1. OkHttpClient调用出现大量CLOSE_WAIT。

问题定位：

　　凡是系统中出现大量的CLOSE_WAIT，说明你的代码写的有问题，即：没有关闭连接。

在OkHttpClient中，默认时 HTTP头字段 Connection 设置值为keep-alive，这样会导致服务端断开连接时，客户端不能及时的断开连接，从而出现大量的CLOSE_WAIT。

问题修改：

　　把HTTP头字段 Connection 设置值为close

如下是一段短连接http调用代码。

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package com.xman.httpclient;

import okhttp3.*;
import org.springframework.stereotype.Service;

import java.io.IOException;
import java.util.concurrent.TimeUnit;

/**

  • Created by wangyaofu on 2018/4/25.br/>*/
    @Service
    public class HttpServiceImpl {

    public final static int CONNECT_TIMEOUT =10000;
    public final static int READ_TIMEOUT=10000;
    public final static int WRITE_TIMEOUT=10000;

    public String httpGet(String url, String userAgent) {
    final Request request = new Request.Builder()
    .url(url).header("User-Agent", userAgent).header("Connection", "close")
    .build();
    OkHttpClient okHttpClient = new OkHttpClient.Builder()
    .readTimeout(READ_TIMEOUT, TimeUnit.MILLISECONDS)
    .writeTimeout(WRITE_TIMEOUT, TimeUnit.MILLISECONDS)
    .connectTimeout(CONNECT_TIMEOUT, TimeUnit.MILLISECONDS)
    .build();
    Response response;
    try {
    response = okHttpClient.newCall(request).execute();
    return response.body().string();
    } catch (Exception e) {
    //logger.error("httpGet err=" + e.getMessage());
    }
    return null;
    }

    public String httpPost(String url, String body) {
    RequestBody requestBody = RequestBody.create(MediaType.parse("application/json; charset=utf-8"), body);
    //创建一个请求对象
    Request request = new Request.Builder()
    .url(url).header("Connection", "close")
    .post(requestBody)
    .build();
    //发送请求获取响应
    try {
    OkHttpClient okHttpClient = new OkHttpClient.Builder()
    .readTimeout(READ_TIMEOUT, TimeUnit.MILLISECONDS)
    .writeTimeout(WRITE_TIMEOUT, TimeUnit.MILLISECONDS)
    .connectTimeout(CONNECT_TIMEOUT, TimeUnit.MILLISECONDS)
    .build();
    Response response=okHttpClient.newCall(request).execute();
    if (response != null && response.body() != null) {
    return response.body().string();
    }
    } catch (Exception e) {
    //logger.error("httpPost err=" + e.getMessage());
    }
    return null;
    }