Nodejs http retry on timeout or error

Question

Nodejs http retry on timeout or error

I'm trying to automatically retry HTTP requests on timeout or error. Currently my code looks like this:

var req = http.get(url, doStuff)
              .on('error', retry)
              .setTimeout(10000, retry);

However, a single request can sometimes trigger both "on error" and "timeout" events. What is a better way of implementing retry?

node.js
http

Answer 1

You could try something like this:

function doRequest(url, callback) {
  var timer,
      req,
      sawResponse = false;
  req = http.get(url, callback)
            .on('error', function(err) {
              clearTimeout(timer);
              req.abort();
              // prevent multiple execution of `callback` if error after
              // response
              if (!sawResponse)
                doRequest(url, callback);
            }).on('socket', function(sock) {
              timer = setTimeout(function() {
                req.abort();
                doRequest(url, callback);
              }, 10000);
            }).once('response', function(res) {
              sawResponse = true;
              clearTimeout(timer);
            });
}

Answer 2

Through trial and error, this was the code that worked for me. The key was to destroy the socket after timeout as well as to check that the response is complete.

function httpGet(url, callback) {
    var retry = function(e) {
        console.log("Got error: " + e.message);
        httpGet(url, callback); //retry
    }

    var req = http.get(url, function(res) {
        var body = new Buffer(0);
        res.on('data', function (chunk) {
            body = Buffer.concat([body, chunk]);
        });
        res.on('end', function () {
            if(this.complete) callback(body);
            else retry({message: "Incomplete response"});
        });
    }).on('error', retry)
    .setTimeout(20000, function(thing){
        this.socket.destroy();
    });
}