MINOR: Various cleanups in raft (#15805)

Reviewers: Chia-Ping Tsai <chia7712@gmail.com>

raft/src/main/java/org/apache/kafka/raft/FileBasedStateStore.java

@@ -93,7 +93,7 @@ public class FileBasedStateStore implements QuorumStateStore {
             }
 
             if (dataVersionNode.asInt() != 0) {
-                throw new UnsupportedVersionException("Unknown data version of " + dataVersionNode.toString());
+                throw new UnsupportedVersionException("Unknown data version of " + dataVersionNode);
             }
 
             final short dataVersion = dataVersionNode.shortValue();

raft/src/main/java/org/apache/kafka/raft/KafkaRaftClient.java

@@ -1881,12 +1881,10 @@ public class KafkaRaftClient<T> implements RaftClient<T> {
             clusterId,
             quorum().localIdOrSentinel(),
             log.topicPartition(),
-            snapshotPartition -> {
+            snapshotPartition -> snapshotPartition
-                return snapshotPartition
+                .setCurrentLeaderEpoch(quorum.epoch())
-                    .setCurrentLeaderEpoch(quorum.epoch())
+                .setSnapshotId(requestSnapshotId)
-                    .setSnapshotId(requestSnapshotId)
+                .setPosition(snapshotSize)
-                    .setPosition(snapshotSize);
-            }
         );
 
         return request.setReplicaId(quorum.localIdOrSentinel());

raft/src/main/java/org/apache/kafka/raft/QuorumConfig.java

@@ -264,7 +264,7 @@ public class QuorumConfig {
             }
 
             @SuppressWarnings("unchecked")
-            List<String> voterStrings = (List) value;
+            List<String> voterStrings = (List<String>) value;
 
             // Attempt to parse the connect strings
             parseVoterConnections(voterStrings);

raft/src/test/java/org/apache/kafka/raft/FileBasedStateStoreTest.java

@@ -130,15 +130,9 @@ public class FileBasedStateStoreTest {
         // We initialized a state from the metadata log
         assertTrue(stateFile.exists());
 
-        final int epoch = 3012;
-        final int leaderId = 9990;
-        final int follower1 = leaderId + 1;
-        final int follower2 = follower1 + 1;
-        Set<Integer> voters = Utils.mkSet(leaderId, follower1, follower2);
         writeToStateFile(stateFile, jsonString);
 
-        assertThrows(UnsupportedVersionException.class, () -> {
+        assertThrows(UnsupportedVersionException.class, () -> stateStore.readElectionState());
-            stateStore.readElectionState(); });
 
         stateStore.clear();
         assertFalse(stateFile.exists());

raft/src/test/java/org/apache/kafka/raft/KafkaNetworkChannelTest.java

@@ -83,7 +83,6 @@ public class KafkaNetworkChannelTest {
         ApiKeys.FETCH
     );
 
-    private final String clusterId = "clusterId";
     private final int requestTimeoutMs = 30000;
     private final Time time = new MockTime();
     private final MockClient client = new MockClient(time, new StubMetadataUpdater());
@@ -220,11 +219,11 @@ public class KafkaNetworkChannelTest {
         AbstractRequest request = client.requests().peek().requestBuilder().build(version);
 
         if (version < 15) {
-            assertTrue(((FetchRequest) request).data().replicaId() == 1);
+            assertEquals(1, ((FetchRequest) request).data().replicaId());
-            assertTrue(((FetchRequest) request).data().replicaState().replicaId() == -1);
+            assertEquals(-1, ((FetchRequest) request).data().replicaState().replicaId());
         } else {
-            assertTrue(((FetchRequest) request).data().replicaId() == -1);
+            assertEquals(-1, ((FetchRequest) request).data().replicaId());
-            assertTrue(((FetchRequest) request).data().replicaState().replicaId() == 1);
+            assertEquals(1, ((FetchRequest) request).data().replicaState().replicaId());
         }
     }
 
@@ -256,6 +255,7 @@ public class KafkaNetworkChannelTest {
     private ApiMessage buildTestRequest(ApiKeys key) {
         int leaderEpoch = 5;
         int leaderId = 1;
+        String clusterId = "clusterId";
         switch (key) {
             case BEGIN_QUORUM_EPOCH:
                 return BeginQuorumEpochRequest.singletonRequest(topicPartition, clusterId, leaderEpoch, leaderId);

raft/src/test/java/org/apache/kafka/raft/KafkaRaftClientSnapshotTest.java

@@ -1873,12 +1873,10 @@ final public class KafkaRaftClientSnapshotTest {
             clusterId,
             replicaId,
             topicPartition,
-            snapshotPartition -> {
+            snapshotPartition -> snapshotPartition
-                return snapshotPartition
+                .setCurrentLeaderEpoch(epoch)
-                    .setCurrentLeaderEpoch(epoch)
+                .setSnapshotId(snapshotId)
-                    .setSnapshotId(snapshotId)
+                .setPosition(position)
-                    .setPosition(position);
-            }
         );
 
         return request.setMaxBytes(maxBytes);
@@ -1963,8 +1961,8 @@ final public class KafkaRaftClientSnapshotTest {
 
     private final static class MemorySnapshotWriter implements RawSnapshotWriter {
         private final OffsetAndEpoch snapshotId;
+        private final AtomicLong frozenPosition;
         private ByteBuffer data;
-        private AtomicLong frozenPosition;
 
         public MemorySnapshotWriter(OffsetAndEpoch snapshotId) {
             this.snapshotId = snapshotId;

raft/src/test/java/org/apache/kafka/raft/LeaderStateTest.java

@@ -571,7 +571,7 @@ public class LeaderStateTest {
     }
 
     private DescribeQuorumResponseData.ReplicaState describeVoterState(
-        LeaderState state,
+        LeaderState<?> state,
         int voterId,
         long currentTimeMs
     ) {
@@ -580,7 +580,7 @@ public class LeaderStateTest {
     }
 
     private DescribeQuorumResponseData.ReplicaState describeObserverState(
-        LeaderState state,
+        LeaderState<?> state,
         int observerId,
         long currentTimeMs
     ) {

raft/src/test/java/org/apache/kafka/raft/MockLogTest.java

@@ -35,7 +35,6 @@ import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 
-import java.io.IOException;
 import java.nio.ByteBuffer;
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -217,7 +216,7 @@ public class MockLogTest {
     }
 
     @Test
-    public void testAppendAsFollower() throws IOException {
+    public void testAppendAsFollower() {
         final long initialOffset = 5;
         final int epoch = 3;
         SimpleRecord recordFoo = new SimpleRecord("foo".getBytes());
@@ -332,8 +331,6 @@ public class MockLogTest {
         LogFetchInfo readInfo = log.read(5, Isolation.UNCOMMITTED);
         assertEquals(5L, readInfo.startOffsetMetadata.offset);
         assertTrue(readInfo.startOffsetMetadata.metadata.isPresent());
-        MockLog.MockOffsetMetadata offsetMetadata = (MockLog.MockOffsetMetadata)
-            readInfo.startOffsetMetadata.metadata.get();
 
         // Update to a high watermark with valid offset metadata
         log.updateHighWatermark(readInfo.startOffsetMetadata);
@@ -381,7 +378,7 @@ public class MockLogTest {
     }
 
     @Test
-    public void testReadOutOfRangeOffset() throws IOException {
+    public void testReadOutOfRangeOffset() {
         final long initialOffset = 5L;
         final int epoch = 3;
         SimpleRecord recordFoo = new SimpleRecord("foo".getBytes());
@@ -431,7 +428,7 @@ public class MockLogTest {
     }
 
     @Test
-    public void testCreateSnapshot() throws IOException {
+    public void testCreateSnapshot() {
         int numberOfRecords = 10;
         int epoch = 0;
         OffsetAndEpoch snapshotId = new OffsetAndEpoch(numberOfRecords, epoch);
@@ -588,7 +585,7 @@ public class MockLogTest {
     }
 
     @Test
-    public void testUpdateLogStartOffset() throws IOException {
+    public void testUpdateLogStartOffset() {
         int offset = 10;
         int epoch = 0;
         OffsetAndEpoch snapshotId = new OffsetAndEpoch(offset, epoch);
@@ -634,7 +631,7 @@ public class MockLogTest {
     }
 
     @Test
-    public void testFailToIncreaseLogStartPastHighWatermark() throws IOException {
+    public void testFailToIncreaseLogStartPastHighWatermark() {
         int offset = 10;
         int epoch = 0;
         OffsetAndEpoch snapshotId = new OffsetAndEpoch(2 * offset, epoch);
@@ -653,7 +650,7 @@ public class MockLogTest {
     }
 
     @Test
-    public void testTruncateFullyToLatestSnapshot() throws IOException {
+    public void testTruncateFullyToLatestSnapshot() {
         int numberOfRecords = 10;
         int epoch = 0;
         OffsetAndEpoch sameEpochSnapshotId = new OffsetAndEpoch(2 * numberOfRecords, epoch);
@@ -686,7 +683,7 @@ public class MockLogTest {
     }
 
     @Test
-    public void testDoesntTruncateFully() throws IOException {
+    public void testDoesntTruncateFully() {
         int numberOfRecords = 10;
         int epoch = 1;
 
@@ -710,7 +707,7 @@ public class MockLogTest {
     }
 
     @Test
-    public void testTruncateWillRemoveOlderSnapshot() throws IOException {
+    public void testTruncateWillRemoveOlderSnapshot() {
         int numberOfRecords = 10;
         int epoch = 1;
 
@@ -734,7 +731,7 @@ public class MockLogTest {
     }
 
     @Test
-    public void testUpdateLogStartOffsetWillRemoveOlderSnapshot() throws IOException {
+    public void testUpdateLogStartOffsetWillRemoveOlderSnapshot() {
         int numberOfRecords = 10;
         int epoch = 1;
 
@@ -771,7 +768,7 @@ public class MockLogTest {
     }
 
     @Test
-    public void testValidateEpochLessThanOldestSnapshotEpoch() throws IOException {
+    public void testValidateEpochLessThanOldestSnapshotEpoch() {
         int offset = 1;
         int epoch = 1;
 
@@ -786,7 +783,7 @@ public class MockLogTest {
     }
 
     @Test
-    public void testValidateOffsetLessThanOldestSnapshotOffset() throws IOException {
+    public void testValidateOffsetLessThanOldestSnapshotOffset() {
         int offset = 2;
         int epoch = 1;
 
@@ -801,7 +798,7 @@ public class MockLogTest {
     }
 
     @Test
-    public void testValidateOffsetEqualToOldestSnapshotOffset() throws IOException {
+    public void testValidateOffsetEqualToOldestSnapshotOffset() {
         int offset = 2;
         int epoch = 1;
 
@@ -816,7 +813,7 @@ public class MockLogTest {
     }
 
     @Test
-    public void testValidateUnknownEpochLessThanLastKnownGreaterThanOldestSnapshot() throws IOException {
+    public void testValidateUnknownEpochLessThanLastKnownGreaterThanOldestSnapshot() {
         int numberOfRecords = 5;
         int offset = 10;
 
@@ -836,7 +833,7 @@ public class MockLogTest {
     }
 
     @Test
-    public void testValidateEpochLessThanFirstEpochInLog() throws IOException {
+    public void testValidateEpochLessThanFirstEpochInLog() {
         int numberOfRecords = 5;
         int offset = 10;
 
@@ -980,7 +977,7 @@ public class MockLogTest {
             Records records = log.read(currentOffset, Isolation.UNCOMMITTED).records;
             List<? extends RecordBatch> batches = Utils.toList(records.batches().iterator());
 
-            assertTrue(batches.size() > 0);
+            assertFalse(batches.isEmpty());
             for (RecordBatch batch : batches) {
                 assertTrue(batch.countOrNull() > 0);
                 assertEquals(currentOffset, batch.baseOffset());

raft/src/test/java/org/apache/kafka/raft/QuorumStateTest.java

@@ -23,7 +23,6 @@ import org.apache.kafka.raft.internals.BatchAccumulator;
 import org.junit.jupiter.api.Test;
 import org.mockito.Mockito;
 
-import java.io.IOException;
 import java.io.UncheckedIOException;
 import java.util.Collections;
 import java.util.Optional;
@@ -45,8 +44,7 @@ public class QuorumStateTest {
     private final int electionTimeoutMs = 5000;
     private final int fetchTimeoutMs = 10000;
     private final MockableRandom random = new MockableRandom(1L);
-
+    private final BatchAccumulator<?> accumulator = Mockito.mock(BatchAccumulator.class);
-    private BatchAccumulator<?> accumulator = Mockito.mock(BatchAccumulator.class);
 
     private QuorumState buildQuorumState(Set<Integer> voters) {
         return buildQuorumState(OptionalInt.of(localId), voters);
@@ -69,7 +67,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testInitializePrimordialEpoch() throws IOException {
+    public void testInitializePrimordialEpoch() {
         Set<Integer> voters = Utils.mkSet(localId);
         assertNull(store.readElectionState());
 
@@ -83,7 +81,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testInitializeAsUnattached() throws IOException {
+    public void testInitializeAsUnattached() {
         int node1 = 1;
         int node2 = 2;
         int epoch = 5;
@@ -104,7 +102,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testInitializeAsFollower() throws IOException {
+    public void testInitializeAsFollower() {
         int node1 = 1;
         int node2 = 2;
         int epoch = 5;
@@ -123,7 +121,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testInitializeAsVoted() throws IOException {
+    public void testInitializeAsVoted() {
         int node1 = 1;
         int node2 = 2;
         int epoch = 5;
@@ -146,7 +144,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testInitializeAsResignedCandidate() throws IOException {
+    public void testInitializeAsResignedCandidate() {
         int node1 = 1;
         int node2 = 2;
         int epoch = 5;
@@ -173,7 +171,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testInitializeAsResignedLeader() throws IOException {
+    public void testInitializeAsResignedLeader() {
         int node1 = 1;
         int node2 = 2;
         int epoch = 5;
@@ -203,7 +201,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testCandidateToCandidate() throws IOException {
+    public void testCandidateToCandidate() {
         int node1 = 1;
         int node2 = 2;
         Set<Integer> voters = Utils.mkSet(localId, node1, node2);
@@ -246,7 +244,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testCandidateToResigned() throws IOException {
+    public void testCandidateToResigned() {
         int node1 = 1;
         int node2 = 2;
         Set<Integer> voters = Utils.mkSet(localId, node1, node2);
@@ -263,7 +261,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testCandidateToLeader() throws IOException {
+    public void testCandidateToLeader()  {
         Set<Integer> voters = Utils.mkSet(localId);
         assertNull(store.readElectionState());
 
@@ -273,14 +271,14 @@ public class QuorumStateTest {
         assertEquals(1, state.epoch());
 
         state.transitionToLeader(0L, accumulator);
-        LeaderState leaderState = state.leaderStateOrThrow();
+        LeaderState<Object> leaderState = state.leaderStateOrThrow();
         assertTrue(state.isLeader());
         assertEquals(1, leaderState.epoch());
         assertEquals(Optional.empty(), leaderState.highWatermark());
     }
 
     @Test
-    public void testCandidateToLeaderWithoutGrantedVote() throws IOException {
+    public void testCandidateToLeaderWithoutGrantedVote() {
         int otherNodeId = 1;
         Set<Integer> voters = Utils.mkSet(localId, otherNodeId);
         QuorumState state = initializeEmptyState(voters);
@@ -295,7 +293,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testCandidateToFollower() throws IOException {
+    public void testCandidateToFollower() {
         int otherNodeId = 1;
         Set<Integer> voters = Utils.mkSet(localId, otherNodeId);
         QuorumState state = initializeEmptyState(voters);
@@ -309,7 +307,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testCandidateToUnattached() throws IOException {
+    public void testCandidateToUnattached() {
         int otherNodeId = 1;
         Set<Integer> voters = Utils.mkSet(localId, otherNodeId);
         QuorumState state = initializeEmptyState(voters);
@@ -323,7 +321,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testCandidateToVoted() throws IOException {
+    public void testCandidateToVoted() {
         int otherNodeId = 1;
         Set<Integer> voters = Utils.mkSet(localId, otherNodeId);
         QuorumState state = initializeEmptyState(voters);
@@ -340,7 +338,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testCandidateToAnyStateLowerEpoch() throws IOException {
+    public void testCandidateToAnyStateLowerEpoch() {
         int otherNodeId = 1;
         Set<Integer> voters = Utils.mkSet(localId, otherNodeId);
         QuorumState state = initializeEmptyState(voters);
@@ -355,7 +353,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testLeaderToLeader() throws IOException {
+    public void testLeaderToLeader() {
         Set<Integer> voters = Utils.mkSet(localId);
         assertNull(store.readElectionState());
 
@@ -372,7 +370,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testLeaderToResigned() throws IOException {
+    public void testLeaderToResigned() {
         Set<Integer> voters = Utils.mkSet(localId);
         assertNull(store.readElectionState());
 
@@ -393,7 +391,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testLeaderToCandidate() throws IOException {
+    public void testLeaderToCandidate() {
         Set<Integer> voters = Utils.mkSet(localId);
         assertNull(store.readElectionState());
 
@@ -410,7 +408,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testLeaderToFollower() throws IOException {
+    public void testLeaderToFollower() {
         int otherNodeId = 1;
         Set<Integer> voters = Utils.mkSet(localId, otherNodeId);
 
@@ -427,7 +425,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testLeaderToUnattached() throws IOException {
+    public void testLeaderToUnattached() {
         int otherNodeId = 1;
         Set<Integer> voters = Utils.mkSet(localId, otherNodeId);
         QuorumState state = initializeEmptyState(voters);
@@ -442,7 +440,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testLeaderToVoted() throws IOException {
+    public void testLeaderToVoted() {
         int otherNodeId = 1;
         Set<Integer> voters = Utils.mkSet(localId, otherNodeId);
         QuorumState state = initializeEmptyState(voters);
@@ -460,7 +458,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testLeaderToAnyStateLowerEpoch() throws IOException {
+    public void testLeaderToAnyStateLowerEpoch() {
         int otherNodeId = 1;
         Set<Integer> voters = Utils.mkSet(localId, otherNodeId);
         QuorumState state = initializeEmptyState(voters);
@@ -477,7 +475,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testCannotFollowOrVoteForSelf() throws IOException {
+    public void testCannotFollowOrVoteForSelf() {
         Set<Integer> voters = Utils.mkSet(localId);
         assertNull(store.readElectionState());
         QuorumState state = initializeEmptyState(voters);
@@ -487,7 +485,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testUnattachedToLeaderOrResigned() throws IOException {
+    public void testUnattachedToLeaderOrResigned() {
         int leaderId = 1;
         int epoch = 5;
         Set<Integer> voters = Utils.mkSet(localId, leaderId);
@@ -500,7 +498,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testUnattachedToVotedSameEpoch() throws IOException {
+    public void testUnattachedToVotedSameEpoch() {
         int otherNodeId = 1;
         Set<Integer> voters = Utils.mkSet(localId, otherNodeId);
         QuorumState state = initializeEmptyState(voters);
@@ -522,7 +520,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testUnattachedToVotedHigherEpoch() throws IOException {
+    public void testUnattachedToVotedHigherEpoch() {
         int otherNodeId = 1;
         Set<Integer> voters = Utils.mkSet(localId, otherNodeId);
         QuorumState state = initializeEmptyState(voters);
@@ -537,7 +535,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testUnattachedToCandidate() throws IOException {
+    public void testUnattachedToCandidate() {
         int otherNodeId = 1;
         Set<Integer> voters = Utils.mkSet(localId, otherNodeId);
         QuorumState state = initializeEmptyState(voters);
@@ -556,7 +554,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testUnattachedToUnattached() throws IOException {
+    public void testUnattachedToUnattached() {
         int otherNodeId = 1;
         Set<Integer> voters = Utils.mkSet(localId, otherNodeId);
         QuorumState state = initializeEmptyState(voters);
@@ -576,7 +574,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testUnattachedToFollowerSameEpoch() throws IOException {
+    public void testUnattachedToFollowerSameEpoch() {
         int otherNodeId = 1;
         Set<Integer> voters = Utils.mkSet(localId, otherNodeId);
         QuorumState state = initializeEmptyState(voters);
@@ -592,7 +590,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testUnattachedToFollowerHigherEpoch() throws IOException {
+    public void testUnattachedToFollowerHigherEpoch() {
         int otherNodeId = 1;
         Set<Integer> voters = Utils.mkSet(localId, otherNodeId);
         QuorumState state = initializeEmptyState(voters);
@@ -608,7 +606,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testUnattachedToAnyStateLowerEpoch() throws IOException {
+    public void testUnattachedToAnyStateLowerEpoch() {
         int otherNodeId = 1;
         Set<Integer> voters = Utils.mkSet(localId, otherNodeId);
         QuorumState state = initializeEmptyState(voters);
@@ -622,7 +620,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testVotedToInvalidLeaderOrResigned() throws IOException {
+    public void testVotedToInvalidLeaderOrResigned() {
         int node1 = 1;
         int node2 = 2;
         Set<Integer> voters = Utils.mkSet(localId, node1, node2);
@@ -634,7 +632,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testVotedToCandidate() throws IOException {
+    public void testVotedToCandidate() {
         int node1 = 1;
         int node2 = 2;
         Set<Integer> voters = Utils.mkSet(localId, node1, node2);
@@ -653,7 +651,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testVotedToVotedSameEpoch() throws IOException {
+    public void testVotedToVotedSameEpoch() {
         int node1 = 1;
         int node2 = 2;
         Set<Integer> voters = Utils.mkSet(localId, node1, node2);
@@ -666,7 +664,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testVotedToFollowerSameEpoch() throws IOException {
+    public void testVotedToFollowerSameEpoch() {
         int node1 = 1;
         int node2 = 2;
         Set<Integer> voters = Utils.mkSet(localId, node1, node2);
@@ -682,7 +680,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testVotedToFollowerHigherEpoch() throws IOException {
+    public void testVotedToFollowerHigherEpoch() {
         int node1 = 1;
         int node2 = 2;
         Set<Integer> voters = Utils.mkSet(localId, node1, node2);
@@ -698,7 +696,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testVotedToUnattachedSameEpoch() throws IOException {
+    public void testVotedToUnattachedSameEpoch() {
         int node1 = 1;
         int node2 = 2;
         Set<Integer> voters = Utils.mkSet(localId, node1, node2);
@@ -709,7 +707,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testVotedToUnattachedHigherEpoch() throws IOException {
+    public void testVotedToUnattachedHigherEpoch() {
         int otherNodeId = 1;
         Set<Integer> voters = Utils.mkSet(localId, otherNodeId);
         QuorumState state = initializeEmptyState(voters);
@@ -729,7 +727,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testVotedToAnyStateLowerEpoch() throws IOException {
+    public void testVotedToAnyStateLowerEpoch() {
         int otherNodeId = 1;
         Set<Integer> voters = Utils.mkSet(localId, otherNodeId);
         QuorumState state = initializeEmptyState(voters);
@@ -743,7 +741,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testFollowerToFollowerSameEpoch() throws IOException {
+    public void testFollowerToFollowerSameEpoch() {
         int node1 = 1;
         int node2 = 2;
         Set<Integer> voters = Utils.mkSet(localId, node1, node2);
@@ -760,7 +758,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testFollowerToFollowerHigherEpoch() throws IOException {
+    public void testFollowerToFollowerHigherEpoch() {
         int node1 = 1;
         int node2 = 2;
         Set<Integer> voters = Utils.mkSet(localId, node1, node2);
@@ -776,7 +774,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testFollowerToLeaderOrResigned() throws IOException {
+    public void testFollowerToLeaderOrResigned() {
         int node1 = 1;
         int node2 = 2;
         Set<Integer> voters = Utils.mkSet(localId, node1, node2);
@@ -788,7 +786,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testFollowerToCandidate() throws IOException {
+    public void testFollowerToCandidate() {
         int node1 = 1;
         int node2 = 2;
         Set<Integer> voters = Utils.mkSet(localId, node1, node2);
@@ -807,7 +805,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testFollowerToUnattachedSameEpoch() throws IOException {
+    public void testFollowerToUnattachedSameEpoch() {
         int node1 = 1;
         int node2 = 2;
         Set<Integer> voters = Utils.mkSet(localId, node1, node2);
@@ -818,7 +816,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testFollowerToUnattachedHigherEpoch() throws IOException {
+    public void testFollowerToUnattachedHigherEpoch() {
         int node1 = 1;
         int node2 = 2;
         Set<Integer> voters = Utils.mkSet(localId, node1, node2);
@@ -837,7 +835,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testFollowerToVotedSameEpoch() throws IOException {
+    public void testFollowerToVotedSameEpoch() {
         int node1 = 1;
         int node2 = 2;
         Set<Integer> voters = Utils.mkSet(localId, node1, node2);
@@ -851,7 +849,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testFollowerToVotedHigherEpoch() throws IOException {
+    public void testFollowerToVotedHigherEpoch() {
         int node1 = 1;
         int node2 = 2;
         Set<Integer> voters = Utils.mkSet(localId, node1, node2);
@@ -871,7 +869,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testFollowerToAnyStateLowerEpoch() throws IOException {
+    public void testFollowerToAnyStateLowerEpoch() {
         int otherNodeId = 1;
         Set<Integer> voters = Utils.mkSet(localId, otherNodeId);
         QuorumState state = initializeEmptyState(voters);
@@ -885,7 +883,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testCannotBecomeFollowerOfNonVoter() throws IOException {
+    public void testCannotBecomeFollowerOfNonVoter() {
         int otherNodeId = 1;
         int nonVoterId = 2;
         Set<Integer> voters = Utils.mkSet(localId, otherNodeId);
@@ -896,7 +894,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testObserverCannotBecomeCandidateOrLeaderOrVoted() throws IOException {
+    public void testObserverCannotBecomeCandidateOrLeaderOrVoted() {
         int otherNodeId = 1;
         Set<Integer> voters = Utils.mkSet(otherNodeId);
         QuorumState state = initializeEmptyState(voters);
@@ -908,7 +906,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testObserverFollowerToUnattached() throws IOException {
+    public void testObserverFollowerToUnattached() {
         int node1 = 1;
         int node2 = 2;
         Set<Integer> voters = Utils.mkSet(node1, node2);
@@ -927,7 +925,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testObserverUnattachedToFollower() throws IOException {
+    public void testObserverUnattachedToFollower() {
         int node1 = 1;
         int node2 = 2;
         Set<Integer> voters = Utils.mkSet(node1, node2);
@@ -959,7 +957,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testInconsistentVotersBetweenConfigAndState() throws IOException {
+    public void testInconsistentVotersBetweenConfigAndState() {
         int otherNodeId = 1;
         Set<Integer> voters = Utils.mkSet(localId, otherNodeId);
 
@@ -975,7 +973,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testHasRemoteLeader() throws IOException {
+    public void testHasRemoteLeader() {
         int otherNodeId = 1;
         Set<Integer> voters = Utils.mkSet(localId, otherNodeId);
 
@@ -1000,7 +998,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testHighWatermarkRetained() throws IOException {
+    public void testHighWatermarkRetained() {
         int otherNodeId = 1;
         Set<Integer> voters = Utils.mkSet(localId, otherNodeId);
 
@@ -1031,7 +1029,7 @@ public class QuorumStateTest {
     }
 
     @Test
-    public void testInitializeWithEmptyLocalId() throws IOException {
+    public void testInitializeWithEmptyLocalId() {
         QuorumState state = buildQuorumState(OptionalInt.empty(), Utils.mkSet(0, 1));
         state.initialize(new OffsetAndEpoch(0L, 0));
 
@@ -1064,7 +1062,7 @@ public class QuorumStateTest {
         assertThrows(IllegalStateException.class, () -> state2.initialize(new OffsetAndEpoch(0, 0)));
     }
 
-    private QuorumState initializeEmptyState(Set<Integer> voters) throws IOException {
+    private QuorumState initializeEmptyState(Set<Integer> voters) {
         QuorumState state = buildQuorumState(voters);
         store.writeElectionState(ElectionState.withUnknownLeader(0, voters));
         state.initialize(new OffsetAndEpoch(0L, logEndEpoch));

raft/src/test/java/org/apache/kafka/raft/RaftClientTestContext.java

@@ -134,10 +134,10 @@ public final class RaftClientTestContext {
         private final MockableRandom random = new MockableRandom(1L);
         private final LogContext logContext = new LogContext();
         private final MockLog log = new MockLog(METADATA_PARTITION, Uuid.METADATA_TOPIC_ID, logContext);
+        private final Uuid clusterId = Uuid.randomUuid();
         private final Set<Integer> voters;
         private final OptionalInt localId;
 
-        private Uuid clusterId = Uuid.randomUuid();
         private int requestTimeoutMs = DEFAULT_REQUEST_TIMEOUT_MS;
         private int electionTimeoutMs = DEFAULT_ELECTION_TIMEOUT_MS;
         private int appendLingerMs = DEFAULT_APPEND_LINGER_MS;
@@ -152,17 +152,17 @@ public final class RaftClientTestContext {
             this.localId = localId;
         }
 
-        Builder withElectedLeader(int epoch, int leaderId) throws IOException {
+        Builder withElectedLeader(int epoch, int leaderId) {
             quorumStateStore.writeElectionState(ElectionState.withElectedLeader(epoch, leaderId, voters));
             return this;
         }
 
-        Builder withUnknownLeader(int epoch) throws IOException {
+        Builder withUnknownLeader(int epoch) {
             quorumStateStore.writeElectionState(ElectionState.withUnknownLeader(epoch, voters));
             return this;
         }
 
-        Builder withVotedCandidate(int epoch, int votedId) throws IOException {
+        Builder withVotedCandidate(int epoch, int votedId) {
             quorumStateStore.writeElectionState(ElectionState.withVotedCandidate(epoch, votedId, voters));
             return this;
         }
@@ -201,14 +201,14 @@ public final class RaftClientTestContext {
             return this;
         }
 
-        Builder withEmptySnapshot(OffsetAndEpoch snapshotId) throws IOException {
+        Builder withEmptySnapshot(OffsetAndEpoch snapshotId) {
             try (RawSnapshotWriter snapshot = log.storeSnapshot(snapshotId).get()) {
                 snapshot.freeze();
             }
             return this;
         }
 
-        Builder deleteBeforeSnapshot(OffsetAndEpoch snapshotId) throws IOException {
+        Builder deleteBeforeSnapshot(OffsetAndEpoch snapshotId) {
             if (snapshotId.offset() > log.highWatermark().offset) {
                 log.updateHighWatermark(new LogOffsetMetadata(snapshotId.offset()));
             }
@@ -227,11 +227,6 @@ public final class RaftClientTestContext {
             return this;
         }
 
-        Builder withClusterId(Uuid clusterId) {
-            this.clusterId = clusterId;
-            return this;
-        }
-
         public RaftClientTestContext build() throws IOException {
             Metrics metrics = new Metrics(time);
             MockNetworkChannel channel = new MockNetworkChannel(voters);
@@ -432,19 +427,19 @@ public final class RaftClientTestContext {
         pollUntil(channel::hasSentRequests);
     }
 
-    void assertVotedCandidate(int epoch, int leaderId) throws IOException {
+    void assertVotedCandidate(int epoch, int leaderId) {
         assertEquals(ElectionState.withVotedCandidate(epoch, leaderId, voters), quorumStateStore.readElectionState());
     }
 
-    public void assertElectedLeader(int epoch, int leaderId) throws IOException {
+    public void assertElectedLeader(int epoch, int leaderId) {
         assertEquals(ElectionState.withElectedLeader(epoch, leaderId, voters), quorumStateStore.readElectionState());
     }
 
-    void assertUnknownLeader(int epoch) throws IOException {
+    void assertUnknownLeader(int epoch) {
         assertEquals(ElectionState.withUnknownLeader(epoch, voters), quorumStateStore.readElectionState());
     }
 
-    void assertResignedLeader(int epoch, int leaderId) throws IOException {
+    void assertResignedLeader(int epoch, int leaderId) {
         assertTrue(client.quorum().isResigned());
         assertEquals(ElectionState.withElectedLeader(epoch, leaderId, voters), quorumStateStore.readElectionState());
     }
@@ -528,7 +523,7 @@ public final class RaftClientTestContext {
         long lastEpochOffset
     ) {
         List<RaftRequest.Outbound> voteRequests = new ArrayList<>();
-        for (RaftMessage raftMessage : channel.drainSendQueue()) {
+        for (RaftRequest.Outbound raftMessage : channel.drainSendQueue()) {
             if (raftMessage.data() instanceof VoteRequestData) {
                 VoteRequestData request = (VoteRequestData) raftMessage.data();
                 VoteRequestData.PartitionData partitionRequest = unwrap(request);
@@ -537,7 +532,7 @@ public final class RaftClientTestContext {
                 assertEquals(localIdOrThrow(), partitionRequest.candidateId());
                 assertEquals(lastEpoch, partitionRequest.lastOffsetEpoch());
                 assertEquals(lastEpochOffset, partitionRequest.lastOffset());
-                voteRequests.add((RaftRequest.Outbound) raftMessage);
+                voteRequests.add(raftMessage);
             }
         }
         return voteRequests;
@@ -764,7 +759,7 @@ public final class RaftClientTestContext {
     ) {
         List<RaftRequest.Outbound> endQuorumRequests = new ArrayList<>();
         Set<Integer> collectedDestinationIdSet = new HashSet<>();
-        for (RaftMessage raftMessage : channel.drainSendQueue()) {
+        for (RaftRequest.Outbound raftMessage : channel.drainSendQueue()) {
             if (raftMessage.data() instanceof EndQuorumEpochRequestData) {
                 EndQuorumEpochRequestData request = (EndQuorumEpochRequestData) raftMessage.data();
 
@@ -777,9 +772,8 @@ public final class RaftClientTestContext {
                     assertEquals(preferredSuccessors, partitionRequest.preferredSuccessors());
                 });
 
-                RaftRequest.Outbound outboundRequest = (RaftRequest.Outbound) raftMessage;
+                collectedDestinationIdSet.add(raftMessage.destinationId());
-                collectedDestinationIdSet.add(outboundRequest.destinationId());
+                endQuorumRequests.add(raftMessage);
-                endQuorumRequests.add(outboundRequest);
             }
         }
         assertEquals(destinationIdSet, collectedDestinationIdSet);

raft/src/test/java/org/apache/kafka/raft/internals/BatchAccumulatorTest.java

@@ -494,7 +494,7 @@ class BatchAccumulatorTest {
     }
 
     int recordSizeInBytes(String record, int numberOfRecords) {
-        int serdeSize = serde.recordSize("a", new ObjectSerializationCache());
+        int serdeSize = serde.recordSize(record, new ObjectSerializationCache());
 
         int recordSizeInBytes = DefaultRecord.sizeOfBodyInBytes(
             numberOfRecords,
@@ -507,23 +507,15 @@ class BatchAccumulatorTest {
         return ByteUtils.sizeOfVarint(recordSizeInBytes) + recordSizeInBytes;
     }
 
-    static interface Appender {
+    interface Appender {
         Long call(BatchAccumulator<String> acc, int epoch, List<String> records);
     }
 
-    static final Appender APPEND_ATOMIC = new Appender() {
+    static final Appender APPEND_ATOMIC = (acc, epoch, records) ->
-        @Override
+            acc.append(epoch, records, OptionalLong.empty(), true);
-        public Long call(BatchAccumulator<String> acc, int epoch, List<String> records) {
-            return acc.append(epoch, records, OptionalLong.empty(), true);
-        }
-    };
 
-    static final Appender APPEND = new Appender() {
+    static final Appender APPEND = (acc, epoch, records) ->
-        @Override
+            acc.append(epoch, records, OptionalLong.empty(), false);
-        public Long call(BatchAccumulator<String> acc, int epoch, List<String> records) {
-            return acc.append(epoch, records, OptionalLong.empty(), false);
-        }
-    };
 
     @ParameterizedTest
     @ValueSource(booleans = {false, true})

raft/src/test/java/org/apache/kafka/raft/internals/BatchBuilderTest.java

@@ -35,8 +35,8 @@ import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
 class BatchBuilderTest {
-    private StringSerde serde = new StringSerde();
+    private final StringSerde serde = new StringSerde();
-    private MockTime time = new MockTime();
+    private final MockTime time = new MockTime();
 
     @ParameterizedTest
     @EnumSource(CompressionType.class)

raft/src/test/java/org/apache/kafka/raft/internals/KafkaRaftMetricsTest.java

@@ -31,7 +31,6 @@ import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.Test;
 import org.mockito.Mockito;
 
-import java.io.IOException;
 import java.util.Collections;
 import java.util.OptionalInt;
 import java.util.OptionalLong;
@@ -51,7 +50,7 @@ public class KafkaRaftMetricsTest {
     private final Random random = new Random(1);
     private KafkaRaftMetrics raftMetrics;
 
-    private BatchAccumulator<?> accumulator = Mockito.mock(BatchAccumulator.class);
+    private final BatchAccumulator<?> accumulator = Mockito.mock(BatchAccumulator.class);
 
     @AfterEach
     public void tearDown() {
@@ -75,7 +74,7 @@ public class KafkaRaftMetricsTest {
     }
 
     @Test
-    public void shouldRecordVoterQuorumState() throws IOException {
+    public void shouldRecordVoterQuorumState() {
         QuorumState state = buildQuorumState(Utils.mkSet(localId, 1, 2));
 
         state.initialize(new OffsetAndEpoch(0L, 0));
@@ -132,7 +131,7 @@ public class KafkaRaftMetricsTest {
     }
 
     @Test
-    public void shouldRecordNonVoterQuorumState() throws IOException {
+    public void shouldRecordNonVoterQuorumState() {
         QuorumState state = buildQuorumState(Utils.mkSet(1, 2, 3));
         state.initialize(new OffsetAndEpoch(0L, 0));
         raftMetrics = new KafkaRaftMetrics(metrics, "raft", state);
@@ -162,7 +161,7 @@ public class KafkaRaftMetricsTest {
     }
 
     @Test
-    public void shouldRecordLogEnd() throws IOException {
+    public void shouldRecordLogEnd() {
         QuorumState state = buildQuorumState(Collections.singleton(localId));
         state.initialize(new OffsetAndEpoch(0L, 0));
         raftMetrics = new KafkaRaftMetrics(metrics, "raft", state);
@@ -177,7 +176,7 @@ public class KafkaRaftMetricsTest {
     }
 
     @Test
-    public void shouldRecordNumUnknownVoterConnections() throws IOException {
+    public void shouldRecordNumUnknownVoterConnections() {
         QuorumState state = buildQuorumState(Collections.singleton(localId));
         state.initialize(new OffsetAndEpoch(0L, 0));
         raftMetrics = new KafkaRaftMetrics(metrics, "raft", state);
@@ -262,7 +261,7 @@ public class KafkaRaftMetricsTest {
     }
 
     @Test
-    public void shouldRecordLatency() throws IOException {
+    public void shouldRecordLatency() {
         QuorumState state = buildQuorumState(Collections.singleton(localId));
         state.initialize(new OffsetAndEpoch(0L, 0));
         raftMetrics = new KafkaRaftMetrics(metrics, "raft", state);
@@ -293,7 +292,7 @@ public class KafkaRaftMetricsTest {
     }
 
     @Test
-    public void shouldRecordRate() throws IOException {
+    public void shouldRecordRate() {
         QuorumState state = buildQuorumState(Collections.singleton(localId));
         state.initialize(new OffsetAndEpoch(0L, 0));
         raftMetrics = new KafkaRaftMetrics(metrics, "raft", state);

raft/src/test/java/org/apache/kafka/snapshot/FileRawSnapshotTest.java

@@ -85,7 +85,7 @@ public final class FileRawSnapshotTest {
     }
 
     @Test
-    public void testWriteReadSnapshot() throws IOException {
+    public void testWriteReadSnapshot() {
         OffsetAndEpoch offsetAndEpoch = new OffsetAndEpoch(10L, 3);
         int bufferSize = 256;
         int numberOfBatches = 10;
@@ -129,7 +129,7 @@ public final class FileRawSnapshotTest {
     }
 
     @Test
-    public void testPartialWriteReadSnapshot() throws IOException {
+    public void testPartialWriteReadSnapshot() {
         Path tempDir = TestUtils.tempDirectory().toPath();
         OffsetAndEpoch offsetAndEpoch = new OffsetAndEpoch(10L, 3);
 
@@ -169,7 +169,7 @@ public final class FileRawSnapshotTest {
     }
 
     @Test
-    public void testBatchWriteReadSnapshot() throws IOException {
+    public void testBatchWriteReadSnapshot() {
         OffsetAndEpoch offsetAndEpoch = new OffsetAndEpoch(10L, 3);
         int bufferSize = 256;
         int batchSize = 3;