BIG PICTURE/SUMMARY:
====================
Need to find a way to have the correct/complete PURGE requests sent to a
Varnish front end cache via CacheFu when using Apache virtual hosting
and Zope Virtual Host Monster (VHM) "Inside-Out" virtual hosting syntax
in the Apache RewriteRule statements.
ENVIRONMENT SNAPSHOT:
=====================
Zope 2.10.5-final
Python 2.4.4
Plone 3.0.5
Archetypes 1.5.5
CacheFu 1.1.1 (SVN/UNRELEASED Rev. 56454)
Red Hat Enterprise Linux AS 4
Setup is a caching/HTTP-server machine in front (running Varnish and
Apache), then several backend machines running ZEO clients, then a
single ZEO Storage Server:
Varnish 1.1.2 (port 80) &
Apache 2.2 (port 81)
|
|
|
ZEO Client(s)
|
|
|
ZEO Storage Server
Let's say we're running Apache/Varnish on a server called
cache.mycompany.com (IP address 10.5.54.156) and the site we're hosting
is http://www.mycompany.com/foo, which maps to a Plone site called
"PloneSite" under the ZODB mount point "mount1" (i.e.,
/mount1/PloneSite) on a ZEO client instance running on port 8080 on a
machine called zopebackend1.mycompany.com (IP address 10.5.54.155). That
is, http://www.mycompany.com/foo maps to
http://zopebackend1.mycompany.com:8080/mount1/PloneSite.
Apache's httpd.conf has rewrite rules such as the following within the
www.company.com <VirtualHost> section:
<VirtualHost 10.5.54.156>
ServerName www.mycompany.com
.
.
.
RewriteRule ^/foo(.*)
http://zopebackend1.mycompany.com:8080/VirtualHostBase/http/www.mycompany.com:80/mount1/PloneSite/VirtualHostRoot/_vh_foo$1
[L,P]
.
.
.
</VirtualHost>
Note the use of the _vh_foo at the end of the Rewrite rule--i.e., we are
using the "Inside-Out" virtual hosting feature of Virtual Host Monster
syntax.
CacheFu is enabled on the Plone site, and left at default settings
except for the following:
Proxy Cache Purge Configuration: Simple Purge (squid/varnish in
front)
Site Domains: http://www.mycompany.com:80
STEPS TO REPRODUCE THE PROBLEM:
===============================
Set up an environment similar to the one described above (Varnish cache
and Apache on same server, Varnish listening on port 80, Apache on port
81; backend ZEO client servers that Apache passes non-cache-hit requests
to; a ZEO storage server). Could probably use a single Zope instance
instead of ZEO, too...the main thing here is what Varnish caches, the
virtual hosting on Apache, and the use of VHM "Inside-Out" virtual
hosting syntax in the Apache RewriteRule statement.
Start up the site and make sure you can get to it and its contents via
the virtual host, and verify that Varnish is caching that site. Then
change some items on the Plone site in order to force a "PURGE" request
to be sent via CacheFu on the Plone site.
EXPECTED RESULT:
================
I believe what's cached by Varnish is the URL it sees coming in. E.g.,
if the client request/GET is http://www.mycompany.com/foo/news Varnish
will cache /foo/news as the object, I believe. It may include the "http"
and hostname...I'm not positive.
For example, say at one point a GET request is done and it logs the
following as an entry in the Varnish NCSA format log file:
67.164.214.168 - - [22/Jan/2008:11:45:29 -1000] "GET
http://www.mycompany.com/foo/office/party-photos/view HTTP/1.1" 404 322
"http://www.mycompany.com/foo/office/index.html"; "Mozilla/4.0
(compatible; MSIE 7.0; Windows NT 5.1; .NET CLR 1.0.3705; .NET CLR
1.1.4322; Media Center PC 4.0)"
Based on this, I would expect the "PURGE" requests sent to Varnish by
the ZEO client instance (caused by CacheFu) when the Plone site content
changes to have the same basic URL..e.g., to be something like the
following (as an entry in the Varnish NCSA format log):
10.5.54.155 - - [22/Jan/2008:12:05:13 -1000] "PURGE
http://www.mycompany.com/foo/office/party-photos/view HTTP/1.1" 404 425
"-" "-"
ACTUAL RESULT:
==============
The actual "PURGE" request sent looks like the following:
10.5.54.155 - - [22/Jan/2008:12:05:13 -1000] "PURGE
http://www.mycompany.com/office/party-photos/view HTTP/1.1" 404 425 "-"
"-"
I.e., it is missing the "foo" in between the "www.mycompany.com/" and
"office/party-photos/view". It appears that, because of this, Varnish
does not purge the object from the cache because the URL does not match
what was originally cached.
The PURGE request is missing the "foo" because, I think, the actual path
after the true "/mount1/PloneSite" Plone site is
"office/party-photos/view" (i.e., the full path would be
"http://zopebackend1.mycompany.com:8080/mount1/PloneSite/office/party-photos/view";
-- the missing "foo" portion is from the virtual hosting, not the
actual Plone site path).
NOTES/QUESTIONS/THOUGHTS:
=========================
If there's an easy way to set the settings of CacheFu to do what I want,
I guess I've missed it. I've tried using the "Purge with Custom URLs"
purge configuration too, but no luck (although I haven't tried modifying
the rewritePurgeUrls.py script...it'd take me a bit to figure out what
to change).
If I try to put something after the port number within a "Site Domains"
section entry, it gets truncated when I hit "Save". E.g., if I put the
following in "Site Domains":
http://www.mycompany.com:80/foo
it gets truncated to
http://www.mycompany.com:80
(i.e., the "/foo" is taken off) when I hit "Save".
I tried this with "Simple Purge" and "Purge with Custom URLs" both
(although I only thought it might work for the custom URLs option). I
did so because I was hoping I could force CacheFu to add the "/foo" to
its PURGE requests.
Actually, if the functionality isn't there, maybe the following can be a
request for a future version of CacheFu (or the current 1.1.1 release
due Feb. 3rd, if it's not too hard to add--perhaps I should submit an
issue/suggestion via the CacheFu development area?):
Allow the addition of something after the port number within the Site
Domains section of CacheFu configs, so that if inside-out virtual
hosting is used, the correct PURGE URL is sent to the front-end cache.
Another suggestion along those lines would be the following:
There may be more than one cache/HTTP-server machine (for redundancy
and load-balancing)--so there would be a need to send the
correct/complete PURGE request to more than one cache proxy...but
perhaps that's taken care of by the "Proxy Cache Domains" setting in
CacheFu?
Thanks ahead of time for any insight and help anyone can give me on this
issue.
Dan K.
[EMAIL PROTECTED]
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