[mapguide-internals] Re: Please review RFC 73

[Kenneth Skovhede, GEOGRAF A/S]

The discussions are spread out a bit:
http://n2.nabble.com/Server-rendering-incomplete-tiles---Defect-or-Feature---tc2785311.html#a2788524
http://trac.osgeo.org/mapguide/ticket/254
http://n2.nabble.com/Allow-access-to-different-layers-based-on-login-tp2940743p2944799.html

There are a number of different implementation strategies:

1) If permission is denied to a layer or featuresource, the map fails to 
load completely.
2) If there is a an error in selecting filtered features, the entire 
feature set is attempted
3) If the featuresource fails, the map is rendered, and the broken 
features are omitted.

I think that only case (1) writes to the error log currently.
MGOS 2.1 will also log (2), not sure about (3).

For now, implementing the RFC with throwing an error if any resource 
fails, would be
the logic move, as that is how it works now.

For future uses, it would be better to return a list of exceptions.
Once a strategy for dealing with such errors has been defined,
the calling code can evaluate the errors and take apropriate action.

For some users, it would make sense to just ignore permission problems,
because this would make it easier to make a map where the login determines
what layers are visible.


Regards, Kenneth Skovhede, GEOGRAF A/S



Christine Bao skrev:
> Hi Kenneth,
>
>      Your question about exception handling is pretty good, thank you.
>      I didn't consider much on this before, and I planned to catch exception once it happened and throw it - "abort method" as it's called. However it seems not a good behavior, is it? Would you please tell me more detail about what's expected? Do you have discussion or ticket about this? Thank you.
>
> Thanks & regards,
> Christine
>
>
> From: "Kenneth Skovhede, GEOGRAF A/S" <ks at geograf.dk>
>
> Subject: Re: [mapguide-internals] Re: Please review RFC 73
>
> To: MapGuide Internals Mail List <mapguide-internals at lists.osgeo.org>
>
> Message-ID: <4A5B3739.60007 at geograf.dk>
>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
>
>
> OK, I was not considering that MgMap.Create was in another process than the repository. Thanks for clearing that up.
>
>
>
>
>
> Another question:
>
> How are permission issues handled if there is a partial error?
>
> Eg. requesting 2 resources, but access is denied to one of them?
>
> An exception could also happen while accessing one of the resources.
>
>
>
> Simply returning an error would follow the current "abort" method on runtime map creation failure.
>
> There has been talk about fixing this behavior.
>
>
>
> If this RFC would at least consider what implications the change would have for fixing this, I would be happy.
>
>
>
> A method could be to return an exception list.
>
>
>
> Regards, Kenneth Skovhede, GEOGRAF A/S
>
>
>
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