用Jetty和redis实现接入服务器adapter
传统的服务器端为若干个客户端提供服务，一般需要开启多个服务器端进程。为了进一步提升服务器端的处理能力，可以如下图所示将服务解耦为两部分（adapter与workers），它们之间通过消息队列传输数据，其中workers处理具体业务，adapter负责接入请求以及反馈结果，具体包含下面两个工作。
1，将所有客户端的请求发送到消息队列（进而传给后台处理）
2，后台处理完毕后将结果返回响应队列，client adapter获取到结果后返回给相应客户端。
流程图如下：
我们选择用Jetty（8），redis以及php简单实现这个场景，主要用到Jetty的continuation机制和redis的list先进先出数据结构
接入服务器：
A.1，先配置一个服务器如下，同时开启一个守护线程阻塞监听response queue（用到json lib库以及jedis库）（使用专用线程处理响应可以避免“惊群”现象，不影响业务线程）
package test; import java.util.HashMap; import java.util.List; import org.eclipse.jetty.continuation.Continuation; import org.eclipse.jetty.server.*; import org.eclipse.jetty.server.nio.SelectChannelConnector; import org.eclipse.jetty.servlet.ServletContextHandler; import org.eclipse.jetty.servlet.ServletHolder; import org.eclipse.jetty.util.thread.QueuedThreadPool; import org.json.simple.*; import redis.clients.jedis.Jedis; public class PJetty{ public static HashMap<String,Continuation>globalMap = new HashMap<String,Continuation>(); // 用一个守护线程阻塞等待结果队列返回数据 public static class DaemonThread extends Thread{ private JSONObject obj = new JSONObject(); private Jedis jedis = new Jedis("127.0.0.1",6379); private List<String> res; public void run(){ while(true){ // 阻塞等待响应队列 res = jedis.brpop(0, "response_queue"); // 获取结果信息 String response = res.get(1); obj=(JSONObject) JSONValue.parse(response); String request_sid = obj.get("request_sid").toString(); String result = obj.get("results").toString(); if(request_sid == null){ continue; } // 通过消息中的连接的sessonid获取到响应的continuation实例，然后设置结果信息再唤醒实例 Continuation con = globalMap.get(request_sid); if(con == null){continue;} globalMap.remove(request_sid); //客户端异常断开这里会抛错 try{ con.setAttribute("results", result); con.resume(); } catch(Exception e){ continue; } } } } public static void main(String[] args) throws Exception { //开启守护线程去阻塞等待响应结果队列，唤醒请求 DaemonThread dt = new DaemonThread(); dt.start(); //设置connectors SelectChannelConnector connector1 = new SelectChannelConnector(); connector1.setPort(1987); connector1.setThreadPool(new QueuedThreadPool(5)); Server server = new Server(); server.setConnectors(new Connector[]{connector1}); //使用servlet处理请求 ServletContextHandler context = new ServletContextHandler(ServletContextHandler.SESSIONS); context.setContextPath("/"); context.addServlet(new ServletHolder(new NonBlockingServlet()), "/fetch"); server.setHandler(context); server.start(); server.join(); } }
A.2，实现自定义的servlets接受前端client连接，将请求信息传入队列request queue
package test; import java.io.IOException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; import org.eclipse.jetty.continuation.Continuation; import org.eclipse.jetty.continuation.ContinuationSupport; import org.json.simple.JSONObject; import redis.clients.jedis.Jedis; public class NonBlockingServlet extends HttpServlet { /** * generated serialize number */ private static final long serialVersionUID = 3313258432391586994L; protected void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException { // 用sleeptime来模拟后台工作量 String sleepTime = request.getParameter("st"); if(sleepTime == null){ sleepTime = "0"; } // 查看结果队列是否返回此连接的请求结果 Object results = request.getAttribute("results"); if (results==null) // 如果异步处理尚未返回结果 { Continuation continuation = ContinuationSupport.getContinuation(request); if(continuation.isInitial()){ // 设置连接超时时间 continuation.setTimeout(10000); response.setContentType("text/plain"); response.getWriter().flush(); HttpSession session=request.getSession(); String sid = session.getId(); Jedis jedis = new Jedis("127.0.0.1",6379); //将请求连接sessionid以及请求内容encode后传到处理队列中 JSONObject obj=new JSONObject(); obj.put("request_sid",sid); obj.put("params",sleepTime); jedis.lpush("request_queue", obj.toJSONString()); //将连接和continuation实例做个映射关系存到全局hashmap中，不确定这里是否应该加锁 PJetty.globalMap.put(sid, continuation); } // 判断是否超时 if (continuation.isExpired()) { // 返回超时Response response.getWriter().println("timeout"); response.getWriter().flush(); return; } // 挂起HTTP连接 continuation.suspend(); return; // or continuation.undispatch(); } // 连接恢复后返回结果 response.getWriter().println("Got Result:\t" + results); response.getWriter().flush(); } }
业务服务器：
B，实现后端worker.php（可以自定义worker进程数，我这里设置为5个php进程，进程数多能获取更好的并发）（用到predis库）
#!/root/bin/php <?php require_once("lib/Predis/Autoloader.php"); function worker_thread() { Predis\Autoloader::register(); $redis = new Predis\Client('tcp://127.0.0.1:6379'); while(true){ try{ $request = $redis->brpop("request_queue", 0); } catch(Exception $e){ continue; } /** demo array(2) { [0]=> string(13) "request_queue" [1]=> string(55) "{"request_sid":"q0muxazo8k1h1k3uw85wuayh","params":"4"}" } */ $request = json_decode($request[1], true); // sleep represents work loads sleep(intval($request["params"])); $results = array("request_sid"=>$request["request_sid"], "results"=>$request["params"]); $response = json_encode($results); $redis->lpush("response_queue",$response); } } //开启多个worker进程提供服务 for ($worker_nbr = 0; $worker_nbr < 5; $worker_nbr++) { $pid = pcntl_fork(); if ($pid == 0) { worker_thread(); return; } } ?>
运行结果如下：
这只是一个简单的demo，为了防止redis，workers进程挂掉或者客户端异常断开，还需要做些异常处理，比如设置请求超时，捕获一些空指针等，超时需要将continuation从globalMap中剔除，防止内存得不到释放。
root # for((i=10;i>=1;i--)) ; do lynx -dump http://127.0.0.1:1987/fetch?st=$i & done [1] 14112 [2] 14113 [3] 14114 [4] 14115 [5] 14116 [6] 14117 [7] 14118 [8] 14119 [9] 14120 [10] 14121 root # Got Result: 3 Got Result: 4 Got Result: 2 Got Result: 7 Got Result: 1 Got Result: 9 Got Result: 6 timeout timeout timeout [1] Done lynx -dump http://127.0.0.1:1987/fetch?st=$i [2] Done lynx -dump http://127.0.0.1:1987/fetch?st=$i [3] Done lynx -dump http://127.0.0.1:1987/fetch?st=$i [4] Done lynx -dump http://127.0.0.1:1987/fetch?st=$i [5] Done lynx -dump http://127.0.0.1:1987/fetch?st=$i [6] Done lynx -dump http://127.0.0.1:1987/fetch?st=$i [7] Done lynx -dump http://127.0.0.1:1987/fetch?st=$i [8] Done lynx -dump http://127.0.0.1:1987/fetch?st=$i [9]- Done lynx -dump http://127.0.0.1:1987/fetch?st=$i [10]+ Done lynx -dump http://127.0.0.1:1987/fetch?st=$i
redis数据库中存储的内容如下，可以看出虽然经后台处理后顺序变化了，但是对应关系正确，接入服务器能够根据request_sid把结果返回给相应的用户：
redis 127.0.0.1:6379> lrange request_queue 0 15
1) "{\"request_sid\":\"igiwkwnb715aphw8uvtfa6rj\",\"params\":\"3\"}"
2) "{\"request_sid\":\"wsrglxa3h6ef19ik5i0nbiiys\",\"params\":\"2\"}"
3) "{\"request_sid\":\"tyiqoj6awj5t16ddpqusftwc8\",\"params\":\"6\"}"
4) "{\"request_sid\":\"1052tgkiyy7c31bmxjtbom7ca\",\"params\":\"5\"}"
5) "{\"request_sid\":\"17jo1xwnnkd3h1mhcqcfplrl5k\",\"params\":\"8\"}"
6) "{\"request_sid\":\"1xk521sq6vmmf6enxauwzduj9\",\"params\":\"4\"}"
7) "{\"request_sid\":\"1cxnir1slgjiq1o2n3xwznh0kk\",\"params\":\"9\"}"
8) "{\"request_sid\":\"961vf8hao3stsv4vt1qif3ws\",\"params\":\"7\"}"
9) "{\"request_sid\":\"35pfn5au6p8qdbri17p636si\",\"params\":\"10\"}"
10) "{\"request_sid\":\"1ca4wy8qsfr7av0hwk8xtlqhp\",\"params\":\"1\"}"
redis 127.0.0.1:6379> lrange response_queue 0 15
1) "{\"request_sid\":\"tyiqoj6awj5t16ddpqusftwc8\",\"results\":\"6\"}"
2) "{\"request_sid\":\"igiwkwnb715aphw8uvtfa6rj\",\"results\":\"3\"}"
3) "{\"request_sid\":\"wsrglxa3h6ef19ik5i0nbiiys\",\"results\":\"2\"}"
4) "{\"request_sid\":\"35pfn5au6p8qdbri17p636si\",\"results\":\"10\"}"
5) "{\"request_sid\":\"1052tgkiyy7c31bmxjtbom7ca\",\"results\":\"5\"}"
6) "{\"request_sid\":\"1cxnir1slgjiq1o2n3xwznh0kk\",\"results\":\"9\"}"
7) "{\"request_sid\":\"17jo1xwnnkd3h1mhcqcfplrl5k\",\"results\":\"8\"}"
8) "{\"request_sid\":\"961vf8hao3stsv4vt1qif3ws\",\"results\":\"7\"}"
9) "{\"request_sid\":\"1xk521sq6vmmf6enxauwzduj9\",\"results\":\"4\"}"
10) "{\"request_sid\":\"1ca4wy8qsfr7av0hwk8xtlqhp\",\"results\":\"1\"}"
