[SAGA-RG] Context attributes

[Steve Fisher]

2009/2/6 Andre Merzky <andre at merzky.net>:
> Hi Steve, Paul,
>
> the set of context attributes is supposed to allow the user
> to point to a specific security token, in a wide set of
> environments.  You are right: apart from 'Type', different
> grid environments will require different attributes to be
> set.  For example, a MyProxy context would probably specify
> 'Server', 'UserID' and 'UserPass', while a X509 proxy
> context would point the 'UserProxy' attribute to the proxie's
> location in the file system.
>
> We hope that the set of attributes cover all currently used
> Grid middlewares (we had the OGF security area check the
> attributes for completeness).  If not, that needs fixing.

In that case the list will just get longer and longer. I was simply
suggesting that it would be better to only have the "Type" and then
allowing other attributes to be specified by the user to match the
implementation he plans to use. If the user explicitly creates a gLite
context there is no point in setting more than the location of his
proxy. At the moment he could try setting other attributes - expecting
them to do something useful - but the implementation will ignore them
or it could report an error if useless attributes are set.

> It is a different story altogether on implementation level
> though: a context representation within the SAGA
> implementation may well keep additional attributes, like
> (for the examples above) the MyProxy server version, or the
> X509 proxy file checksum.  That might be useful information
> for the implementation to keep, and to pass around with the
> context - but these attributes do not need exposure on API
> level

> (that is why the context attributes are not > extensible).

Here I think  you are confusing the API and the implementation. The
attributes can be extensible - but should not be used by the
implementation to cache information. If the implementation changes a
context created by the user (other than the default one) such that the
user can see that it has been changed - then that implementation is
broken.

> I think the latter is what causes confusion for Paul in the
> implementation (will send a separate mail on that on the
> devel list).

Yes I think that Paul was wrong to try to set the VO in the context as
all the information is defined in the proxy. In fact what he needs to
store is all the information unpacked from the proxy which for a VOMS
proxy is more complex than can be represented easily by attributes -
even if multi-valued. This should be a private structure and not
visible to the user via the API. However I am tying to keep my nose
out of the C++ implementation.

Steve