JAkutenshi commented on code in PR #7242: URL: https://github.com/apache/ignite-3/pull/7242#discussion_r2743026038
########## modules/raft/src/test/java/org/apache/ignite/internal/raft/client/LeaderAvailabilityStateTest.java: ########## @@ -0,0 +1,516 @@ +/* + * 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.ignite.internal.raft.client; + +import static org.apache.ignite.internal.testframework.IgniteTestUtils.deriveUuidFrom; +import static org.hamcrest.MatcherAssert.assertThat; +import static org.hamcrest.Matchers.instanceOf; +import static org.junit.jupiter.api.Assertions.assertEquals; +import static org.junit.jupiter.api.Assertions.assertFalse; +import static org.junit.jupiter.api.Assertions.assertSame; +import static org.junit.jupiter.api.Assertions.assertThrows; +import static org.junit.jupiter.api.Assertions.assertTrue; + +import java.util.concurrent.CompletableFuture; +import java.util.concurrent.CompletionException; +import java.util.concurrent.CountDownLatch; +import java.util.concurrent.TimeUnit; +import java.util.concurrent.atomic.AtomicLong; +import org.apache.ignite.internal.network.ClusterNodeImpl; +import org.apache.ignite.internal.network.InternalClusterNode; +import org.apache.ignite.internal.raft.client.LeaderAvailabilityState.State; +import org.apache.ignite.internal.testframework.BaseIgniteAbstractTest; +import org.apache.ignite.network.NetworkAddress; +import org.junit.jupiter.api.Test; + +/** + * Tests for {@link LeaderAvailabilityState} state machine. + */ +public class LeaderAvailabilityStateTest extends BaseIgniteAbstractTest { + + /** Initial state should be WAITING_FOR_LEADER with term -1. */ + @Test + void testInitialState() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + + assertEquals(State.WAITING_FOR_LEADER, state.currentState()); + assertEquals(-1, state.currentTerm()); + } + + /** awaitLeader returns incomplete future when no leader elected. */ + @Test + void testAwaitLeaderWhenNoLeader() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + + CompletableFuture<Long> future = state.awaitLeader(); + + assertFalse(future.isDone(), "Future should not be completed when no leader"); + } + + /** awaitLeader returns completed future when leader is available. */ + @Test + void testAwaitLeaderWhenLeaderAvailable() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leaderNode = createNode("leader-node"); + + state.onLeaderElected(leaderNode, 1); + + CompletableFuture<Long> future = state.awaitLeader(); + + assertTrue(future.isDone(), "Future should be completed when leader available"); + assertEquals(1L, future.join()); + } + + /** onLeaderElected transitions to LEADER_AVAILABLE state. */ + @Test + void testOnLeaderElectedTransition() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leaderNode = createNode("leader-node"); + + state.onLeaderElected(leaderNode, 1); + + assertEquals(State.LEADER_AVAILABLE, state.currentState()); + assertEquals(1, state.currentTerm()); + } + + /** onLeaderElected completes waiting futures. */ + @Test + void testOnLeaderElectedCompletesWaiters() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leaderNode = createNode("leader-node"); + + CompletableFuture<Long> waiter = state.awaitLeader(); + assertFalse(waiter.isDone()); + + state.onLeaderElected(leaderNode, 5); + + assertTrue(waiter.isDone()); + assertEquals(5L, waiter.join()); + } + + /** Stale term notifications are ignored. */ + @Test + void testStaleTermIgnored() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leaderNode1 = createNode("leader-1"); + InternalClusterNode leaderNode2 = createNode("leader-2"); + + state.onLeaderElected(leaderNode1, 5); + assertEquals(5, state.currentTerm()); + + // Stale notification with lower term should be ignored + state.onLeaderElected(leaderNode2, 3); + assertEquals(5, state.currentTerm()); + } + + /** Equal term notifications are ignored. */ + @Test + void testEqualTermIgnored() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leaderNode = createNode("leader"); + + state.onLeaderElected(leaderNode, 5); + assertEquals(5, state.currentTerm()); + + // Same term should be ignored + state.onLeaderElected(leaderNode, 5); + assertEquals(5, state.currentTerm()); + } + + /** Higher term updates current term. */ + @Test + void testHigherTermUpdates() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leaderNode1 = createNode("leader-1"); + InternalClusterNode leaderNode2 = createNode("leader-2"); + + state.onLeaderElected(leaderNode1, 1); + assertEquals(1, state.currentTerm()); + + state.onLeaderElected(leaderNode2, 5); + assertEquals(5, state.currentTerm()); + } + + /** onGroupUnavailable transitions back to WAITING_FOR_LEADER. */ + @Test + void testOnGroupUnavailableTransition() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leaderNode = createNode("leader-node"); + + state.onLeaderElected(leaderNode, 1); + assertEquals(State.LEADER_AVAILABLE, state.currentState()); + + state.onGroupUnavailable(1); + assertEquals(State.WAITING_FOR_LEADER, state.currentState()); + } + + /** onGroupUnavailable ignored if term changed. */ + @Test + void testOnGroupUnavailableIgnoredIfTermChanged() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leaderNode = createNode("leader-node"); + + state.onLeaderElected(leaderNode, 1); + state.onLeaderElected(leaderNode, 2); + assertEquals(State.LEADER_AVAILABLE, state.currentState()); + assertEquals(2, state.currentTerm()); + + // Should be ignored because term changed from 1 to 2 + state.onGroupUnavailable(1); + assertEquals(State.LEADER_AVAILABLE, state.currentState()); + } + + /** onGroupUnavailable has no effect when already in WAITING_FOR_LEADER. */ + @Test + void testOnGroupUnavailableWhenAlreadyWaiting() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + + // Already in WAITING_FOR_LEADER, should have no effect + state.onGroupUnavailable(0); + assertEquals(State.WAITING_FOR_LEADER, state.currentState()); + } + + /** After onGroupUnavailable, new waiters get fresh future. */ + @Test + void testNewWaitersAfterUnavailable() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leaderNode = createNode("leader-node"); + + state.onLeaderElected(leaderNode, 1); + CompletableFuture<Long> future1 = state.awaitLeader(); + assertTrue(future1.isDone()); + + state.onGroupUnavailable(1); + + CompletableFuture<Long> future2 = state.awaitLeader(); + assertFalse(future2.isDone(), "New waiter should get incomplete future after unavailable"); + } + + /** Multiple waiters are all completed on leader election. */ + @Test + void testMultipleWaitersCompleted() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leaderNode = createNode("leader-node"); + + CompletableFuture<Long> waiter1 = state.awaitLeader(); + CompletableFuture<Long> waiter2 = state.awaitLeader(); + CompletableFuture<Long> waiter3 = state.awaitLeader(); + + assertFalse(waiter1.isDone()); + assertFalse(waiter2.isDone()); + assertFalse(waiter3.isDone()); + + state.onLeaderElected(leaderNode, 10); + + assertTrue(waiter1.isDone()); + assertTrue(waiter2.isDone()); + assertTrue(waiter3.isDone()); + + assertEquals(10L, waiter1.join()); + assertEquals(10L, waiter2.join()); + assertEquals(10L, waiter3.join()); + } + + /** Term 0 is accepted as first valid term. */ + @Test + void testTermZeroAccepted() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leaderNode = createNode("leader"); + + assertEquals(-1, state.currentTerm()); + + state.onLeaderElected(leaderNode, 0); + + assertEquals(0, state.currentTerm()); + assertEquals(State.LEADER_AVAILABLE, state.currentState()); + } + + /** Concurrent leader elections with different terms. */ + @Test + void testConcurrentLeaderElections() throws Exception { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + int threadCount = 10; + CountDownLatch startLatch = new CountDownLatch(1); + CountDownLatch doneLatch = new CountDownLatch(threadCount); + AtomicLong maxTerm = new AtomicLong(-1); + + Thread[] threads = new Thread[threadCount]; + for (int i = 0; i < threadCount; i++) { + int term = i; + threads[i] = new Thread(() -> { + try { + startLatch.await(); + InternalClusterNode leader = createNode("leader-" + term); + state.onLeaderElected(leader, term); + maxTerm.updateAndGet(current -> Math.max(current, term)); + } catch (InterruptedException e) { + Thread.currentThread().interrupt(); + } finally { + doneLatch.countDown(); + } + }); + threads[i].start(); + } + + startLatch.countDown(); + assertTrue(doneLatch.await(5, TimeUnit.SECONDS)); + + // The final term should be the maximum term that was set + assertEquals(threadCount - 1, state.currentTerm()); + } + + /** State machine handles rapid state transitions. */ + @Test + void testRapidStateTransitions() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leader = createNode("leader"); + + for (int i = 0; i < 100; i++) { + state.onLeaderElected(leader, i); + assertEquals(State.LEADER_AVAILABLE, state.currentState()); + assertEquals(i, state.currentTerm()); + + state.onGroupUnavailable(i); + assertEquals(State.WAITING_FOR_LEADER, state.currentState()); + } + } + + /** awaitLeader returns same future for multiple calls when waiting. */ + @Test + void testAwaitLeaderReturnsSameFuture() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + + CompletableFuture<Long> future1 = state.awaitLeader(); + CompletableFuture<Long> future2 = state.awaitLeader(); + + // Should return the same future instance when in WAITING_FOR_LEADER state + assertSame(future1, future2, "Should return same future instance when waiting"); + } + + /** awaitLeader returns new completed future for multiple calls when leader available. */ + @Test + void testAwaitLeaderReturnsNewCompletedFuture() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leader = createNode("leader"); + + state.onLeaderElected(leader, 1); + + CompletableFuture<Long> future1 = state.awaitLeader(); + CompletableFuture<Long> future2 = state.awaitLeader(); + + // Both should be completed + assertTrue(future1.isDone()); + assertTrue(future2.isDone()); + } + + /** Stop completes waiting futures exceptionally. */ + @Test + void testStopCompletesExceptionally() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + RuntimeException testException = new RuntimeException("Test shutdown"); + + CompletableFuture<Long> waiter = state.awaitLeader(); + assertFalse(waiter.isDone()); + + state.stop(testException); + + assertTrue(waiter.isDone()); + assertTrue(waiter.isCompletedExceptionally()); + + CompletionException thrown = assertThrows(CompletionException.class, waiter::join); + assertSame(testException, thrown.getCause()); + } + + /** Stop completes multiple waiters exceptionally. */ + @Test + void testStopCompletesMultipleWaiters() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + RuntimeException testException = new RuntimeException("Test shutdown"); + + // All waiters share the same future + CompletableFuture<Long> waiter1 = state.awaitLeader(); + CompletableFuture<Long> waiter2 = state.awaitLeader(); + CompletableFuture<Long> waiter3 = state.awaitLeader(); + + assertFalse(waiter1.isDone()); + assertFalse(waiter2.isDone()); + assertFalse(waiter3.isDone()); + + state.stop(testException); + + assertTrue(waiter1.isCompletedExceptionally()); + assertTrue(waiter2.isCompletedExceptionally()); + assertTrue(waiter3.isCompletedExceptionally()); + } + + /** Stop causes subsequent awaitLeader to fail immediately. */ + @Test + void testStopFailsSubsequentWaiters() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + RuntimeException testException = new RuntimeException("Test shutdown"); + + CompletableFuture<Long> waiter1 = state.awaitLeader(); + state.stop(testException); + + assertTrue(waiter1.isCompletedExceptionally()); + + // New waiter should immediately fail with the same exception + CompletableFuture<Long> waiter2 = state.awaitLeader(); + assertTrue(waiter2.isDone(), "New waiter should be immediately completed"); + assertTrue(waiter2.isCompletedExceptionally()); + + CompletionException thrown = assertThrows(CompletionException.class, waiter2::join); + assertSame(testException, thrown.getCause()); + } + + /** Stop when no waiters are pending still marks state as stopped. */ + @Test + void testStopWhenNoWaiters() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + RuntimeException testException = new RuntimeException("Test shutdown"); + + // Stop without any waiters - should not throw + state.stop(testException); + + assertTrue(state.stopped()); + + // Subsequent awaitLeader should fail + CompletableFuture<Long> waiter = state.awaitLeader(); + assertTrue(waiter.isDone()); + assertTrue(waiter.isCompletedExceptionally()); + + CompletionException thrown = assertThrows(CompletionException.class, waiter::join); + assertSame(testException, thrown.getCause()); + } + + /** Stop when leader is available fails subsequent awaitLeader. */ + @Test + void testStopWhenLeaderAvailable() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leader = createNode("leader"); + RuntimeException testException = new RuntimeException("Test shutdown"); + + state.onLeaderElected(leader, 1); + assertEquals(State.LEADER_AVAILABLE, state.currentState()); + + state.stop(testException); + + assertTrue(state.stopped()); + + // awaitLeader should fail after stop, even though leader was available + CompletableFuture<Long> waiter = state.awaitLeader(); + assertTrue(waiter.isDone()); + assertTrue(waiter.isCompletedExceptionally()); + + CompletionException thrown = assertThrows(CompletionException.class, waiter::join); + assertSame(testException, thrown.getCause()); + } + + /** Multiple stop calls are idempotent. */ + @Test + void testMultipleStopCalls() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + RuntimeException exception1 = new RuntimeException("Shutdown 1"); + RuntimeException exception2 = new RuntimeException("Shutdown 2"); + + CompletableFuture<Long> waiter1 = state.awaitLeader(); + state.stop(exception1); + assertTrue(waiter1.isCompletedExceptionally()); + + // Second stop call should be ignored + state.stop(exception2); + + // Subsequent awaitLeader should fail with the FIRST exception + CompletableFuture<Long> waiter2 = state.awaitLeader(); + assertTrue(waiter2.isDone()); + + CompletionException thrown = assertThrows(CompletionException.class, waiter2::join); + assertSame(exception1, thrown.getCause(), "Should use exception from first stop call"); + } + + /** onLeaderElected is ignored after stop. */ + @Test + void testOnLeaderElectedIgnoredAfterStop() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leader = createNode("leader"); + RuntimeException testException = new RuntimeException("Test shutdown"); + + CompletableFuture<Long> waiter1 = state.awaitLeader(); + state.stop(testException); + assertTrue(waiter1.isCompletedExceptionally()); + + // Leader election after stop should be ignored + state.onLeaderElected(leader, 5); + + // State should still be stopped. + assertTrue(state.stopped()); + + // New waiter should still fail + CompletableFuture<Long> waiter2 = state.awaitLeader(); + assertTrue(waiter2.isDone()); + assertTrue(waiter2.isCompletedExceptionally()); + } + + /** onGroupUnavailable is ignored after stop. */ + @Test + void testOnGroupUnavailableIgnoredAfterStop() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leader = createNode("leader"); + RuntimeException testException = new RuntimeException("Test shutdown"); + + state.onLeaderElected(leader, 1); + assertEquals(State.LEADER_AVAILABLE, state.currentState()); + + state.stop(testException); + + // Group unavailable after stop should be ignored + state.onGroupUnavailable(1); + + assertTrue(state.stopped()); + } + + /** Stop preserves exception type. */ + @Test + void testStopPreservesExceptionType() { Review Comment: Resolved, the test was removed. ########## modules/raft/src/test/java/org/apache/ignite/internal/raft/client/LeaderAvailabilityStateTest.java: ########## @@ -0,0 +1,516 @@ +/* + * 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.ignite.internal.raft.client; + +import static org.apache.ignite.internal.testframework.IgniteTestUtils.deriveUuidFrom; +import static org.hamcrest.MatcherAssert.assertThat; +import static org.hamcrest.Matchers.instanceOf; +import static org.junit.jupiter.api.Assertions.assertEquals; +import static org.junit.jupiter.api.Assertions.assertFalse; +import static org.junit.jupiter.api.Assertions.assertSame; +import static org.junit.jupiter.api.Assertions.assertThrows; +import static org.junit.jupiter.api.Assertions.assertTrue; + +import java.util.concurrent.CompletableFuture; +import java.util.concurrent.CompletionException; +import java.util.concurrent.CountDownLatch; +import java.util.concurrent.TimeUnit; +import java.util.concurrent.atomic.AtomicLong; +import org.apache.ignite.internal.network.ClusterNodeImpl; +import org.apache.ignite.internal.network.InternalClusterNode; +import org.apache.ignite.internal.raft.client.LeaderAvailabilityState.State; +import org.apache.ignite.internal.testframework.BaseIgniteAbstractTest; +import org.apache.ignite.network.NetworkAddress; +import org.junit.jupiter.api.Test; + +/** + * Tests for {@link LeaderAvailabilityState} state machine. + */ +public class LeaderAvailabilityStateTest extends BaseIgniteAbstractTest { + + /** Initial state should be WAITING_FOR_LEADER with term -1. */ + @Test + void testInitialState() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + + assertEquals(State.WAITING_FOR_LEADER, state.currentState()); + assertEquals(-1, state.currentTerm()); + } + + /** awaitLeader returns incomplete future when no leader elected. */ + @Test + void testAwaitLeaderWhenNoLeader() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + + CompletableFuture<Long> future = state.awaitLeader(); + + assertFalse(future.isDone(), "Future should not be completed when no leader"); + } + + /** awaitLeader returns completed future when leader is available. */ + @Test + void testAwaitLeaderWhenLeaderAvailable() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leaderNode = createNode("leader-node"); + + state.onLeaderElected(leaderNode, 1); + + CompletableFuture<Long> future = state.awaitLeader(); + + assertTrue(future.isDone(), "Future should be completed when leader available"); + assertEquals(1L, future.join()); + } + + /** onLeaderElected transitions to LEADER_AVAILABLE state. */ + @Test + void testOnLeaderElectedTransition() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leaderNode = createNode("leader-node"); + + state.onLeaderElected(leaderNode, 1); + + assertEquals(State.LEADER_AVAILABLE, state.currentState()); + assertEquals(1, state.currentTerm()); + } + + /** onLeaderElected completes waiting futures. */ + @Test + void testOnLeaderElectedCompletesWaiters() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leaderNode = createNode("leader-node"); + + CompletableFuture<Long> waiter = state.awaitLeader(); + assertFalse(waiter.isDone()); + + state.onLeaderElected(leaderNode, 5); + + assertTrue(waiter.isDone()); + assertEquals(5L, waiter.join()); + } + + /** Stale term notifications are ignored. */ + @Test + void testStaleTermIgnored() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leaderNode1 = createNode("leader-1"); + InternalClusterNode leaderNode2 = createNode("leader-2"); + + state.onLeaderElected(leaderNode1, 5); + assertEquals(5, state.currentTerm()); + + // Stale notification with lower term should be ignored + state.onLeaderElected(leaderNode2, 3); + assertEquals(5, state.currentTerm()); + } + + /** Equal term notifications are ignored. */ + @Test + void testEqualTermIgnored() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leaderNode = createNode("leader"); + + state.onLeaderElected(leaderNode, 5); + assertEquals(5, state.currentTerm()); + + // Same term should be ignored + state.onLeaderElected(leaderNode, 5); + assertEquals(5, state.currentTerm()); + } + + /** Higher term updates current term. */ + @Test + void testHigherTermUpdates() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leaderNode1 = createNode("leader-1"); + InternalClusterNode leaderNode2 = createNode("leader-2"); + + state.onLeaderElected(leaderNode1, 1); + assertEquals(1, state.currentTerm()); + + state.onLeaderElected(leaderNode2, 5); + assertEquals(5, state.currentTerm()); + } + + /** onGroupUnavailable transitions back to WAITING_FOR_LEADER. */ + @Test + void testOnGroupUnavailableTransition() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leaderNode = createNode("leader-node"); + + state.onLeaderElected(leaderNode, 1); + assertEquals(State.LEADER_AVAILABLE, state.currentState()); + + state.onGroupUnavailable(1); + assertEquals(State.WAITING_FOR_LEADER, state.currentState()); + } + + /** onGroupUnavailable ignored if term changed. */ + @Test + void testOnGroupUnavailableIgnoredIfTermChanged() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leaderNode = createNode("leader-node"); + + state.onLeaderElected(leaderNode, 1); + state.onLeaderElected(leaderNode, 2); + assertEquals(State.LEADER_AVAILABLE, state.currentState()); + assertEquals(2, state.currentTerm()); + + // Should be ignored because term changed from 1 to 2 + state.onGroupUnavailable(1); + assertEquals(State.LEADER_AVAILABLE, state.currentState()); + } + + /** onGroupUnavailable has no effect when already in WAITING_FOR_LEADER. */ + @Test + void testOnGroupUnavailableWhenAlreadyWaiting() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + + // Already in WAITING_FOR_LEADER, should have no effect + state.onGroupUnavailable(0); + assertEquals(State.WAITING_FOR_LEADER, state.currentState()); + } + + /** After onGroupUnavailable, new waiters get fresh future. */ + @Test + void testNewWaitersAfterUnavailable() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leaderNode = createNode("leader-node"); + + state.onLeaderElected(leaderNode, 1); + CompletableFuture<Long> future1 = state.awaitLeader(); + assertTrue(future1.isDone()); + + state.onGroupUnavailable(1); + + CompletableFuture<Long> future2 = state.awaitLeader(); + assertFalse(future2.isDone(), "New waiter should get incomplete future after unavailable"); + } + + /** Multiple waiters are all completed on leader election. */ + @Test + void testMultipleWaitersCompleted() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leaderNode = createNode("leader-node"); + + CompletableFuture<Long> waiter1 = state.awaitLeader(); + CompletableFuture<Long> waiter2 = state.awaitLeader(); + CompletableFuture<Long> waiter3 = state.awaitLeader(); + + assertFalse(waiter1.isDone()); + assertFalse(waiter2.isDone()); + assertFalse(waiter3.isDone()); + + state.onLeaderElected(leaderNode, 10); + + assertTrue(waiter1.isDone()); + assertTrue(waiter2.isDone()); + assertTrue(waiter3.isDone()); + + assertEquals(10L, waiter1.join()); + assertEquals(10L, waiter2.join()); + assertEquals(10L, waiter3.join()); + } + + /** Term 0 is accepted as first valid term. */ + @Test + void testTermZeroAccepted() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leaderNode = createNode("leader"); + + assertEquals(-1, state.currentTerm()); + + state.onLeaderElected(leaderNode, 0); + + assertEquals(0, state.currentTerm()); + assertEquals(State.LEADER_AVAILABLE, state.currentState()); + } + + /** Concurrent leader elections with different terms. */ + @Test + void testConcurrentLeaderElections() throws Exception { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + int threadCount = 10; + CountDownLatch startLatch = new CountDownLatch(1); + CountDownLatch doneLatch = new CountDownLatch(threadCount); + AtomicLong maxTerm = new AtomicLong(-1); + + Thread[] threads = new Thread[threadCount]; + for (int i = 0; i < threadCount; i++) { + int term = i; + threads[i] = new Thread(() -> { + try { + startLatch.await(); + InternalClusterNode leader = createNode("leader-" + term); + state.onLeaderElected(leader, term); + maxTerm.updateAndGet(current -> Math.max(current, term)); + } catch (InterruptedException e) { + Thread.currentThread().interrupt(); + } finally { + doneLatch.countDown(); + } + }); + threads[i].start(); + } + + startLatch.countDown(); + assertTrue(doneLatch.await(5, TimeUnit.SECONDS)); + + // The final term should be the maximum term that was set + assertEquals(threadCount - 1, state.currentTerm()); + } + + /** State machine handles rapid state transitions. */ + @Test + void testRapidStateTransitions() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leader = createNode("leader"); + + for (int i = 0; i < 100; i++) { + state.onLeaderElected(leader, i); + assertEquals(State.LEADER_AVAILABLE, state.currentState()); + assertEquals(i, state.currentTerm()); + + state.onGroupUnavailable(i); + assertEquals(State.WAITING_FOR_LEADER, state.currentState()); + } + } + + /** awaitLeader returns same future for multiple calls when waiting. */ + @Test + void testAwaitLeaderReturnsSameFuture() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + + CompletableFuture<Long> future1 = state.awaitLeader(); + CompletableFuture<Long> future2 = state.awaitLeader(); + + // Should return the same future instance when in WAITING_FOR_LEADER state + assertSame(future1, future2, "Should return same future instance when waiting"); + } + + /** awaitLeader returns new completed future for multiple calls when leader available. */ + @Test + void testAwaitLeaderReturnsNewCompletedFuture() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leader = createNode("leader"); + + state.onLeaderElected(leader, 1); + + CompletableFuture<Long> future1 = state.awaitLeader(); + CompletableFuture<Long> future2 = state.awaitLeader(); + + // Both should be completed + assertTrue(future1.isDone()); + assertTrue(future2.isDone()); + } + + /** Stop completes waiting futures exceptionally. */ + @Test + void testStopCompletesExceptionally() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + RuntimeException testException = new RuntimeException("Test shutdown"); + + CompletableFuture<Long> waiter = state.awaitLeader(); + assertFalse(waiter.isDone()); + + state.stop(testException); + + assertTrue(waiter.isDone()); + assertTrue(waiter.isCompletedExceptionally()); + + CompletionException thrown = assertThrows(CompletionException.class, waiter::join); + assertSame(testException, thrown.getCause()); + } + + /** Stop completes multiple waiters exceptionally. */ + @Test + void testStopCompletesMultipleWaiters() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + RuntimeException testException = new RuntimeException("Test shutdown"); + + // All waiters share the same future + CompletableFuture<Long> waiter1 = state.awaitLeader(); + CompletableFuture<Long> waiter2 = state.awaitLeader(); + CompletableFuture<Long> waiter3 = state.awaitLeader(); + + assertFalse(waiter1.isDone()); + assertFalse(waiter2.isDone()); + assertFalse(waiter3.isDone()); + + state.stop(testException); + + assertTrue(waiter1.isCompletedExceptionally()); + assertTrue(waiter2.isCompletedExceptionally()); + assertTrue(waiter3.isCompletedExceptionally()); + } + + /** Stop causes subsequent awaitLeader to fail immediately. */ + @Test + void testStopFailsSubsequentWaiters() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + RuntimeException testException = new RuntimeException("Test shutdown"); + + CompletableFuture<Long> waiter1 = state.awaitLeader(); + state.stop(testException); + + assertTrue(waiter1.isCompletedExceptionally()); + + // New waiter should immediately fail with the same exception + CompletableFuture<Long> waiter2 = state.awaitLeader(); + assertTrue(waiter2.isDone(), "New waiter should be immediately completed"); + assertTrue(waiter2.isCompletedExceptionally()); + + CompletionException thrown = assertThrows(CompletionException.class, waiter2::join); + assertSame(testException, thrown.getCause()); + } + + /** Stop when no waiters are pending still marks state as stopped. */ + @Test + void testStopWhenNoWaiters() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + RuntimeException testException = new RuntimeException("Test shutdown"); + + // Stop without any waiters - should not throw + state.stop(testException); + + assertTrue(state.stopped()); + + // Subsequent awaitLeader should fail + CompletableFuture<Long> waiter = state.awaitLeader(); + assertTrue(waiter.isDone()); + assertTrue(waiter.isCompletedExceptionally()); + + CompletionException thrown = assertThrows(CompletionException.class, waiter::join); + assertSame(testException, thrown.getCause()); + } + + /** Stop when leader is available fails subsequent awaitLeader. */ + @Test + void testStopWhenLeaderAvailable() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leader = createNode("leader"); + RuntimeException testException = new RuntimeException("Test shutdown"); + + state.onLeaderElected(leader, 1); + assertEquals(State.LEADER_AVAILABLE, state.currentState()); + + state.stop(testException); + + assertTrue(state.stopped()); + + // awaitLeader should fail after stop, even though leader was available + CompletableFuture<Long> waiter = state.awaitLeader(); + assertTrue(waiter.isDone()); + assertTrue(waiter.isCompletedExceptionally()); + + CompletionException thrown = assertThrows(CompletionException.class, waiter::join); + assertSame(testException, thrown.getCause()); + } + + /** Multiple stop calls are idempotent. */ + @Test + void testMultipleStopCalls() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + RuntimeException exception1 = new RuntimeException("Shutdown 1"); + RuntimeException exception2 = new RuntimeException("Shutdown 2"); + + CompletableFuture<Long> waiter1 = state.awaitLeader(); + state.stop(exception1); + assertTrue(waiter1.isCompletedExceptionally()); + + // Second stop call should be ignored + state.stop(exception2); + + // Subsequent awaitLeader should fail with the FIRST exception + CompletableFuture<Long> waiter2 = state.awaitLeader(); + assertTrue(waiter2.isDone()); + + CompletionException thrown = assertThrows(CompletionException.class, waiter2::join); + assertSame(exception1, thrown.getCause(), "Should use exception from first stop call"); + } + + /** onLeaderElected is ignored after stop. */ + @Test + void testOnLeaderElectedIgnoredAfterStop() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leader = createNode("leader"); + RuntimeException testException = new RuntimeException("Test shutdown"); + + CompletableFuture<Long> waiter1 = state.awaitLeader(); + state.stop(testException); + assertTrue(waiter1.isCompletedExceptionally()); + + // Leader election after stop should be ignored + state.onLeaderElected(leader, 5); + + // State should still be stopped. + assertTrue(state.stopped()); + + // New waiter should still fail + CompletableFuture<Long> waiter2 = state.awaitLeader(); + assertTrue(waiter2.isDone()); + assertTrue(waiter2.isCompletedExceptionally()); + } + + /** onGroupUnavailable is ignored after stop. */ + @Test + void testOnGroupUnavailableIgnoredAfterStop() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leader = createNode("leader"); + RuntimeException testException = new RuntimeException("Test shutdown"); + + state.onLeaderElected(leader, 1); + assertEquals(State.LEADER_AVAILABLE, state.currentState()); + + state.stop(testException); + + // Group unavailable after stop should be ignored + state.onGroupUnavailable(1); + + assertTrue(state.stopped()); + } + + /** Stop preserves exception type. */ + @Test + void testStopPreservesExceptionType() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + IllegalStateException testException = new IllegalStateException("Component stopping"); + + CompletableFuture<Long> waiter = state.awaitLeader(); + state.stop(testException); + + CompletionException thrown = assertThrows(CompletionException.class, waiter::join); + assertThat(thrown.getCause(), instanceOf(IllegalStateException.class)); + assertEquals("Component stopping", thrown.getCause().getMessage()); + } + + /** stopped() returns false before stop and true after. */ + @Test + void testStopped() { Review Comment: Resolved. ########## modules/raft/src/test/java/org/apache/ignite/internal/raft/client/LeaderAvailabilityStateTest.java: ########## @@ -0,0 +1,516 @@ +/* + * 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.ignite.internal.raft.client; + +import static org.apache.ignite.internal.testframework.IgniteTestUtils.deriveUuidFrom; +import static org.hamcrest.MatcherAssert.assertThat; +import static org.hamcrest.Matchers.instanceOf; +import static org.junit.jupiter.api.Assertions.assertEquals; +import static org.junit.jupiter.api.Assertions.assertFalse; +import static org.junit.jupiter.api.Assertions.assertSame; +import static org.junit.jupiter.api.Assertions.assertThrows; +import static org.junit.jupiter.api.Assertions.assertTrue; + +import java.util.concurrent.CompletableFuture; +import java.util.concurrent.CompletionException; +import java.util.concurrent.CountDownLatch; +import java.util.concurrent.TimeUnit; +import java.util.concurrent.atomic.AtomicLong; +import org.apache.ignite.internal.network.ClusterNodeImpl; +import org.apache.ignite.internal.network.InternalClusterNode; +import org.apache.ignite.internal.raft.client.LeaderAvailabilityState.State; +import org.apache.ignite.internal.testframework.BaseIgniteAbstractTest; +import org.apache.ignite.network.NetworkAddress; +import org.junit.jupiter.api.Test; + +/** + * Tests for {@link LeaderAvailabilityState} state machine. + */ +public class LeaderAvailabilityStateTest extends BaseIgniteAbstractTest { + + /** Initial state should be WAITING_FOR_LEADER with term -1. */ + @Test + void testInitialState() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + + assertEquals(State.WAITING_FOR_LEADER, state.currentState()); + assertEquals(-1, state.currentTerm()); + } + + /** awaitLeader returns incomplete future when no leader elected. */ + @Test + void testAwaitLeaderWhenNoLeader() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + + CompletableFuture<Long> future = state.awaitLeader(); + + assertFalse(future.isDone(), "Future should not be completed when no leader"); + } + + /** awaitLeader returns completed future when leader is available. */ + @Test + void testAwaitLeaderWhenLeaderAvailable() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leaderNode = createNode("leader-node"); + + state.onLeaderElected(leaderNode, 1); + + CompletableFuture<Long> future = state.awaitLeader(); + + assertTrue(future.isDone(), "Future should be completed when leader available"); + assertEquals(1L, future.join()); + } + + /** onLeaderElected transitions to LEADER_AVAILABLE state. */ + @Test + void testOnLeaderElectedTransition() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leaderNode = createNode("leader-node"); + + state.onLeaderElected(leaderNode, 1); + + assertEquals(State.LEADER_AVAILABLE, state.currentState()); + assertEquals(1, state.currentTerm()); + } + + /** onLeaderElected completes waiting futures. */ + @Test + void testOnLeaderElectedCompletesWaiters() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leaderNode = createNode("leader-node"); + + CompletableFuture<Long> waiter = state.awaitLeader(); + assertFalse(waiter.isDone()); + + state.onLeaderElected(leaderNode, 5); + + assertTrue(waiter.isDone()); + assertEquals(5L, waiter.join()); + } + + /** Stale term notifications are ignored. */ + @Test + void testStaleTermIgnored() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leaderNode1 = createNode("leader-1"); + InternalClusterNode leaderNode2 = createNode("leader-2"); + + state.onLeaderElected(leaderNode1, 5); + assertEquals(5, state.currentTerm()); + + // Stale notification with lower term should be ignored + state.onLeaderElected(leaderNode2, 3); + assertEquals(5, state.currentTerm()); + } + + /** Equal term notifications are ignored. */ + @Test + void testEqualTermIgnored() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leaderNode = createNode("leader"); + + state.onLeaderElected(leaderNode, 5); + assertEquals(5, state.currentTerm()); + + // Same term should be ignored + state.onLeaderElected(leaderNode, 5); + assertEquals(5, state.currentTerm()); + } + + /** Higher term updates current term. */ + @Test + void testHigherTermUpdates() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leaderNode1 = createNode("leader-1"); + InternalClusterNode leaderNode2 = createNode("leader-2"); + + state.onLeaderElected(leaderNode1, 1); + assertEquals(1, state.currentTerm()); Review Comment: Resolved. ########## modules/raft/src/test/java/org/apache/ignite/internal/raft/client/LeaderAvailabilityStateTest.java: ########## @@ -0,0 +1,516 @@ +/* + * 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.ignite.internal.raft.client; + +import static org.apache.ignite.internal.testframework.IgniteTestUtils.deriveUuidFrom; +import static org.hamcrest.MatcherAssert.assertThat; +import static org.hamcrest.Matchers.instanceOf; +import static org.junit.jupiter.api.Assertions.assertEquals; +import static org.junit.jupiter.api.Assertions.assertFalse; +import static org.junit.jupiter.api.Assertions.assertSame; +import static org.junit.jupiter.api.Assertions.assertThrows; +import static org.junit.jupiter.api.Assertions.assertTrue; + +import java.util.concurrent.CompletableFuture; +import java.util.concurrent.CompletionException; +import java.util.concurrent.CountDownLatch; +import java.util.concurrent.TimeUnit; +import java.util.concurrent.atomic.AtomicLong; +import org.apache.ignite.internal.network.ClusterNodeImpl; +import org.apache.ignite.internal.network.InternalClusterNode; +import org.apache.ignite.internal.raft.client.LeaderAvailabilityState.State; +import org.apache.ignite.internal.testframework.BaseIgniteAbstractTest; +import org.apache.ignite.network.NetworkAddress; +import org.junit.jupiter.api.Test; + +/** + * Tests for {@link LeaderAvailabilityState} state machine. + */ +public class LeaderAvailabilityStateTest extends BaseIgniteAbstractTest { + + /** Initial state should be WAITING_FOR_LEADER with term -1. */ + @Test + void testInitialState() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + + assertEquals(State.WAITING_FOR_LEADER, state.currentState()); + assertEquals(-1, state.currentTerm()); + } + + /** awaitLeader returns incomplete future when no leader elected. */ + @Test + void testAwaitLeaderWhenNoLeader() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + + CompletableFuture<Long> future = state.awaitLeader(); + + assertFalse(future.isDone(), "Future should not be completed when no leader"); + } + + /** awaitLeader returns completed future when leader is available. */ + @Test + void testAwaitLeaderWhenLeaderAvailable() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leaderNode = createNode("leader-node"); + + state.onLeaderElected(leaderNode, 1); + + CompletableFuture<Long> future = state.awaitLeader(); + + assertTrue(future.isDone(), "Future should be completed when leader available"); + assertEquals(1L, future.join()); + } + + /** onLeaderElected transitions to LEADER_AVAILABLE state. */ + @Test + void testOnLeaderElectedTransition() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leaderNode = createNode("leader-node"); + + state.onLeaderElected(leaderNode, 1); + + assertEquals(State.LEADER_AVAILABLE, state.currentState()); + assertEquals(1, state.currentTerm()); + } + + /** onLeaderElected completes waiting futures. */ + @Test + void testOnLeaderElectedCompletesWaiters() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leaderNode = createNode("leader-node"); + + CompletableFuture<Long> waiter = state.awaitLeader(); + assertFalse(waiter.isDone()); + + state.onLeaderElected(leaderNode, 5); + + assertTrue(waiter.isDone()); + assertEquals(5L, waiter.join()); + } + + /** Stale term notifications are ignored. */ + @Test + void testStaleTermIgnored() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leaderNode1 = createNode("leader-1"); + InternalClusterNode leaderNode2 = createNode("leader-2"); + + state.onLeaderElected(leaderNode1, 5); + assertEquals(5, state.currentTerm()); + + // Stale notification with lower term should be ignored + state.onLeaderElected(leaderNode2, 3); + assertEquals(5, state.currentTerm()); + } + + /** Equal term notifications are ignored. */ + @Test + void testEqualTermIgnored() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leaderNode = createNode("leader"); + + state.onLeaderElected(leaderNode, 5); + assertEquals(5, state.currentTerm()); + + // Same term should be ignored + state.onLeaderElected(leaderNode, 5); + assertEquals(5, state.currentTerm()); + } + + /** Higher term updates current term. */ + @Test + void testHigherTermUpdates() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leaderNode1 = createNode("leader-1"); + InternalClusterNode leaderNode2 = createNode("leader-2"); + + state.onLeaderElected(leaderNode1, 1); + assertEquals(1, state.currentTerm()); + + state.onLeaderElected(leaderNode2, 5); + assertEquals(5, state.currentTerm()); + } + + /** onGroupUnavailable transitions back to WAITING_FOR_LEADER. */ + @Test + void testOnGroupUnavailableTransition() { + LeaderAvailabilityState state = new LeaderAvailabilityState(); + InternalClusterNode leaderNode = createNode("leader-node"); + + state.onLeaderElected(leaderNode, 1); + assertEquals(State.LEADER_AVAILABLE, state.currentState()); + + state.onGroupUnavailable(1); Review Comment: Resolved, covered by `testOnGroupUnavailableIgnoredIfTermChanged`. ########## modules/raft/src/main/java/org/apache/ignite/internal/raft/client/LeaderAvailabilityState.java: ########## @@ -0,0 +1,220 @@ +/* + * 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.ignite.internal.raft.client; + +import java.util.concurrent.CompletableFuture; +import org.apache.ignite.internal.logger.IgniteLogger; +import org.apache.ignite.internal.logger.Loggers; +import org.apache.ignite.internal.network.InternalClusterNode; +import org.jetbrains.annotations.VisibleForTesting; + +/** + * State machine for tracking leader availability. + * + * <p>Manages transitions between two states: + * <ul> + * <li>{@link State#WAITING_FOR_LEADER} - No leader is currently known, operations must wait</li> + * <li>{@link State#LEADER_AVAILABLE} - A leader is known, operations can proceed</li> + * </ul> + * + * <p>State transitions: + * <pre> + * WAITING_FOR_LEADER --[onLeaderElected]--> LEADER_AVAILABLE + * LEADER_AVAILABLE --[onGroupUnavailable]--> WAITING_FOR_LEADER + * Any state --[stop]--> stopped (terminal state) + * </pre> + * + * <p>Thread-safe: all public methods are synchronized or use proper synchronization. + */ +@VisibleForTesting +class LeaderAvailabilityState { + /** The logger. */ + private static final IgniteLogger LOG = Loggers.forClass(LeaderAvailabilityState.class); + + /** Possible states of leader availability. */ + enum State { + /** No leader is known, waiting for leader election. */ + WAITING_FOR_LEADER, + /** A leader is available and operations can proceed. */ + LEADER_AVAILABLE + } + + /** Current state. Guarded by {@code this}. */ + private State currentState = State.WAITING_FOR_LEADER; + + /** Current leader term. Initialized to -1 to accept term 0 as the first valid term. Guarded by {@code this}. */ + private long currentTerm = -1; + + /** Future that waiters block on. Guarded by {@code this}. */ + private CompletableFuture<Long> waiters = new CompletableFuture<>(); + + /** Whether the state machine has been stopped. Guarded by {@code this}. */ + private boolean stopped = false; + + /** Exception used to fail futures after destruction. Guarded by {@code this}. */ + private Throwable stopException; + + /** + * Returns a future that completes when a leader becomes available. + * + * <p>If a leader is already available, returns an already-completed future with the current term. + * Otherwise, returns a future that will complete when {@link #onLeaderElected} is called. + * If the state machine has been destroyed, returns a failed future. + * + * @return Future that completes with the leader term when a leader is available. + */ + synchronized CompletableFuture<Long> awaitLeader() { + if (stopped) { + return CompletableFuture.failedFuture(stopException); + } + if (currentState == State.LEADER_AVAILABLE) { + return CompletableFuture.completedFuture(currentTerm); + } + return waiters; + } + + /** + * Handles leader election notification. + * + * <p>Transitions from {@link State#WAITING_FOR_LEADER} to {@link State#LEADER_AVAILABLE} + * if the new term is greater than the current term. Stale notifications (with term <= current) + * are ignored. Has no effect if the state machine has been stopped. + * + * @param leader The newly elected leader node. + * @param term The term of the new leader. + */ + void onLeaderElected(InternalClusterNode leader, long term) { + CompletableFuture<Long> futureToComplete = null; + + synchronized (this) { Review Comment: Resolved with internal `mutex` field object. -- 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]
