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   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements. See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to You under the Apache License, Version 2.0
   * (the "License"); you may not use this file except in compliance with
   * the License. You may obtain a copy of the License at
   *
   *    http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.kafka.raft.internals;
  
  import org.apache.kafka.common.Uuid;
  import org.apache.kafka.common.metrics.KafkaMetric;
  import org.apache.kafka.common.metrics.Metrics;
  import org.apache.kafka.common.utils.LogContext;
  import org.apache.kafka.common.utils.MockTime;
  import org.apache.kafka.common.utils.Time;
  import org.apache.kafka.raft.LogOffsetMetadata;
  import org.apache.kafka.raft.MockQuorumStateStore;
  import org.apache.kafka.raft.QuorumState;
  import org.apache.kafka.raft.ReplicaKey;
  import org.apache.kafka.raft.VoterSet;
  import org.apache.kafka.raft.VoterSetTest;
  import org.apache.kafka.server.common.Feature;
  import org.apache.kafka.server.common.KRaftVersion;
  import org.apache.kafka.server.common.OffsetAndEpoch;
  
  import org.junit.jupiter.api.AfterEach;
  import org.junit.jupiter.params.ParameterizedTest;
  import org.junit.jupiter.params.provider.EnumSource;
  import org.mockito.Mockito;
  
  import java.util.Map;
  import java.util.OptionalInt;
  import java.util.OptionalLong;
  import java.util.Random;
  import java.util.stream.IntStream;
  
  import static org.junit.jupiter.api.Assertions.assertEquals;
  import static org.junit.jupiter.api.Assertions.assertNull;
  
  public class KafkaRaftMetricsTest {
  
      private final int localId = 0;
      private final Uuid localDirectoryId = Uuid.randomUuid();
      private final int electionTimeoutMs = 5000;
      private final int fetchTimeoutMs = 10000;
  
      private final Time time = new MockTime();
      private final Metrics metrics = new Metrics(time);
      private final Random random = new Random(1);
      private KafkaRaftMetrics raftMetrics;
  
      private final BatchAccumulator<?> accumulator = Mockito.mock(BatchAccumulator.class);
  
      @AfterEach
      public void tearDown() {
          if (raftMetrics != null) {
              raftMetrics.close();
          }
          metrics.close();
      }
  
      private QuorumState buildQuorumState(VoterSet voterSet, KRaftVersion kraftVersion) {
          KRaftControlRecordStateMachine mockPartitionState = Mockito.mock(KRaftControlRecordStateMachine.class);
  
          Mockito
              .when(mockPartitionState.lastVoterSet())
              .thenReturn(voterSet);
          Mockito
              .when(mockPartitionState.lastVoterSetOffset())
              .thenReturn(kraftVersion.isReconfigSupported() ? OptionalLong.of(0) : OptionalLong.empty());
          Mockito
              .when(mockPartitionState.lastKraftVersion())
              .thenReturn(kraftVersion);
  
          return new QuorumState(
              OptionalInt.of(localId),
              localDirectoryId,
              mockPartitionState,
              voterSet.listeners(localId),
              Feature.KRAFT_VERSION.supportedVersionRange(),
              electionTimeoutMs,
              fetchTimeoutMs,
              new MockQuorumStateStore(),
              time,
              new LogContext("kafka-raft-metrics-test"),
              random,
              raftMetrics
          );
      }
  
      private VoterSet localStandaloneVoterSet(KRaftVersion kraftVersion) {
          boolean withDirectoryId = kraftVersion.featureLevel() > 0;
          return VoterSetTest.voterSet(
              Map.of(
                  localId,
                  VoterSetTest.voterNode(
                      ReplicaKey.of(
                          localId,
                          withDirectoryId ? localDirectoryId : ReplicaKey.NO_DIRECTORY_ID
                      )
                  )
              )
          );
      }
  
      @ParameterizedTest
      @EnumSource(value = KRaftVersion.class)
      public void shouldRecordVoterQuorumState(KRaftVersion kraftVersion) {
          boolean withDirectoryId = kraftVersion.featureLevel() > 0;
          Map<Integer, VoterSet.VoterNode> voterMap = VoterSetTest.voterMap(IntStream.of(1, 2), withDirectoryId);
          Uuid voter2DirectoryId = voterMap.get(2).voterKey().directoryId().orElse(Uuid.ZERO_UUID);
          voterMap.put(
              localId,
              VoterSetTest.voterNode(
                  ReplicaKey.of(
                      localId,
                      withDirectoryId ? localDirectoryId : ReplicaKey.NO_DIRECTORY_ID
                  )
              )
          );
          VoterSet voters = VoterSetTest.voterSet(voterMap);
          raftMetrics = new KafkaRaftMetrics(metrics, "raft");
          QuorumState state = buildQuorumState(voters, kraftVersion);
  
          raftMetrics.initialize(state);
          state.initialize(new OffsetAndEpoch(0L, 0));
  
          // unattached
          assertEquals("unattached", getMetric(metrics, "current-state").metricValue());
          assertEquals((double) -1, getMetric(metrics, "current-leader").metricValue());
          assertEquals((double) -1, getMetric(metrics, "current-vote").metricValue());
          assertEquals(
              Uuid.ZERO_UUID.toString(),
              getMetric(metrics, "current-vote-directory-id").metricValue()
          );
          assertEquals((double) 0, getMetric(metrics, "current-epoch").metricValue());
          assertEquals((double) -1, getMetric(metrics, "high-watermark").metricValue());
  
          // prospective
          state.transitionToProspective();
          assertEquals("prospective", getMetric(metrics, "current-state").metricValue());
          assertEquals((double) -1, getMetric(metrics, "current-leader").metricValue());
          assertEquals((double) -1, getMetric(metrics, "current-vote").metricValue());
          assertEquals(
              Uuid.ZERO_UUID.toString(),
              getMetric(metrics, "current-vote-directory-id").metricValue()
          );
          assertEquals((double) 0, getMetric(metrics, "current-epoch").metricValue());
          assertEquals((double) -1L, getMetric(metrics, "high-watermark").metricValue());
  
          // prospective with votedKey
          state.prospectiveAddVotedState(0, ReplicaKey.of(1, ReplicaKey.NO_DIRECTORY_ID));
          assertEquals("prospective-voted", getMetric(metrics, "current-state").metricValue());
          assertEquals((double) -1, getMetric(metrics, "current-leader").metricValue());
          assertEquals((double) 1, getMetric(metrics, "current-vote").metricValue());
          assertEquals(
              Uuid.ZERO_UUID.toString(),
              getMetric(metrics, "current-vote-directory-id").metricValue()
          );
          assertEquals((double) 0, getMetric(metrics, "current-epoch").metricValue());
          assertEquals((double) -1L, getMetric(metrics, "high-watermark").metricValue());
  
          // follower with votedKey and leader
          state.transitionToFollower(0, 2, voters.listeners(2));
          assertEquals("follower", getMetric(metrics, "current-state").metricValue());
          assertEquals((double) 2, getMetric(metrics, "current-leader").metricValue());
          assertEquals((double) 1, getMetric(metrics, "current-vote").metricValue());
          assertEquals(
              Uuid.ZERO_UUID.toString(),
              getMetric(metrics, "current-vote-directory-id").metricValue()
          );
          assertEquals((double) 0, getMetric(metrics, "current-epoch").metricValue());
          assertEquals((double) -1L, getMetric(metrics, "high-watermark").metricValue());
  
          // follower with updated HW
          state.followerStateOrThrow().updateHighWatermark(OptionalLong.of(5L));
          assertEquals((double) 5L, getMetric(metrics, "high-watermark").metricValue());
  
          // prospective with votedKey and leader
          state.transitionToProspective();
          assertEquals("prospective-voted", getMetric(metrics, "current-state").metricValue());
          assertEquals((double) 2, getMetric(metrics, "current-leader").metricValue());
          assertEquals((double) 1, getMetric(metrics, "current-vote").metricValue());
          assertEquals(
              Uuid.ZERO_UUID.toString(),
              getMetric(metrics, "current-vote-directory-id").metricValue()
          );
          assertEquals((double) 0, getMetric(metrics, "current-epoch").metricValue());
          assertEquals((double) 5L, getMetric(metrics, "high-watermark").metricValue());
  
          // candidate
          state.transitionToCandidate();
          assertEquals("candidate", getMetric(metrics, "current-state").metricValue());
          assertEquals((double) -1, getMetric(metrics, "current-leader").metricValue());
          assertEquals((double) localId, getMetric(metrics, "current-vote").metricValue());
          assertEquals(
              localDirectoryId.toString(),
              getMetric(metrics, "current-vote-directory-id").metricValue()
          );
          assertEquals((double) 1, getMetric(metrics, "current-epoch").metricValue());
          assertEquals((double) 5L, getMetric(metrics, "high-watermark").metricValue());
  
          // leader
          state.candidateStateOrThrow().recordGrantedVote(1);
          state.transitionToLeader(2L, accumulator);
          assertEquals("leader", getMetric(metrics, "current-state").metricValue());
          assertEquals((double) localId, getMetric(metrics, "current-leader").metricValue());
          assertEquals((double) localId, getMetric(metrics, "current-vote").metricValue());
          assertEquals(
              localDirectoryId.toString(),
              getMetric(metrics, "current-vote-directory-id").metricValue()
          );
          assertEquals((double) 1, getMetric(metrics, "current-epoch").metricValue());
          assertEquals((double) -1L, getMetric(metrics, "high-watermark").metricValue()); // todo, bug fix
  
          // leader with updated HW
          state.leaderStateOrThrow().updateLocalState(new LogOffsetMetadata(10L), voters);
          state.leaderStateOrThrow().updateReplicaState(
              voterMap.get(1).voterKey(),
              0,
              new LogOffsetMetadata(10L)
          );
          assertEquals((double) 10L, getMetric(metrics, "high-watermark").metricValue());
  
          // follower
          state.transitionToFollower(2, 1, voters.listeners(1));
          assertEquals("follower", getMetric(metrics, "current-state").metricValue());
          assertEquals((double) 1, getMetric(metrics, "current-leader").metricValue());
          assertEquals((double) -1, getMetric(metrics, "current-vote").metricValue());
          assertEquals(
              Uuid.ZERO_UUID.toString(),
              getMetric(metrics, "current-vote-directory-id").metricValue()
          );
          assertEquals((double) 2, getMetric(metrics, "current-epoch").metricValue());
          assertEquals((double) 10L, getMetric(metrics, "high-watermark").metricValue());
  
          // unattached with votedKey
          state.transitionToUnattached(3, OptionalInt.empty());
          state.unattachedAddVotedState(3, ReplicaKey.of(2, voter2DirectoryId));
          assertEquals("unattached-voted", getMetric(metrics, "current-state").metricValue());
          assertEquals((double) -1, getMetric(metrics, "current-leader").metricValue());
          assertEquals((double) 2, getMetric(metrics, "current-vote").metricValue());
          assertEquals(
              voter2DirectoryId.toString(),
              getMetric(metrics, "current-vote-directory-id").metricValue()
          );
          assertEquals((double) 3, getMetric(metrics, "current-epoch").metricValue());
          assertEquals((double) 10L, getMetric(metrics, "high-watermark").metricValue());
  
          // unattached with leader without votedKey
          state.transitionToUnattached(4, OptionalInt.of(1));
          assertEquals("unattached", getMetric(metrics, "current-state").metricValue());
          assertEquals((double) 1, getMetric(metrics, "current-leader").metricValue());
          assertEquals((double) -1, getMetric(metrics, "current-vote").metricValue());
          assertEquals(
              Uuid.ZERO_UUID.toString(),
              getMetric(metrics, "current-vote-directory-id").metricValue()
          );
          assertEquals((double) 4, getMetric(metrics, "current-epoch").metricValue());
          assertEquals((double) 10L, getMetric(metrics, "high-watermark").metricValue());
      }
  
      @ParameterizedTest
      @EnumSource(value = KRaftVersion.class)
      public void shouldRecordNonVoterQuorumState(KRaftVersion kraftVersion) {
          boolean withDirectoryId = kraftVersion.featureLevel() > 0;
          VoterSet voters = VoterSetTest.voterSet(
              VoterSetTest.voterMap(IntStream.of(1, 2, 3), withDirectoryId)
          );
          raftMetrics = new KafkaRaftMetrics(metrics, "raft");
          QuorumState state = buildQuorumState(voters, kraftVersion);
          raftMetrics.initialize(state);
          state.initialize(new OffsetAndEpoch(0L, 0));
  
          assertEquals("unattached", getMetric(metrics, "current-state").metricValue());
          assertEquals((double) -1L, getMetric(metrics, "current-leader").metricValue());
          assertEquals((double) -1L, getMetric(metrics, "current-vote").metricValue());
          assertEquals(
              Uuid.ZERO_UUID.toString(),
              getMetric(metrics, "current-vote-directory-id").metricValue()
          );
          assertEquals((double) 0, getMetric(metrics, "current-epoch").metricValue());
          assertEquals((double) -1L, getMetric(metrics, "high-watermark").metricValue());
  
          state.transitionToFollower(2, 1, voters.listeners(1));
          assertEquals("observer", getMetric(metrics, "current-state").metricValue());
          assertEquals((double) 1, getMetric(metrics, "current-leader").metricValue());
          assertEquals((double) -1, getMetric(metrics, "current-vote").metricValue());
          assertEquals(
              Uuid.ZERO_UUID.toString(),
              getMetric(metrics, "current-vote-directory-id").metricValue()
          );
          assertEquals((double) 2, getMetric(metrics, "current-epoch").metricValue());
          assertEquals((double) -1L, getMetric(metrics, "high-watermark").metricValue());
  
          state.followerStateOrThrow().updateHighWatermark(OptionalLong.of(10L));
          assertEquals((double) 10L, getMetric(metrics, "high-watermark").metricValue());
  
          state.transitionToUnattached(4, OptionalInt.empty());
          assertEquals("unattached", getMetric(metrics, "current-state").metricValue());
          assertEquals((double) -1, getMetric(metrics, "current-leader").metricValue());
          assertEquals((double) -1, getMetric(metrics, "current-vote").metricValue());
          assertEquals(
              Uuid.ZERO_UUID.toString(),
              getMetric(metrics, "current-vote-directory-id").metricValue()
          );
          assertEquals((double) 4, getMetric(metrics, "current-epoch").metricValue());
          assertEquals((double) 10L, getMetric(metrics, "high-watermark").metricValue());
      }
  
      @ParameterizedTest
      @EnumSource(value = KRaftVersion.class)
      public void shouldRecordLogEnd(KRaftVersion kraftVersion) {
          raftMetrics = new KafkaRaftMetrics(metrics, "raft");
          QuorumState state = buildQuorumState(localStandaloneVoterSet(kraftVersion), kraftVersion);
          raftMetrics.initialize(state);
          state.initialize(new OffsetAndEpoch(0L, 0));
  
          assertEquals((double) 0L, getMetric(metrics, "log-end-offset").metricValue());
          assertEquals((double) 0, getMetric(metrics, "log-end-epoch").metricValue());
  
          raftMetrics.updateLogEnd(new OffsetAndEpoch(5L, 1));
  
          assertEquals((double) 5L, getMetric(metrics, "log-end-offset").metricValue());
          assertEquals((double) 1, getMetric(metrics, "log-end-epoch").metricValue());
      }
  
      @ParameterizedTest
      @EnumSource(value = KRaftVersion.class)
      public void shouldRecordNumUnknownVoterConnections(KRaftVersion kraftVersion) {
          raftMetrics = new KafkaRaftMetrics(metrics, "raft");
          QuorumState state = buildQuorumState(localStandaloneVoterSet(kraftVersion), kraftVersion);
          raftMetrics.initialize(state);
          state.initialize(new OffsetAndEpoch(0L, 0));
  
          assertEquals((double) 0, getMetric(metrics, "number-unknown-voter-connections").metricValue());
  
          raftMetrics.updateNumUnknownVoterConnections(2);
  
          assertEquals((double) 2, getMetric(metrics, "number-unknown-voter-connections").metricValue());
      }
  
      @ParameterizedTest
      @EnumSource(value = KRaftVersion.class)
      public void shouldRecordPollIdleRatio(KRaftVersion kraftVersion) {
          raftMetrics = new KafkaRaftMetrics(metrics, "raft");
          QuorumState state = buildQuorumState(localStandaloneVoterSet(kraftVersion), kraftVersion);
          raftMetrics.initialize(state);
          state.initialize(new OffsetAndEpoch(0L, 0));
  
          // First recording is discarded (in order to align the interval of measurement)
          raftMetrics.updatePollStart(time.milliseconds());
          raftMetrics.updatePollEnd(time.milliseconds());
  
          // Idle for 100ms
          raftMetrics.updatePollStart(time.milliseconds());
          time.sleep(100L);
          raftMetrics.updatePollEnd(time.milliseconds());
  
          // Busy for 100ms
          time.sleep(100L);
  
          // Idle for 200ms
          raftMetrics.updatePollStart(time.milliseconds());
          time.sleep(200L);
          raftMetrics.updatePollEnd(time.milliseconds());
  
          assertEquals(0.75, getMetric(metrics, "poll-idle-ratio-avg").metricValue());
  
          // Busy for 100ms
          time.sleep(100L);
  
          // Idle for 75ms
          raftMetrics.updatePollStart(time.milliseconds());
          time.sleep(75L);
          raftMetrics.updatePollEnd(time.milliseconds());
  
          // Idle for 25ms
          raftMetrics.updatePollStart(time.milliseconds());
          time.sleep(25L);
          raftMetrics.updatePollEnd(time.milliseconds());
  
          // Idle for 0ms
          raftMetrics.updatePollStart(time.milliseconds());
          raftMetrics.updatePollEnd(time.milliseconds());
  
          assertEquals(0.5, getMetric(metrics, "poll-idle-ratio-avg").metricValue());
  
          // Busy for 40ms
          time.sleep(40);
  
          // Idle for 60ms
          raftMetrics.updatePollStart(time.milliseconds());
          time.sleep(60);
          raftMetrics.updatePollEnd(time.milliseconds());
  
          // Busy for 10ms
          time.sleep(10);
  
          // Begin idle time for 5ms
          raftMetrics.updatePollStart(time.milliseconds());
          time.sleep(5);
  
          // Measurement arrives before poll end, so we have 40ms busy time and 60ms idle.
          // The subsequent interval time is not counted until the next measurement.
          assertEquals(0.6, getMetric(metrics, "poll-idle-ratio-avg").metricValue());
  
          // More idle time for 5ms
          time.sleep(5);
          raftMetrics.updatePollEnd(time.milliseconds());
  
          // The measurement includes the interval beginning at the last recording.
          // This counts 10ms of busy time and 5ms + 5ms = 10ms of idle time.
          assertEquals(0.5, getMetric(metrics, "poll-idle-ratio-avg").metricValue());
      }
  
      @ParameterizedTest
      @EnumSource(value = KRaftVersion.class)
      public void shouldRecordLatency(KRaftVersion kraftVersion) {
          raftMetrics = new KafkaRaftMetrics(metrics, "raft");
          QuorumState state = buildQuorumState(localStandaloneVoterSet(kraftVersion), kraftVersion);
          raftMetrics.initialize(state);
          state.initialize(new OffsetAndEpoch(0L, 0));
  
          raftMetrics.updateElectionStartMs(time.milliseconds());
          time.sleep(1000L);
          raftMetrics.maybeUpdateElectionLatency(time.milliseconds());
  
          assertEquals((double) 1000, getMetric(metrics, "election-latency-avg").metricValue());
          assertEquals((double) 1000, getMetric(metrics, "election-latency-max").metricValue());
  
          raftMetrics.updateElectionStartMs(time.milliseconds());
          time.sleep(800L);
          raftMetrics.maybeUpdateElectionLatency(time.milliseconds());
  
          assertEquals((double) 900, getMetric(metrics, "election-latency-avg").metricValue());
          assertEquals((double) 1000, getMetric(metrics, "election-latency-max").metricValue());
  
          raftMetrics.updateCommitLatency(50, time.milliseconds());
  
          assertEquals(50.0, getMetric(metrics, "commit-latency-avg").metricValue());
          assertEquals(50.0, getMetric(metrics, "commit-latency-max").metricValue());
  
          raftMetrics.updateCommitLatency(60, time.milliseconds());
  
          assertEquals(55.0, getMetric(metrics, "commit-latency-avg").metricValue());
          assertEquals(60.0, getMetric(metrics, "commit-latency-max").metricValue());
      }
  
      @ParameterizedTest
      @EnumSource(value = KRaftVersion.class)
      public void shouldRecordRate(KRaftVersion kraftVersion) {
          raftMetrics = new KafkaRaftMetrics(metrics, "raft");
          QuorumState state = buildQuorumState(localStandaloneVoterSet(kraftVersion), kraftVersion);
          raftMetrics.initialize(state);
          state.initialize(new OffsetAndEpoch(0L, 0));
  
          raftMetrics.updateAppendRecords(12);
          assertEquals(0.4, getMetric(metrics, "append-records-rate").metricValue());
  
          raftMetrics.updateAppendRecords(9);
          assertEquals(0.7, getMetric(metrics, "append-records-rate").metricValue());
  
          raftMetrics.updateFetchedRecords(24);
          assertEquals(0.8, getMetric(metrics, "fetch-records-rate").metricValue());
  
          raftMetrics.updateFetchedRecords(48);
          assertEquals(2.4, getMetric(metrics, "fetch-records-rate").metricValue());
      }
  
      @ParameterizedTest
      @EnumSource(value = KRaftVersion.class)
      public void testNumberOfVoters(KRaftVersion kraftVersion) {
          raftMetrics = new KafkaRaftMetrics(metrics, "raft");
          QuorumState state = buildQuorumState(localStandaloneVoterSet(kraftVersion), kraftVersion);
          raftMetrics.initialize(state);
          state.initialize(new OffsetAndEpoch(0L, 0));
  
          assertEquals(0, getMetric(metrics, "number-of-voters").metricValue());
  
          raftMetrics.updateNumVoters(3);
          assertEquals(3, getMetric(metrics, "number-of-voters").metricValue());
      }
  
      @ParameterizedTest
      @EnumSource(value = KRaftVersion.class)
      public void testLeaderMetrics(KRaftVersion kraftVersion) {
          raftMetrics = new KafkaRaftMetrics(metrics, "raft");
          QuorumState state = buildQuorumState(localStandaloneVoterSet(kraftVersion), kraftVersion);
          raftMetrics.initialize(state);
          state.initialize(new OffsetAndEpoch(0L, 0));
  
          assertNull(getMetric(metrics, "number-of-observers"));
          assertNull(getMetric(metrics, "uncommitted-voter-change"));
  
          raftMetrics.addLeaderMetrics();
  
          assertEquals(0, getMetric(metrics, "number-of-observers").metricValue());
          assertEquals(0, getMetric(metrics, "uncommitted-voter-change").metricValue());
  
          raftMetrics.updateNumObservers(1);
          raftMetrics.updateUncommittedVoterChange(true);
  
          assertEquals(1, getMetric(metrics, "number-of-observers").metricValue());
          assertEquals(1, getMetric(metrics, "uncommitted-voter-change").metricValue());
  
          raftMetrics.removeLeaderMetrics();
  
          assertNull(getMetric(metrics, "number-of-observers"));
          assertNull(getMetric(metrics, "uncommitted-voter-change"));
  
          // Check that these metrics are reset to default values when added back
          raftMetrics.addLeaderMetrics();
  
          assertEquals(0, getMetric(metrics, "number-of-observers").metricValue());
          assertEquals(0, getMetric(metrics, "uncommitted-voter-change").metricValue());
      }
  
      private KafkaMetric getMetric(final Metrics metrics, final String name) {
          return metrics.metrics().get(metrics.metricName(name, "raft-metrics"));
      }
  }
  