If-Modified-Since HTTP header broken for DataSources in Chrome

[TheUserRyan]

We're using a data source to poll XML data into a grid from a rest service that uses the "If-Modified-Since" HTTP request header to identify whether the XML data has changed. This looks to be broken versus Chrome.

Given the following request made via DataSource:

	public void refreshOnlyRecentTests() {
		final Timer timer = new Timer() {
			public void run() {
				refreshOnlyRecentTests();
			}
		};
		
		DataSource dataSource = new DataSource("rest/test/instances/by-status/finished/0/33");
		dataSource.setRecordXPath("//DartTestInstance");
		DSRequest requestParams = new DSRequest();
		HashMap<String, String> httpHeaders = new HashMap<String, String>();
		httpHeaders.put("If-Modified-Since", "Tue, 01 Feb 2013 02:03:04 GMT");
		requestParams.setHttpHeaders(httpHeaders);
		dataSource.fetchData(null, new DSCallback() { public void execute(DSResponse response, Object rawData, DSRequest request) {
			// Schedule this whole action again 
			timer.schedule(5 * 1000);
		}}, requestParams);
	}

I see the following request header in Chrome:

If-Modified-Since: Thu, 01 Jan 1970 00:00:00 GMT, Tue, 01 Feb 2013 02:03:04 GMT

...and the following request header in Firefox:

If-Modified-Since: Tue, 01 Feb 2013 02:03:04 GMT

Interestingly, if I drop the "dataSource.setRecordXPath()" call, I see this header in Chrome and Firefox:

If-Modified-Since: Thu, 01 Jan 1970 00:00:00 GMT

I tried using a plain old request builder, and it seems to work great in Firefox and Chrome:

	public void refreshOnlyRecentTests() {
		final Timer timer = new Timer() {
			public void run() {
				refreshOnlyRecentTests();
			}
		};

		RequestBuilder request = new RequestBuilder(RequestBuilder.GET,  "http://localhost:8080/dart/rest/test/instances/by-status/finished/0/66");
		request.setHeader("If-Modified-Since", "Tue, 01 Feb 2013 02:03:04 GMT");
		try {
			request.setCallback(new RequestCallback() { 
				public void onError(Request request, Throwable e) {} 
				public void onResponseReceived(Request request, Response response) {
					timer.schedule(5 * 1000);
				}});
			request.send();
		} catch (RequestException e) {
			SC.warn("REQUEST ERROR: "+e.getClass().getName()+": "+e.getMessage());
		}
	}

Here is the request header from both Firefox and Chrome:

If-Modified-Since: Tue, 01 Feb 2013 02:03:04 GMT

Here are the versions I'm using. I'd quote you the output from the debug console, but I'm just worn out from trying to get it to function.

Chrome 24
Firefox 17
SmartGWT 3.1
GWT 2.5

[Isomorphic]

DataSources assume that you do not want HTTP-level caching by default. To disable this, set dataSource/operationBinding.preventHttpCaching:false.

At that point the 1970 date won't be involved, so Chrome's bug with combining two If-Modified-Since headers won't arise.

[TheUserRyan]

Thank you.

For those following along at home. This added line fixed my problem:

...
		DataSource dataSource = new DataSource("rest/test/instances/by-status/finished/0/33");
		dataSource.setRecordXPath("//DartTestInstance");

		// Tada
		dataSource.setPreventHTTPCaching(false);

		DSRequest requestParams = new DSRequest();
		HashMap<String, String> httpHeaders = new HashMap<String, String>();
...