Tuesday, September 28, 2010

Re: Multiple RPC from same page gives Error 500

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 <vvbiju2005@googlemail.com> 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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