LoadBalancer.java

/*
   Copyright (c) 2012 LinkedIn Corp.

   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 com.linkedin.d2.balancer;

import com.linkedin.d2.balancer.properties.ServiceProperties;
import com.linkedin.d2.discovery.event.PropertyEventThread.PropertyEventShutdownCallback;
import com.linkedin.common.callback.Callback;
import com.linkedin.r2.message.Request;
import com.linkedin.r2.message.RequestContext;
import com.linkedin.r2.transport.common.bridge.client.TransportClient;
import com.linkedin.common.util.None;


/**
 * The interface for load balancing a request. The main method is to return a client
 * to which the requester can pass the request, given request and some context.
 */
public interface LoadBalancer
{
  TransportClient getClient(Request request, RequestContext requestContext) throws ServiceUnavailableException;

  void start(Callback<None> callback);

  void shutdown(PropertyEventShutdownCallback shutdown);

  ServiceProperties getLoadBalancedServiceProperties(String serviceName) throws ServiceUnavailableException;
}