jsancio commented on code in PR #18240:
URL: https://github.com/apache/kafka/pull/18240#discussion_r1890554341
##########
raft/src/main/java/org/apache/kafka/raft/KafkaRaftClient.java:
##########
@@ -926,29 +973,16 @@ private boolean handleVoteResponse(
if (quorum.isLeader()) {
logger.debug("Ignoring vote response {} since we already
became leader for epoch {}",
partitionResponse, quorum.epoch());
- } else if (quorum.isCandidate()) {
- CandidateState state = quorum.candidateStateOrThrow();
- if (partitionResponse.voteGranted()) {
- state.recordGrantedVote(remoteNodeId);
- maybeTransitionToLeader(state, currentTimeMs);
- } else {
- state.recordRejectedVote(remoteNodeId);
-
- // If our vote is rejected, we go immediately to the
random backoff. This
- // ensures that we are not stuck waiting for the election
timeout when the
- // vote has become gridlocked.
- if (state.isVoteRejected() && !state.isBackingOff()) {
- logger.info("Insufficient remaining votes to become
leader (rejected by {}). " +
- "We will backoff before retrying election again",
state.rejectingVoters());
-
- state.startBackingOff(
- currentTimeMs,
- binaryExponentialElectionBackoffMs(state.retries())
- );
- }
- }
+ } else if (quorum.isVotingState()) {
+ NomineeState state = quorum.votingStateOrThrow();
Review Comment:
Let's use the same word you used in the `NomineeState`: `isNomineeState()`
and `nomineeStateOrThrow()`.
##########
raft/src/main/java/org/apache/kafka/raft/EpochElection.java:
##########
@@ -0,0 +1,167 @@
+/*
+ * 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.kafka.raft;
Review Comment:
Can we try moving this to the internal module? Anything public in this
package can be used outside the `raft` module.
##########
raft/src/main/java/org/apache/kafka/raft/EpochElection.java:
##########
@@ -0,0 +1,167 @@
+/*
+ * 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.kafka.raft;
+
+import java.util.Collection;
+import java.util.Collections;
+import java.util.Map;
+import java.util.Set;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+public class EpochElection {
+ private Map<Integer, VoterState> voterStates;
+
+ EpochElection(Set<ReplicaKey> voters) {
+ this.voterStates = voters.stream()
+ .collect(Collectors.toMap(
+ ReplicaKey::id,
+ VoterState::new
+ ));
+ }
+
+ VoterState getVoterStateOrThrow(int voterId) {
+ VoterState voterState = voterStates.get(voterId);
+ if (voterState == null) {
+ throw new IllegalArgumentException("Attempt to access voter state
of non-voter " + voterId);
+ }
+ return voterState;
+ }
+
+ boolean recordVote(int voterId, boolean isGranted) {
Review Comment:
Please write Java doc for all public methods.
##########
raft/src/main/java/org/apache/kafka/raft/NomineeState.java:
##########
@@ -0,0 +1,43 @@
+/*
+ * 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.kafka.raft;
+
+interface NomineeState extends EpochState {
+ EpochElection epochElection();
+
+ /**
+ * Record a granted vote from one of the voters.
+ *
+ * @param remoteNodeId The id of the voter
+ * @return true if the voter had not been previously recorded
+ * @throws IllegalArgumentException
+ */
+ boolean recordGrantedVote(int remoteNodeId);
+
+ /**
+ * Record a rejected vote from one of the voters.
+ *
+ * @param remoteNodeId The id of the voter
+ * @return true if the rejected vote had not been previously recorded
+ * @throws IllegalArgumentException
+ */
+ boolean recordRejectedVote(int remoteNodeId);
+
+ boolean hasElectionTimeoutExpired(long currentTimeMs);
+
+ long remainingElectionTimeMs(long currentTimeMs);
Review Comment:
Let's write Java doc for all public methods.
##########
raft/src/main/java/org/apache/kafka/raft/KafkaRaftClient.java:
##########
@@ -883,6 +923,13 @@ private boolean handleVoteResponse(
VoteResponseData response = (VoteResponseData) responseMetadata.data();
Errors topLevelError = Errors.forCode(response.errorCode());
if (topLevelError != Errors.NONE) {
+ if (topLevelError == Errors.UNSUPPORTED_VERSION &&
quorum.isProspective()) {
+ logger.warn("Prospective received unsupported version error in
vote response in epoch {}, " +
+ "transitioning to Candidate state immediately since
entire quorum does not support PreVote.",
+ quorum.epoch());
Review Comment:
This is not a warning. This is a valid state or condition. We should be able
to log this message at INFO level. It should be rare because there are
backoff/timeout logic in Candidate, Follower and Unattached which limit how
quickly a replica transitions to Prospective. What do you think?
##########
raft/src/main/java/org/apache/kafka/raft/EpochElection.java:
##########
@@ -0,0 +1,167 @@
+/*
+ * 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.kafka.raft;
+
+import java.util.Collection;
+import java.util.Collections;
+import java.util.Map;
+import java.util.Set;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+public class EpochElection {
Review Comment:
Can we explicitly mark a private any method that is not used outside of this
class?
##########
raft/src/main/java/org/apache/kafka/raft/ProspectiveState.java:
##########
@@ -0,0 +1,195 @@
+/*
+ * 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.kafka.raft;
+
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.apache.kafka.common.utils.Timer;
+import org.slf4j.Logger;
+
+import java.util.Optional;
+import java.util.OptionalInt;
+
+public class ProspectiveState implements NomineeState {
+ private final int localId;
+ private final int epoch;
+ private final OptionalInt leaderId;
+ private final Optional<Endpoints> leaderEndpoints;
+ private final Optional<ReplicaKey> votedKey;
+ private final VoterSet voters;
+ private final EpochElection epochElection;
+ private final Optional<LogOffsetMetadata> highWatermark;
+ private final Timer electionTimer;
+ private final Logger log;
+
+ /**
+ * The lifetime of a prospective state is the following.
+ *
+ * 1. Once started, it will keep record of the received votes and continue
to fetch from bootstrap voters.
+ * 2. If it receives a fetch response denoting a leader with a higher
epoch, it will transition to follower state.
+ * 3. If majority votes granted, it will transition to leader state.
+ * 4. If majority votes rejected or election times out, it will enter a
backing off phase;
+ * after the backoff phase completes, it will send out another round
of PreVote requests.
+ */
+ public ProspectiveState(
+ Time time,
+ int localId,
+ int epoch,
+ OptionalInt leaderId,
+ Optional<Endpoints> leaderEndpoints,
+ Optional<ReplicaKey> votedKey,
+ VoterSet voters,
+ Optional<LogOffsetMetadata> highWatermark,
+ int electionTimeoutMs,
+ LogContext logContext
+ ) {
+ this.localId = localId;
+ this.epoch = epoch;
+ this.leaderId = leaderId;
+ this.leaderEndpoints = leaderEndpoints;
+ this.votedKey = votedKey;
+ this.voters = voters;
+ this.highWatermark = highWatermark;
+ this.electionTimer = time.timer(electionTimeoutMs);
+ this.log = logContext.logger(ProspectiveState.class);
+
+ this.epochElection = new EpochElection(voters.voterKeys());
+ epochElection.recordVote(localId, true);
//voterStates().get(localId).setState(State.GRANTED);
+ }
+
+ public int localId() {
+ return localId;
+ }
+
+ public Optional<ReplicaKey> votedKey() {
+ return votedKey;
+ }
+
+ @Override
+ public EpochElection epochElection() {
+ return epochElection;
+ }
+
+ @Override
+ public boolean recordGrantedVote(int remoteNodeId) {
+ return epochElection().recordVote(remoteNodeId, true);
+ }
+
+ @Override
+ public boolean recordRejectedVote(int remoteNodeId) {
+ if (remoteNodeId == localId) {
+ throw new IllegalStateException("Attempted to reject vote from
ourselves");
Review Comment:
`IllegalArgumentException` seems like a better exception type.
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