bdeggleston commented on code in PR #49: URL: https://github.com/apache/cassandra-accord/pull/49#discussion_r1223237647
########## accord-core/src/main/java/accord/impl/AbstractConfigurationService.java: ########## @@ -0,0 +1,337 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you 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. + */ + +package accord.impl; + +import java.util.ArrayList; +import java.util.List; + +import com.google.common.annotations.VisibleForTesting; +import com.google.common.primitives.Ints; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import accord.api.ConfigurationService; +import accord.local.Node; +import accord.topology.Topology; +import accord.utils.Invariants; +import accord.utils.async.AsyncResult; +import accord.utils.async.AsyncResults; + +public abstract class AbstractConfigurationService<EpochState extends AbstractConfigurationService.AbstractEpochState, + EpochHistory extends AbstractConfigurationService.AbstractEpochHistory<EpochState>> + implements ConfigurationService +{ + private static final Logger logger = LoggerFactory.getLogger(AbstractConfigurationService.class); + + protected final Node.Id localId; + + protected final EpochHistory epochs = createEpochHistory(); + + protected final List<Listener> listeners = new ArrayList<>(); + + public abstract static class AbstractEpochState + { + protected final long epoch; + protected final AsyncResult.Settable<Topology> received = AsyncResults.settable(); + protected final AsyncResult.Settable<Void> acknowledged = AsyncResults.settable(); + protected AsyncResult<Void> reads = null; + + protected Topology topology = null; + + public AbstractEpochState(long epoch) + { + this.epoch = epoch; + } + + public long epoch() + { + return epoch; + } + + @Override + public String toString() + { + return "EpochState{" + epoch + '}'; + } + } + + @VisibleForTesting + public abstract static class AbstractEpochHistory<EpochState extends AbstractEpochState> + { + // TODO (low priority): move pendingEpochs / FetchTopology into here? + private List<EpochState> epochs = new ArrayList<>(); + + protected long lastReceived = 0; + protected long lastAcknowledged = 0; + + protected abstract EpochState createEpochState(long epoch); + + public long minEpoch() + { + return epochs.isEmpty() ? 0L : epochs.get(0).epoch; + } + + public long maxEpoch() + { + int size = epochs.size(); + return size == 0 ? 0L : epochs.get(size - 1).epoch; + } + + @VisibleForTesting + EpochState atIndex(int idx) + { + return epochs.get(idx); + } + + @VisibleForTesting + int size() + { + return epochs.size(); + } + + EpochState getOrCreate(long epoch) + { + Invariants.checkArgument(epoch > 0); + if (epochs.isEmpty()) + { + EpochState state = createEpochState(epoch); + epochs.add(state); + return state; + } + + long minEpoch = minEpoch(); + if (epoch < minEpoch) + { + int prepend = Ints.checkedCast(minEpoch - epoch); + List<EpochState> next = new ArrayList<>(epochs.size() + prepend); + for (long addEpoch=epoch; addEpoch<minEpoch; addEpoch++) + next.add(createEpochState(addEpoch)); + next.addAll(epochs); + epochs = next; + minEpoch = minEpoch(); + Invariants.checkState(minEpoch == epoch); + } + long maxEpoch = maxEpoch(); + int idx = Ints.checkedCast(epoch - minEpoch); + + // add any missing epochs + for (long addEpoch = maxEpoch + 1; addEpoch <= epoch; addEpoch++) + epochs.add(createEpochState(addEpoch)); + + return epochs.get(idx); + } + + public void receive(Topology topology) + { + long epoch = topology.epoch(); + Invariants.checkState(lastReceived == epoch - 1 || epoch == 0 || lastReceived == 0); + lastReceived = epoch; + EpochState state = getOrCreate(epoch); + if (state != null) + { + state.topology = topology; + state.received.setSuccess(topology); + } + } + + AsyncResult<Topology> receiveFuture(long epoch) + { + return getOrCreate(epoch).received; + } + + Topology topologyFor(long epoch) + { + return getOrCreate(epoch).topology; + } + + public void acknowledge(EpochReady ready) + { + long epoch = ready.epoch; + Invariants.checkState(lastAcknowledged == epoch - 1 || epoch == 0 || lastAcknowledged == 0); + lastAcknowledged = epoch; + EpochState state = getOrCreate(epoch); + state.reads = ready.reads; + state.acknowledged.setSuccess(null); + } + + AsyncResult<Void> acknowledgeFuture(long epoch) + { + return getOrCreate(epoch).acknowledged; + } + + void truncateUntil(long epoch) + { + Invariants.checkArgument(epoch <= maxEpoch()); + long minEpoch = minEpoch(); + int toTrim = Ints.checkedCast(epoch - minEpoch); + if (toTrim <=0) + return; + + epochs = new ArrayList<>(epochs.subList(toTrim, epochs.size())); + } + } + + public AbstractConfigurationService(Node.Id localId) + { + this.localId = localId; + } + + protected abstract EpochHistory createEpochHistory(); + + protected EpochState getOrCreateEpochState(long epoch) + { + return epochs.getOrCreate(epoch); + } + + @Override + public synchronized void registerListener(Listener listener) + { + listeners.add(listener); + } + + @Override + public synchronized Topology currentTopology() + { + return epochs.topologyFor(epochs.lastReceived); + } + + @Override + public synchronized Topology getTopologyForEpoch(long epoch) + { + return epochs.topologyFor(epoch); + } + + protected abstract void fetchTopologyInternal(long epoch); + + @Override + public synchronized void fetchTopologyForEpoch(long epoch) + { + if (epoch <= epochs.lastReceived) + return; + + fetchTopologyInternal(epoch); + } + + protected abstract void localSyncComplete(Topology topology); + + @Override + public synchronized void acknowledgeEpoch(EpochReady ready) + { + ready.metadata.addCallback(() -> epochs.acknowledge(ready)); + ready.coordination.addCallback(() -> localSyncComplete(epochs.getOrCreate(ready.epoch).topology)); + } + + protected void topologyUpdatePreListenerNotify(Topology topology) {} + protected void topologyUpdatePostListenerNotify(Topology topology) {} + + public synchronized AsyncResult<Void> reportTopology(Topology topology, boolean startSync) + { + long lastReceived = epochs.lastReceived; + if (topology.epoch() <= lastReceived) + return AsyncResults.success(null); + + if (lastReceived > 0 && topology.epoch() > lastReceived + 1) + { + fetchTopologyForEpoch(lastReceived + 1); + epochs.receiveFuture(lastReceived + 1).addCallback(() -> reportTopology(topology, startSync)); Review Comment: That's right, it would fill in any gaps, and then re-submit topology at epoch 5. -- This is an automated message from the Apache Git Service. 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