diff options
Diffstat (limited to 'synapse')
| -rw-r--r-- | synapse/appservice/api.py | 8 | ||||
| -rw-r--r-- | synapse/federation/federation_client.py | 2 | ||||
| -rw-r--r-- | synapse/federation/federation_server.py | 22 | ||||
| -rw-r--r-- | synapse/handlers/federation.py | 31 | ||||
| -rw-r--r-- | synapse/handlers/message.py | 78 | ||||
| -rw-r--r-- | synapse/handlers/room_list.py | 38 | ||||
| -rw-r--r-- | synapse/handlers/room_member.py | 13 | ||||
| -rw-r--r-- | synapse/handlers/sync.py | 16 | ||||
| -rw-r--r-- | synapse/replication/http/send_event.py | 18 | ||||
| -rw-r--r-- | synapse/storage/event_federation.py | 57 | ||||
| -rw-r--r-- | synapse/storage/events.py | 49 | ||||
| -rw-r--r-- | synapse/util/caches/response_cache.py | 88 |
12 files changed, 260 insertions, 160 deletions
diff --git a/synapse/appservice/api.py b/synapse/appservice/api.py index 11e9c37c63..00efff1464 100644 --- a/synapse/appservice/api.py +++ b/synapse/appservice/api.py @@ -18,7 +18,6 @@ from synapse.api.constants import ThirdPartyEntityKind from synapse.api.errors import CodeMessageException from synapse.http.client import SimpleHttpClient from synapse.events.utils import serialize_event -from synapse.util.logcontext import preserve_fn, make_deferred_yieldable from synapse.util.caches.response_cache import ResponseCache from synapse.types import ThirdPartyInstanceID @@ -194,12 +193,7 @@ class ApplicationServiceApi(SimpleHttpClient): defer.returnValue(None) key = (service.id, protocol) - result = self.protocol_meta_cache.get(key) - if not result: - result = self.protocol_meta_cache.set( - key, preserve_fn(_get)() - ) - return make_deferred_yieldable(result) + return self.protocol_meta_cache.wrap(key, _get) @defer.inlineCallbacks def push_bulk(self, service, events, txn_id=None): diff --git a/synapse/federation/federation_client.py b/synapse/federation/federation_client.py index 38440da5b5..8e2c0c4cd2 100644 --- a/synapse/federation/federation_client.py +++ b/synapse/federation/federation_client.py @@ -394,7 +394,7 @@ class FederationClient(FederationBase): seen_events = yield self.store.get_events(event_ids, allow_rejected=True) signed_events = seen_events.values() else: - seen_events = yield self.store.have_events(event_ids) + seen_events = yield self.store.have_seen_events(event_ids) signed_events = [] failed_to_fetch = set() diff --git a/synapse/federation/federation_server.py b/synapse/federation/federation_server.py index e4ce037acf..12843fe179 100644 --- a/synapse/federation/federation_server.py +++ b/synapse/federation/federation_server.py @@ -30,7 +30,6 @@ import synapse.metrics from synapse.types import get_domain_from_id from synapse.util import async from synapse.util.caches.response_cache import ResponseCache -from synapse.util.logcontext import make_deferred_yieldable, preserve_fn from synapse.util.logutils import log_function # when processing incoming transactions, we try to handle multiple rooms in @@ -212,16 +211,17 @@ class FederationServer(FederationBase): if not in_room: raise AuthError(403, "Host not in room.") - result = self._state_resp_cache.get((room_id, event_id)) - if not result: - with (yield self._server_linearizer.queue((origin, room_id))): - d = self._state_resp_cache.set( - (room_id, event_id), - preserve_fn(self._on_context_state_request_compute)(room_id, event_id) - ) - resp = yield make_deferred_yieldable(d) - else: - resp = yield make_deferred_yieldable(result) + # we grab the linearizer to protect ourselves from servers which hammer + # us. In theory we might already have the response to this query + # in the cache so we could return it without waiting for the linearizer + # - but that's non-trivial to get right, and anyway somewhat defeats + # the point of the linearizer. + with (yield self._server_linearizer.queue((origin, room_id))): + resp = yield self._state_resp_cache.wrap( + (room_id, event_id), + self._on_context_state_request_compute, + room_id, event_id, + ) defer.returnValue((200, resp)) diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py index 080aca3d71..ea6cb879fc 100644 --- a/synapse/handlers/federation.py +++ b/synapse/handlers/federation.py @@ -149,10 +149,6 @@ class FederationHandler(BaseHandler): auth_chain = [] - have_seen = yield self.store.have_events( - [ev for ev, _ in pdu.prev_events] - ) - fetch_state = False # Get missing pdus if necessary. @@ -168,7 +164,7 @@ class FederationHandler(BaseHandler): ) prevs = {e_id for e_id, _ in pdu.prev_events} - seen = set(have_seen.keys()) + seen = yield self.store.have_seen_events(prevs) if min_depth and pdu.depth < min_depth: # This is so that we don't notify the user about this @@ -196,8 +192,7 @@ class FederationHandler(BaseHandler): # Update the set of things we've seen after trying to # fetch the missing stuff - have_seen = yield self.store.have_events(prevs) - seen = set(have_seen.iterkeys()) + seen = yield self.store.have_seen_events(prevs) if not prevs - seen: logger.info( @@ -248,8 +243,7 @@ class FederationHandler(BaseHandler): min_depth (int): Minimum depth of events to return. """ # We recalculate seen, since it may have changed. - have_seen = yield self.store.have_events(prevs) - seen = set(have_seen.keys()) + seen = yield self.store.have_seen_events(prevs) if not prevs - seen: return @@ -361,9 +355,7 @@ class FederationHandler(BaseHandler): if auth_chain: event_ids |= {e.event_id for e in auth_chain} - seen_ids = set( - (yield self.store.have_events(event_ids)).keys() - ) + seen_ids = yield self.store.have_seen_events(event_ids) if state and auth_chain is not None: # If we have any state or auth_chain given to us by the replication @@ -633,7 +625,7 @@ class FederationHandler(BaseHandler): failed_to_fetch = missing_auth - set(auth_events) - seen_events = yield self.store.have_events( + seen_events = yield self.store.have_seen_events( set(auth_events.keys()) | set(state_events.keys()) ) @@ -1736,7 +1728,8 @@ class FederationHandler(BaseHandler): event_key = None if event_auth_events - current_state: - have_events = yield self.store.have_events( + # TODO: can we use store.have_seen_events here instead? + have_events = yield self.store.get_seen_events_with_rejections( event_auth_events - current_state ) else: @@ -1759,12 +1752,12 @@ class FederationHandler(BaseHandler): origin, event.room_id, event.event_id ) - seen_remotes = yield self.store.have_events( + seen_remotes = yield self.store.have_seen_events( [e.event_id for e in remote_auth_chain] ) for e in remote_auth_chain: - if e.event_id in seen_remotes.keys(): + if e.event_id in seen_remotes: continue if e.event_id == event.event_id: @@ -1791,7 +1784,7 @@ class FederationHandler(BaseHandler): except AuthError: pass - have_events = yield self.store.have_events( + have_events = yield self.store.get_seen_events_with_rejections( [e_id for e_id, _ in event.auth_events] ) seen_events = set(have_events.keys()) @@ -1876,13 +1869,13 @@ class FederationHandler(BaseHandler): local_auth_chain, ) - seen_remotes = yield self.store.have_events( + seen_remotes = yield self.store.have_seen_events( [e.event_id for e in result["auth_chain"]] ) # 3. Process any remote auth chain events we haven't seen. for ev in result["auth_chain"]: - if ev.event_id in seen_remotes.keys(): + if ev.event_id in seen_remotes: continue if ev.event_id == event.event_id: diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py index 54cd691f91..21628a8540 100644 --- a/synapse/handlers/message.py +++ b/synapse/handlers/message.py @@ -37,7 +37,6 @@ from ._base import BaseHandler from canonicaljson import encode_canonical_json import logging -import random import simplejson logger = logging.getLogger(__name__) @@ -433,7 +432,7 @@ class EventCreationHandler(object): @defer.inlineCallbacks def create_event(self, requester, event_dict, token_id=None, txn_id=None, - prev_event_ids=None): + prev_events_and_hashes=None): """ Given a dict from a client, create a new event. @@ -447,7 +446,13 @@ class EventCreationHandler(object): event_dict (dict): An entire event token_id (str) txn_id (str) - prev_event_ids (list): The prev event ids to use when creating the event + + prev_events_and_hashes (list[(str, dict[str, str], int)]|None): + the forward extremities to use as the prev_events for the + new event. For each event, a tuple of (event_id, hashes, depth) + where *hashes* is a map from algorithm to hash. + + If None, they will be requested from the database. Returns: Tuple of created event (FrozenEvent), Context @@ -485,7 +490,7 @@ class EventCreationHandler(object): event, context = yield self.create_new_client_event( builder=builder, requester=requester, - prev_event_ids=prev_event_ids, + prev_events_and_hashes=prev_events_and_hashes, ) defer.returnValue((event, context)) @@ -588,39 +593,44 @@ class EventCreationHandler(object): @measure_func("create_new_client_event") @defer.inlineCallbacks - def create_new_client_event(self, builder, requester=None, prev_event_ids=None): - if prev_event_ids: - prev_events = yield self.store.add_event_hashes(prev_event_ids) - prev_max_depth = yield self.store.get_max_depth_of_events(prev_event_ids) - depth = prev_max_depth + 1 - else: - latest_ret = yield self.store.get_latest_event_ids_and_hashes_in_room( - builder.room_id, + def create_new_client_event(self, builder, requester=None, + prev_events_and_hashes=None): + """Create a new event for a local client + + Args: + builder (EventBuilder): + + requester (synapse.types.Requester|None): + + prev_events_and_hashes (list[(str, dict[str, str], int)]|None): + the forward extremities to use as the prev_events for the + new event. For each event, a tuple of (event_id, hashes, depth) + where *hashes* is a map from algorithm to hash. + + If None, they will be requested from the database. + + Returns: + Deferred[(synapse.events.EventBase, synapse.events.snapshot.EventContext)] + """ + + if prev_events_and_hashes is not None: + assert len(prev_events_and_hashes) <= 10, \ + "Attempting to create an event with %i prev_events" % ( + len(prev_events_and_hashes), ) + else: + prev_events_and_hashes = \ + yield self.store.get_prev_events_for_room(builder.room_id) - # We want to limit the max number of prev events we point to in our - # new event - if len(latest_ret) > 10: - # Sort by reverse depth, so we point to the most recent. - latest_ret.sort(key=lambda a: -a[2]) - new_latest_ret = latest_ret[:5] - - # We also randomly point to some of the older events, to make - # sure that we don't completely ignore the older events. - if latest_ret[5:]: - sample_size = min(5, len(latest_ret[5:])) - new_latest_ret.extend(random.sample(latest_ret[5:], sample_size)) - latest_ret = new_latest_ret - - if latest_ret: - depth = max([d for _, _, d in latest_ret]) + 1 - else: - depth = 1 + if prev_events_and_hashes: + depth = max([d for _, _, d in prev_events_and_hashes]) + 1 + else: + depth = 1 - prev_events = [ - (event_id, prev_hashes) - for event_id, prev_hashes, _ in latest_ret - ] + prev_events = [ + (event_id, prev_hashes) + for event_id, prev_hashes, _ in prev_events_and_hashes + ] builder.prev_events = prev_events builder.depth = depth diff --git a/synapse/handlers/room_list.py b/synapse/handlers/room_list.py index 8028d793c2..add3f9b009 100644 --- a/synapse/handlers/room_list.py +++ b/synapse/handlers/room_list.py @@ -20,7 +20,6 @@ from ._base import BaseHandler from synapse.api.constants import ( EventTypes, JoinRules, ) -from synapse.util.logcontext import make_deferred_yieldable, preserve_fn from synapse.util.async import concurrently_execute from synapse.util.caches.descriptors import cachedInlineCallbacks from synapse.util.caches.response_cache import ResponseCache @@ -78,18 +77,11 @@ class RoomListHandler(BaseHandler): ) key = (limit, since_token, network_tuple) - result = self.response_cache.get(key) - if not result: - logger.info("No cached result, calculating one.") - result = self.response_cache.set( - key, - preserve_fn(self._get_public_room_list)( - limit, since_token, network_tuple=network_tuple - ) - ) - else: - logger.info("Using cached deferred result.") - return make_deferred_yieldable(result) + return self.response_cache.wrap( + key, + self._get_public_room_list, + limit, since_token, network_tuple=network_tuple, + ) @defer.inlineCallbacks def _get_public_room_list(self, limit=None, since_token=None, @@ -423,18 +415,14 @@ class RoomListHandler(BaseHandler): server_name, limit, since_token, include_all_networks, third_party_instance_id, ) - result = self.remote_response_cache.get(key) - if not result: - result = self.remote_response_cache.set( - key, - repl_layer.get_public_rooms( - server_name, limit=limit, since_token=since_token, - search_filter=search_filter, - include_all_networks=include_all_networks, - third_party_instance_id=third_party_instance_id, - ) - ) - return result + return self.remote_response_cache.wrap( + key, + repl_layer.get_public_rooms, + server_name, limit=limit, since_token=since_token, + search_filter=search_filter, + include_all_networks=include_all_networks, + third_party_instance_id=third_party_instance_id, + ) class RoomListNextBatch(namedtuple("RoomListNextBatch", ( diff --git a/synapse/handlers/room_member.py b/synapse/handlers/room_member.py index c45142d38d..714583f1d5 100644 --- a/synapse/handlers/room_member.py +++ b/synapse/handlers/room_member.py @@ -149,7 +149,7 @@ class RoomMemberHandler(object): @defer.inlineCallbacks def _local_membership_update( self, requester, target, room_id, membership, - prev_event_ids, + prev_events_and_hashes, txn_id=None, ratelimit=True, content=None, @@ -175,7 +175,7 @@ class RoomMemberHandler(object): }, token_id=requester.access_token_id, txn_id=txn_id, - prev_event_ids=prev_event_ids, + prev_events_and_hashes=prev_events_and_hashes, ) # Check if this event matches the previous membership event for the user. @@ -314,7 +314,12 @@ class RoomMemberHandler(object): 403, "Invites have been disabled on this server", ) - latest_event_ids = yield self.store.get_latest_event_ids_in_room(room_id) + prev_events_and_hashes = yield self.store.get_prev_events_for_room( + room_id, + ) + latest_event_ids = ( + event_id for (event_id, _, _) in prev_events_and_hashes + ) current_state_ids = yield self.state_handler.get_current_state_ids( room_id, latest_event_ids=latest_event_ids, ) @@ -403,7 +408,7 @@ class RoomMemberHandler(object): membership=effective_membership_state, txn_id=txn_id, ratelimit=ratelimit, - prev_event_ids=latest_event_ids, + prev_events_and_hashes=prev_events_and_hashes, content=content, ) defer.returnValue(res) diff --git a/synapse/handlers/sync.py b/synapse/handlers/sync.py index 06d17ab20c..c6946831ab 100644 --- a/synapse/handlers/sync.py +++ b/synapse/handlers/sync.py @@ -15,7 +15,7 @@ from synapse.api.constants import Membership, EventTypes from synapse.util.async import concurrently_execute -from synapse.util.logcontext import LoggingContext, make_deferred_yieldable, preserve_fn +from synapse.util.logcontext import LoggingContext from synapse.util.metrics import Measure, measure_func from synapse.util.caches.response_cache import ResponseCache from synapse.push.clientformat import format_push_rules_for_user @@ -180,15 +180,11 @@ class SyncHandler(object): Returns: A Deferred SyncResult. """ - result = self.response_cache.get(sync_config.request_key) - if not result: - result = self.response_cache.set( - sync_config.request_key, - preserve_fn(self._wait_for_sync_for_user)( - sync_config, since_token, timeout, full_state - ) - ) - return make_deferred_yieldable(result) + return self.response_cache.wrap( + sync_config.request_key, + self._wait_for_sync_for_user, + sync_config, since_token, timeout, full_state, + ) @defer.inlineCallbacks def _wait_for_sync_for_user(self, sync_config, since_token, timeout, diff --git a/synapse/replication/http/send_event.py b/synapse/replication/http/send_event.py index c6a6551d24..a9baa2c1c3 100644 --- a/synapse/replication/http/send_event.py +++ b/synapse/replication/http/send_event.py @@ -23,7 +23,6 @@ from synapse.events.snapshot import EventContext from synapse.http.servlet import RestServlet, parse_json_object_from_request from synapse.util.async import sleep from synapse.util.caches.response_cache import ResponseCache -from synapse.util.logcontext import make_deferred_yieldable, preserve_fn from synapse.util.metrics import Measure from synapse.types import Requester, UserID @@ -118,17 +117,12 @@ class ReplicationSendEventRestServlet(RestServlet): self.response_cache = ResponseCache(hs, "send_event", timeout_ms=30 * 60 * 1000) def on_PUT(self, request, event_id): - result = self.response_cache.get(event_id) - if not result: - result = self.response_cache.set( - event_id, - self._handle_request(request) - ) - else: - logger.warn("Returning cached response") - return make_deferred_yieldable(result) - - @preserve_fn + return self.response_cache.wrap( + event_id, + self._handle_request, + request + ) + @defer.inlineCallbacks def _handle_request(self, request): with Measure(self.clock, "repl_send_event_parse"): diff --git a/synapse/storage/event_federation.py b/synapse/storage/event_federation.py index 00ee82d300..a183fc6b50 100644 --- a/synapse/storage/event_federation.py +++ b/synapse/storage/event_federation.py @@ -12,6 +12,7 @@ # 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 random from twisted.internet import defer @@ -133,7 +134,47 @@ class EventFederationWorkerStore(EventsWorkerStore, SignatureWorkerStore, retcol="event_id", ) + @defer.inlineCallbacks + def get_prev_events_for_room(self, room_id): + """ + Gets a subset of the current forward extremities in the given room. + + Limits the result to 10 extremities, so that we can avoid creating + events which refer to hundreds of prev_events. + + Args: + room_id (str): room_id + + Returns: + Deferred[list[(str, dict[str, str], int)]] + for each event, a tuple of (event_id, hashes, depth) + where *hashes* is a map from algorithm to hash. + """ + res = yield self.get_latest_event_ids_and_hashes_in_room(room_id) + if len(res) > 10: + # Sort by reverse depth, so we point to the most recent. + res.sort(key=lambda a: -a[2]) + + # we use half of the limit for the actual most recent events, and + # the other half to randomly point to some of the older events, to + # make sure that we don't completely ignore the older events. + res = res[0:5] + random.sample(res[5:], 5) + + defer.returnValue(res) + def get_latest_event_ids_and_hashes_in_room(self, room_id): + """ + Gets the current forward extremities in the given room + + Args: + room_id (str): room_id + + Returns: + Deferred[list[(str, dict[str, str], int)]] + for each event, a tuple of (event_id, hashes, depth) + where *hashes* is a map from algorithm to hash. + """ + return self.runInteraction( "get_latest_event_ids_and_hashes_in_room", self._get_latest_event_ids_and_hashes_in_room, @@ -182,22 +223,6 @@ class EventFederationWorkerStore(EventsWorkerStore, SignatureWorkerStore, room_id, ) - @defer.inlineCallbacks - def get_max_depth_of_events(self, event_ids): - sql = ( - "SELECT MAX(depth) FROM events WHERE event_id IN (%s)" - ) % (",".join(["?"] * len(event_ids)),) - - rows = yield self._execute( - "get_max_depth_of_events", None, - sql, *event_ids - ) - - if rows: - defer.returnValue(rows[0][0]) - else: - defer.returnValue(1) - def _get_min_depth_interaction(self, txn, room_id): min_depth = self._simple_select_one_onecol_txn( txn, diff --git a/synapse/storage/events.py b/synapse/storage/events.py index da44b52fd6..5fe4a0e56c 100644 --- a/synapse/storage/events.py +++ b/synapse/storage/events.py @@ -16,6 +16,7 @@ from collections import OrderedDict, deque, namedtuple from functools import wraps +import itertools import logging import simplejson as json @@ -1320,13 +1321,49 @@ class EventsStore(EventsWorkerStore): defer.returnValue(set(r["event_id"] for r in rows)) - def have_events(self, event_ids): + @defer.inlineCallbacks + def have_seen_events(self, event_ids): """Given a list of event ids, check if we have already processed them. + Args: + event_ids (iterable[str]): + Returns: - dict: Has an entry for each event id we already have seen. Maps to - the rejected reason string if we rejected the event, else maps to - None. + Deferred[set[str]]: The events we have already seen. + """ + results = set() + + def have_seen_events_txn(txn, chunk): + sql = ( + "SELECT event_id FROM events as e WHERE e.event_id IN (%s)" + % (",".join("?" * len(chunk)), ) + ) + txn.execute(sql, chunk) + for (event_id, ) in txn: + results.add(event_id) + + # break the input up into chunks of 100 + input_iterator = iter(event_ids) + for chunk in iter(lambda: list(itertools.islice(input_iterator, 100)), + []): + yield self.runInteraction( + "have_seen_events", + have_seen_events_txn, + chunk, + ) + defer.returnValue(results) + + def get_seen_events_with_rejections(self, event_ids): + """Given a list of event ids, check if we rejected them. + + Args: + event_ids (list[str]) + + Returns: + Deferred[dict[str, str|None): + Has an entry for each event id we already have seen. Maps to + the rejected reason string if we rejected the event, else maps + to None. """ if not event_ids: return defer.succeed({}) @@ -1348,9 +1385,7 @@ class EventsStore(EventsWorkerStore): return res - return self.runInteraction( - "have_events", f, - ) + return self.runInteraction("get_rejection_reasons", f) @defer.inlineCallbacks def count_daily_messages(self): diff --git a/synapse/util/caches/response_cache.py b/synapse/util/caches/response_cache.py index 066fa423fd..7f79333e96 100644 --- a/synapse/util/caches/response_cache.py +++ b/synapse/util/caches/response_cache.py @@ -12,9 +12,15 @@ # 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 twisted.internet import defer from synapse.util.async import ObservableDeferred from synapse.util.caches import metrics as cache_metrics +from synapse.util.logcontext import make_deferred_yieldable, run_in_background + +logger = logging.getLogger(__name__) class ResponseCache(object): @@ -31,6 +37,7 @@ class ResponseCache(object): self.clock = hs.get_clock() self.timeout_sec = timeout_ms / 1000. + self._name = name self._metrics = cache_metrics.register_cache( "response_cache", size_callback=lambda: self.size(), @@ -43,15 +50,21 @@ class ResponseCache(object): def get(self, key): """Look up the given key. - Returns a deferred which doesn't follow the synapse logcontext rules, - so you'll probably want to make_deferred_yieldable it. + Can return either a new Deferred (which also doesn't follow the synapse + logcontext rules), or, if the request has completed, the actual + result. You will probably want to make_deferred_yieldable the result. + + If there is no entry for the key, returns None. It is worth noting that + this means there is no way to distinguish a completed result of None + from an absent cache entry. Args: - key (str): + key (hashable): Returns: - twisted.internet.defer.Deferred|None: None if there is no entry - for this key; otherwise a deferred result. + twisted.internet.defer.Deferred|None|E: None if there is no entry + for this key; otherwise either a deferred result or the result + itself. """ result = self.pending_result_cache.get(key) if result is not None: @@ -68,19 +81,17 @@ class ResponseCache(object): you should wrap normal synapse deferreds with logcontext.run_in_background). - Returns a new Deferred which also doesn't follow the synapse logcontext - rules, so you will want to make_deferred_yieldable it - - (TODO: before using this more widely, it might make sense to refactor - it and get() so that they do the necessary wrapping rather than having - to do it everywhere ResponseCache is used.) + Can return either a new Deferred (which also doesn't follow the synapse + logcontext rules), or, if *deferred* was already complete, the actual + result. You will probably want to make_deferred_yieldable the result. Args: - key (str): - deferred (twisted.internet.defer.Deferred): + key (hashable): + deferred (twisted.internet.defer.Deferred[T): Returns: - twisted.internet.defer.Deferred + twisted.internet.defer.Deferred[T]|T: a new deferred, or the actual + result. """ result = ObservableDeferred(deferred, consumeErrors=True) self.pending_result_cache[key] = result @@ -97,3 +108,52 @@ class ResponseCache(object): result.addBoth(remove) return result.observe() + + def wrap(self, key, callback, *args, **kwargs): + """Wrap together a *get* and *set* call, taking care of logcontexts + + First looks up the key in the cache, and if it is present makes it + follow the synapse logcontext rules and returns it. + + Otherwise, makes a call to *callback(*args, **kwargs)*, which should + follow the synapse logcontext rules, and adds the result to the cache. + + Example usage: + + @defer.inlineCallbacks + def handle_request(request): + # etc + defer.returnValue(result) + + result = yield response_cache.wrap( + key, + handle_request, + request, + ) + + Args: + key (hashable): key to get/set in the cache + + callback (callable): function to call if the key is not found in + the cache + + *args: positional parameters to pass to the callback, if it is used + + **kwargs: named paramters to pass to the callback, if it is used + + Returns: + twisted.internet.defer.Deferred: yieldable result + """ + result = self.get(key) + if not result: + logger.info("[%s]: no cached result for [%s], calculating new one", + self._name, key) + d = run_in_background(callback, *args, **kwargs) + result = self.set(key, d) + elif not isinstance(result, defer.Deferred) or result.called: + logger.info("[%s]: using completed cached result for [%s]", + self._name, key) + else: + logger.info("[%s]: using incomplete cached result for [%s]", + self._name, key) + return make_deferred_yieldable(result) |