Hi Michael,
Thanks for this note. We haven't done any proxying of Tomcat so I'd like
to add your text to our documentation if you don't mind.
I was looking at the Tomcat docs
(http://tomcat.apache.org/tomcat-6.0-doc/proxy-howto.html) and it
mentions adding a <Connector> element to the Tomcat configuration. Did
you do this step as well? Or maybe this is an alternate to the
"ProxyPreserveHost On" line?
Anyone else with experience in this matter have comments or additions?
Thanks,
Ethan
Godin, Michael wrote:
I have not seen this come up in the THREDDS discussion or documentation, and I
was scratching my head for a while today to get it to work right, so here's a
tech note for consideration in the THREDDS documentation:
THREDDS and Apache ProxyPass
If you are using Tomcat on port 8080 (for example) and Apache on the default
port 80, you can use the Apache proxy module to hide the Tomcat port in the
URLs used to connect to THREDDS. This may be critical if your server is behind
a firewall that only allows port 80 access. It is also important if THREDDS is
running on a machine that is completely behind a firewall, but you have a
server running Apache that can talk to the machine.
You will need to edit the Apache httpd.conf file (on Linux, it is stored in /etc/httpd/conf/).
Find the lines that start with "<IfModule mod_proxy.c>" and end with
"</IfModule>". These lines may need to be uncommented. Between these lines, make sure the
following line exists and is uncommented:
ProxyRequests On
Then add the following lines:
ProxyPreserveHost On
<Location /thredds>
ProxyPass http://myhost.mydomain:8080/thredds
ProxyPassReverse http://myhost.mydomain:8080/thredds
</Location>
<Proxy http://myhost.mydomain:8080/thredds>
AllowOverride None
Order allow,deny
Allow from All
</Proxy>
You of course need to replace "http://myhost.mydomain:8080/thredds"; with the
full URL of the THREDDS web application.
The section between <Proxy... And </Proxy> can usually be omitted, but in some
cases a server is sufficiently locked down that you need to explicitly allow access to
resources. It can also be edited to restrict access to registered users via Apache
authentication mechanisms.
Finally, on the server command line (as a super/admin user), execute:
apachectl graceful
In my configuration, I initially failed to add the line "ProxyPreserveHost On", which caused me many headaches as links generated by THREDDS kept directing the client back to port 8080 (which was blocked by a firewall).
Best of luck,
Mike
_____________________________________________
Michael A. Godin
Software Engineer
Monterey Bay Aquarium Research Institute
http://www.mbari.org
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Software Engineer Fax: (303) 497-8690
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