Tomcat下WebSocket最大连接数测试调优

Tomcat下WebSocket最大连接数测试调优

默认情况下，Tomcat的WebSocket最大连接数为200。

WebSocket后台代码

package com.chat.demo;

/*
 *  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.
 */

import java.io.IOException;
import java.util.Set;
import java.util.concurrent.CopyOnWriteArraySet;
import java.util.concurrent.atomic.AtomicInteger;

import javax.websocket.OnClose;
import javax.websocket.OnError;
import javax.websocket.OnMessage;
import javax.websocket.OnOpen;
import javax.websocket.Session;
import javax.websocket.server.ServerEndpoint;

//import org.apache.juli.logging.Log;
//import org.apache.juli.logging.LogFactory;

//import util.HTMLFilter;

@ServerEndpoint(value = "/websocket/chat")
public class ChatAnnotation {

    //private static final Log log = LogFactory.getLog(ChatAnnotation.class);

    private static final String GUEST_PREFIX = "Guest";
    private static final AtomicInteger connectionIds = new AtomicInteger(0);
    private static final Set<ChatAnnotation> connections =
            new CopyOnWriteArraySet<ChatAnnotation>();

    private final String nickname;
    private Session session;

    public ChatAnnotation() {
        nickname = GUEST_PREFIX + connectionIds.getAndIncrement();
    }


    @OnOpen
    public void start(Session session) {
        this.session = session;
        connections.add(this);
        String message = String.format("* %s %s", nickname, "has joined.");
        broadcast(message);
    }


    @OnClose
    public void end() {
        connections.remove(this);
        String message = String.format("* %s %s",
                nickname, "has disconnected.");
        broadcast(message);
    }


    @OnMessage
    public void incoming(String message) {
        // Never trust the client
        String filteredMessage = String.format("%s: %s",
                nickname, message.toString());
        broadcast(filteredMessage);
    }




    @OnError
    public void onError(Throwable t) throws Throwable {
        System.out.println("Chat Error: " + t.toString());
    }


    private static void broadcast(String msg) {
        for (ChatAnnotation client : connections) {
            try {
                synchronized (client) {
                    client.session.getBasicRemote().sendText(msg);
                }
            } catch (IOException e) {
                //log.debug("Chat Error: Failed to send message to client", e);
                connections.remove(client);
                try {
                    client.session.close();
                } catch (IOException e1) {
                    // Ignore
                }
                String message = String.format("* %s %s",
                        client.nickname, "has been disconnected.");
                broadcast(message);
            }
        }
    }
}

启动Tomcat,注意ws的地址，然后运行测试WebSocket连接数代码

package com.jiafuwei.java.snake;

import java.net.URI;


import javax.websocket.ClientEndpoint;
import javax.websocket.ContainerProvider;
import javax.websocket.Session;
import javax.websocket.WebSocketContainer;


@ClientEndpoint
public class WebSocketTest {


    private String deviceId;

    private Session session;

    public WebSocketTest () {
        
    }

    public WebSocketTest (String deviceId) {
        this.deviceId = deviceId;
    }

    protected boolean start() {
        WebSocketContainer Container = ContainerProvider.getWebSocketContainer();
        String uri = "ws://localhost:8028/lhychat/websocket/chat";
        System.out.println("Connecting to " + uri);
        try {
            session = Container.connectToServer(WebSocketTest.class, URI.create(uri));
            System.out.println("count: " + deviceId);
        } catch (Exception e) {
            e.printStackTrace();
            return false;
        }
        return true;
    }

    public static void main(String[] args) {
        for (int i = 1; i< 1000; i++) {
            WebSocketTest wSocketTest = new WebSocketTest(String.valueOf(i));
            if (!wSocketTest.start()) {
                System.out.println("测试结束！");
                break;
            }
        }
    }
}

运行结果为每次循环到第200个的时候，测试结束了，WebSocket后台代码开始报错。

如何增加并发数呢，只需在server.xml文件中，增加 maxThreads=”300″ 这样最大的并发数就变成了300。

<Connector maxConnections="300"  maxThreads="300"  URIEncoding="UTF-8" connectionTimeout="20000" port="8028" protocol="HTTP/1.1" redirectPort="8443" useBodyEncodingForURI="true"/>

但是需要强调的是：完全依赖于片面的调大maxThreads是不行的，应用服务器优化是一个系统性的问题。

你得根据实际情况适当调整，包括最大线程数、队列大小、超时、内存参数等。
你首先得弄清楚目前的业务瓶颈在哪里，如果是业务处理花时间多，你maxThreads设置的再大，过多请求进来排队也得超时。

如果一个tomcat节点已经很吃力，也没有其他明显的性能瓶颈，那你就该考虑用tomcat集群了。

所以到这里你就明白了，自己开发和维护websocket服务，在高并发高连接数需求下，是一件吃力不讨好的事情。如果这个时候有一套即开即用的高性能websocket第三方服务，那该是多美好的一件事件啊。

这样美好的事情还真有！

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