content: /*
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements. See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to You under the Apache License, Version 2.0
   * (the "License"); you may not use this file except in compliance with
   * the License. You may obtain a copy of the License at
   *
   *    http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.kafka.raft;
  
  import org.apache.kafka.common.utils.LogContext;
  import org.apache.kafka.common.utils.Time;
  import org.apache.kafka.common.utils.Timer;
  
  import org.slf4j.Logger;
  
  import java.util.Optional;
  import java.util.OptionalInt;
  import java.util.Set;
  
  import static org.apache.kafka.raft.QuorumState.unattachedOrProspectiveCanGrantVote;
  
  /**
   * A replica is "unattached" when it doesn't know the leader or the leader's endpoint.
   *
   * Typically, a replica doesn't know the leader if the KRaft topic is undergoing an election cycle.
   *
   * It is also possible for a replica to be unattached if it doesn't know the leader's endpoint.
   * This typically happens when a replica starts up and the known leader id is not part of the local
   * voter set. In that case, during startup the replica transitions to unattached instead of
   * transitioning to follower. The unattached replica discovers the leader and leader's endpoint
   * either through random Fetch requests to the bootstrap servers or through BeginQuorumEpoch
   * request from the leader.
   */
  
  public class UnattachedState implements EpochState {
      private final int epoch;
      private final OptionalInt leaderId;
      private final Optional<ReplicaKey> votedKey;
      private final Set<Integer> voters;
      private final long electionTimeoutMs;
      private final Timer electionTimer;
      private final Optional<LogOffsetMetadata> highWatermark;
      private final Logger log;
  
      public UnattachedState(
          Time time,
          int epoch,
          OptionalInt leaderId,
          Optional<ReplicaKey> votedKey,
          Set<Integer> voters,
          Optional<LogOffsetMetadata> highWatermark,
          long electionTimeoutMs,
          LogContext logContext
      ) {
          this.epoch = epoch;
          this.leaderId = leaderId;
          this.votedKey = votedKey;
          this.voters = voters;
          this.highWatermark = highWatermark;
          this.electionTimeoutMs = electionTimeoutMs;
          this.electionTimer = time.timer(electionTimeoutMs);
          this.log = logContext.logger(UnattachedState.class);
      }
  
      @Override
      public ElectionState election() {
          if (leaderId.isPresent()) {
              return ElectionState.withElectedLeader(epoch, leaderId.getAsInt(), votedKey, voters);
          } else if (votedKey.isPresent()) {
              return ElectionState.withVotedCandidate(epoch, votedKey.get(), voters);
          } else {
              return ElectionState.withUnknownLeader(epoch, voters);
          }
      }
  
      @Override
      public int epoch() {
          return epoch;
      }
  
      @Override
      public Endpoints leaderEndpoints() {
          return Endpoints.empty();
      }
  
      @Override
      public String name() {
          return "Unattached";
      }
  
      public Optional<ReplicaKey> votedKey() {
          return votedKey;
      }
  
      public long electionTimeoutMs() {
          return electionTimeoutMs;
      }
  
      public long remainingElectionTimeMs(long currentTimeMs) {
          electionTimer.update(currentTimeMs);
          return electionTimer.remainingMs();
      }
  
      public boolean hasElectionTimeoutExpired(long currentTimeMs) {
          electionTimer.update(currentTimeMs);
          return electionTimer.isExpired();
      }
  
      @Override
      public Optional<LogOffsetMetadata> highWatermark() {
          return highWatermark;
      }
  
      @Override
      public boolean canGrantVote(ReplicaKey replicaKey, boolean isLogUpToDate, boolean isPreVote) {
          return unattachedOrProspectiveCanGrantVote(
              leaderId,
              votedKey,
              epoch,
              replicaKey,
              isLogUpToDate,
              isPreVote,
              log
          );
      }
  
      @Override
      public String toString() {
          return String.format(
              "UnattachedState(epoch=%d, leaderId=%s, votedKey=%s, voters=%s, " +
              "electionTimeoutMs=%d, highWatermark=%s)",
              epoch,
              leaderId,
              votedKey,
              voters,
              electionTimeoutMs,
              highWatermark
          );
      }
  
      @Override
      public void close() {}
  }
  