SzyWilliam commented on code in PR #898: URL: https://github.com/apache/ratis/pull/898#discussion_r1333127748
########## ratis-server/src/main/java/org/apache/ratis/server/impl/LeaderLease.java: ########## @@ -0,0 +1,92 @@ +/* + * 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.ratis.server.impl; + +import org.apache.ratis.conf.RaftProperties; +import org.apache.ratis.protocol.RaftPeerId; +import org.apache.ratis.server.RaftServerConfigKeys; +import org.apache.ratis.server.leader.FollowerInfo; +import org.apache.ratis.util.Preconditions; +import org.apache.ratis.util.Timestamp; + +import java.util.List; +import java.util.Optional; +import java.util.concurrent.TimeUnit; +import java.util.concurrent.atomic.AtomicReference; +import java.util.function.Predicate; +import java.util.stream.Collectors; +import java.util.stream.Stream; + +class LeaderLease { + + private final long leaseTimeoutMs; + // TODO invalidate leader lease when stepDown / transferLeader + private final AtomicReference<Timestamp> lease = new AtomicReference<>(Timestamp.currentTime()); + + LeaderLease(RaftProperties properties) { + final double leaseRatio = RaftServerConfigKeys.Read.leaderLeaseTimeoutRatio(properties); + Preconditions.assertTrue(leaseRatio > 0.0 && leaseRatio <= 1.0, + "leader ratio should sit in (0,1], now is " + leaseRatio); + this.leaseTimeoutMs = RaftServerConfigKeys.Rpc.timeoutMin(properties) + .multiply(leaseRatio) + .toIntExact(TimeUnit.MILLISECONDS); + } + + boolean isValid() { + return lease.get().elapsedTimeMs() < leaseTimeoutMs; + } + + /** + * try extending the lease based on group heartbeats + * @param old nullable + */ + void extend(List<FollowerInfo> current, List<FollowerInfo> old, Predicate<List<RaftPeerId>> hasMajority) { + final List<RaftPeerId> activePeers = + // check the latest heartbeats of all peers (including those in transitional) + Stream.concat(current.stream(), Optional.ofNullable(old).map(List::stream).orElse(Stream.empty())) + .filter(f -> f.getLastRespondedAppendEntriesSendTime().elapsedTimeMs() < leaseTimeoutMs) + .map(FollowerInfo::getId) + .collect(Collectors.toList()); + + if (!hasMajority.test(activePeers)) { + return; + } + + // update the new lease + final Timestamp newLease = + Timestamp.earliest(getMaxTimestampWithMajorityAck(current), getMaxTimestampWithMajorityAck(old)); + lease.set(newLease); + } + + /** + * return maximum timestamp at when the majority of followers are known to be active + * return {@link Timestamp#currentTime()} if peers are empty + */ + private Timestamp getMaxTimestampWithMajorityAck(List<FollowerInfo> peers) { + if (peers == null || peers.isEmpty()) { + return Timestamp.currentTime(); + } + + final List<Timestamp> lastRespondedAppendEntriesSendTimes = peers.stream() + .map(FollowerInfo::getLastRespondedAppendEntriesSendTime) + .sorted() + .collect(Collectors.toList()); + + return lastRespondedAppendEntriesSendTimes.get(lastRespondedAppendEntriesSendTimes.size() / 2); + } Review Comment: Thanks a lot for the reviews! Didn't know we can use limit and skip. Now the code is more light-weighted! -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
