PUBLIC MARKS with tags jboss & cluster

ClusterSSH controls a number of xterm windows via a single graphical console window to allow commands to be interactively run on multiple servers over an ssh connection.

Les EJB sont particulièrement nécessaires pour des applications critiques sur de grosses architectures matérielles, là où les ressources ne sont qu’un problème secondaire et où les avantages des EJB (gestion déclarative des transactions, distribution d’objets et support de la persistence automatique) prennent tout leur sens. Dans ce type de contexte, la tolérance aux pannes et la répartition de la charge sont des élements vitaux. Le clustering est la technologie permettant de répondre à ces 2 préoccupations. Ce document va donc s’intéresser à la bonne façon de le mettre en oeuvre en tentant de mettre en avant les pièges inhérents à l’utilisation d’un cluster.

Web tier clustering is an important part of J2EE scalability and high availability. Traditionally, load balancing is done via front end load balancer (either software- or hardware-based) while the session replication (for fail-over) is done by the web container. Here we have done a benchmark study of http session replication using JBoss Application Server (AS). We also compare JBoss performance against the Tomcat standalone. Please note that JBoss web container also uses embedded Tomcat in non-clustered mode. They differ only in the clustering solution module. For details of both implementation, please refer to both the JBoss and Tomcat documentation. The HttpSession replication performance comparisons are based on JBoss AS 4.0.3SP1 (with JBossCache 1.2.4 and JGroups 2.2.9). Previously, we have published results based on JBoss AS 4.0.2 (August 2005). But the current version has been found to provide dramatic performance improvement.

Clustering allows us to run an applications on several parallel servers (a.k.a cluster nodes). The load is distributed across different servers, and even if any of the servers fails, the application is still accessible via other cluster nodes. Clustering is crucial for scalable enterprise applications, as you can improve performance by simply adding more nodes to the cluster. The JBoss Application Server (AS) comes with clustering support out of the box. The simplest way to start a JBoss server cluster is to start several JBoss instances on the same local network, using the run -c all command for each instance. Those server instances, all started in the all configuration, detect each other and automatically form a cluster. In the first section of this chapter, I discuss basic concepts behind JBoss's clustering services. It is important that you understand those concepts before reading the rest of the chapter. Clustering configurations for specific types of applications are covered after this section.