使用HttpClient请求时- I/O exception (java.net.SocketException) caught when processing request: 连接时

背景

调用第三方api，出现请求超时的错误，导致业务失败，springMVC项目使用的是httpClient4，部署环境是centos。

问题排查

开始debug，具体日志如下图，从日志拿到关键信息，[total kept alive: 1; route allocated: 1 of 100; total allocated: 1 of 400]（下文做认识介绍）这个是httpclient的连接池debug日志，从这里面没有看到是连接池的问题。

连接池主要信息介绍：

[total kept alive: 1; route allocated: 1 of 100; total allocated: 1 of 400]

线上服务调用第三方api出现以下错误，

Caused by: java.net.SocketException: Connection reset
        at java.net.SocketInputStream.read(SocketInputStream.java:209)
        at java.net.SocketInputStream.read(SocketInputStream.java:141)
        at sun.security.ssl.InputRecord.readFully(InputRecord.java:465)
        at sun.security.ssl.InputRecord.read(InputRecord.java:503)
        at sun.security.ssl.SSLSocketImpl.readRecord(SSLSocketImpl.java:973)
        at sun.security.ssl.SSLSocketImpl.readDataRecord(SSLSocketImpl.java:930)
        at sun.security.ssl.AppInputStream.read(AppInputStream.java:105)
        at org.apache.http.impl.io.SessionInputBufferImpl.streamRead(SessionInputBufferImpl.java:137)
        at org.apache.http.impl.io.SessionInputBufferImpl.fillBuffer(SessionInputBufferImpl.java:153)
        at org.apache.http.impl.io.SessionInputBufferImpl.readLine(SessionInputBufferImpl.java:280)
        at org.apache.http.impl.conn.DefaultHttpResponseParser.parseHead(DefaultHttpResponseParser.java:138)
        at org.apache.http.impl.conn.DefaultHttpResponseParser.parseHead(DefaultHttpResponseParser.java:56)
        at org.apache.http.impl.io.AbstractMessageParser.parse(AbstractMessageParser.java:259)
        at org.apache.http.impl.DefaultBHttpClientConnection.receiveResponseHeader(DefaultBHttpClientConnection.java:163)
        at org.apache.http.impl.conn.CPoolProxy.receiveResponseHeader(CPoolProxy.java:157)
        at org.apache.http.protocol.HttpRequestExecutor.doReceiveResponse(HttpRequestExecutor.java:273)
        at org.apache.http.protocol.HttpRequestExecutor.execute(HttpRequestExecutor.java:125)
        at org.apache.http.impl.execchain.MainClientExec.execute(MainClientExec.java:272)
        at org.apache.http.impl.execchain.ProtocolExec.execute(ProtocolExec.java:186)
        at org.apache.http.impl.execchain.RetryExec.execute(RetryExec.java:89)
        at org.apache.http.impl.execchain.RedirectExec.execute(RedirectExec.java:110)
        at org.apache.http.impl.client.InternalHttpClient.doExecute(InternalHttpClient.java:185)
        at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:83)
        at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:108)
        at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:56)

排查分析

从上得知从创建链接放到连接池，整个流程是没有问题的，如果有问题就不会有空闲连接池。
那么我们先从请求流程来分析，httpclient接到任务，会先去连接池查看是否有可用同路由的链接，如果有就拿来使用，如果没有就创建一个，使用后然后放到连接池里面，因为没有配置连接池空闲等待时长，默认就是永久，那会不会服务器把这个tcp链接给kill掉了?????。
那么问题真的来了啊，看下连接池中的链接信息：
timeToLive是当前连接存活时间，-1就是永久存活。
其中expiry就是过期时间，看着明显很大，expiry=当前时间 timeToLive。
既然定位到问题那么就开始解决。

解决方案：

问题原因已经算是找到了，那么我们尝试增加连接池空闲存活时长，然后修改配置httpClient配置文件，原来只是增加连接池管理器空闲连接存活时间，现实并没有生效，debug发现并没有时间到期后并没有closeExpiredConnections和closeIdleConnections方法。通过官方查到需要实现清楚策略，原因是我的版本是httpClient4。

---

那么再次开启修复之路：

官方给的策略：

1. 先增加配置

http.pool.request.timeToLive=5
http.pool.request.tunit=SECONDS
http.pool.request.idle.maxIdleTime=3
http.pool.request.idle.maxIdleTimeUnit=SECONDS

2. 清理空闲链接控制器实现：

/*
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 * 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
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 * <http://www.apache.org/>.
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 */

package com.fhlkd.client.config;

import org.apache.http.conn.HttpClientConnectionManager;
import org.apache.http.util.Args;

import java.util.concurrent.ThreadFactory;
import java.util.concurrent.TimeUnit;

/**
 * This class maintains a background thread to enforce an eviction policy for expired / idle
 * persistent connections kept alive in the connection pool.
 *
 * @since 4.4
 */
public final class IdleConnectionEvictor {

    private final HttpClientConnectionManager connectionManager;
    private final ThreadFactory threadFactory;
    private final Thread thread;
    private final long sleepTimeMs;
    private final long maxIdleTimeMs;

    private volatile Exception exception;

    public IdleConnectionEvictor(
            final HttpClientConnectionManager connectionManager,
            final ThreadFactory threadFactory,
            final long sleepTime, final TimeUnit sleepTimeUnit,
            final long maxIdleTime, final TimeUnit maxIdleTimeUnit) {
        this.connectionManager = Args.notNull(connectionManager, "Connection manager");
        this.threadFactory = threadFactory != null ? threadFactory : new DefaultThreadFactory();
        this.sleepTimeMs = sleepTimeUnit != null ? sleepTimeUnit.toMillis(sleepTime) : sleepTime;
        this.maxIdleTimeMs = maxIdleTimeUnit != null ? maxIdleTimeUnit.toMillis(maxIdleTime) : maxIdleTime;
        this.thread = this.threadFactory.newThread(new Runnable() {
            @Override
            public void run() {
                try {
                    while (!Thread.currentThread().isInterrupted()) {
                        Thread.sleep(sleepTimeMs);
                        //关闭失效连接
                        connectionManager.closeExpiredConnections();
                        if (maxIdleTimeMs > 0) {
                            //关闭空闲超过配置
                            connectionManager.closeIdleConnections(maxIdleTimeMs, TimeUnit.MILLISECONDS);
                        }
                    }
                } catch (final Exception ex) {
                    exception = ex;
                }

            }
        });
    }

    public IdleConnectionEvictor(
            final HttpClientConnectionManager connectionManager,
            final long sleepTime, final TimeUnit sleepTimeUnit,
            final long maxIdleTime, final TimeUnit maxIdleTimeUnit) {
        this(connectionManager, null, sleepTime, sleepTimeUnit, maxIdleTime, maxIdleTimeUnit);
    }

    public IdleConnectionEvictor(
            final HttpClientConnectionManager connectionManager,
            final long maxIdleTime, final TimeUnit maxIdleTimeUnit) {
        this(connectionManager, null,
                maxIdleTime > 0 ? maxIdleTime : 5, maxIdleTimeUnit != null ? maxIdleTimeUnit : TimeUnit.SECONDS,
                maxIdleTime, maxIdleTimeUnit);
    }

    public void start() {
        thread.start();
    }

    public void shutdown() {
        thread.interrupt();
    }

    public boolean isRunning() {
        return thread.isAlive();
    }

    public void awaitTermination(final long time, final TimeUnit timeUnit) throws InterruptedException {
        thread.join((timeUnit != null ? timeUnit : TimeUnit.MILLISECONDS).toMillis(time));
    }

    static class DefaultThreadFactory implements ThreadFactory {

        @Override
        public Thread newThread(final Runnable r) {
            final Thread t = new Thread(r, "Connection evictor");
            t.setDaemon(true);
            return t;
        }

    };


}

3. 实例化清楚空闲链接控制器
   

结果

timeToLive为5，说明已经生效了，且已正常运行了，没有再出现连接超时了。

到此为止：
其实问题主要原因是，服务器防火墙会把空闲时间大于7秒的链接给kill掉，所以才会导致这个问题出现，我们只需要处理在防火墙kill掉链接之前给该链接从连接池清除掉即可

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