/**
* 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.hcatalog.utils;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.IOException;
import java.io.ObjectOutputStream;
import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Properties;
import org.apache.hcatalog.common.HCatException;
import org.apache.hcatalog.data.transfer.DataTransferFactory;
import org.apache.hcatalog.data.transfer.HCatReader;
import org.apache.hcatalog.data.transfer.ReadEntity;
import org.apache.hcatalog.data.transfer.ReaderContext;
public class DataReaderMaster {
public static void main(String[] args) throws FileNotFoundException, IOException {
// This config contains all the configuration that master node wants to provide
// to the HCatalog.
Properties externalConfigs = new Properties();
externalConfigs.load(new FileReader(args[0]));
Map<String, String> config = new HashMap<String, String>();
for (Entry<Object, Object> kv : externalConfigs.entrySet()) {
config.put((String) kv.getKey(), (String) kv.getValue());
}
// This piece of code runs in master node and gets necessary context.
ReaderContext context = runsInMaster(config);
ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(new File(args[1])));
oos.writeObject(context);
oos.flush();
oos.close();
// Master node will serialize readercontext and will make it available at slaves.
}
private static ReaderContext runsInMaster(Map<String, String> config) throws HCatException {
ReadEntity.Builder builder = new ReadEntity.Builder();
ReadEntity entity = builder.withTable(config.get("table")).build();
HCatReader reader = DataTransferFactory.getHCatReader(entity, config);
ReaderContext cntxt = reader.prepareRead();
return cntxt;
}
}