org.apache.hadoop.hdfs.server.aliasmap.InMemoryAliasMapProtocol Maven / Gradle / Ivy
/*
* 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.hadoop.hdfs.server.aliasmap;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.hdfs.protocol.Block;
import org.apache.hadoop.hdfs.protocol.ProvidedStorageLocation;
import org.apache.hadoop.hdfs.server.common.FileRegion;
import org.apache.hadoop.io.retry.Idempotent;
import javax.annotation.Nonnull;
import java.io.IOException;
import java.util.List;
import java.util.Optional;
/**
* Protocol used by clients to read/write data about aliases of
* provided blocks for an in-memory implementation of the
* {@link org.apache.hadoop.hdfs.server.common.blockaliasmap.BlockAliasMap}.
*/
@InterfaceAudience.Private
@InterfaceStability.Unstable
public interface InMemoryAliasMapProtocol {
/**
* The result of a read from the in-memory aliasmap. It contains the
* a list of FileRegions that are returned, along with the next block
* from which the read operation must continue.
*/
class IterationResult {
private final List batch;
private final Optional nextMarker;
public IterationResult(List batch, Optional nextMarker) {
this.batch = batch;
this.nextMarker = nextMarker;
}
public List getFileRegions() {
return batch;
}
public Optional getNextBlock() {
return nextMarker;
}
}
/**
* List the next batch of {@link FileRegion}s in the alias map starting from
* the given {@code marker}. To retrieve all {@link FileRegion}s stored in the
* alias map, multiple calls to this function might be required.
* @param marker the next block to get fileregions from.
* @return the {@link IterationResult} with a set of
* FileRegions and the next marker.
* @throws IOException
*/
@Idempotent
InMemoryAliasMap.IterationResult list(Optional marker)
throws IOException;
/**
* Gets the {@link ProvidedStorageLocation} associated with the
* specified block.
* @param block the block to lookup
* @return the associated {@link ProvidedStorageLocation}.
* @throws IOException
*/
@Nonnull
@Idempotent
Optional read(@Nonnull Block block)
throws IOException;
/**
* Stores the block and it's associated {@link ProvidedStorageLocation}
* in the alias map.
* @param block
* @param providedStorageLocation
* @throws IOException
*/
@Idempotent
void write(@Nonnull Block block,
@Nonnull ProvidedStorageLocation providedStorageLocation)
throws IOException;
/**
* Get the associated block pool id.
* @return the block pool id associated with the Namenode running
* the in-memory alias map.
*/
@Idempotent
String getBlockPoolId() throws IOException;
}