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.cassandra.tcm.transformations;
  
  import java.io.IOException;
  
  import org.apache.cassandra.io.util.DataInputPlus;
  import org.apache.cassandra.io.util.DataOutputPlus;
  import org.apache.cassandra.tcm.ClusterMetadata;
  import org.apache.cassandra.tcm.Transformation;
  import org.apache.cassandra.tcm.sequences.LockedRanges;
  import org.apache.cassandra.tcm.serialization.AsymmetricMetadataSerializer;
  import org.apache.cassandra.tcm.serialization.Version;
  
  /**
   * Snapshots are used during startup or catchup between peers to avoid having to replay or transmit the entire log.
   * This transformation simply inserts a marker entry into the metadata log. Enacting the epoch on a peer triggers the
   * snapshot action on that peer. By default, taking a snapshot taking is an asynchonous action, and we generally do not
   * rely on the fact snapshot is, in fact going to be available immediately (or even durably).
   */
  public class TriggerSnapshot implements Transformation
  {
      public static final Serializer serializer = new Serializer();
  
      public static TriggerSnapshot instance = new TriggerSnapshot();
  
      private TriggerSnapshot(){}
  
      @Override
      public Kind kind()
      {
          return Kind.TRIGGER_SNAPSHOT;
      }
  
      @Override
      public boolean allowDuringUpgrades()
      {
          return true;
      }
  
      @Override
      public Result execute(ClusterMetadata prev)
      {
          return Transformation.success(prev.transformer(), LockedRanges.AffectedRanges.EMPTY);
      }
  
      static class Serializer implements AsymmetricMetadataSerializer<Transformation, TriggerSnapshot>
      {
          public void serialize(Transformation t, DataOutputPlus out, Version version) throws IOException
          {
              assert t == instance;
          }
  
          public TriggerSnapshot deserialize(DataInputPlus in, Version version) throws IOException
          {
              return instance;
          }
  
          public long serializedSize(Transformation t, Version version)
          {
              return 0;
          }
      }
  
      @Override
      public String toString()
      {
          return "TriggerSnapshot{}";
      }
  }
  