解决:HttpClient导致应用出现过多Close_Wait的问题

最近发现一个问题,在服务器上通过netstat命令发现有大量的Close_Wait长时间存在,甚至有时候数量接近1000:

查看服务器参数(etc/sysctl.conf):

net.ipv4.tcp_keepalive_time 网管已经修改成1200。

参数值还可以改小,但似乎是治标不治本,出现这种问题,肯定是某个地方的程序本身存在问题。

根据ip及端口信息,不难发现是什么地方除问题了,项目中有涉及到图片上传,于是找到图片上传的代码,结果发现代码非常简单,一行上传权限初始化代码,一行CDN官方提供的一个静态方法,之后就是处理响应结果的代码了。代码少且简单,上传调用代码没什么问题,那么问题可能出在CDN官方提供的jar包了,好在CDN有提供源码,于是查看源码,源码中使用apache 的是httpClient包,调用代码大致如下:

        String response = "";
        HttpPost httpPost = null;
        CloseableHttpResponse ht = null;
        String startTime = formatter.format(new Date());//请求时间
        String endTime = "-";
        String statusCode = "-";
        String contentLength = "-";
        String contentType = "-";
        try {
            httpPost = new HttpPost(url);
            List<NameValuePair> paramsList = new ArrayList<NameValuePair>();

            if (file != null) {
                MultipartEntityBuilder mEntityBuilder = MultipartEntityBuilder.create();

                BandwithLimiterFileBody fileBody = new BandwithLimiterFileBody(file, null, "application/octet-stream", null, BaseBlockUtil.maxRate, progressNotifier);
                mEntityBuilder.addPart("file", fileBody);
                mEntityBuilder.addTextBody("desc", file.getName());

                if (params != null && params.size() > 0) {
                    for (String name : params.keySet()) {
                        mEntityBuilder.addTextBody(name, params.get(name), ContentType.create("text/plain", Charset.forName("UTF-8")));
                    }
                }

                httpPost.setEntity(mEntityBuilder.build());
            } else if (params != null && params.size() > 0) {
                for (String name : params.keySet()) {
                    paramsList.add(new BasicNameValuePair(name, params.get(name)));
                }
                HttpEntity he = new UrlEncodedFormEntity(paramsList, "utf-8");
                httpPost.setEntity(he);
            }

            if (headMap != null && headMap.size() > 0) {
                for (String name : headMap.keySet()) {
                    httpPost.addHeader(name, headMap.get(name));
                }
            }
            if(!httpPost.containsHeader("User-Agent"))
                httpPost.addHeader("User-Agent", Config.VERSION_NO);
            CloseableHttpClient hc = HttpClients.createDefault();
            RequestConfig requestConfig = RequestConfig.custom().setSocketTimeout(30000).setConnectTimeout(30000).build();//设置请求和传输超时时间
            httpPost.setConfig(requestConfig);
            ht = hc.execute(httpPost);
            endTime = formatter.format(new Date());

            Header[] headerArr = ht.getAllHeaders();
            for (Header header : headerArr) {
                BufferedHeader bh = (BufferedHeader) header;
                if (bh.getBuffer().toString().contains("Content-Length")) {
                    contentLength = bh.getValue();
                } else if (bh.getBuffer().toString().contains("Content-Type")) {
                    contentType = bh.getValue();
                }
            }
            HttpEntity het = ht.getEntity();
            InputStream is = het.getContent();
            BufferedReader br = new BufferedReader(new InputStreamReader(is, "utf8"));
            String readLine;
            while ((readLine = br.readLine()) != null) {
                response = response + readLine;
            }

            is.close();
            br.close();
            int status = ht.getStatusLine().getStatusCode();
            statusCode = String.valueOf(status);
            if (status == 200) {
                if (!new JsonValidator().validate(response)) {
                    response = EncodeUtils.urlsafeDecodeString(response);
                }
            }
            return new HttpClientResult(status, response);
        } catch (Exception e) {
            statusCode = "500";
            endTime = formatter.format(new Date());
            throw new HttpClientException(e);
        } finally {
            if (httpPost != null) {
                httpPost.releaseConnection();
            }
            if (ht != null) {
                try {
                    ht.close();
                } catch (IOException ignored) {
                }
            }
            writeHttpLog(startTime, url, "-", (null != params ? params.get("token") : "-"), (null != file ? file.getName() : "-"), "-", "-", endTime, statusCode, contentType, contentLength, response);
        }

 查看TCP协议端口状态说明 , 如果一直保持在CLOSE_WAIT状态,那么只有一种情况,就是在对方关闭连接之后服务器程序自己没有进一步发出ack信号。因此要解决这个问题大致有以下几种方案:

a、实例化httpClient 时,使用alwaysClose 的SimpleHttpConnectionManager

  通常默认情况实例化httpClient 的时候使用的是无参构造的SimpleHttpConnectionManager,因此可替换为带参构造:

new HttpClient(new SimpleHttpConnectionManager(true));

b、在method.releaseConnection() 之后 通过获取HttpConnectionManager,进行关闭(getConnectionManager方法在httpclient 4.3之后已经标记为过期,后期可能会移除该方法):

hc.getConnectionManager().shutdown();

c、在method.releaseConnection() 之后 通过获取HttpConnectionManager 调用closeIdleConnections方法进行关闭,(getConnectionManager方法在httpclient 4.3之后已经标记为过期,后期可能会移除该方法):

hc.getConnectionManager().releaseConnection(conn, validDuration, timeUnit);

d、通过设置header由服务端自动关闭.

method.setHeader("Connection", "close"); 

HTTP协议中有关于这个属性的定义: 
HTTP/1.1 defines the "close" connection option for the sender to signal that the connection will be closed after completion of the response. For example:
      Connection: close 

e、使用MultiThreadedHttpConnectionManager 进行复用,但同时也必须在合适的地方进行关闭处理;

f、请求之后未收到响应信息时,调用method.abort()进行处理

可参考:http://wiki.apache.org/HttpComponents/FrequentlyAskedConnectionManagementQuestions

    http://www.softlab.ntua.gr/facilities/documentation/unix/unix-socket-faq/unix-socket-faq-2.html#ss2.7 

    http://hc.apache.org/httpclient-legacy/tutorial.html

    TCP/IP详解卷一

 

 

 

 

posted on 2016-06-26 09:02  jessezeng  阅读(25191)  评论(0编辑  收藏

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