Minor Coral Upgrades ...

John Shott shott at snf.stanford.edu
Tue Jan 30 13:54:28 PST 2001

SNF Lab Members:

We are going to install a slightly modified version of the Coral clients and
servers this afternoon ... and will likely install a second set of
modifications later this week.  Those of you running Coral remotely will have
to download and install the new client ... and, in fact, the old client won't
work once the new servers are in place.  While Java Web Start should make this
a painless process, we apologiize for any inconvenience that it may cause.

Without boring you with too many of the underlying details, let me explain why
we needed to make some changes ... and where performance should inprove with
these changes:

One of the "behind the scenes" elements of Coral is something called the event
manager.  The event manager is basically an information clearing house that
notifies all of the existing clients anytime anything "interesting" happens so
that they can update their displayed information. For example, everytime that
you enable a piece of equipment, all clients need to be informed that "Member
x has enabled equipment y" so that the piece of equipment is shown on all
clients as being enabled (by listing your name in parentheses following the
equipment name).  Things get updated every time a reservation is made/deleted,
equipment is enabled/deleted, or a problem or shutdown is reported/cleared.
As the lab has gotten busier and, in particular, because we typically have a
number of remote clients to notify in addition to all of the sessions running
in the lab, the performance of the event manager has begun to be a
bottleneck.  You may have noticed this: the delay between when you click "OK"
to make a reservation and when it actually shows up on your screen is the time
that the event manager is notifying all clients.  While it is often a very
short delay ... sometimes it is annoyingly long.

This afternoon, we are releasing a version of Coral that has a "new and
improved" event manager ... and we have it instrumented so we can measure the
time that it takes to notify people so that we can monitor whether we have
improved the notification times significantly.

As a secondary matter, not everyone exits Coral "cleanly" by clicking "Exit"
on the upper left pulldown menu labelled "Window".  When people exit properly,
their client tells the event manager "Don't bother to update me anymore". 
However, when people exit "less gracefully" ... by just killing the window,
clicking the Sun CDE Exit button at the bottom of the screen, or because of
rolling brown-out ...the event manager doesn't know that a session is gone and
it continues to try to notify these sessions everytime ... which slows
everything down.  As a result, phase 2 of this upgrade is an improved means of
detecting when a client has disappeared (for whatever reason) and removing it
from the notification list.  That is the upgrade that we hope to install later
this week.

So, while we apologize for any inconvenience that these upgrades may cause, we
hope that you will all begin to notice the improved response time that these
changes should produce.  If you  have any problems or questions, please don't
hesitate to contact us.

Thanks for your continued support,

Your Coral Development Team
coral at snf.stanford.edu

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