A status code of 0 is symptomatic of network errors (or if you unload the
page –navigate away or reload– while there are pending RPC requests: they'd
be aborted with a status code of 0), so it's expected that you don't see
anything on your server logs: the requests aren't reaching it.
Now so as to understand why this is the case, I don't have a single idea,
sorry. It might be proxies/firewalls blocking them (maybe they don't like
the GWT-specific custom content-type and/or headers), or real connectivity
issues.
On Friday, March 30, 2012 6:29:21 AM UTC+2, John Malpas wrote:
>
> I have several apps out there written in GWT 2.4
> Over the last few months, users have started to complain
> about seemingly random RPC failures, both reading and writing.
> I have never yet experienced these errors from my own computer,
> but there are enough users writing in about it that
> it seems that there must be something going wrong -- not just
> one user with a questionable internet connection.
>
> The manifestation in the onFailure() method of an AsyncCallback
> is usually
> com.google.gwt.user.client.rpc.StatusCodeException: 0
>
> I found one cooperative user who has been willing to beat on the
> apps for me and send me results.He gets the errors with Firefox 8, IE 8,
> and Chrome.When the RPC calls work, I see custom log messages in
> the tomcat log. When the calls do not work, I see no evidence of any
> activity
> in either the tomcat log or the apache log, so it appears that the RPC
> calls are not reaching the server.
>
> This morning I changed one of the apps to include a symbol table,
> and to print out a stack trace in a dialog when the failure happens, and
> then
> asked my precious user to try it. He sent back this stack trace,
> copied from the dialog:
>
> fail to write
> CAUGHT com.google.gwt.user.client.rpc.StatusCodeException: 0
> 0 : Unknown.Em(StackTraceCreator.java:168)
> 1 : Unknown.Jl(StackTraceCreator.java:421)
> 2 : Unknown.RF(StatusCodeException.java:35)
> 3 : Unknown.bH(RequestCallbackAdapter.java:209)
> 4 : Unknown.bs(Request.java:287)
> 5 : Unknown.Bs(RequestBuilder.java:395)
> 6 : Unknown.anonymous(XMLHttpRequest.java:287)
> 7 : Unknown._l(Impl.java:168)
> 8 : Unknown.cm(Impl.java:213)
> 9 : Unknown.anonymous(Impl.java:57)
>
> In broad strokes, I understand that the exception is
> thrown because the browser is unable to do an XMLHttpRequest.
> But more than that, why? I have looked up the line references
> in the 2.4 source modules mentioned in the stack trace above,
> but am still at a loss. The last one is this:
>
> public final native void setOnReadyStateChange(ReadyStateChangeHandler
> handler) /*-{
> // The 'this' context is always supposed to point to the xhr object in
> the
> // onreadystatechange handler, but we reference it via closure to be
> extra sure.
> var _this = this;
> this.onreadystatechange = $entry(function() {
> 287:
> handl...@com.google.gwt.xhr.client.ReadyStateChangeHandler::onReadyStateChange(Lcom/google/gwt/xhr/client/XMLHttpRequest;)(_this);
> });
> }-*/;
>
> Any suggestions would be greatly appreciated.
>
>
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