/**
 * 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.yarn.client;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.security.PrivilegedAction;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.security.UserGroupInformation;
import org.apache.hadoop.yarn.ipc.YarnRPC;

@InterfaceAudience.Public
@InterfaceStability.Evolving
@SuppressWarnings("unchecked")
public class AHSProxy<T> {

  private static final Log LOG = LogFactory.getLog(AHSProxy.class);

  public static <T> T createAHSProxy(final Configuration conf,
      final Class<T> protocol, InetSocketAddress ahsAddress) throws IOException {
    LOG.info("Connecting to Application History server at " + ahsAddress);
    return (T) getProxy(conf, protocol, ahsAddress);
  }

  protected static <T> T getProxy(final Configuration conf,
      final Class<T> protocol, final InetSocketAddress rmAddress)
      throws IOException {
    return UserGroupInformation.getCurrentUser().doAs(
      new PrivilegedAction<T>() {
        @Override
        public T run() {
          return (T) YarnRPC.create(conf).getProxy(protocol, rmAddress, conf);
        }
      });
  }
}