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;
  
  import java.io.IOException;
  import java.util.function.BiFunction;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import org.apache.cassandra.db.TypeSizes;
  import org.apache.cassandra.io.IVersionedSerializer;
  import org.apache.cassandra.io.util.DataInputPlus;
  import org.apache.cassandra.io.util.DataOutputPlus;
  import org.apache.cassandra.metrics.TCMMetrics;
  import org.apache.cassandra.net.IVerbHandler;
  import org.apache.cassandra.net.Message;
  import org.apache.cassandra.net.MessagingService;
  import org.apache.cassandra.schema.DistributedMetadataLogKeyspace;
  import org.apache.cassandra.tcm.log.LogState;
  import org.apache.cassandra.utils.FBUtilities;
  
  public class FetchCMSLog
  {
      public static final Serializer serializer = new Serializer();
  
      public final Epoch lowerBound;
      public final boolean consistentFetch;
  
      public FetchCMSLog(Epoch lowerBound, boolean consistentFetch)
      {
          this.lowerBound = lowerBound;
          this.consistentFetch = consistentFetch;
      }
  
      public String toString()
      {
          return "FetchCMSLog{" +
                 "consistentFetch=" + consistentFetch +
                 ", lowerBound=" + lowerBound +
                 '}';
      }
  
      static class Serializer implements IVersionedSerializer<FetchCMSLog>
      {
  
          public void serialize(FetchCMSLog t, DataOutputPlus out, int version) throws IOException
          {
              Epoch.serializer.serialize(t.lowerBound, out);
              out.writeBoolean(t.consistentFetch);
          }
  
          public FetchCMSLog deserialize(DataInputPlus in, int version) throws IOException
          {
              Epoch epoch = Epoch.serializer.deserialize(in);
              boolean consistentFetch = in.readBoolean();
              return new FetchCMSLog(epoch, consistentFetch);
          }
  
          public long serializedSize(FetchCMSLog t, int version)
          {
              return Epoch.serializer.serializedSize(t.lowerBound)
                     + TypeSizes.BOOL_SIZE;
          }
      }
  
      static class Handler implements IVerbHandler<FetchCMSLog>
      {
          private static final Logger logger = LoggerFactory.getLogger(Handler.class);
  
          /**
           * Receives epoch we need to fetch state up to, and a boolean specifying whether the consistency can be downgraded
           * to node-local (which only relevant in cases of CMS expansions/shrinks, and can only be requested by the
           * CMS node that collects the highest epoch from the quorum of peers).
           */
          private final BiFunction<Epoch, Boolean, LogState> logStateSupplier;
  
          public Handler()
          {
              this(DistributedMetadataLogKeyspace::getLogState);
          }
  
          public Handler(BiFunction<Epoch, Boolean, LogState> logStateSupplier)
          {
              this.logStateSupplier = logStateSupplier;
          }
  
          public void doVerb(Message<FetchCMSLog> message) throws IOException
          {
              FetchCMSLog request = message.payload;
  
              if (logger.isTraceEnabled())
                  logger.trace("Received log fetch request {} from {}: start = {}, current = {}", request, message.from(), message.payload.lowerBound, ClusterMetadata.current().epoch);
  
              if (request.consistentFetch && !ClusterMetadataService.instance().isCurrentMember(FBUtilities.getBroadcastAddressAndPort()))
                  throw new NotCMSException("This node is not in the CMS, can't generate a consistent log fetch response to " + message.from());
  
              // If both we and the other node believe it should be caught up with a linearizable read
              boolean consistentFetch = request.consistentFetch && !ClusterMetadataService.instance().isCurrentMember(message.from());
  
              LogState delta = logStateSupplier.apply(message.payload.lowerBound, consistentFetch);
              TCMMetrics.instance.cmsLogEntriesServed(message.payload.lowerBound, delta.latestEpoch());
              logger.info("Responding to {}({}) with log delta: {}", message.from(), request, delta);
              MessagingService.instance().send(message.responseWith(delta), message.from());
          }
      }
  }
  