HttpClient在多线程环境下踩坑总结

时间 2019-12-05

原文原文链接

问题现场

在多线程环境下使用HttpClient组件对某个HTTP服务发起请求，运行一段时间以后发现客户端主机CPU利用率呈现出降低趋势，而不是一个稳定的状态。
并且，从程序日志中判断有线程处于hang住的状态，应该是被阻塞了。
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问题排查

一开始找不到缘由，怀疑是多线程并发致使的死锁问题，可是经过代码审查并未定位到任何可能的多线程并发问题。
甚至开始怀疑是不是由于内存资源不够引发JVM频繁GC到致使业务线程被暂停，可是从GC的日志输出结果看，GC是正常的。
因而，进入一种丈二和尚摸不着头脑头脑的状态，再次Review代码，发现并未设置请求超时时间，因而设置超时控制，发现问题依然存在，完全懵逼了。
最后，dump线程堆栈和内存堆栈，再对堆栈数据进行分析。从分析结果看，确认是由于Socket链接在读取数据时被阻塞引发线程hang住。搜索“httpclient 超时”关键字，找到各式各样设置HttpClient超时控制的方式，均尝试过可是并未生效。
实际上到后来才知道，HttpCient的超时控制在不一样的版本中设置请求超时参数的方式均各不相同，这才致使了我使用了网上看到的方式设置以后并未生效。固然,根本缘由仍是由于对HttpClient这个组件不熟悉致使的.java

问题重现

1.HttpClient版本git

<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
    <version>4.5.2</version>
</dependency>

2.Java代码github

public class HttpClientTest {
    private AtomicInteger counter = new AtomicInteger(0);
    private String url = "http://www.baidu.com/";

    public static void main(String[] args) {
        new HttpClientTest().test();
    }

    // 执行测试
    private void test() {
        int number = 100000; // 总请求数
        int concurrent = 50; // 每次并发请求数
        CountDownLatch countDownLatch = new CountDownLatch(number); // 计数器
        ExecutorService threadPool = Executors.newFixedThreadPool(concurrent); // 线程池
        int concurrentPer = concurrent;
        boolean over = false;
        while(!over) {
            number = number - concurrent;
            if(number <= 0) {
                concurrentPer = number + concurrent;
                over = true;
            }

            // 线程池批量提交
            for(int i = 0; i < concurrentPer; i++) {
                threadPool.execute(new Runnable() {
                    @Override
                    public void run() {
                        try {
                            request(url);
                            Thread.sleep(100);
                        } catch (IOException | InterruptedException e) {
                            e.printStackTrace();
                        } finally {
                            countDownLatch.countDown();
                        }
                    }
                });
            }
        }
        try {
            countDownLatch.await();
            threadPool.shutdown();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    // 访问指定地址
    private void request(String url) throws IOException {
        HttpGet httpGet = new HttpGet(url);
        commnicate(httpGet);
    }

    // 负责底层通讯处理
    private void commnicate(HttpRequestBase request) throws IOException {
        ResponseHandler<String> responseHandler = new ResponseHandler<String>() {
            @Override
            public String handleResponse(HttpResponse response) throws ClientProtocolException, IOException {
                return EntityUtils.toString(response.getEntity());
            }
        };

        HttpClient client = HttpClients.createDefault();
        String body = client.execute(request, responseHandler); // 线程可能会在这里被阻塞
        System.out.println(String.format("body size: %s, counter: %s", body.length(), counter.incrementAndGet()));
    }
}

运行上述代码一段时间后很容易能够重现出问题,以下为运行控制台信息:
shell

而且线程所有hang住,进程没法正常结束.apache

查看端口状态存在大量请求处于创建链接状态(ESTABLISHED):性能优化

# netstat -anpt
tcp        0      0 172.17.7.81:56408           180.118.128.179:56033       ESTABLISHED 3766/java           
tcp        0      0 172.17.7.81:57644           115.202.238.177:27016       ESTABLISHED 3847/java           
tcp        0      0 172.17.7.81:36616           117.57.21.0:25719           ESTABLISHED 3766/java           
tcp        0      0 172.17.7.81:59944           112.245.197.118:57220       ESTABLISHED 3847/java           
tcp        0      0 172.17.7.81:48722           218.5.215.10:40835          ESTABLISHED 4007/java           
tcp        0      0 172.17.7.81:52734           115.194.17.14:45210         ESTABLISHED 4007/java           
tcp        0      0 172.17.7.81:60586           59.32.37.129:16637          ESTABLISHED 3686/java           
tcp        0      0 172.17.7.81:36776           222.89.86.109:21667         ESTABLISHED 3766/java           
tcp        0      0 172.17.7.81:51690           60.161.249.162:59039        ESTABLISHED 3927/java           
tcp        0      0 172.17.7.81:42226           58.218.200.59:80            TIME_WAIT   -                   
tcp        0      0 172.17.7.81:56566           117.70.47.194:40879         ESTABLISHED 3686/java           
tcp        0      0 172.17.7.81:43266           182.120.202.204:45893       ESTABLISHED 3766/java           
tcp        0      0 172.17.7.81:55630           60.169.223.16:21280         ESTABLISHED 3927/java           
tcp        0      0 172.17.7.81:54922           60.168.81.26:25464          ESTABLISHED 3927/java           
tcp        0      0 172.17.7.81:53352           112.252.97.83:53584         ESTABLISHED 3847/java           
tcp        0      0 172.17.7.81:52684           113.121.242.43:14447        ESTABLISHED 3927/java           
tcp        0      0 172.17.7.81:54750           113.121.241.168:45173       ESTABLISHED 3686/java           
tcp        0      0 172.17.7.81:41510           113.105.202.106:47288       ESTABLISHED 4007/java           
tcp        0      0 172.17.7.81:38804           121.232.148.62:57938        ESTABLISHED 3847/java           
tcp        0      0 172.17.7.81:41468           113.105.202.106:47288       ESTABLISHED 3927/java           
tcp        0      0 172.17.7.81:45444           123.163.81.185:22012        ESTABLISHED 3766/java           
tcp        0      0 172.17.7.81:54810           113.121.241.168:45173       ESTABLISHED 4007/java           
tcp        0      0 172.17.7.81:51542           175.153.23.147:20766        ESTABLISHED 3927/java           
tcp        0      0 172.17.7.81:45644           218.5.215.10:40835          ESTABLISHED 4007/java           
tcp        0      0 172.17.7.81:35730           116.53.197.198:30042        ESTABLISHED 3766/java           
tcp        0      0 172.17.7.81:54738           113.121.241.168:45173       ESTABLISHED 3686/java           
tcp        0      0 172.17.7.81:60600           59.32.37.129:16637          ESTABLISHED 3686/java           
tcp        0      0 172.17.7.81:54862           113.121.241.168:45173       ESTABLISHED 4007/java           
tcp        0      0 172.17.7.81:40980           115.225.153.215:17292       ESTABLISHED 3686/java           
tcp        0      0 172.17.7.81:54166           123.149.162.129:18269       ESTABLISHED 3766/java           
tcp        0      0 172.17.7.81:60712           120.35.190.184:33054        ESTABLISHED 3766/java           
tcp        0      0 172.17.7.81:55802           106.42.211.65:59547         ESTABLISHED 3766/java

同时,分析线程堆栈信息(jstack -F -l pid > thread_stack.log)能够看到以下信息:多线程

"pool-1-thread-45" #55 prio=5 os_prio=0 tid=0x00007f78702df000 nid=0x33d5 runnable [0x00007f7830c1d000]
   java.lang.Thread.State: RUNNABLE
    at java.net.SocketInputStream.socketRead0(Native Method)
    at java.net.SocketInputStream.socketRead(SocketInputStream.java:116)
    at java.net.SocketInputStream.read(SocketInputStream.java:171)
    at java.net.SocketInputStream.read(SocketInputStream.java:141)
    at org.apache.http.impl.io.SessionInputBufferImpl.streamRead(SessionInputBufferImpl.java:139)
    at org.apache.http.impl.io.SessionInputBufferImpl.fillBuffer(SessionInputBufferImpl.java:155)
    at org.apache.http.impl.io.SessionInputBufferImpl.readLine(SessionInputBufferImpl.java:284)
    at org.apache.http.impl.conn.DefaultHttpResponseParser.parseHead(DefaultHttpResponseParser.java:140)
    at org.apache.http.impl.conn.DefaultHttpResponseParser.parseHead(DefaultHttpResponseParser.java:57)
    at org.apache.http.impl.io.AbstractMessageParser.parse(AbstractMessageParser.java:261)
    at org.apache.http.impl.DefaultBHttpClientConnection.receiveResponseHeader(DefaultBHttpClientConnection.java:165)
    at org.apache.http.impl.conn.CPoolProxy.receiveResponseHeader(CPoolProxy.java:167)
    at org.apache.http.protocol.HttpRequestExecutor.doReceiveResponse(HttpRequestExecutor.java:272)
    at org.apache.http.protocol.HttpRequestExecutor.execute(HttpRequestExecutor.java:124)
    at org.apache.http.impl.execchain.MainClientExec.execute(MainClientExec.java:271)
    at org.apache.http.impl.execchain.ProtocolExec.execute(ProtocolExec.java:184)
    at org.apache.http.impl.execchain.RetryExec.execute(RetryExec.java:88)
    at org.apache.http.impl.execchain.RedirectExec.execute(RedirectExec.java:110)
    at org.apache.http.impl.client.InternalHttpClient.doExecute(InternalHttpClient.java:184)
    at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:71)
    at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:220)
    at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:164)
    at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:139)
    at org.chench.extra.HttpClientTest.commnicate(HttpClientTest.java:106) # 线程在这里阻塞
    at org.chench.extra.HttpClientTest.request(HttpClientTest.java:93)
    at org.chench.extra.HttpClientTest.access$100(HttpClientTest.java:31)
    at org.chench.extra.HttpClientTest$1.run(HttpClientTest.java:62)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at java.lang.Thread.run(Thread.java:748)

   Locked ownable synchronizers:
    - <0x0000000086d50638> (a java.util.concurrent.ThreadPoolExecutor$Worker)

从堆栈日志中能够看到,线程处于RUNNABLE状态,而且阻塞在at org.chench.extra.HttpClientTest.commnicate(HttpClientTest.java:106)处.并发

解决方案

经过线程堆栈日志分析能够定位到线程hang住是由于HttpClient在执行访问时被阻塞了,结合源代码找到阻塞缘由是由于未设置请求超时时间.app

上述问题本质上是由于HttpClient组件并未设置请求超时控制致使的:虽然链接超时,可是读取失败,致使线程一直被阻塞.
那么,应该如何设置HttpClient的超时时间呢?鉴于HttpClient的官方文档没有明确说明,而且不一样版本的HttpClient组件设置超时控制的方式不一致,因此建议直接查看源码.
HttpClient执行访问请求时序图以下:

顺藤摸瓜,在MainClientExec.java的execute()方法中看到有2处使用了timeout参数,其含义各不相同:
(1)在获取HttpClientConnection对象时须要读取配置参数中的ConnectionRequestTimeout值,该参数用于控制获取链接的超时时间.

(2)获取到HttpClientConnection对象以后读取配置参数中的SocketTimeout值,设置Socket超时时间.

显然,这2个timeout参数都须要从RequestConfig对象中获取.
既然找到了使用timeout参数的地方,下一步须要肯定该参数是如何设置的.沿着HttpClient的请求时序图路径往回查找,在InternalHttpClient.java类的doExecute()方法中能够很清晰地看到设置了RequestConfig对象参数.

@Override
    protected CloseableHttpResponse doExecute(
            final HttpHost target,
            final HttpRequest request,
            final HttpContext context) throws IOException, ClientProtocolException {
        Args.notNull(request, "HTTP request");
        HttpExecutionAware execAware = null;
        if (request instanceof HttpExecutionAware) {
            execAware = (HttpExecutionAware) request;
        }
        try {
            final HttpRequestWrapper wrapper = HttpRequestWrapper.wrap(request, target);
            final HttpClientContext localcontext = HttpClientContext.adapt(
                    context != null ? context : new BasicHttpContext());
            // 经过RequestConfig对象配置链接参数
            RequestConfig config = null; 
            if (request instanceof Configurable) {
                // 若是在HttpRequest对象中设置了RequestConfig属性,直接使用
                config = ((Configurable) request).getConfig(); 
            }
            if (config == null) {
                // 若是在HttpRequest对象中未设置RequestConfig对象属性,则获取HttpParams属性构造RequestConfig对象
                final HttpParams params = request.getParams(); 
                if (params instanceof HttpParamsNames) {
                    if (!((HttpParamsNames) params).getNames().isEmpty()) {
                        config = HttpClientParamConfig.getRequestConfig(params);
                    }
                } else {
                    config = HttpClientParamConfig.getRequestConfig(params);
                }
            }
            if (config != null) {
                // 使用RequestConfig对象配置链接参数
                localcontext.setRequestConfig(config); 
            }
            setupContext(localcontext);
            final HttpRoute route = determineRoute(target, wrapper, localcontext);
            return this.execChain.execute(route, wrapper, localcontext, execAware);
        } catch (final HttpException httpException) {
            throw new ClientProtocolException(httpException);
        }
    }

(3)HttpClient默认使用的链接池为PoolingHttpClientConnectionManager,在创建链接时(connect()方法)会使用其中的SocketConfig配置参数对Socket进行配置,以下所示:

PoolingHttpClientConnectionManager.java

@Override
public void connect(
        final HttpClientConnection managedConn,
        final HttpRoute route,
        final int connectTimeout,
        final HttpContext context) throws IOException {
    Args.notNull(managedConn, "Managed Connection");
    Args.notNull(route, "HTTP route");
    final ManagedHttpClientConnection conn;
    synchronized (managedConn) {
        final CPoolEntry entry = CPoolProxy.getPoolEntry(managedConn);
        conn = entry.getConnection();
    }
    final HttpHost host;
    if (route.getProxyHost() != null) {
        host = route.getProxyHost();
    } else {
        host = route.getTargetHost();
    }
    final InetSocketAddress localAddress = route.getLocalSocketAddress();
    SocketConfig socketConfig = this.configData.getSocketConfig(host);
    if (socketConfig == null) {
        // 使用配置参数SocketConfig
        socketConfig = this.configData.getDefaultSocketConfig();
    }
    if (socketConfig == null) {
        socketConfig = SocketConfig.DEFAULT;
    }
    this.connectionOperator.connect(
            conn, host, localAddress, connectTimeout, socketConfig, context);
}

DefaultHttpClientConnectionOperator.java

@Override
    public void connect(
            final ManagedHttpClientConnection conn,
            final HttpHost host,
            final InetSocketAddress localAddress,
            final int connectTimeout,
            final SocketConfig socketConfig,
            final HttpContext context) throws IOException {
        final Lookup<ConnectionSocketFactory> registry = getSocketFactoryRegistry(context);
        final ConnectionSocketFactory sf = registry.lookup(host.getSchemeName());
        if (sf == null) {
            throw new UnsupportedSchemeException(host.getSchemeName() +
                    " protocol is not supported");
        }
        final InetAddress[] addresses = host.getAddress() != null ?
                new InetAddress[] { host.getAddress() } : this.dnsResolver.resolve(host.getHostName());
        final int port = this.schemePortResolver.resolve(host);
        for (int i = 0; i < addresses.length; i++) {
            final InetAddress address = addresses[i];
            final boolean last = i == addresses.length - 1;

            Socket sock = sf.createSocket(context);
            // 使用socketConfig参数中的超时时间对Socket进行配置
            sock.setSoTimeout(socketConfig.getSoTimeout());
            sock.setReuseAddress(socketConfig.isSoReuseAddress());
            sock.setTcpNoDelay(socketConfig.isTcpNoDelay());
            sock.setKeepAlive(socketConfig.isSoKeepAlive());
            if (socketConfig.getRcvBufSize() > 0) {
                sock.setReceiveBufferSize(socketConfig.getRcvBufSize());
            }
            if (socketConfig.getSndBufSize() > 0) {
                sock.setSendBufferSize(socketConfig.getSndBufSize());
            }

            final int linger = socketConfig.getSoLinger();
            if (linger >= 0) {
                sock.setSoLinger(true, linger);
            }
            conn.bind(sock);

            // ...
        }
    }

通过源码解读能够很明确地知道,在HttpClient 4.5.2版本中,设置链接参数有3种方式:
(1)在HttpRequest对象中设置RequestConfig对象属性
(2)在HttpRequest对象中设置HttpParams对象属性.
(3)在链接池对象中设置SocketConfig对象属性

既然找到了根源,下面分别经过这3种方式设置超时参数进行验证.
方式1: 经过RequestConfig对象设置超时参数

int timeOut = 5000;
RequestConfig requestConfig = RequestConfig.custom()
        .setConnectionRequestTimeout(timeOut) // 获取链接超时时间
        .setConnectTimeout(timeOut) // 设置HTTP链接超时时间
        .setSocketTimeout(timeOut) // 设置Socket超时时间
        .build();
request.setConfig(requestConfig);

方式2: 经过HttpParams对象设置超时参数

int timeOut = 5000;
HttpParams  params = new BasicHttpParams();
params.setParameter(CoreConnectionPNames.SO_TIMEOUT, timeOut);  // 设置Socket超时时间
params.setParameter(CoreConnectionPNames.CONNECTION_TIMEOUT, timeOut); // 设置HTTP链接超时时间
request.setParams(params);

方式3: 经过链接池对象设置超时参数

int timeOut = 5000;
PoolingHttpClientConnectionManager connManager = new PoolingHttpClientConnectionManager();
// 对链接池设置SocketConfig对象
connManager.setDefaultSocketConfig(SocketConfig.custom().setSoTimeout(timeOut).build());
client = HttpClients.custom().setConnectionManager(connManager).build();

经过上述3种方式分别设置超时参数验证,虽然在运行过程当中会有报错,可是不会致使线程被阻塞,进程能正常运行结束:

解决问题以后客户端CPU使用率恢复正常:

总结/教训/反思

之因此会遇到这样的问题，仍是由于对HttpClient组件不熟悉致使的；另外，在发现问题以后如何快速定位问题，并搜索稳定的解决方案很重要。
HttpClient组件每一个版本的API变化都比较大，在使用时必定要完全清楚当前使用的版本是如何设置超时时间的。而如何肯定知道超时时间控制，经过源代码查看最为稳当.
在Java平台使用Http客户端组件，能够有多个选择：
(1)直接使用JDK提供的URL类访问
(2)使用HttpClient组件，有坑，不一样版本设置参数的方式变更较大，最好是阅读一下当前使用版本的源码实现，正确设置好超时时间等参数
(3)若是使用了Spring MVC框架，还可使用Spring MVC提供的RestTemplate组件，底层是使用Netty实现的客户端
遇到的这个坑自己并不属于技术难点,可是面对这个问题的解决思路值得总结:
(1)程序日志，运行日志很是关键,是定位问题时第一时间须要查看的
(2)代码review，逐行逐行地审查,首先排除可能存在的代码逻辑问题,好比:死锁等
(3)经过jstack命令查看线程堆栈信息: jstack -l -F <pid> > stack.log
(4)经过jmap命令查看内存堆栈信息: jmap -dump:live format=b,file=heap.bin <pid>
(5)若是结合搜索引擎和上述排查步骤依然未能解决问题,应该第一时间考虑直接阅读组件的源代码实现,特别是使用了开源组件时这可能才是真正解决问题的最佳路径

【参考】 https://blog.csdn.net/u011191463/article/details/78664896 HttpClient超时设置详解 https://my.oschina.net/jywm/blog/1834702 解决httpclient超时设置不生效的问题 https://www.jianshu.com/p/4b3e172c4f2d HttpClient 4.5.2-（四）链接超时的配置 https://www.jianshu.com/p/6a41c95855e3 HttpClient 4.5.2-（五）链接池的配置 https://www.jianshu.com/p/c852cbcf3d68 HttpClient高并发下性能优化-http链接池 https://blog.csdn.net/u011402596/article/details/44619443 HttpClient 多线程处理 https://field-notes.iteye.com/blog/2383759 多线程消费使用HttpClient引起的坑 http://blog.51cto.com/lihao001/1788490 httpclient4.3 致使线程阻塞 https://study121007.iteye.com/blog/2304274 HttpClient4.5.2 链接管理 https://www.jianshu.com/p/c852cbcf3d68 HttpClient高并发下性能优化-http链接池 https://alafqq.iteye.com/blog/2325041 httpclient 多线程执行（网上版本太多了。。。误人子弟） https://gaozzsoft.iteye.com/blog/2352241 HttpClient 4.5.2版本设置链接超时时间-CloseableHttpClient设置Timeout https://www.cnblogs.com/softidea/p/6964347.html HttpClient 专题 https://blog.csdn.net/Fhaohaizi/article/details/78217903 httpclient4.5如何确保资源释放 https://blog.csdn.net/u010634066/article/details/83120122 一场HttpClient调用未关闭流引起的问题 https://www.cnblogs.com/mumuxinfei/p/5066633.html Apache HttpClient使用之阻塞陷阱 https://issues.apache.org/jira/browse/HTTPCLIENT-1584 CloseableHttpClient - SSL Handshake has no Socket Timeout https://monkeyissexy.github.io/2016/11/11/httpclient_ssl_handshake_socketTimeout_bug/ httpclient ssl handshake socketTimeout bug 分析解决过程 http://geekerwang.com/2017/10/22/%E8%AE%B0%E5%BD%95%E4%B8%80%E6%AC%A1%E5%9D%91%EF%BC%9AsocketRead-hang/ 记录一次坑：socketRead hang https://www.cnblogs.com/jessezeng/p/7448636.html 解决: httpclient ssl 验证致使死锁问题 http://itbang.me/solu/detail/201 JAVA线程卡死问题如何定位？