Java相關

1. OkHttpClient調用出現大量CLOSE_WAIT。

問題定位：

　　凡是系統中出現大量的CLOSE_WAIT，說明你的代碼寫的有問題，即：沒有關閉連接。

在OkHttpClient中，默認時 HTTP頭字段 Connection 設置值爲keep-alive，這樣會導致服務端斷開連接時，客戶端不能及時的斷開連接，從而出現大量的CLOSE_WAIT。

問題修改：

　　把HTTP頭字段 Connection 設置值爲close

如下是一段短連接http調用代碼。

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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);
  //創建一個請求對象
  Request request = new Request.Builder()
  .url(url).header("Connection", "close")
  .post(requestBody)
  .build();
  //發送請求獲取響應
  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;
  }