Express request is called twice

To learn node.js I'm creating a small app that get some rss feeds stored in mongoDB, process them and create a single feed (ordered by date) from these ones. It parses a list of ~50 rss feeds, with ~1000 blog items, so it's quite long to parse the whole, so I put the following `req.connection.setTimeout(60*1000);` to get a long enough time out to fetch and parse all the feeds. Everything runs quite fine, but the request is called twice. (I checked with wireshark, I don't think it's about favicon here). I really don't get it. You can test yourself here : http://mighty-springs-9162.herokuapp.com/feed/mde/20 (it should create a rss feed with the last 20 articles about "mde"). The code is here: https://github.com/xseignard/rss-unify And if we focus on the interesting bits : I have a route defined like this : `app.get('/feed/:name/:size?', topics.getFeed);` And the `topics.getFeed` is like this : ``` function getFeed(req, res) { // 1 minute timeout to get enough time for the request to be processed req.connection.setTimeout(60*1000); var name = req.params.name; var callback = function(err, topic) { // if the topic has been found if (topic) { // aggregate the corresponding feeds rssAggregator.aggregate(topic, function(err, rssFeed) { if (err) { res.status(500).send({error: 'Error while creating feed'}); } else { res.send(rssFeed); } }, req); } else { res.status(404).send({error: 'Topic not found'}); }}; // look for the topic in the db findTopicByName(name, callback); } ``` So nothing fancy, but still, this getFeed function is called twice. What's wrong there? Any idea?