2 mirror installations of apache httpd and dns round robin them. I
could be wrong, but at some point you will have single point of failure
-- either at apache httpd level or dns level.
Dennis
Leo Sakhvoruk wrote:
Yeah, I've read the docs on mod_jk. It seems a self-defeating purpose to
set up Apache httpd for load balancing and fail over because it
introduces a single point of failure on the part of the Apache httpd.
That's why I originally asked if the only way to set up fail over was
via integration with httpd. It would've been nice to just be able to do
a fail over cluster with DNS round-robin where after one Tomcat server
went down the next one in the DNS chain would be able to resume the
session. But from what I've been able to gather Apache httpd is required
for that kind of setup. Pity.
Dennis Sinelnikov wrote:
Take a look at mod_jk, there are some great examples on apache's httpd
website.
Dennis
Leo Sakhvoruk wrote:
Excellent points Patrick! I will most certainly consider them as I
look at clustering further.
Thanks,
Leo
Patrick Moore wrote:
Hi Leo --
From my experience, these are the questions that you should make sure
were asked first:
1. What is the effect on the user experience if the new server does
not have the session information?
2. How large a memory footprint does each session occupy?
3. How often do session variables change?
It has been my experience that session replication is almost never
worth the trouble it causes in terms of extra load on network and
webapps. Failure at the web app level usually has so little
consequences that usually it is enough to simply:
1. just redirect the user to a new web server
2. the new server asks them to reauthenticate
3. looks for any work in progress that was significant enough to store
in the database ( which the app is probably already doing as it is)
4. If it finds such work offers to take them back to that flow.
Think about just storing every significant checkpoint in your app as a
cookie that deserializes to a bookmark that takes them to an
IExternalPage that will continue their work. You are using
IExternalPage and bookmarks, right? right? (hint, hint) :-)
-Pat
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