ThriftHelper.java

/*
 * Copyright © 2014 Cask Data, Inc.
 *
 * Licensed 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 co.cask.cdap.gateway.handlers.util;

import co.cask.cdap.common.discovery.EndpointStrategy;
import co.cask.cdap.common.service.ServerException;
import org.apache.thrift.protocol.TBinaryProtocol;
import org.apache.thrift.protocol.TProtocol;
import org.apache.thrift.transport.TFramedTransport;
import org.apache.thrift.transport.TSocket;
import org.apache.thrift.transport.TTransport;
import org.apache.thrift.transport.TTransportException;
import org.apache.twill.discovery.Discoverable;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Utility to get a thrift client using a service discovery.
 */
public class ThriftHelper {

  private static final Logger LOG = LoggerFactory.getLogger(ThriftHelper.class);

  /**
   * generic method to discover a thrift service and start up the
   * thrift transport and protocol layer.
   */
  public static TProtocol getThriftProtocol(String serviceName, EndpointStrategy endpointStrategy) throws
    ServerException {
    Discoverable endpoint = endpointStrategy.pick();
    if (endpoint == null) {
      String message = String.format("Service '%s' is not registered in discovery service.", serviceName);
      LOG.error(message);
      throw new ServerException(message);
    }
    TTransport transport = new TFramedTransport(
      new TSocket(endpoint.getSocketAddress().getHostName(), endpoint.getSocketAddress().getPort()));
    try {
      transport.open();
    } catch (TTransportException e) {
      String message = String.format("Unable to connect to thrift service %s at %s. Reason: %s",
                                     serviceName, endpoint.getSocketAddress(), e.getMessage());
      LOG.error(message);
      throw new ServerException(message, e);
    }
    // now try to connect the thrift client
    return new TBinaryProtocol(transport);
  }
}