Stream ordering and out of order insertions.
Handle the fact that events can be persisted out of order, and so to get the "current max" stream token becomes non trivial - as we need to make sure that *all* stream tokens less than the current max have also successfully been persisted.
This commit is contained in:
Erik Johnston
parent
22d7a59306
commit
8ad0f4912e
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@ -22,6 +22,8 @@ from synapse.util.logcontext import PreserveLoggingContext, LoggingContext
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from synapse.util.lrucache import LruCache
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import synapse.metrics
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from util.id_generators import IdGenerator, StreamIdGenerator
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from twisted.internet import defer
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from collections import namedtuple, OrderedDict
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@ -29,7 +31,6 @@ import functools
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import simplejson as json
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import sys
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import time
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import threading
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logger = logging.getLogger(__name__)
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@ -232,46 +233,6 @@ class PerformanceCounters(object):
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return top_n_counters
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class IdGenerator(object):
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def __init__(self, table, column, store):
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self.table = table
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self.column = column
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self.store = store
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self._lock = threading.Lock()
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self._next_id = None
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@defer.inlineCallbacks
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def get_next(self):
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with self._lock:
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if not self._next_id:
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res = yield self.store._execute_and_decode(
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"IdGenerator_%s" % (self.table,),
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"SELECT MAX(%s) as mx FROM %s" % (self.column, self.table,)
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)
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self._next_id = (res and res[0] and res[0]["mx"]) or 1
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i = self._next_id
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self._next_id += 1
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defer.returnValue(i)
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def get_next_txn(self, txn):
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with self._lock:
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if self._next_id:
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i = self._next_id
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self._next_id += 1
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return i
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else:
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txn.execute(
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"SELECT MAX(%s) FROM %s" % (self.column, self.table,)
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)
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val, = txn.fetchone()
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self._next_id = val or 2
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return 1
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class SQLBaseStore(object):
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_TXN_ID = 0
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@ -297,7 +258,7 @@ class SQLBaseStore(object):
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# Pretend the getEventCache is just another named cache
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caches_by_name["*getEvent*"] = self._get_event_cache
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self._stream_id_gen = IdGenerator("events", "stream_ordering", self)
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self._stream_id_gen = StreamIdGenerator()
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self._transaction_id_gen = IdGenerator("sent_transactions", "id", self)
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self._state_groups_id_gen = IdGenerator("state_groups", "id", self)
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self._access_tokens_id_gen = IdGenerator("access_tokens", "id", self)
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@ -363,7 +324,6 @@ class SQLBaseStore(object):
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*args, **kwargs
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)
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except self.database_engine.module.DatabaseError as e:
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logger.warn("[TXN DEADLOCK] {%s} %r, %r", name, e.errno, e.sqlstate)
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if self.database_engine.is_deadlock(e):
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logger.warn("[TXN DEADLOCK] {%s} %d/%d", name, i, N)
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if i < N:
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@ -52,7 +52,6 @@ class EventsStore(SQLBaseStore):
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is_new_state=is_new_state,
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current_state=current_state,
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)
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self.get_room_events_max_id.invalidate()
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except _RollbackButIsFineException:
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pass
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@ -97,7 +96,13 @@ class EventsStore(SQLBaseStore):
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self._get_event_cache.pop(event.event_id)
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if stream_ordering is None:
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stream_ordering = self._stream_id_gen.get_next_txn(txn)
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with self._stream_id_gen.get_next_txn(txn) as stream_ordering:
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return self._persist_event_txn(
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txn, event, context, backfilled,
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stream_ordering=stream_ordering,
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is_new_state=is_new_state,
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current_state=current_state,
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)
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# We purposefully do this first since if we include a `current_state`
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# key, we *want* to update the `current_state_events` table
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@ -413,12 +413,10 @@ class StreamStore(SQLBaseStore):
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"get_recent_events_for_room", get_recent_events_for_room_txn
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)
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@cached(num_args=0)
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@defer.inlineCallbacks
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def get_room_events_max_id(self):
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return self.runInteraction(
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"get_room_events_max_id",
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self._get_room_events_max_id_txn
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)
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token = yield self._stream_id_gen.get_max_token(self)
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defer.returnValue("s%d" % (token,))
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@defer.inlineCallbacks
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def _get_min_token(self):
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@ -433,21 +431,6 @@ class StreamStore(SQLBaseStore):
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defer.returnValue(self.min_token)
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def _get_room_events_max_id_txn(self, txn):
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txn.execute(
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"SELECT MAX(stream_ordering) as m FROM events"
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)
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res = self.cursor_to_dict(txn)
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logger.debug("get_room_events_max_id: %s", res)
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if not res or not res[0] or not res[0]["m"]:
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return "s0"
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key = res[0]["m"]
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return "s%d" % (key,)
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@staticmethod
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def _set_before_and_after(events, rows):
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for event, row in zip(events, rows):
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@ -0,0 +1,14 @@
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# -*- coding: utf-8 -*-
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# Copyright 2014, 2015 OpenMarket Ltd
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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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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@ -0,0 +1,126 @@
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# -*- coding: utf-8 -*-
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# Copyright 2014, 2015 OpenMarket Ltd
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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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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from twisted.internet import defer
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from collections import deque
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import contextlib
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import threading
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class IdGenerator(object):
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def __init__(self, table, column, store):
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self.table = table
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self.column = column
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self.store = store
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self._lock = threading.Lock()
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self._next_id = None
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@defer.inlineCallbacks
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def get_next(self):
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with self._lock:
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if not self._next_id:
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res = yield self.store._execute_and_decode(
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"IdGenerator_%s" % (self.table,),
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"SELECT MAX(%s) as mx FROM %s" % (self.column, self.table,)
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)
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self._next_id = (res and res[0] and res[0]["mx"]) or 1
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i = self._next_id
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self._next_id += 1
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defer.returnValue(i)
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def get_next_txn(self, txn):
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with self._lock:
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if self._next_id:
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i = self._next_id
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self._next_id += 1
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return i
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else:
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txn.execute(
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"SELECT MAX(%s) FROM %s" % (self.column, self.table,)
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)
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val, = txn.fetchone()
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self._next_id = val or 2
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return 1
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class StreamIdGenerator(object):
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"""Used to generate new stream ids when persisting events while keeping
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track of which transactions have been completed.
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This allows us to get the "current" stream id, i.e. the stream id such that
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all ids less than or equal to it have completed. This handles the fact that
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persistence of events can complete out of order.
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Usage:
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with stream_id_gen.get_next_txn(txn) as stream_id:
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# ... persist event ...
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"""
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def __init__(self):
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self._lock = threading.Lock()
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self._current_max = None
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self._unfinished_ids = deque()
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def get_next_txn(self, txn):
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"""
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Usage:
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with stream_id_gen.get_next_txn(txn) as stream_id:
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# ... persist event ...
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"""
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with self._lock:
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if not self._current_max:
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self._compute_current_max(txn)
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self._current_max += 1
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next_id = self._current_max
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self._unfinished_ids.append(next_id)
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@contextlib.contextmanager
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def manager():
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yield next_id
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with self._lock:
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self._unfinished_ids.remove(next_id)
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return manager()
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def get_max_token(self, store):
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"""Returns the maximum stream id such that all stream ids less than or
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equal to it have been successfully persisted.
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"""
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with self._lock:
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if self._unfinished_ids:
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return self._unfinished_ids[0] - 1
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if not self._current_max:
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return store.runInteraction(
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"_compute_current_max",
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self._compute_current_max,
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)
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return self._current_max
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def _compute_current_max(self, txn):
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txn.execute("SELECT MAX(stream_ordering) FROM events")
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val, = txn.fetchone()
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self._current_max = int(val) if val else 1
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return self._current_max
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