too many xhr requests in chrome - google-chrome

Question

I have a tight loop that fetches PNG files via xhr2. Works fine in FF and IE10. In Chrome when I list of files hits about 5,500 I start getting xhr errors. I like the async interface since I am interleaving these requests with local indexedDB store requests.
Code below (I am using xhr2lib for fetches and PouchDB for the IndexedDB API).
I know that it is the XHR2 that is failing, since when this works, in Chrome, all the XHR2 calls are processed before the SaveDB() calls. When It fails, I never get the save calls.
function getBlobs(fileList) {
console.log("starting to fetch blobs");
$.each(fileList, function (i, val) {
var path = baseURL + val.id + "." + imageType;
$xhr.ajax({
url: path,
dataType: "blob",
success: function (data) { saveBlob(data, val.size, val.id); }
});
});
}
function saveBlob(blob, length, id) {
if (blob.size != length) {
console.error("Blob Length found: " + blob.size + " expected: " + length);
}
putBlob(blob, id);
++fetchCnt;
if (fetchCnt == manifest.files.length) {
setTimeout(fetchComplete, 0);
}
}
function fetchComplete() {
var startTime = vm.get("startTime");
var elapsed = new Date() - startTime;
var fetchTime = ms2Time(elapsed);
vm.set("fetchTime", fetchTime);
}
function putBlob(blob, id) {
var cnt;
var type = blob.type;
DB.putAttachment(id + "/pic", blob, type, function (err, response) {
if (err) {
console.error("Could store blob: error: " + err.error + " reason: " + err.reason + " status: " + err.status);
} else {
console.log("saved: ", response.id + " rev: " + response.rev);
cnt = vm.get("blobCount");
vm.set("blobCount", ++cnt);
if (cnt == manifest.files.length) {
setTimeout(storeComplete, 0);
}
}
});
}

Answer 1

The chromium folks acknowledge this is something that they should fix: https://code.google.com/p/chromium/issues/detail?id=244910, but in the meantime I have implemented throttling using jquery defer/resolve to keep the number of threads low.