[THREDDS #BOZ-874608]: preferred procedure for upgrading the TDS

Hi Rich,

> When I want to upgrade the TDS, I follow this procedure:
> 
> cd <tomcat>/webapps
> ../bin/shutdown.sh
> rm thredds.war
> rm -rf thredds
> wget ftp://ftp.unidata.ucar.edu/pub/thredds/4.0/thredds.war
> ../bin/startup.sh
> 
> This was okay when only I was using the system, but now that it's
> getting popular I'm wondering if I can be let disruptive.
> Is this all necessary?

Shutting down Tomcat is not absolutely necessary. You can instead undeploy the 
running TDS and then deploy the new version. But PermGen OutOfMemoryErrors 
start to come up (see the note below [1].) Also, I don't think it is any less 
disruptive than your method; there is still a time when the TDS is down.

I tend to use the Tomcat manager, but I still shutdown and startup Tomcat most 
times I deploy a new version. Besides the PermGen issue[1], another reason I 
shutdown/startup Tomcat is so that I can clean up the log file directories 
without worrying about which files Tomcat is using.
 
> Also, if the TDS is reloaded while someone is accessing data from the
> TDS, what happens?

I believe shutdown and stop/undeploy are fairly graceful in that things that 
have started are allowed to finish. While the TDS is down, of course, requests 
will get either 404 not found responses or, if Tomcat is down, no connection 
will be made. During the startup/deploy process, things might be a bit sluggish 
but requests should be handled normally.

Hope that helps,

Ethan


Notes:
[1] PermGen OutOfMemoryErrors can crop up if you undeploy/deploy TDS rather 
than stop/start Tomcat. Some notes on that in the TDS Tutorial:

http://www.unidata.ucar.edu/projects/THREDDS/tech/tutorial/BasicTomcatAndTDSSecurity.html#PermGenProblem

and a good article on the topic:

"Return of the PermGen" - 
http://my.opera.com/karmazilla/blog/2007/09/29/return-of-the-permgen

Ticket Details
===================
Ticket ID: BOZ-874608
Department: Support THREDDS
Priority: Normal
Status: Closed