PingUrl.java

/*
*
* Copyright 2013 Netflix, 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 com.netflix.loadbalancer;

import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpUriRequest;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.util.EntityUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;


/**
 * Ping implementation if you want to do a "health check" kind of Ping. This
 * will be a "real" ping. As in a real http/s call is made to this url e.g.
 * http://ec2-75-101-231-85.compute-1.amazonaws.com:7101/cs/hostRunning
 * 
 * Some services/clients choose PingDiscovery - which is quick but is not a real
 * ping. i.e It just asks discovery (eureka) in-memory cache if the server is present
 * in its Roster PingUrl on the other hand, makes an actual call. This is more
 * expensive - but its the "standard" way most VIPs and other services perform
 * HealthChecks.
 * 
 * Choose your Ping based on your needs.
 * 
 * @author stonse
 * 
 */
public class PingUrl implements IPing {
    private static final Logger LOGGER = LoggerFactory.getLogger(PingUrl.class);

		String pingAppendString = "";
		boolean isSecure = false;
		
		String expectedContent = null;

		/*
		 *
		 * Send one ping only.
		 *
		 * Well, send what you need to determine whether or not the
		 * server is still alive.  Should return within a "reasonable"
		 * time.
		 */
		
		public PingUrl() {
		}
		
		public PingUrl(boolean isSecure, String pingAppendString) {
			this.isSecure = isSecure;
			this.pingAppendString = (pingAppendString != null) ? pingAppendString : "";
		}

		public void setPingAppendString(String pingAppendString) {
				this.pingAppendString = (pingAppendString != null) ? pingAppendString : "";
		}

		public String getPingAppendString() {
				return pingAppendString;
		}

		public boolean isSecure() {
			return isSecure;
		}

		/**
		 * Should the Secure protocol be used to Ping
		 * @param isSecure
		 */
		public void setSecure(boolean isSecure) {
			this.isSecure = isSecure;
		}
		

		public String getExpectedContent() {
			return expectedContent;
		}

		/**
		 * Is there a particular content you are hoping to see?
		 * If so -set this here.
		 * for e.g. the WCS server sets the content body to be 'true'
		 * Please be advised that this content should match the actual 
		 * content exactly for this to work. Else yo may get false status.
		 * @param expectedContent
		 */
		public void setExpectedContent(String expectedContent) {
			this.expectedContent = expectedContent;
		}

		public boolean isAlive(Server server) {
				String urlStr   = "";
				if (isSecure){
					urlStr = "https://";
				}else{
					urlStr = "http://";
				}
				urlStr += server.getId();
				urlStr += getPingAppendString();

				boolean isAlive = false;

				HttpClient httpClient = new DefaultHttpClient();
				HttpUriRequest getRequest = new HttpGet(urlStr);
				String content=null;
				try {
					HttpResponse response = httpClient.execute(getRequest);
					content = EntityUtils.toString(response.getEntity());
					isAlive = (response.getStatusLine().getStatusCode() == 200);
					if (getExpectedContent()!=null){
						LOGGER.debug("content:" + content);
						if (content == null){
							isAlive = false;
						}else{
							if (content.equals(getExpectedContent())){
								isAlive = true;
							}else{
								isAlive = false;
							}
						}
					}
				} catch (IOException e) {
					e.printStackTrace();
				}finally{
					// Release the connection.
					getRequest.abort();
				}

				return isAlive;
		}
		
		public static void main(String[] args){
		    PingUrl p = new PingUrl(false,"/cs/hostRunning");
		    p.setExpectedContent("true");
		    Server s = new Server("ec2-75-101-231-85.compute-1.amazonaws.com", 7101);
		    
		    boolean isAlive = p.isAlive(s);
		    System.out.println("isAlive:" + isAlive);
		}
}