[Zope] Advice needed: load balancing wih ZEO and Apache on Solaris.

[Phil Harris]

Tone,

In advance I'll say that this isn't the best way to do this, Sean Upton has
better advice, but this is a simple way to test that all works as planned.

The rewrite rules in Apache can make use of a file to do 'random' server
selections.  I do this when I'm testing new ZEO services, getting them
serving in a 'round-robin' fashion.

I have a httpd.conf in work that will do exactly what you want, but I can
give you a few pointers right away.

Mail me on Monday, and I'll send you the relevant parts of my httpd.conf.

Anyway on with the show:

Take a look at this document,
http://httpd.apache.org/docs-2.0/mod/mod_rewrite.html.  Search for
'Randomised Plain Text' and there's your recipe.

Basically, you need to create a file that has these lines in, call it
map.txt (the name doesn't really matter though):

localhost    port1|port2|port3

replace port1 .. port 3 with the exact ports you are using:

localhost    8080|8081|8082

You can put as many options on this line as you need.

Then change your final rewrite rule to be like this:

    RewriteMap servers rnd:/path/to/file/map.txt
    RewriteRule ^/(.*)
http://localhost:$(servers:localhost)/VirtualHostBase/http/myserver.ncl.ac.u
k:80/VirtualHostRoot/$1 [P]

This will put a random port number into the line thereby giving you pseudo
'round-robin' functionality.  The ${servers:localhost} is the clever part,
'servers' is the name of the map, and localhost is a parameter telling the
map which line of the map.txt file to choose from.

And that's it, job done, next please....

hth

Phil
phil.harris@zope.co.uk




----- Original Message -----
From: "Tony McDonald" <tony.mcdonald@ncl.ac.uk>
To: "Zope" <zope@zope.org>
Sent: Saturday, August 25, 2001 5:13 PM
Subject: [Zope] Advice needed: load balancing wih ZEO and Apache on Solaris.


> Hi,
> I've followed the instructions at
> <http://www.zope.org/Members/dshaw/AdvancedSiteSetup> to set up a ZEO
server
> and client (on the same machine). These instructions are very clear and
I'd
> recommend them to people wanting to experiment with ZEO.
>
> We serve our content up through Apache (fast delivery of static content,
CGI
> scripts and PHP4 served too).
>
> I'm using the VHM method of routing Apache requests through to my ZServer
> installation so (only a snippet shown, and this is an example);
>
>         RewriteEngine on
>         RewriteRule ^/cgi-bin   - [L]
>         RewriteRule ^/static    - [L]
>         RewriteRule ^/ltsn_images - [L]
>         RewriteRule ^/(.*)
>
http://localhost:18080/VirtualHostBase/http/myserver.ncl.ac.uk:80/VirtualHos
> tRoot/$1 [P]
>
> Following the instructions from Dave Shaws' page I have a ZEO server
running
> on port 8080 and a client running on port 8081
>
> One idea I've had from reading the Apache Rewrite rules page at
> <http://httpd.apache.org/docs/misc/rewriteguide.html>
> Is to use ProxyPassReverse (in some way), i.e.
>
>
> ProxyPassReverse  /  http://localhost:8080/
> ProxyPassReverse  /  http://localhost:8081/
>
>
> My question is this;
>
> What can I do to get requests from myserver.ncl.ac.uk farmed out to my ZEO
> server-client farm?
>
> Any pointers would be really appreciated.
> Cheers
> Tone.
> --
> Dr Tony McDonald,  Assistant Director, FMCC, http://www.fmcc.org.uk/
> The Medical School, Newcastle University Tel: +44 191 243 6140
> A Zope list for UK HE/FE  http://www.fmcc.org.uk/mailman/listinfo/zope
>
>
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