[mapserver-users] WMS Client Error Handling

[Chris Hodgson]

Thanks Daniel, that seems to be working well. The biggest problem I have 
is that I need to parse the name of the layer that had the error out of 
the error->message - this works but obviously the format of the error 
message could change in the future which would break my parser. I guess 
there is potentially a lot of different things that could be involved in 
the error so having a separate field in the error object for each of 
them might be too much to ask, but a field for the layer name would 
certainly be handy for me in this case :)

Cheers,
Chris

Daniel Morissette wrote:
> Chris Hodgson wrote:
>> I'm implementing a WMS proxy server using PHP mapscript. I'm fetching 
>> the capabilities programmatically and storing them in a database and 
>> then building a mapfile on the fly. The mapfile contains multiple 
>> "connectiontype WMS" layers, and I'd like to be able to (a) determine 
>> when one of the WMS client requests has failed, and (b) get the error 
>> message returned for each failed layer. I'm starting to think this 
>> may not be possible currently, and it seems that the code for doing 
>> anything like this has been pushed back for a while [ 
>> http://trac.osgeo.org/mapserver/ticket/1246 ].
>>
>> Any chance that I'm wrong and there is already a way to do this? 
>> Anybody else interested in this feature? Anybody already done 
>> something like this?
>>
>
> Ticket 1246 is only about the *default* exception format, but using 
> the wms_exceptions_format metadata you can override the default and 
> request text/xml or application/vnd.ogc.se_xml exceptions (depending 
> on WMS version).
>
> Then if an exception is received MapServer will try to read the 
> exception message and pass it to msSetError() with an error code of 
> MS_WMSERR (24). This does not cause a fatal error and won't stop your 
> script though, the message is only stored in the error stack. In 
> MapScript you should be able to read the error stack (errorObj) and 
> extract the error messages.
>
> More about the errorObj at 
> http://mapserver.org/trunk/en/mapscript/php/index.html#errorobj-class
>
> I think the handling of WMS exceptions could be greatly improved, but 
> you may be able to get along with this basic stuff.
>
> Daniel