PUBLIC MARKS with tags load & web

CDNs (Content Delivery Networks) are becoming increasingly popular. The obvious benefit is that they can help websites to give end users a speedier web surfing experience, but there is also another very positive side effect for the entire Internet, and it will become more noticeable the more common CDNs become. The positive side effect is this: More CDN usage means less load on the Internet backbone.

Certaines personnes pensent qu’il ne faut pas trop se focaliser sur les problèmes de montée en charge lorsqu’on démarre le développement d’un nouveau service Internet. A quelques exceptions près (comme par exemple un site de partage de vidéos), il n’est peut-être pas en effet très judicieux de perdre du temps sur cet aspect très technique sans savoir si le succès sera au rendez-vous : on parle alors d’optimisation prématurée.

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.). From the HAProxy web site: "HAProxy is a free, very fast and reliable solution offering high availability, load balancing, and proxying for TCP and HTTP-based applications. It is particularly suited for web sites crawling under very high loads while needing persistence or Layer7 processing. Supporting tens of thousands of connections is clearly realistic with todays hardware. Its mode of operation makes its integration into existing architectures very easy and riskless, while still offering the possibility not to expose fragile web servers to the Net."

Pour gérer des milliers ou des millions d'utilisateurs, un site web se doit de mettre en place un certain nombre de technologies afin que les visites des utilisateurs soient garanties et agréables. En termes techniques, on parle de redondance et de répartition de charge (load balancing en anglais). L'association de ces deux paramètres permet d'atteindre ce qu'on appelle la haute disponibilité : en gros un service qui ne peut pas tomber en panne et qui peut facilement monter en charge.

AWBot is an easy to use tool to test a web site.: AWbot connects to your web site and make URL requests like any other visitors. AWBot is not a web indexing robot but a web client tool that emulate some visitors browsing on your web site to test its stability after a development change, to test its reliability and/or response to heavy load. You choose which pages you want to test in a test/config file (parameters in URLs or forms can be easily supplied). Then you can launch AWbot as often as you want to test your site, get benchmarks information or make some load benchmarking (AWBot can be launched with several simultaneous process).

WebInject is a free tool for automated testing of web applications and web services. It can be used to test individual system components that have HTTP interfaces (JSP, ASP, CGI, PHP, Servlets, HTML Forms, XML/SOAP Web Services, etc), and can be used as a test harness to create a suite of [HTTP level] automated functional, acceptance, and regression tests. A test harness, also referred to as a test driver or a test framework, allows you to run many test cases and collect/report your results. WebInject offers real-time results display and may also be used for monitoring system response times. WebInject can be used as a complete test framework that is controlled by the WebInject User Interface (GUI). Optionally, it can be used as a standalone test runner (text/console application) which can be integrated and called from other test frameworks or applications.

Perlbal is our Perl-based reverse proxy load balancer and web server. Perlbal is a single-threaded event-based server supporting HTTP load balancing, web serving, and a mix of the two (see below).