[WIP] KAFKA-18562: standardize election/fetch timeout between Unattached and Followers

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

@@ -3279,7 +3279,7 @@ private long pollUnattachedAsVoter(UnattachedState state, long currentTimeMs) {
             // If shutting down, then remain in this state until either the
             // shutdown completes or an epoch bump forces another state transition
             return shutdown.remainingTimeMs();
-        } else if (state.hasElectionTimeoutExpired(currentTimeMs)) {
+        } else if (state.hasFetchTimeoutExpired(currentTimeMs)) {
             transitionToProspective(currentTimeMs);
             return 0L;
         } else {

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

@@ -45,7 +45,7 @@
  *
  * Unattached transitions to:
  *    Unattached:  After learning of a new election with a higher epoch or after giving a binding vote
- *    Prospective: After expiration of the election timeout
+ *    Prospective: After expiration of the fetch timeout
  *    Follower:    After discovering a leader with an equal or larger epoch
  *
  * Prospective transitions to:
@@ -170,6 +170,7 @@ public void initialize(OffsetAndEpoch logEndOffsetAndEpoch) throws IllegalStateE
                 partitionState.lastVoterSet().voterIds(),
                 Optional.empty(),
                 randomElectionTimeoutMs(),
+                fetchTimeoutMs,
                 logContext
             );
         } else if (localId.isPresent() && election.isLeader(localId.getAsInt())) {
@@ -230,6 +231,7 @@ public void initialize(OffsetAndEpoch logEndOffsetAndEpoch) throws IllegalStateE
                     partitionState.lastVoterSet().voterIds(),
                     Optional.empty(),
                     randomElectionTimeoutMs(),
+                    fetchTimeoutMs,
                     logContext
                 );
             } else {
@@ -254,6 +256,7 @@ public void initialize(OffsetAndEpoch logEndOffsetAndEpoch) throws IllegalStateE
                 partitionState.lastVoterSet().voterIds(),
                 Optional.empty(),
                 randomElectionTimeoutMs(),
+                fetchTimeoutMs,
                 logContext
             );
         }
@@ -418,6 +421,7 @@ public void transitionToUnattached(int epoch, OptionalInt leaderId) {
             partitionState.lastVoterSet().voterIds(),
             state.highWatermark(),
             electionTimeoutMs,
+            fetchTimeoutMs,
             logContext
         ));
     }
@@ -467,6 +471,7 @@ public void unattachedAddVotedState(
                 partitionState.lastVoterSet().voterIds(),
                 state.highWatermark(),
                 randomElectionTimeoutMs(),
+                fetchTimeoutMs,
                 logContext
             )
         );

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

@@ -47,7 +47,9 @@ public class UnattachedState implements EpochState {
     private final Optional<ReplicaKey> votedKey;
     private final Set<Integer> voters;
     private final long electionTimeoutMs;
+    private final int fetchTimeoutMs;
     private final Timer electionTimer;
+    private final Timer fetchTimer;
     private final Optional<LogOffsetMetadata> highWatermark;
     private final Logger log;
 
@@ -59,6 +61,7 @@ public UnattachedState(
         Set<Integer> voters,
         Optional<LogOffsetMetadata> highWatermark,
         long electionTimeoutMs,
+        int fetchTimeoutMs,
         LogContext logContext
     ) {
         this.epoch = epoch;
@@ -67,7 +70,9 @@ public UnattachedState(
         this.voters = voters;
         this.highWatermark = highWatermark;
         this.electionTimeoutMs = electionTimeoutMs;
+        this.fetchTimeoutMs = fetchTimeoutMs;
         this.electionTimer = time.timer(electionTimeoutMs);
+        this.fetchTimer = time.timer(fetchTimeoutMs);
         this.log = logContext.logger(UnattachedState.class);
     }
 
@@ -105,6 +110,10 @@ public long electionTimeoutMs() {
         return electionTimeoutMs;
     }
 
+    public int fetchTimeoutMs() {
+        return fetchTimeoutMs;
+    }
+
     public long remainingElectionTimeMs(long currentTimeMs) {
         electionTimer.update(currentTimeMs);
         return electionTimer.remainingMs();
@@ -115,6 +124,11 @@ public boolean hasElectionTimeoutExpired(long currentTimeMs) {
         return electionTimer.isExpired();
     }
 
+    public boolean hasFetchTimeoutExpired(long currentTimeMs) {
+        fetchTimer.update(currentTimeMs);
+        return fetchTimer.isExpired();
+    }
+
     @Override
     public Optional<LogOffsetMetadata> highWatermark() {
         return highWatermark;

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

@@ -321,15 +321,16 @@ public void testInitializeAsResignedAndUnableToContactQuorum(boolean withKip853R
         assertEquals(0L, context.log.endOffset().offset());
         context.assertElectedLeader(epoch, localId);
 
-        // Election timeout
-        context.time.sleep(context.electionTimeoutMs());
+        // fetch timeout
+        context.time.sleep(context.fetchTimeoutMs);
         context.client.poll();
 
         // Become unattached with expired election timeout
         assertTrue(context.client.quorum().isUnattached());
         assertEquals(epoch + 1, context.currentEpoch());
 
-        // Become prospective immediately
+        // Become prospective after the fetch timeout
+        context.time.sleep(context.fetchTimeoutMs);
         context.client.poll();
         assertTrue(context.client.quorum().isProspective());
 
@@ -763,15 +764,15 @@ public void testElectionTimeoutAfterUserInitiatedResign(boolean withKip853Rpc) t
             OptionalInt.of(localId)
         );
 
-        // After the election timer, local should become unattached.
-        context.time.sleep(2L * context.electionTimeoutMs());
+        // After the fetch timeout, local should become unattached.
+        context.time.sleep(context.fetchTimeoutMs);
         context.pollUntil(context.client.quorum()::isUnattached);
         assertEquals(resignedEpoch + 1, context.currentEpoch());
         assertEquals(new LeaderAndEpoch(OptionalInt.empty(), resignedEpoch + 1),
             context.listener.currentLeaderAndEpoch());
 
-        // Local will become prospective right away
         assertEquals(0, context.client.quorum().unattachedStateOrThrow().electionTimeoutMs());
+        context.time.sleep(context.fetchTimeoutMs);
         context.client.poll();
         assertTrue(context.client.quorum().isProspective());
     }
@@ -886,8 +887,8 @@ public void testInitializeAsUnattachedAndBecomeLeader(boolean withKip853Rpc) thr
         assertTrue(context.client.quorum().isUnattached());
         assertTrue(context.client.quorum().isVoter());
 
-        // after election timeout should become prospective
-        context.time.sleep(context.electionTimeoutMs() * 2L);
+        // after fetch timeout should become prospective
+        context.time.sleep(context.fetchTimeoutMs);
         context.pollUntilRequest();
         assertTrue(context.client.quorum().isProspective());
 
@@ -1604,7 +1605,7 @@ public void testHandleVoteRequestAsProspectiveWithVotedCandidate(boolean withKip
             .build();
 
         // Sleep a little to ensure that we become a prospective
-        context.time.sleep(context.electionTimeoutMs() * 2L);
+        context.time.sleep(context.fetchTimeoutMs);
         context.client.poll();
         assertTrue(context.client.quorum().isProspectiveAndVoted());
         context.assertVotedCandidate(epoch, votedCandidateKey.id());
@@ -4113,7 +4114,7 @@ public void testClusterAuthorizationFailedInBeginQuorumEpoch(boolean withKip853R
             .withKip853Rpc(withKip853Rpc)
             .build();
 
-        context.time.sleep(context.electionTimeoutMs());
+        context.time.sleep(context.fetchTimeoutMs);
         context.expectAndGrantPreVotes(epoch - 1);
         context.expectAndGrantVotes(epoch);
 

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

@@ -572,7 +572,7 @@ static MemoryRecords buildBatch(
     }
 
     public void unattachedToCandidate() throws Exception {
-        time.sleep(electionTimeoutMs * 2L);
+        time.sleep(fetchTimeoutMs);
         expectAndGrantPreVotes(currentEpoch());
     }
 

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

@@ -39,6 +39,7 @@ public class UnattachedStateTest {
     private final LogContext logContext = new LogContext();
     private final int epoch = 5;
     private final int electionTimeoutMs = 10000;
+    private final int fetchTimeoutMs = 15000;
     private final Set<Integer> voters = Set.of(1, 2, 3);
     private final ReplicaKey voter1Key = ReplicaKey.of(1, Uuid.randomUuid());
     private final ReplicaKey votedKey = voter1Key;
@@ -55,6 +56,7 @@ private UnattachedState newUnattachedState(
             voters,
             Optional.empty(),
             electionTimeoutMs,
+            fetchTimeoutMs,
             logContext
         );
     }