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This tutorial shows how to set up a two-node Apache web server cluster that provides high-availability. In front of the Apache cluster we create a load balancer that splits up incoming requests between the two Apache nodes. Because we do not want the load balancer to become another "Single Point Of Failure", we must provide high-availability for the load balancer, too. Therefore our load balancer will in fact consist out of two load balancer nodes that monitor each other using heartbeat, and if one load balancer fails, the other takes over silently.

This document describes how to set up a two-node load balancer in an active/passive configuration with HAProxy and heartbeat on Fedora 8. The load balancer acts between the user and two (or more) Apache web servers that hold the same content. The load balancer passes the requests to the web servers and it also checks their health. If one of them is down, all requests will automatically be redirected to the remaining web server(s). In addition to that, the two load balancer nodes monitor each other using heartbeat. If the master fails, the slave becomes the master - users will not notice any disruption of the service. HAProxy is session-aware - you can use it with any web application that makes use of sessions like forums, shopping carts, etc.

This article explains how to set up a two-node load balancer in an active/passive configuration with HAProxy and heartbeat on Debian Etch. The load balancer sits between the user and two (or more) backend Apache web servers that hold the same content. Not only does the load balancer distribute the requests to the two backend Apache servers, it also checks the health of the backend servers. If one of them is down, all requests will automatically be redirected to the remaining backend server. In addition to that, the two load balancer nodes monitor each other using heartbeat, and if the master fails, the slave becomes the master, which means the users will not notice any disruption of the service. HAProxy is session-aware, which means you can use it with any web application that makes use of sessions (such as forums, shopping carts, etc.).

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Have they learned nothing since the '80's?

Our current printer, the very capable Brother color laser printer (MFC-9840CDW), will print either single sided or double sided. But the interface options for selecting it are very confusing. Rather than give the user the option for "Single Sided" or "Double Sided", you are presented with this option (buried in the middle of a screen of other printer options):

Duplex/Booklet: None, Duplex, Booklet

Most printer users don't know that double sided printing is called "duplex printing" (just as they didn't know that PC LOAD LETTER means to add paper to the 8.5x11 paper cassette).

Rendering a landscape

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