Salut,
sorry for the delay.
glassfish_at_javadesktop.org wrote:
> I've been using simple ajax polling from my web client to check when a value on my MySQL database has changed but as the number of clients has grown it is obviously not scaling well.
>
> Would someone help put me on the right track? Basically what I want to do is have each client browser, say 1000 of them, be able to have database updates pushed to them when something they are interested in changes in the database.
>
> I think I can use GlassFish and Grizzly to implement this, correct?
Correct.
How do I poll the database from the servlet to check if data has been
updated?
Here is a high level description of how you can achieve that.
1. Client sent a GET request and the Servlet suspend
(CometContext.addCometHandler) and then register that connection to a
CometContext (a topic or shareable group. in your case a MySql topic)
(cometContext.addCometHandler(yourHandler)).
2. Your Servlet spawn a thread at startup (a single one) that check when
the database has update by polling MySQL).
3. When an update comes in, that Thread invokes
CometContext.notify(MySqlUpdate), which in turn will invoke all the
suspended connection, resume them, write the response, and depending on
the comet technique you are interested (long polling or streaming).
Take a look at this blog[1]. Mainly, you can probably re-use the
ReflectorCometHandler[2] directly, so it should be as simple as:
public void doGet(...){
ReflectorCometHandler rh = new RelectorCometHandler(useHttpStreaming);
rh.attach(HttpServletResponse.getWriter());
CometContext ctx = CometEngine.getEngine().register("mySQL-push");
ctx.addCometHandler(rh); // Suspend the connection.
}
Then from you spawned thread, just do:
ctx.notify(MySqlUpdate);
That's it :-) Let us know if you need more information.
A+
-- Jeanfrancois
[1]
http://weblogs.java.net/blog/jfarcand/archive/2008/11/writing_a_twitt.html
[2]
https://grizzly.dev.java.net/nonav/xref/com/sun/grizzly/comet/handlers/ReflectorCometHandler.html
How do I push the update to the client?
>
> I'm still trying to learn how this all works so any help would be appreciated.
>
> Thanks.
> bondo.
> [Message sent by forum member 'bondo' (bondo)]
>
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