Node.js Express应用程序在负载测试下花费了太多时间来处理出站HTTP请求

Question

I have an express (node.js v0.10.29) proxy on a linux machine (Ubuntu 12.04 64bit, 3.75GB Memory, 1 Core) which is making some outbound HTTP requests for each incoming request. While load testing I found out that the response time becomes very slow (around 30 seconds for a request that making 4 outbound requests when firing 1000). After some investigation I made sure that the outbound requests are the bottleneck and eliminated the machine limitation (the cpu and memory are not getting higher then 20%, and I increased the number of open files to 10000). First I was using request module for the outbound request, tried changing it to http module, and for both of them tried increasing the globalAgent.maxSockets , using agent = false , using my own agent with any number of maxSockets , setting request.setNoDelay(true) , using cluster , but nothing made any change on the results of my load testing.

what can be the problem?

Here is my latest code for the HTTP request:

var http = require('http');
var agent = new http.Agent();
agent.maxSockets = 100;

var doPost = function(reqUrl, body, next, onError) {
    var stringBody = JSON.stringify(body);
    var headers = {
        'Content-Type': 'application/json',
        'Accept-Encoding': 'gzip',
        'Content-Length': stringBody.length
    };
    var parsedUrl = url.parse(reqUrl);
    var options = {
        host: parsedUrl.host,
        path: parsedUrl.path,
        method: 'POST',
        headers: headers,
        //agent: false
        agent: agent
    };

    doHttpRequest(options, stringBody, next, onError);
};


function doHttpRequest(options, body, next, onError, HttpContext){
    var req = http.request(options, function(res) {
         var chunks = [];
         res.on('data', function (chunk) {
            chunks.push(chunk);
         });

         res.on('end', function(){
            var buffer = Buffer.concat(chunks);
            var encoding = res.headers['content-encoding'];
            if (encoding == 'gzip') {
                zlib.gunzip(buffer, function(error, decoded) {
                    var jsonRes = JSON.parse(decoded && decoded.toString());
                    next(jsonRes);
                });
            } else if (encoding == 'deflate') {
                zlib.inflate(buffer, function(error, decoded) {
                    var jsonRes = JSON.parse(decoded && decoded.toString());
                    next(jsonRes);  
                });
            } else {
                next(null, buffer.toString());
            }
        });
    });

    req.setNoDelay(true);
    req.write(body);
    req.end();
    req.on('error', function(e) {
        log(e);
    });
}

the "next" method will call the "doPost" function a few times (in this case 4 times).

Answer 1

I am seeing the same behaviour, I have simple proxy module created. When I call a endpoint directly its taking 50ms, but via proxy server (which internal make another req and pipe to original req) it taking double ~100ms. I have also tried all options what you mentioned here.

I am glad I am not alone having this issue, will be digging into further. Will let you know if found something.

UPDATE

After setting keepAlive=true on agent, I was able to get result for proxied request with ~5ms more than direct call.