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.bifromq.basekv.localengine.memory;
  
  import static org.apache.bifromq.basekv.localengine.metrics.KVSpaceMeters.getGauge;
  
  import org.apache.bifromq.basekv.localengine.ICPableKVSpace;
  import org.apache.bifromq.basekv.localengine.IKVSpaceCheckpoint;
  import org.apache.bifromq.basekv.localengine.metrics.GeneralKVSpaceMetric;
  import org.apache.bifromq.basekv.localengine.metrics.KVSpaceOpMeters;
  import com.github.benmanes.caffeine.cache.Cache;
  import com.github.benmanes.caffeine.cache.Caffeine;
  import io.micrometer.core.instrument.Gauge;
  import io.micrometer.core.instrument.Tags;
  import java.util.HashMap;
  import java.util.Optional;
  import java.util.UUID;
  import org.slf4j.Logger;
  
  public class InMemCPableKVSpace extends InMemKVSpace<InMemCPableKVEngine, InMemCPableKVSpace>
      implements ICPableKVSpace {
      private final Cache<String, InMemKVSpaceCheckpoint> checkpoints;
      private final Gauge checkpointGauge;
      private volatile InMemKVSpaceCheckpoint latestCheckpoint;
  
      protected InMemCPableKVSpace(String id,
                                   InMemKVEngineConfigurator configurator,
                                   InMemCPableKVEngine engine,
                                   Runnable onDestroy,
                                   KVSpaceOpMeters opMeters,
                                   Logger logger,
                                   String... tags) {
          super(id, configurator, engine, onDestroy, opMeters, logger);
          checkpoints = Caffeine.newBuilder().weakValues().build();
          checkpointGauge = getGauge(id, GeneralKVSpaceMetric.CheckpointNumGauge, checkpoints::estimatedSize,
              Tags.of(tags));
      }
  
      @Override
      public String checkpoint() {
          synchronized (this) {
              return metadataRefresher.call(() -> {
                  String cpId = UUID.randomUUID().toString();
                  latestCheckpoint = new InMemKVSpaceCheckpoint(id, cpId, new HashMap<>(metadataMap), rangeData.clone(),
                      opMeters, logger);
                  checkpoints.put(cpId, latestCheckpoint);
                  return cpId;
              });
          }
      }
  
      @Override
      public Optional<IKVSpaceCheckpoint> openCheckpoint(String checkpointId) {
          return Optional.ofNullable(checkpoints.getIfPresent(checkpointId));
      }
  
      @Override
      public void close() {
          super.close();
          checkpointGauge.close();
      }
  }
  