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.coordinator.common.runtime;
  
  import org.apache.kafka.common.TopicPartition;
  import org.apache.kafka.common.requests.TransactionResult;
  import org.apache.kafka.common.utils.LogContext;
  import org.apache.kafka.image.MetadataDelta;
  import org.apache.kafka.image.MetadataImage;
  import org.apache.kafka.timeline.SnapshotRegistry;
  
  import org.slf4j.Logger;
  
  /**
   * SnapshottableCoordinator is a wrapper on top of the coordinator state machine. This object is not accessed concurrently
   * but multiple threads access it while loading the coordinator partition and therefore requires all methods to be
   * synchronized.
   */
  public class SnapshottableCoordinator<S extends CoordinatorShard<U>, U> implements CoordinatorPlayback<U> {
      /**
       * The logger.
       */
      private final Logger log;
  
      /**
       * The snapshot registry backing the coordinator.
       */
      private final SnapshotRegistry snapshotRegistry;
  
      /**
       * The actual state machine.
       */
      private final S coordinator;
  
      /**
       * The topic partition.
       */
      private final TopicPartition tp;
  
      /**
       * The last offset written to the partition.
       */
      private long lastWrittenOffset;
  
      /**
       * The last offset committed. This represents the high
       * watermark of the partition.
       */
      private long lastCommittedOffset;
  
      SnapshottableCoordinator(
          LogContext logContext,
          SnapshotRegistry snapshotRegistry,
          S coordinator,
          TopicPartition tp
      ) {
          this.log = logContext.logger(SnapshottableCoordinator.class);
          this.coordinator = coordinator;
          this.snapshotRegistry = snapshotRegistry;
          this.tp = tp;
          this.lastWrittenOffset = 0;
          this.lastCommittedOffset = 0;
          snapshotRegistry.idempotentCreateSnapshot(0);
      }
  
      /**
       * Reverts the last written offset. This also reverts the snapshot
       * registry to this offset. All the changes applied after the offset
       * are lost.
       *
       * @param offset The offset to revert to.
       */
      synchronized void revertLastWrittenOffset(
          long offset
      ) {
          if (offset > lastWrittenOffset) {
              throw new IllegalStateException("New offset " + offset + " of " + tp +
                  " must be smaller than " + lastWrittenOffset + ".");
          }
  
          log.debug("Revert last written offset of {} to {}.", tp, offset);
          lastWrittenOffset = offset;
          snapshotRegistry.revertToSnapshot(offset);
      }
  
      /**
       * Replays the record onto the state machine.
       *
       * @param offset        The offset of the record in the log.
       * @param producerId    The producer id.
       * @param producerEpoch The producer epoch.
       * @param record        A record.
       */
      @Override
      public synchronized void replay(
          long offset,
          long producerId,
          short producerEpoch,
          U record
      ) {
          coordinator.replay(offset, producerId, producerEpoch, record);
      }
  
      /**
       * Applies the end transaction marker.
       *
       * @param producerId    The producer id.
       * @param producerEpoch The producer epoch.
       * @param result        The result of the transaction.
       */
      @Override
      public synchronized void replayEndTransactionMarker(
          long producerId,
          short producerEpoch,
          TransactionResult result
      ) {
          coordinator.replayEndTransactionMarker(producerId, producerEpoch, result);
      }
  
      /**
       * Updates the last written offset. This also create a new snapshot
       * in the snapshot registry.
       *
       * @param offset The new last written offset.
       */
      @Override
      public synchronized void updateLastWrittenOffset(Long offset) {
          if (offset <= lastWrittenOffset) {
              throw new IllegalStateException("New last written offset " + offset + " of " + tp +
                  " must be greater than " + lastWrittenOffset + ".");
          }
  
          lastWrittenOffset = offset;
          snapshotRegistry.idempotentCreateSnapshot(offset);
          log.debug("Updated last written offset of {} to {}.", tp, offset);
      }
  
      /**
       * Updates the last committed offset. This completes all the deferred
       * events waiting on this offset. This also cleanups all the snapshots
       * prior to this offset.
       *
       * @param offset The new last committed offset.
       */
      @Override
      public synchronized void updateLastCommittedOffset(Long offset) {
          if (offset < lastCommittedOffset) {
              throw new IllegalStateException("New committed offset " + offset + " of " + tp +
                  " must be greater than or equal to " + lastCommittedOffset + ".");
          }
  
          if (offset > lastWrittenOffset) {
              throw new IllegalStateException("New committed offset " + offset + " of " + tp +
                  " must be less than or equal to " + lastWrittenOffset + ".");
          }
  
          lastCommittedOffset = offset;
          snapshotRegistry.deleteSnapshotsUpTo(offset);
          log.debug("Updated committed offset of {} to {}.", tp, offset);
      }
  
      /**
       * The coordinator has been loaded. This is used to apply any
       * post loading operations.
       *
       * @param newImage  The metadata image.
       */
      synchronized void onLoaded(MetadataImage newImage) {
          this.coordinator.onLoaded(newImage);
      }
  
      /**
       * The coordinator has been unloaded. This is used to apply
       * any post unloading operations.
       */
      synchronized void onUnloaded() {
          if (this.coordinator != null) {
              this.coordinator.onUnloaded();
          }
      }
  
      /**
       * @return The last written offset.
       */
      synchronized long lastWrittenOffset() {
          return this.lastWrittenOffset;
      }
  
      /**
       * A new metadata image is available. This is only called after {@link SnapshottableCoordinator#onLoaded(MetadataImage)}
       * is called to signal that the coordinator has been fully loaded.
       *
       * @param newImage  The new metadata image.
       * @param delta     The delta image.
       */
      synchronized void onNewMetadataImage(MetadataImage newImage, MetadataDelta delta) {
          this.coordinator.onNewMetadataImage(newImage, delta);
      }
  
      /**
       * @return The last committed offset.
       */
      synchronized long lastCommittedOffset() {
          return this.lastCommittedOffset;
      }
  
      /**
       * @return The coordinator.
       */
      synchronized S coordinator() {
          return this.coordinator;
      }
  
      /**
       * @return The snapshot registry.
       *
       * Only used for testing.
       */
      synchronized SnapshotRegistry snapshotRegistry() {
          return this.snapshotRegistry;
      }
  }
  