I'm long-polling node.js route with JQuery's ajax request (xhr). This sends a GET request to my Express server and listens for message bus events. I'm setting a timeout on that GET request (as my proxy would kill long requests). So after the timeout, an abort event should be sent by the client to the server.
I want to catch that abort/close/finish event and remove the relevant message bus listener/subscriber.
But I struggle. I tried req.on("close"..) and the on-finished npm module, but that didn't work for me. I'm also not much more clever after reading the http documentation of node: https://nodejs.org/api/http.html.
Any ideas how to tackle this beast? Or better ways to remove listeners to prevent memory leaks?
Server side essentials:
// server.js
var express = require("express");
var EventEmitter = require("events").EventEmitter;
var messageBus = new EventEmitter();
messageBus.setMaxListeners(20);
var REST_PORT = (process.env.PORT || 5000);
var app = express();
app.get("/events", (req, res) => {
var listener = function(res) {
messageBus.once("message", function(data) {
res.status(200).json(data);
});
};
req.on("abort", function() { //I tried also "aborted", "close", "closed", "finish", "finished"..no luck
messageBus.removeListener("message", listener);
});
listener(res);
console.log("Total listeners to 'message' events:", messageBus.listeners("message").length);
});
// other messageBus.emit logic ..
app.listen(REST_PORT, () => {
console.log("Application ready on port " + REST_PORT);
});
Client side essentials:
//client.js
$.ajax({
method: "GET",
async: true,
url: "/events",
success: function(data) {
callback(data);
},
complete: function(request, status, err) {
if (status == "timeout" || status == "success") {
console.log("LOG: Normal long-polling timeout or successful poll, continuing.");
longPoll();
} else {
console.warn("WARN: Server probably offline, retrying in 2 sec.");
setTimeout(function() {
longPoll();
}, 2000);
}
},
timeout: 30000
});
Thank you!
