org.apache.hadoop.hdfs.util.CombinedHostsFileReader 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 com.fasterxml.jackson.core.JsonFactory;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.ObjectReader;
import java.io.File;
import java.io.InputStreamReader;
import java.io.IOException;
import java.io.Reader;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.hdfs.protocol.DatanodeAdminProperties;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Reader 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 CombinedHostsFileReader {
public static final Logger LOG =
LoggerFactory.getLogger(CombinedHostsFileReader.class);
private CombinedHostsFileReader() {
}
private static final String REFER_TO_DOC_MSG = " For the correct JSON" +
" format please refer to the documentation (https://hadoop.apache" +
".org/docs/current/hadoop-project-dist/hadoop-hdfs/HdfsDataNodeAd" +
"minGuide.html#JSON-based_configuration)";
/**
* Deserialize a set of DatanodeAdminProperties from a json file.
* @param hostsFilePath the input json file to read from
* @return the set of DatanodeAdminProperties
* @throws IOException
*/
public static DatanodeAdminProperties[]
readFile(final String hostsFilePath) throws IOException {
DatanodeAdminProperties[] allDNs = new DatanodeAdminProperties[0];
ObjectMapper objectMapper = new ObjectMapper();
File hostFile = new File(hostsFilePath);
boolean tryOldFormat = false;
if (hostFile.length() > 0) {
try (Reader input =
new InputStreamReader(
Files.newInputStream(hostFile.toPath()), "UTF-8")) {
allDNs = objectMapper.readValue(input, DatanodeAdminProperties[].class);
} catch (JsonMappingException jme) {
// The old format doesn't have json top-level token to enclose
// the array.
// For backward compatibility, try parsing the old format.
tryOldFormat = true;
}
} else {
LOG.warn(hostsFilePath + " is empty." + REFER_TO_DOC_MSG);
}
if (tryOldFormat) {
ObjectReader objectReader =
objectMapper.readerFor(DatanodeAdminProperties.class);
JsonFactory jsonFactory = new JsonFactory();
List all = new ArrayList<>();
try (Reader input =
new InputStreamReader(Files.newInputStream(Paths.get(hostsFilePath)),
"UTF-8")) {
Iterator iterator =
objectReader.readValues(jsonFactory.createParser(input));
while (iterator.hasNext()) {
DatanodeAdminProperties properties = iterator.next();
all.add(properties);
}
LOG.warn(hostsFilePath + " has legacy JSON format." + REFER_TO_DOC_MSG);
} catch (Throwable ex) {
LOG.warn(hostsFilePath + " has invalid JSON format." + REFER_TO_DOC_MSG,
ex);
}
allDNs = all.toArray(new DatanodeAdminProperties[all.size()]);
}
return allDNs;
}
}