[gembud] 20140407: Concerning Unidata's Data Services

Users of Unidata Data Services:

On Friday, March 28, 2014 the Unidata Program Center (UPC) updated the
demonstration THREDDS Data Server (TDS) running on thredds.ucar.edu to
version 4.5 of the TDS software. After encountering some issues with the
updated version, including problems with community members' IDV bundles
not loading as expected from thredds.ucar.edu, UPC staff reverted the
demonstration server to version 4.3 on April 1st.

What happened?

UPC staff had became aware that TDS version 4.3 running on
thredds.ucar.edu was not keeping some dataset indexes up to date
automatically. This situation required manual intervention by UPC staff
to keep the indices updated, which, coupled with changes in UPC security
procedures following the intrusion on February 20, 2014, increased the
urgency of releasing a new TDS version that fixed the problem. After
internal testing convinced us that TDS version 4.5 was functioning
properly, we followed the normal procedure of updating UPC servers
(specifically thredds.ucar.edu) before releasing the package to other
sites. This staged release process normally allows us to find and fix
"real world" issues that are not caught by internal testing.

In the case of TDS 4.5, however, the update brought to light a difference
between our internal test servers and the public demonstration server
thredds.ucar.edu. These differences caused the demonstration server
to crash entirely, which resulted in several problems, including the
inability of some IDV bundles to access relevant data.

Additionally, there was a problem with the way the new GRIB indexer
handled GRIB1 timeType=10 and some changes to GRIB tables from NCEP were
not handled in TDS 4.5.

What did Unidata do?

After receiving problem reports on Monday, March 31, UPC staff reverted
the thredds.ucar.edu demonstration server to TDS version 4.3 on Tuesday,
April 1. The problems discovered in TDS version 4.5 have since been
rectified, but thredds.ucar.edu has not yet been re-updated to TDS
version 4.5.

What will Unidata do in the future?

While the UPC is not funded to be operational data center, and we do not
have resources available to ensure 24/7 access to all of our demonstration
systems, we understand that many in our community rely on access to UPC
servers for teaching and research.  We strive to balance the daily needs
of community members who use servers managed by the Program Center with
development and testing activities aimed at creating tools that can
be usefully installed at community members' home sites. (See Unidata's
Use Policy.)

As a result of this the problems encountered during the recently attempted
upgrade, we have committed to implement the following changes to our
system configuration and software deployment procedures:

1) We have created a new mailing list, data-service-announce@xxxxxxxxxxxxxxxx,
   that will serve as a vehicle for UPC announcements of upcoming
   changes to data servers operated by the UPC (e.g., IDD, TDS,
   RAMADDA, ADDE) to our community. This mail list will carry brief
   synopses of upcoming changes, information about testing processes
   (including how community members can test the new services), and
   provide links to additional information on the Unidata web site.
   The new list will be the conduit for announcements about data
   servers run by the UPC. We anticipate that this mailing list
   will have very low traffic, and we encourage anyone who uses data
   servers run by the UPC to subscribe by sending an e-mail message to

   NB: Be sure to send your message from the e-mail account you want to
   receive the mailing list messages.  To activate your subscription,
   follow the instructions in the confirmation message that will be sent
   following your request.

2) We will augment the UPC's core data servers (thredds.ucar.edu,
   adde.ucar.edu, etc.) with "backup" servers that will allow users
   to revert to using the most recent stable version if problems are
   found during an upgrade or other transition. Backup servers will
   operate during transitions and until reported problems have been
   addressed. IDV version 5.0, due to be released later this Spring,
   will include a way for users to switch to the "backup" TDS server
   if needed. We expect this to be used for critical functions such as
   teaching classes.

3) We will institute a mechanism whereby community members can submit
   IDV bundles for inclusion in Unidata's test suite, allowing us to
   determine when a server change causes the bundles to "break".
   Note that while being able to include community members' IDV bundles
   in our in-house, automated testing of new server releases will alert
   us to some problems, it is not a full substitute for interactive user
   testing. We will provide more information about the bundle-testing
   program as we work out the details.

We plan to re-update thredds.ucar.edu to TDS 4.5 in mid-May 2014; we
will provide at least one week's notice and testing period (announced
via the data-service-announce mailing list) prior to this update.

Please send any questions/comments/recommendations about any of the ideas
above to:

Unidata Datastream Support <support-datastream@xxxxxxxxxxxxxxxx>

This message is also available on the Unidata web site:


Best Regards,

The Unidata Program Center Staff
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