org.apache.hadoop.hdfs.protocol.CachePoolIterator.java Source code

Introduction

Here is the source code for org.apache.hadoop.hdfs.protocol.CachePoolIterator.java

Source

/**
 * 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.protocol;

import java.io.IOException;

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.fs.BatchedRemoteIterator;
import org.apache.htrace.core.TraceScope;
import org.apache.htrace.core.Tracer;

/**
 * CachePoolIterator is a remote iterator that iterates cache pools.
 * It supports retrying in case of namenode failover.
 */
@InterfaceAudience.Private
@InterfaceStability.Evolving
public class CachePoolIterator extends BatchedRemoteIterator<String, CachePoolEntry> {

    private final ClientProtocol namenode;
    private final Tracer tracer;

    public CachePoolIterator(ClientProtocol namenode, Tracer tracer) {
        super("");
        this.namenode = namenode;
        this.tracer = tracer;
    }

    @Override
    public BatchedEntries<CachePoolEntry> makeRequest(String prevKey) throws IOException {
        try (TraceScope ignored = tracer.newScope("listCachePools")) {
            return namenode.listCachePools(prevKey);
        }
    }

    @Override
    public String elementToPrevKey(CachePoolEntry entry) {
        return entry.getInfo().getPoolName();
    }
}