org.apache.hadoop.hdfs.util.CombinedHostsFileWriter 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.util;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.Writer;
import java.util.Set;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.hdfs.protocol.DatanodeAdminProperties;
/**
* Writer support for JSON-based datanode configuration, an alternative format
* to the exclude/include files configuration.
* The JSON file format defines the array of elements where each element
* in the array describes the properties of a datanode. The properties of
* a datanode is defined by {@link DatanodeAdminProperties}. For example,
*
* [
* {"hostName": "host1"},
* {"hostName": "host2", "port": 50, "upgradeDomain": "ud0"},
* {"hostName": "host3", "port": 0, "adminState": "DECOMMISSIONED"}
* ]
*/
@InterfaceAudience.LimitedPrivate({"HDFS"})
@InterfaceStability.Unstable
public final class CombinedHostsFileWriter {
private CombinedHostsFileWriter() {
}
/**
* Serialize a set of DatanodeAdminProperties to a json file.
* @param hostsFile the json file name.
* @param allDNs the set of DatanodeAdminProperties
* @throws IOException
*/
public static void writeFile(final String hostsFile,
final Set allDNs) throws IOException {
final ObjectMapper objectMapper = new ObjectMapper();
try (Writer output =
new OutputStreamWriter(new FileOutputStream(hostsFile), "UTF-8")) {
objectMapper.writeValue(output, allDNs);
}
}
}