FWIW, your RPC calls just happen to use the HTTP protocol.
500 responses are not unusual (especially most recently).

If its immediate then you've pushing the limit of the browser's capacity;
at 30 seconds, its a harddeadline exception.

The browser is single threaded and has a limited number of open connections
to the same host (2 or 4 I think). It is relatively easy for a click happy
user to overwhelm a long duration RPC handler.
Using push/pull libraries like Comet or Facebook take up capacity too.

I've successfully used Microsoft's Fiddler proxy and HttpFox to trace
communication request/response issues both locally and on production
instances.
I suggest building in a simple retry solution and make sure your RPCs are
discrete.



On Mon, Sep 27, 2010 at 10:19 AM, GWTViju <[email protected]> wrote:

> e are using GWT 2.0.3 and Spring in the backend. Facing the below
> issue in IE(6,7,8) as well as Firefox. A proxy is placed between the
> Browser and the Application Server.
>
> In our application, we make multiple RPC calls to display the page.
> The scenario is described below
>
> RPC A and RPC B is executed when a menu is clicked. RPC A and RPC B
> are triggered in parallel.
> When RPC A completes successfully, RPC C call is triggered.
> When RPC B completes successfully,  RPC D call is triggered.
>
> The RPC C and RPC D are not triggered in the onSuccess method. The
> onSuccess transfers command to the browser, browser does some display
> work and then fires off the associated RPC..
> The UI event then fires the RPC C and RPC D to the server.
>
> In some cases (not always), I get 'Error : 500:Server response is
> invalid. Please re-try or contact admin.'
>
> I added some debug statements in my servlet and found that in such
> error scenarios, the payload is returned as Empty.
> The content length however gives a valid number like 199 or 223.
> From the browser, I checked the request and the request has the
> expected payload.
>
> 1. Is there an issue in chaining the RPC invocations to the server ,
> in my case, 4 RPC calls are made.
>
> 2. Has anyone seen a case in which the RPC request sent from the
> browser is lost before it reaches the server?
>
>
> Any help would be useful.
>
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