Question

I have a client/service.

The service has a method that takes a long time to do (it interacts with a database).

I’m call this method via a AJAX request from the page to the client, then to the service and back.

My service code:

[WebMethod]
public static string LookupUPC(string sessionId, string upc) {
    string response = "";
    var client = new SmartShopService.SmartShopInterfaceClient();
    try {
        response = client.LookupUPC(sessionId, upc);
    }
    catch (Exception e) {
        throw e;
    }
    finally {
        if (client.State == System.ServiceModel.CommunicationState.Faulted)
            client.Abort();
        else
            client.Close();
    }
    return response;
}

It is called from the page by an AJAX request

for(var i = 0;i<10; i++){
$.ajax({
    type: "POST",
    url: "SmartShopGUI.aspx/LookupUPC",
    contentType: "application/json; charset=utf-8",
    data: DataCreator(allData),
    dataType: "json",
    success: function (result) {
        $(upcName).html(result.d);      
    },
    error: AjaxFailed
});
}

Now, this is done asynchronously on the page, but the client is sending the requests synchronously. I want to change it so that if it asks for 10 all at once, it’ll send 10 different requests to the service.

http://www.screencast-o-matic.com/watch/cX1Qo8qV2

Here is a video that might help.

Answer 1

Remove the reliance on Session in the webmethod, you’ll probably find that session access is serial and that is what the block is.

http://msdn.microsoft.com/en-us/library/ms178581.aspx

Concurrent Requests and Session State

Access to ASP.NET session state is
exclusive per session, which means
that if two different users make
concurrent requests, access to each
separate session is granted
concurrently. However, if two
concurrent requests are made for the
same session (by using the same
SessionID value), the first request
gets exclusive access to the session
information. The second request
executes only after the first request
is finished. (The second session can
also get access if the exclusive lock
on the information is freed because
the first request exceeds the lock
time-out.) If the EnableSessionState
value in the @ Page directive is set
to ReadOnly, a request for the
read-only session information does not
result in an exclusive lock on the
session data. However, read-only
requests for session data might still
have to wait for a lock set by a
read-write request for session data to
clear.