NodeJS CouchDB Long Polling Debacle - node.js

Question

I have a web app that is published via ExpressJS on NodeJS, of course. It uses CouchDB as it's data source. I implemented long polling to keep the app in sync at all times between all users. To accomplish this I use the following logic:
User logs into app and an initial long poll request is made to Node via an Express route.
Node in turn makes a long poll request to CouchDB.
When Couch is updated it responds to the request from Node.
Lastly Node responds to the browser.
Simple. What is happening, though, is that when I refresh the browser it freezes up on every fifth refresh. Huh? very wierd. But I can reproduce it over and over, even in my test environment. Every fifth refresh without fail freezes up Node and causes the app to freeze. Rebooting Node fixes the issue.
After much hair pulling I THOUGHT I solved it by changing this:
app.get('/_changes/:since*', security, routes.changes);
To this:
app.get('/_changes/:since*', security, function () { routes.changes });
However, after further testing this is just failing to run routes.changes. So no actual solution. Any ideas why long polling CouchDb from Node would do such a strange thing? On the fifth refresh I can have a break point in node on the first line of my routing code and it never get's hit. However, in the browser I can break on the request to node for long polling and it seems to go out. It's like Node is not accepting the connection for some reason...
Should I be approaching long polling from Node to CouchDB in a different way? I'm using feed=longpoll, should I maybe be doing feed=continuous? If I turn down the changes_timeout in couchdb to 5 seconds it doesn't get rid of the issue, but it does make it easier to cope with since the freezes only last 5 seconds tops. So this would seem to indicate that node can't handle having several outstanding requests to couch. Maybe I will try a continuous feed and see what happens.
self.getChanges = function (since) {
Browser:
$.ajax({
url: "/_changes/" + since,
type: "GET", dataType: "json", cache: false,
success: function (data) {
try {
self.processChanges(data.results);
self.lastSeq(data.last_seq);
self.getChanges(self.lastSeq());
self.longPollErrorCount(0);
} catch (e) {
self.longPollErrorCount(self.longPollErrorCount() + 1);
if (self.longPollErrorCount() < 10) {
setTimeout(function () {
self.getChanges(self.lastSeq());
}, 3000);
} else {
alert("You have lost contact with the server. Please refresh your browser.");
}
}
},
error: function (data) {
self.longPollErrorCount(self.longPollErrorCount() + 1);
if (self.longPollErrorCount() < 10) {
setTimeout(function () {
self.getChanges(self.lastSeq());
}, 3000);
} else {
alert("You have lost contact with the server. Please refresh your browser.");
}
}
});
}
Node:
Routing:
exports.changes = function (req, res) {
var args = {};
args.since = req.params.since;
db.changes(args, function (err, body, headers) {
if (err) {
console.log("Error retrieving changes feed: "+err);
res.send(err.status_code);
} else {
//send my response... code removed here
}
})
}
Database long poll calls:
self.changes = function (args, callback) {
console.log("changes");
if (args.since == 0) {
request(self.url + '/work_orders/_changes?descending=true&limit=1', function (err, res, headers) {
var body = JSON.parse(res.body);
var since = body.last_seq;
console.log("Since change: "+since);
self.longPoll(since, callback);
});
} else {
self.longPoll(args.since, callback);
}
}
self.longPoll = function (since, callback) {
console.log("about to request with: "+since);
request(self.url + '/work_orders/_changes?feed=continuous&include_docs=true&since=' + since,
function (err, res, headers) {
console.log("finished request.")
if (err) { console.log("Error starting long poll: "+err.reason); return; } //if err send it back
callback(err, res.body);
});
}

Answer 1

Socket.io will automatically fall back to long polling, and doesn't have a problem like the one you are having. So just use that. Also for CouchDB changes use this https://github.com/iriscouch/follow or maybe this one https://npmjs.org/package/changes like the other guy suggested.
Its very bad practice to reinvent things when we have popular modules that already do what you need. There are currently more than 52,000 node modules on https://npmjs.org/. People make a big deal about copying and pasting code. In my mind reinventing basic stuff is even worse than that.
I know with so many modules its hard to know about all of them, so I'm not saying you can never solve the same problem as someone else. But take a look at npmjs.org first and also sites like http://node-modules.com/ which may give better search results.