perfsonar development work

[Jason Zurawski <>]

All;

This is a request for the MDM LS specifically, but the issue pertains to 
all services that pass along eventTypes and datum-messages regarding 
system errors.

My dilemma: Trying to do what I thought was a simple query to both MDM 
and pS instances of the hLS for a web page.  The query I sent:

      
/nmwg:store[@type="LSStore"]/nmwg:metadata

The pS hLS responded ok, but the MDM hLS gave me this initially:

  eT:           error.common.storage.xmldb.open</nmwg:eventType>
  datum:	XQuery by HTTP failed. Could not connect to eXist via pure 
http,  nested exception was: class 
org.perfsonar.service.base.storage.xmldb.exist.rest.ExistDbErrorException: 
eXist DB responsed with HTTP error code code [202] additional message 
was [Accepted]</nmwgr:datum>

I would have pegged this as a configuration error with the service since 
the eventType appears to be 'system' related.  I figured out quickly 
that every MDM LS out in the wild responded like this, so it appears to 
be my fault.  After some poking I realized I should have sent this 
variant instead:

      declare namespace nmwg="http://ggf.org/ns/nmwg/base/2.0/";;
      
/nmwg:store[@type="LSStore"]/nmwg:metadata

My thoughts:

1) I am sure the above message comes from eXist directly, which is 
unfortunately vauge.  Since my problem was really a syntax/formulation 
error with the XQuery/XPath statement, I would much rather see this sort 
of error message (cleaned up a little of course): "Hey Dummy, learn 
XPath!".

Perhaps we need to spend some time decoding the error messages that 
would come from supporting software (e.g. RRD, XMLDB, eXist, MySQL) into 
more user/protocol friendly descriptions and having the services simply 
look these up.  Standardizing across services/implementations would be a 
bonus.

2) Even though this wasn't a system error, would a system error be 
returned via the message protocol?  I think we touched on this years ago 
but where do we draw the line between what is good to tell the users and 
what is good to tell the sysadmin via logging.

Thanks;

-jason

P.S. New *development* version of the 'tree' GUI that has a feature to 
dump hLS contents:

http://dc211.internet2.edu/cgi-bin/pA/tree.cgi