IRules 101 - #05 - Selecting Pools, Pool Members, and Nodes

Posted on January 14, 2014 – 01:08 am
Cover-Pools®, Swimming Pool and Spa Covers

About Deb 6:21:26 PM Test -- is this supposed to be publicly viewable?

A very common use of iRules is to choose an appropriate destination based on the current traffic or request details. In this article I'll review the iRules commands you should have in your repertoire for selecting the right pool, pool member or destination address under specific conditions. Other articles in the series:

Selecting a destination

Command: pool

In most cases, the destination you want to specify is a just a specific pool of servers serving the same content.

The command to choose a pool is simply "pool":

You can either specify a literal pool name:

pool HTTP_pool
or use a variable to specify one:

pool $myPool
You can also choose a specific pool member using the pool command:

pool HTTP_pool member 80
Command: node

The "node" command is useful if you want to send traffic to a specific IP/port combination that is not defined as a pool member:

when HTTP_REQUEST { if { [HTTP::uri] starts_with "/admin" } { node 8080 } else { pool HTTP_pool } }
When is the "default pool" not the default pool?

When configuring a standard virtual server, you can specify a default pool and/or any number of iRules as resources for the virtual server. iRules applied to the virtual may or may not select a pool or pool member. If not, the default pool configured on the virtual server will be used for all traffic. If the iRule does select a pool for a connection or request, the selected pool (rather than the configured default pool) then becomes the default pool for the remainder of that connection unless another pool is specifically selected. That's important to remember for transaction-based protocols such as HTTP for which traffic is often split per request.

Consider the following example (simplified for demonstration purposes):

A single keepalive HTTP connection to the virtual server is established.
The first HTTP request on that connection is for an HTML page, then several subsequent requests are made for graphics and stylesheets, then another HTML page, then more graphics, etc.

HTML pages are hosted on one set of servers, graphics on another, and style sheets on a third set. The virtual server configuration includes html_pool as the default pool, and the following iRule to distribute traffic to each pool based on content:

when HTTP_REQUEST { switch -glob [HTTP::path] { *.css { pool css_pool } *.jpg { pool jpg_pool } } }
Here's is the breakdown of where traffic would be sent using this iRule:

index.html - - > html_pool
logo.jpg - - > jpg_pool
style.css - - >


Rizzoli Pools
Book (Rizzoli)

Pools, of course

2010-08-02 13:49:15 by kozzy

Dangerous on many levels, especially above ground pools and pools without fencing to code.
But this thread is actually about enforcement. While I understand the pool thing and even enforcing it via google earth, the enforcement is likely NOT motivated by any safety concern: L...s about revenue. If it was about safety, the next step would be to HELP people get into compliance and I'd bet a dozen doughnuts the next step that is actually taken is issuing a fine.
The point where it crosses the line is when it changes from helping residents do things the right way as the real goal, to generating money for the city/county/state as the goal (although they NEVER admit it)

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