches.dictionary_cache import DictionaryCache
from synapse.util.caches.multi_key_response_cache import MultiKeyResponseCache
logger = logging.getLogger(__name__)
# XXX
UNKNOWN = Any # TODO
MAX_STATE_DELTA_HOPS = 100
@@ -91,6 +99,18 @@ class StateGroupDataStore(StateBackgroundUpdateStore, SQLBaseStore):
500000,
)
# XXX ADD TYPE
self._state_group_inflight_cache: MultiKeyResponseCache[
...
] = MultiKeyResponseCache(
self.hs.get_clock(),
"*stateGroupInflightCache*",
# As the results from this transaction immediately go into the
# immediate caches _state_group_cache and _state_group_members_cache,
# we do not keep them in the in-flight cache when done.
timeout_ms=0,
)
def get_max_state_group_txn(txn: Cursor):
txn.execute("SELECT COALESCE(max(id), 0) FROM state_groups")
return txn.fetchone()[0]
@@ -168,13 +188,18 @@ class StateGroupDataStore(StateBackgroundUpdateStore, SQLBaseStore):
return results
def _get_state_for_group_using_cache(self, cache, group, state_filter):
def _get_state_for_group_using_cache(
self,
cache: DictionaryCache[int, UNKNOWN],
group: int,
state_filter: StateFilter,
) -> Tuple[MutableStateMap[UNKNOWN], bool]:
"""Checks if group is in cache. See `_get_state_for_groups`
Args:
cache(DictionaryCache): the state group cache to use
group(int): The state group to lookup
state_filter (StateFilter): The state filter used to fetch state
cache: the state group cache to use
group: The state group to lookup
state_filter: The state filter used to fetch state
from the database.
Returns 2-tuple (`state_dict`, `got_all`).
@@ -212,7 +237,7 @@ class StateGroupDataStore(StateBackgroundUpdateStore, SQLBaseStore):
self, groups: Iterable[int], state_filter: Optional[StateFilter] = None
) -> Dict[int, MutableStateMap[str]]:
"""Gets the state at each of a list of state groups, optionally
filtering by type/state_key
filtering by type/state_key.
Args:
groups: list of state groups for which we want
@@ -221,11 +246,38 @@ class StateGroupDataStore(StateBackgroundUpdateStore, SQLBaseStore):
from the database.
Returns:
Dict of state group to state map.
"""
state_filter = state_filter or StateFilter.all()
The flow for this function looks as follows:
* Query the immediate caches (self._state_group_cache,
| self._state_group_members_cache).
NONSTOP |
|
* Query the in-flight cache (self._state_group_inflight_cache)
| for immediate-cache misses.
NONSTOP |
|
* Service cache misses:
| - Expand the state filter (to help cache hit ratio).
| - Start a new transaction to fetch outstanding groups.
| - Register entries in the in-flight cache for this transaction.
| - (When the transaction is finished) Register entries in
| the immediate caches.
|
* Wait for in-flight requests to finish...
|
* Assemble everything together and filter out anything we didn't
ask for.
The sections marked NONSTOP must not contain any `await`s, otherwise
race conditions could occur and the cache could be made less effective.
"""
state_filter = state_filter or StateFilter.all()
member_filter, non_member_filter = state_filter.get_member_split()
# QUERY THE IMMEDIATE CACHES
# Now we look them up in the member and non-member caches
(
non_member_state,
@@ -242,43 +294,147 @@ class StateGroupDataStore(StateBackgroundUpdateStore, SQLBaseStore):
for group in groups:
state[group].update(member_state[group])
# Now fetch any missing groups from the database
incomplete_groups = incomplete_groups_m | incomplete_groups_nm
if not incomplete_groups:
return state
cache_sequence_nm = self._state_group_cache.sequence
cache_sequence_m = self._state_group_members_cache.sequence
# QUERY THE IN-FLIGHT CACHE
# list (group ID -> Deferred that will contain a result for that group)
inflight_requests: List[Tuple[int, Deferred[Dict[int, StateMap[str]]]]] = []
inflight_cache_misses: List[int] = []
# Help the cache hit ratio by expanding the filter a bit
# When we get around to requesting state from the database, we help the
# cache hit ratio by expanding the filter a bit.
# However, we need to know this now so that we can properly query the
# in-flight cache where include_others is concerned.
db_state_filter = state_filter.return_expanded()
group_to_state_dict = await self._get_state_groups_from_groups(
list(incomplete_groups), state_filter=db_state_filter
)
for group in incomplete_groups:
event_type: str
state_keys: Optional[FrozenSet[str]]
# Now lets update the caches
self._insert_into_cache(
group_to_state_dict,
db_state_filter,
cache_seq_num_members=cache_sequence_m,
cache_seq_num_non_members=cache_sequence_nm,
)
# First check if our exact state filter is being looked up.
result = self._state_group_inflight_cache.get((group, db_state_filter))
if result is not None:
inflight_requests.append((group, make_deferred_yieldable(result)))
continue
# Then check if the universal state filter is being looked up.
result = self._state_group_inflight_cache.get((group, StateFilter.all()))
if result is not None:
inflight_requests.append((group, make_deferred_yieldable(result)))
continue
if state_filter.include_others:
# if the state filter includes others, we only match against the
# state filter directly, so we give up here.
# This is because it's too complex to cache this case properly.
inflight_cache_misses.append(group)
continue
elif not db_state_filter.include_others:
# TODO IS THIS USEFUL
# Try looking to see if the same filter but with include_others
# is being looked up.
result = self._state_group_inflight_cache.get(
(group, attr.evolve(db_state_filter, include_others=True))
)
if result is not None:
inflight_requests.append((group, make_deferred_yieldable(result)))
continue
for event_type, state_keys in state_filter.types.items():
result = self._state_group_inflight_cache.get((group, event_type, None))
if result is not None:
inflight_requests.append((group, make_deferred_yieldable(result)))
continue
if state_keys is not None:
got_all_state_keys = False
for state_key in state_keys:
result = self._state_group_inflight_cache.get(
(group, event_type, state_key)
)
if result is not None:
inflight_requests.append(
(group, make_deferred_yieldable(result))
)
else:
break
else:
got_all_state_keys = True
if not got_all_state_keys:
# we still have to request against this group.
inflight_cache_misses.append(group)
break
# SERVICE CACHE MISSES
if inflight_cache_misses:
cache_sequence_nm = self._state_group_cache.sequence
cache_sequence_m = self._state_group_members_cache.sequence
async def get_state_groups_from_groups_then_add_to_cache() -> Dict[
int, StateMap[str]
]:
groups_to_state_dict = await self._get_state_groups_from_groups(
list(inflight_cache_misses), state_filter=db_state_filter
)
# Now let's update the caches.
self._insert_into_cache(
groups_to_state_dict,
db_state_filter,
cache_seq_num_members=cache_sequence_m,
cache_seq_num_non_members=cache_sequence_nm,
)
return groups_to_state_dict
# make a list of keys for us to store in the in-flight cache
# this should list all the keys that the request will pick up from
# the database.
keys: List[
Union[Tuple[int, StateFilter], Tuple[int, str, Optional[str]]]
] = []
for group in inflight_cache_misses:
if db_state_filter.include_others:
# we can't intelligently cache include_others under any other keys
# because we don't know what keys are included.
keys.append((group, db_state_filter))
continue
for event_type, state_keys in db_state_filter.types.items():
if state_keys is None:
keys.append((group, event_type, None))
else:
for state_key in state_keys:
keys.append((group, event_type, state_key))
spawned_request = self._state_group_inflight_cache.set_and_compute(
tuple(keys), get_state_groups_from_groups_then_add_to_cache
)
for group in inflight_cache_misses:
inflight_requests.append((group, spawned_request))
# WAIT FOR IN-FLIGHT REQUESTS TO FINISH
for group, inflight_request in inflight_requests:
request_result = await inflight_request
state[group].update(request_result[group])
# ASSEMBLE
# And finally update the result dict, by filtering out any extra
# stuff we pulled out of the database.
for group, group_state_dict in group_to_state_dict.items():
for group in groups:
# We just replace any existing entries, as we will have loaded
# everything we need from the database anyway.
state[group] = state_filter.filter_state(group_state_dict)
state[group] = state_filter.filter_state(state[group])
return state
def _get_state_for_groups_using_cache(
self, groups: Iterable[int], cache: DictionaryCache, state_filter: StateFilter
) -> Tuple[Dict[int, StateMap[str]], Set[int]]:
) -> Tuple[Dict[int, MutableStateMap[str]], Set[int]]:
"""Gets the state at each of a list of state groups, optionally
filtering by type/state_key, querying from a specific cache.

210
synapse/util/caches/multi_key_response_cache.py Normal file
View File

@@ -0,0 +1,210 @@
# Copyright 2016 OpenMarket Ltd
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import logging
from typing import Any, Awaitable, Callable, Dict, Generic, Optional, Tuple, TypeVar
import attr
from twisted.internet import defer
from synapse.logging.context import make_deferred_yieldable, run_in_background
from synapse.util import Clock
from synapse.util.async_helpers import ObservableDeferred
from synapse.util.caches import register_cache
logger = logging.getLogger(__name__)
# the type of the key in the cache
KV = TypeVar("KV")
# the type of the result from the operation
RV = TypeVar("RV")
@attr.s(auto_attribs=True)
class MultiKeyResponseCacheContext(Generic[KV]):
"""Information about a missed MultiKeyResponseCache hit
This object can be passed into the callback for additional feedback
"""
cache_keys: Tuple[KV, ...]
"""The cache key that caused the cache miss
This should be considered read-only.
TODO: in attrs 20.1, make it frozen with an on_setattr.
"""
should_cache: bool = True
"""Whether the result should be cached once the request completes.
This can be modified by the callback if it decides its result should not be cached.
"""
class MultiKeyResponseCache(Generic[KV]):
"""
This caches a deferred response. Until the deferred completes it will be
returned from the cache. This means that if the client retries the request
while the response is still being computed, that original response will be
used rather than trying to compute a new response.
Unlike the plain ResponseCache, this cache admits multiple keys to the
deferred response.
"""
def __init__(self, clock: Clock, name: str, timeout_ms: float = 0):
# This is poorly-named: it includes both complete and incomplete results.
# We keep complete results rather than switching to absolute values because
# that makes it easier to cache Failure results.
self.pending_result_cache: Dict[KV, ObservableDeferred] = {}
self.clock = clock
self.timeout_sec = timeout_ms / 1000.0
self._name = name
self._metrics = register_cache(
"multikey_response_cache", name, self, resizable=False
)
def size(self) -> int:
return len(self.pending_result_cache)
def __len__(self) -> int:
return self.size()
def get(self, key: KV) -> Optional[defer.Deferred]:
"""Look up the given key.
Returns a new Deferred (which also doesn't follow the synapse
logcontext rules). You will probably want to make_deferred_yieldable the result.
If there is no entry for the key, returns None.
Args:
key: key to get/set in the cache
Returns:
None if there is no entry for this key; otherwise a deferred which
resolves to the result.
"""
result = self.pending_result_cache.get(key)
if result is not None:
self._metrics.inc_hits()
return result.observe()
else:
self._metrics.inc_misses()
return None
def _set(
self, context: MultiKeyResponseCacheContext[KV], deferred: defer.Deferred
) -> defer.Deferred:
"""Set the entry for the given key to the given deferred.
*deferred* should run its callbacks in the sentinel logcontext (ie,
you should wrap normal synapse deferreds with
synapse.logging.context.run_in_background).
Returns a new Deferred (which also doesn't follow the synapse logcontext rules).
You will probably want to make_deferred_yieldable the result.
Args:
context: Information about the cache miss
deferred: The deferred which resolves to the result.
Returns:
A new deferred which resolves to the actual result.
"""
result = ObservableDeferred(deferred, consumeErrors=True)
keys = context.cache_keys
for key in keys:
if key not in self.pending_result_cache:
# we only add the key if it's not already there, since we assume
# that we won't overtake prior entries.
self.pending_result_cache[key] = result
def on_complete(r):
# if this cache has a non-zero timeout, and the callback has not cleared
# the should_cache bit, we leave it in the cache for now and schedule
# its removal later.
if self.timeout_sec and context.should_cache:
for key in keys:
# TODO sketch, should do this in only one call_later.
self.clock.call_later(
self.timeout_sec, self.pending_result_cache.pop, key, None
)
else:
for key in keys:
# otherwise, remove the result immediately.
self.pending_result_cache.pop(key, None)
return r
# make sure we do this *after* adding the entry to pending_result_cache,
# in case the result is already complete (in which case flipping the order would
# leave us with a stuck entry in the cache).
result.addBoth(on_complete)
return result.observe()
def set_and_compute(
self,
keys: Tuple[KV, ...],
callback: Callable[..., Awaitable[RV]],
*args: Any,
cache_context: bool = False,
**kwargs: Any,
) -> defer.Deferred[RV]:
"""Perform a *set* call, taking care of logcontexts
Makes a call to *callback(*args, **kwargs)*, which should
follow the synapse logcontext rules, and adds the result to the cache.
Example usage:
async def handle_request(request):
# etc
return result
result = await response_cache.wrap(
key,
handle_request,
request,
)
Args:
keys: keys to get/set in the cache
callback: function to call
*args: positional parameters to pass to the callback, if it is used
cache_context: if set, the callback will be given a `cache_context` kw arg,
which will be a ResponseCacheContext object.
**kwargs: named parameters to pass to the callback, if it is used
Returns:
The result of the callback (from the cache, or otherwise)
"""
# TODO sketch logger.debug(
# "[%s]: no cached result for [%s], calculating new one", self._name, key
# )
context = MultiKeyResponseCacheContext(cache_keys=keys)
if cache_context:
kwargs["cache_context"] = context
d = run_in_background(callback, *args, **kwargs)
result = self._set(context, d)
return make_deferred_yieldable(result)