[GitHub] [iotdb] SzyWilliam commented on a diff in pull request #5939: [IOTDB-3188] Multi leader consensus algorithm implementation

[GitBox <gi...@apache.org>]

SzyWilliam commented on code in PR #5939:
URL: https://github.com/apache/iotdb/pull/5939#discussion_r883299526


##########
consensus/src/main/java/org/apache/iotdb/consensus/multileader/MultiLeaderConsensus.java:
##########
@@ -0,0 +1,241 @@
+/*
+ * 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.iotdb.consensus.multileader;
+
+import org.apache.iotdb.common.rpc.thrift.TEndPoint;
+import org.apache.iotdb.commons.consensus.ConsensusGroupId;
+import org.apache.iotdb.commons.exception.StartupException;
+import org.apache.iotdb.commons.service.RegisterManager;
+import org.apache.iotdb.consensus.IConsensus;
+import org.apache.iotdb.consensus.IStateMachine;
+import org.apache.iotdb.consensus.IStateMachine.Registry;
+import org.apache.iotdb.consensus.common.Peer;
+import org.apache.iotdb.consensus.common.request.IConsensusRequest;
+import org.apache.iotdb.consensus.common.response.ConsensusGenericResponse;
+import org.apache.iotdb.consensus.common.response.ConsensusReadResponse;
+import org.apache.iotdb.consensus.common.response.ConsensusWriteResponse;
+import org.apache.iotdb.consensus.exception.ConsensusGroupAlreadyExistException;
+import org.apache.iotdb.consensus.exception.ConsensusGroupNotExistException;
+import org.apache.iotdb.consensus.exception.IllegalPeerNumException;
+import org.apache.iotdb.consensus.multileader.service.MultiLeaderRPCService;
+import org.apache.iotdb.consensus.multileader.service.MultiLeaderRPCServiceProcessor;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.DirectoryStream;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+public class MultiLeaderConsensus implements IConsensus {
+
+  private final Logger logger = LoggerFactory.getLogger(MultiLeaderConsensus.class);
+
+  private final TEndPoint thisNode;
+  private final File storageDir;
+  private final IStateMachine.Registry registry;
+  private final Map<ConsensusGroupId, MultiLeaderServerImpl> stateMachineMap =
+      new ConcurrentHashMap<>();
+  private final MultiLeaderRPCService service;
+  private final RegisterManager registerManager = new RegisterManager();
+
+  public MultiLeaderConsensus(TEndPoint thisNode, File storageDir, Registry registry) {
+    this.thisNode = thisNode;
+    this.storageDir = storageDir;
+    this.registry = registry;
+    this.service = new MultiLeaderRPCService(thisNode);
+  }
+
+  @Override
+  public void start() throws IOException {
+    initAndRecover();
+    service.initSyncedServiceImpl(new MultiLeaderRPCServiceProcessor(this));
+    try {
+      registerManager.register(service);
+    } catch (StartupException e) {
+      throw new IOException(e);
+    }
+  }
+
+  private void initAndRecover() throws IOException {
+    if (!storageDir.exists()) {
+      if (!storageDir.mkdirs()) {
+        logger.warn("Unable to create consensus dir at {}", storageDir);
+      }
+    } else {
+      try (DirectoryStream<Path> stream = Files.newDirectoryStream(storageDir.toPath())) {
+        for (Path path : stream) {
+          String[] items = path.getFileName().toString().split("_");
+          ConsensusGroupId consensusGroupId =
+              ConsensusGroupId.Factory.create(
+                  Integer.parseInt(items[0]), Integer.parseInt(items[1]));
+          MultiLeaderServerImpl consensus =
+              new MultiLeaderServerImpl(
+                  path.toString(),
+                  new Peer(consensusGroupId, thisNode),
+                  new ArrayList<>(),
+                  registry.apply(consensusGroupId));
+          stateMachineMap.put(consensusGroupId, consensus);
+          consensus.start();
+        }
+      }
+    }
+  }
+
+  @Override
+  public void stop() {
+    stateMachineMap.values().parallelStream().forEach(MultiLeaderServerImpl::stop);
+    registerManager.deregisterAll();
+  }
+
+  @Override
+  public ConsensusWriteResponse write(ConsensusGroupId groupId, IConsensusRequest request) {
+    MultiLeaderServerImpl impl = stateMachineMap.get(groupId);
+    if (impl == null) {
+      return ConsensusWriteResponse.newBuilder()
+          .setException(new ConsensusGroupNotExistException(groupId))
+          .build();
+    }
+    return ConsensusWriteResponse.newBuilder().setStatus(impl.write(request)).build();
+  }
+
+  @Override
+  public ConsensusReadResponse read(ConsensusGroupId groupId, IConsensusRequest request) {
+    MultiLeaderServerImpl impl = stateMachineMap.get(groupId);
+    if (impl == null) {
+      return ConsensusReadResponse.newBuilder()
+          .setException(new ConsensusGroupNotExistException(groupId))
+          .build();
+    }
+    return ConsensusReadResponse.newBuilder().setDataSet(impl.read(request)).build();
+  }
+
+  @Override
+  public ConsensusGenericResponse addConsensusGroup(ConsensusGroupId groupId, List<Peer> peers) {

Review Comment:
   Is is possible that `thisNode` is not contained in `peers`?



##########
consensus/src/main/java/org/apache/iotdb/consensus/multileader/client/DispatchLogHandler.java:
##########
@@ -0,0 +1,100 @@
+/*
+ * 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.iotdb.consensus.multileader.client;
+
+import org.apache.iotdb.consensus.multileader.conf.MultiLeaderConsensusConfig;
+import org.apache.iotdb.consensus.multileader.logdispatcher.LogDispatcher.LogDispatcherThread;
+import org.apache.iotdb.consensus.multileader.logdispatcher.PendingBatch;
+import org.apache.iotdb.consensus.multileader.thrift.TSyncLogRes;
+import org.apache.iotdb.rpc.TSStatusCode;
+
+import org.apache.thrift.async.AsyncMethodCallback;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.concurrent.CompletableFuture;
+
+public class DispatchLogHandler implements AsyncMethodCallback<TSyncLogRes> {
+
+  private final Logger logger = LoggerFactory.getLogger(DispatchLogHandler.class);
+
+  private final LogDispatcherThread thread;
+  private final PendingBatch batch;
+  private int retryCount;
+
+  public DispatchLogHandler(LogDispatcherThread thread, PendingBatch batch) {
+    this.thread = thread;
+    this.batch = batch;
+  }
+
+  @Override
+  public void onComplete(TSyncLogRes response) {
+    if (response.getStatus().size() == 1
+        && response.getStatus().get(0).getCode()
+            == TSStatusCode.INTERNAL_SERVER_ERROR.getStatusCode()) {
+      logger.warn(
+          "Can not send {} to peer {} for {} times because {}",
+          batch,
+          thread.getPeer(),
+          ++retryCount,
+          response.getStatus().get(0).getMessage());
+      sleepCorrespondingTimeAndRetryAsynchronous();
+    } else {
+      thread.getSyncStatus().removeBatch(batch);
+    }
+  }
+
+  @Override
+  public void onError(Exception exception) {
+    logger.warn(
+        "Can not send {} to peer for {} times {} because {}",
+        batch,
+        thread.getPeer(),
+        ++retryCount,
+        exception);
+    sleepCorrespondingTimeAndRetryAsynchronous();
+  }
+
+  private void sleepCorrespondingTimeAndRetryAsynchronous() {
+    // TODO handle forever retry
+    CompletableFuture.runAsync(
+        () -> {
+          try {
+            long defaultSleepTime =
+                (long)
+                    (MultiLeaderConsensusConfig.BASIC_RETRY_WAIT_TIME_MS * Math.pow(2, retryCount));

Review Comment:
   Should we add an upper-limit on defaultSleepTime, like 2 ^ 16 ms?



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