WinJS.xhr Timeout Loses Requests? - timeout

Question

What I'm trying to do (though I fully suspect there's a better way to do it) is to send HTTP requests to a range of hosts on my network. I can hit every host by calling WinJS.xhr in a loop. However, it takes too long to complete the range.
Inspecting in Fiddler shows that a dozen or so requests are sent at a time, wait to time out, and then move on to the next dozen or so. So I figured I'd try to reduce the timeout for each request. For my needs, if the host doesn't respond in 500 ms, it's not going to respond.
Following the documentation, I tried wrapping the call to WinJS.xhr in a call to WinJS.Promise.timeout with a small enough setting, but there was no change. Changing the promise timeout didn't really affect the actual request.
A little more searching led me to a suggestion whereby I could modify the XMLHttpRequest object that WinJS.xhr uses and set the timeout on that. This worked like a charm in terms of blasting out requests at a faster rate. However, there seems to be a side-effect.
Watching the requests in Fiddler, about a dozen or so fire off very quickly and then the whole thing ends. The "next dozen or so" never come. Sometimes (based on the semi-randomness of asynchronous calls) the first dozen or so that shows up in fiddler includes 9-10 from the low and of the range and 2-3 from the top end of the range, or close to it.
Is there something else I can try, or some other way to accomplish the end goal here? (Within the scope of this question the end goal is to send a large number of requests in a reasonable amount of time, but any suggestions on a better overall way to scan for a particular service on a network is also welcome.)

Answer 1

Can you write out the code you're using for timeout, i wrote something like this but it wasn't working, so I'm curious as to how you're doing it:
var timeoutFired = function () {
console.log("derp");
};
var options = {
url: "http://somesite.com",
responseType: "document",
customRequestInitializer: function (req) {
req.timeout = 1;
req.ontimeout = timeoutFired;
//do something with the XmlHttpRequest object req
}
};
WinJS.xhr(options).
....
Here are some alternatives that you may find helpful, not sure how/why timeout wasn't working but I tried to write out a custom timeout function:
(function (global) {
var options = {
url: "http://something.com",
responseType: "document",
};
var request = WinJS.xhr(options).then(
function (xmlHttpRequest) {
console.log("completed");
},
function (xmlHttpRequest) {
//error or cancel() will throw err
console.log("error"+ xmlHttpRequest.message);
},
function (xmlHttpRequest) {
console.log("progress")
});
function waitTime() {
return new WinJS.Promise(
function (complete, error, progress) {
var seconds = 0;
var interval = window.setInterval(
function () {
seconds++;
progress(seconds);
//prob should be called milliseconds
if (seconds > 5) {
window.clearInterval(interval);
complete();
}
}, 100);
});
};
waitTime().done(
function () {
console.log("complete");
request.cancel();
},
function () {
console.log("error")
},
function (seconds) {
console.log("progress:" + seconds)
});
});
Another cool little trick is using promise.any (vs .join) which fires off when one OR the other finishes first, so taking that into account you can write something like this:
(function (global) {
var options = {
url: "http://url.com",
responseType: "document",
};
var request = {
runRequest: function () {
return WinJS.xhr(options).then(
function (xmlHttpRequest) {
console.log("completed");
},
function (xmlHttpRequest) {
//error or cancel() will throw err
console.log("error" + xmlHttpRequest.message);
},
function (xmlHttpRequest) {
console.log("progress")
});
}
};
WinJS.Promise.any([WinJS.Promise.timeout(500), request.runRequest()]).done(
function () {
console.log("any complete");
});
})();