[Feature] Implement Configurable XHR Request Timeout in com.vaadin.client.communication.XhrConnection Vaadin 8

[samwatts98]

Current Issue

In Vaadin 8.11, our clients are experiencing intermittent issues where some UIDL XHR requests are taking ~5 minutes to resolve at random. Upon looking into configurable timeouts for XHR requests I found that this feature is currently a TODO in com.vaadin.client.communication.XhrConnection#send(JsonObject) in both v8.11 and v8.12:

    RequestBuilder rb = new RequestBuilder(RequestBuilder.POST, getUri());

    addXsrfHeaderFromCookie(rb);

    // TODO enable timeout
    // rb.setTimeoutMillis(timeoutMillis);
    // TODO this should be configurable
    rb.setHeader("Content-Type", JsonConstants.JSON_CONTENT_TYPE);
    rb.setRequestData(payload.toJson());

Expected behavior

A configurable value, whether this is done as a Servlet initial parameter, or through the UI instance, to set a timeout on XHR requests from the Client-side browser -> Vaadin Webserver.

Actual behavior

XHR Requests never timeout and if the response is never received the application is completely frozen until the user hard refreshes.

[samie]

Depending on your application runtime environment and requirements, you could use a workaround setting all XHR requests timeout in JavaScript:

!function(send){
    XMLHttpRequest.prototype.send = function (data) {
        this.timeout=10000;
        console.log("Using XHR timeout:"+this.timeout);
        send.call(this, data);
    }
}(XMLHttpRequest.prototype.send);