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server-sent event in HTML5

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    #1

    server-sent event in HTML5

    In my shopping cart I tell the user how many "Apples" are available but this is found at the time they request an "Apple".
    I realise I could do a call back at a regular interval to update this value but that will put extra load on the server.
    I would like the server to refresh the page if an "Apple" is sold.

    There is a server-sent event in HTML5 to help with this.

    I would like to use code similar to this ASP block

    <%
    Response.ContentType = "text/event-stream"
    Response.Expires = -1
    Response.Write("data: " & now())
    Response.Flush()
    %>

    Does anyone know how I would do this?

    Michael
    Tags: None
    #2
    Re: server-sent event in HTML5

    Is it your shopping cart... iow... did you build it? Is it an a5w page... a grid... a ux?

    You write...

    There is a server-sent event in HTML5 to help with this.

    Do you mean... Is there a server-sent event in HTML5 to help with this?

    When you sell an Apple... how about performing your ajax callback at that point to go and get the number of apples.

    The code you reference, in Alpha terms, looks like it would be an a5w page containing a query string and just prints data out to the display.

    I would think at the time you sell the apple you'd perform an ajax callback, get the number of apples and update something on whatever your cart is.

    Need a bit more info.

    Comment

      #3
      Re: server-sent event in HTML5

      The shopping card works on a number of levels. Yes in the most practical way it is built.

      I need to do 2 things the first is to save it to local storage so that I can let the user navigate away from the page/website and still hold their choices.
      The second thing is to report to the user the current stock of "Apples".

      I am trying to do as little on the server as possible. As you probably remember this is a Bagel delivery website and we expect it to be very busy at peak times. The estimated figures from Alpha on a single Server capacity seems to be at our predicted use level.

      The code I posted is ASP.

      I read about http://www.w3schools.com/html/html5_...sentevents.asp

      This looks like it will reduce the server load. I was wondering if anyone had used it will Alpha.

      My problem is not the main process when it occurs at a fast pace but rather a person who logs on and then does not save the shopping cart immediately.
      I want to update the current stock levels without too much server load.
      Forcing the user to refresh is not very elegant.

      Michael

      Comment

        #4
        Re: server-sent event in HTML5

        HTML5 localstorage will look after your local storage needs.

        To me it looks like setting up SSE is just another layer of complexity that's not going to do much for you. First... can the Alpha server do it? Second, not support by IE which I could give 2 crackers about because even if they did support it they'd probably mess it up. Third, it seems as if SSE keeps a connection open... or at least tries to. Fourth... you're still running something on the server... it's still a server load... maybe less... but is it worth the hassle? Fifth... even with SSE your stock levels may still be out of date, depending on how often your SSE runs.

        If you want real stock levels, or as close as you can get, I'd just go get my apple count when the apple is selected... and again at checkout. That's two calls as opposed to how many times the SSE will run in a loop on the server. You don't have to make the user refresh. They're performing an action anyway that you piggyback on.

        If the user picks a apple and walks away from their cart for an hour, comes back and your SSE has updated the apple to out of stock... then great... no apples.
        If they come back and click check out and then find out there are no more apples I don't see the difference. Except 2 callbacks compared to a lot more SSE.

        How often would you have the SSE running?

        Comment

          #5
          Re: server-sent event in HTML5

          OK

          The logic seems good.
          I am like a kid in a smarty (Similar to M&M's) shop see something new and want to try it.

          What happened to Markham or where ever?

          Michael

          Comment

            #6
            Re: server-sent event in HTML5

            I think Smarties were around long be M&Ms... althought I prefer the peanut M&Ms, I was pretty much raised on Smarties.
            Markham is still here... incorporated as a City a few years ago and becoming more stupid, just like a city, every day. The mayor and his cronies are selling every single piece of green space for development.
            Unionville is actually an historic village within Markham (well... as historic as Canada can get, although it does date back to the late 1700's) and it's somewhat protected from political greed and downright dumbness.

            Still... it would be interesting to find out how, if possible, to get an SSE to run from Alpha, and to run some tests.

            Comment

              #7
              Re: server-sent event in HTML5

              I read most of the previous post thinking it was related to the original question!

              I am sure this is said below, you use an Ajax callback to update the quantity in the database at the appropriate time during the sale, and then an Ajax callback to get the quantity when needed, and then (to avoid the browser refresh) javascript to update the browser to show the new quantity when needed.

              As an example go to my Store at http://alphatogo.com/products.a5w. Click Add to Cart for the first item. It pops up a message, click OK on the message. As soon as you click OK, a message appears on the screen detailing what has just been purchased. (Note - the popup message is not important, it does not affect the rest of this example). If you continue to add items to the cart, the information in that box is updated. And notice in the far upper right, the Cart values continue to increment up as you add items. None of that required a browser refresh.

              Now, if so inclined, click Check out and buy something
              Steve Wood
              See my profile on IADN

              Comment

                #8
                Re: server-sent event in HTML5

                OK

                Thanks David and Steve, I will stick to the solid and tested. I already do a call back each time I add an item to the cart; I do this to check the product is still available.
                I will wait until the validate before save to do a final browser check.

                Michael

                Comment

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