[AG-TECH] AccessGrid 3: What information is available

Steve Smith ssmith at vislab.usyd.edu.au
Fri May 20 05:56:56 CDT 2005

> I would have thought that the notifications, security, lifecycle management,
> and statefulness of either GT3 or WSRF to work reasonably well for what we're
> doing, although I don't claim to be an expert on the subject.
> What are the specific weaknesses that you see with the current design (that
> are due to the use of web services and globus)?

The problem is it's extremely easy to confuse globus about state.  Try
this: login to an AG session on one machine, proceed to another machine
and login to another session.  Now, on the first machine kill -9 the
original session.  Notice that the session still exists in the other AG
client.  Restart the session.  You now have two instances of the first
session; the old one will remain for a few minutes.  Do again for three.
Do in a loop to bog the server down to a crawl.  (This isn't
hypothetical, by the way, I've seen this happen with a buggy client.)
This isn't a problem using the statefulness of a connection-oriented
protocol; killing the client causes the OS to kill the connection which
kills the session on the server.

The irony is that Globus implements statefulness  on top of stateless
protocols (HTTP/web-services), which are implemented by making and
breaking stateful connections (TCP).  The question is why don't we just
use the extremely well understood semantics of TCP to maintain
connection state?

I should point out that I'm not saying that there's a fundamental
problem with the globus/ws architecture itself, just that it's a poor
match for the AG.


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