sashapolo commented on code in PR #1542: URL: https://github.com/apache/ignite-3/pull/1542#discussion_r1104733255
########## modules/metastorage/src/main/java/org/apache/ignite/internal/metastorage/impl/MetaStorageRaftGroupEventsListener.java: ########## @@ -0,0 +1,230 @@ +/* + * 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 org.apache.ignite.internal.metastorage.impl; + +import static java.util.concurrent.CompletableFuture.allOf; +import static java.util.concurrent.CompletableFuture.completedFuture; +import static java.util.stream.Collectors.toSet; + +import java.util.List; +import java.util.Set; +import java.util.concurrent.CompletableFuture; +import java.util.function.Function; +import java.util.function.Supplier; +import org.apache.ignite.internal.cluster.management.topology.api.LogicalTopologyEventListener; +import org.apache.ignite.internal.cluster.management.topology.api.LogicalTopologyService; +import org.apache.ignite.internal.cluster.management.topology.api.LogicalTopologySnapshot; +import org.apache.ignite.internal.logger.IgniteLogger; +import org.apache.ignite.internal.logger.Loggers; +import org.apache.ignite.internal.raft.Peer; +import org.apache.ignite.internal.raft.PeersAndLearners; +import org.apache.ignite.internal.raft.RaftGroupEventsListener; +import org.apache.ignite.internal.raft.service.RaftGroupService; +import org.apache.ignite.internal.util.IgniteSpinBusyLock; +import org.apache.ignite.network.ClusterNode; +import org.apache.ignite.network.ClusterService; + +/** + * Raft Group Events listener that registers Logical Topology listener for updating the list of Meta Storage Raft group listeners. + */ +public class MetaStorageRaftGroupEventsListener implements RaftGroupEventsListener { + private static final IgniteLogger LOG = Loggers.forClass(MetaStorageManagerImpl.class); + + private final IgniteSpinBusyLock busyLock; + + private final String nodeName; + + private final LogicalTopologyService logicalTopologyService; + + private final CompletableFuture<MetaStorageServiceImpl> metaStorageSvcFut; + + /** + * Future required to enable serialized processing of topology events. + * + * <p>While Logical Topology events are linearized, we usually start a bunch of async operations inside the event listener and need + * them to finish in the same order. + * + * <p>Multi-threaded access is guarded by {@code serializationFutureMux}. + */ + private CompletableFuture<Void> serializationFuture = null; + + private final Object serializationFutureMux = new Object(); + + MetaStorageRaftGroupEventsListener( + IgniteSpinBusyLock busyLock, + ClusterService clusterService, + LogicalTopologyService logicalTopologyService, + CompletableFuture<MetaStorageServiceImpl> metaStorageSvcFut + ) { + this.busyLock = busyLock; + this.nodeName = clusterService.localConfiguration().getName(); + this.logicalTopologyService = logicalTopologyService; + this.metaStorageSvcFut = metaStorageSvcFut; + } + + @Override + public void onLeaderElected(long term) { + synchronized (serializationFutureMux) { + registerTopologyEventListeners(); + + // Update learner configuration (in case we missed some topology updates) and initialize the serialization future. + serializationFuture = executeIfLeaderImpl(this::resetLearners); + } + } + + private void registerTopologyEventListeners() { + logicalTopologyService.addEventListener(new LogicalTopologyEventListener() { + @Override + public void onNodeValidated(ClusterNode validatedNode) { + executeIfLeader((service, term) -> addLearner(service.raftGroupService(), validatedNode)); Review Comment: > We do call onNodeValidated, ..., onNodeLeft are called within raft thread, is that correct? yes > You didn't introduce any synchronous long running logic, e.g. network communication as a reaction to such events, did you? serializationFuture? How is it possible to introduce synchronous network calls in our code? All such stuff is done asynchronously. That's exactly why I need the `serializationFuture` - to chain a bunch of asynchronous calls to preserve Raft linearization guarantees. But I never wait on on this future. > You didn't introduce any logic that may prevent CMG state-machine idempotentancy, did you? Meaning, that if we'll have an exception within onSmt on Node A and won't have such an exception on Node B, CMG listener won't be effected, is that true? Since all operations are asynchronous, I expect all exception to simply fail on the related thread and be possibly logged somewhere. > Who is responsible for exception handling for serializationFuture? E.g. logging. Logging is done inside the action that is passed to `executeIfLeaderImpl`. For example, see the `updateConfigUnderLock` method, it should do all the logging. -- This is an automated message from the Apache Git Service. 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