Open Access

Daniel Reuther

• With the ever-growing need for more scalable and fault-tolerant enterprise-level intranet and extranet solutions, application vendors are trying to prepare their products for multiple-machine environments. Apart from the traditional clustering approach of balancing and distributing user requests equally over several nodes, applications can be designed to handle greater loads by allowing designated background processes to run independently and be scaled separately from the main business logic and client request handling processes. Liferay Portal, a web-based enterprise-level portal and CMS solution developed by the company of the same name, already offers support for modeling a multi-node setup by utilizing well-known clustering paradigms in the manner of search index replication or cache invalidation as well as taking the application server's session replication mechanisms into account. Its upcoming release, however, will introduce long-running, CPU-bound features like creating document previews and encoding video or audio files , which will intensify the need for a concept that allows for queuing and equally distributing processor time