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[ Enhydra Director: Load Balancer and Failover Module for Enhydra ]

About Enhydra Director


Load sharing and balancing are critical features in any serious application framework. The levels of usage commonly experienced by successful Internet applications can easily overwhelm even the fastest single machine. In addition, a number of popular enterprise server machines can realize a performance benefit by distributing application load among several application instances on the same machine.

Enhydra Director is an open source project that has implemented such load balancer as a web server plug-in. It is designed to work with the Enhydra application server. The Enhydra Director architecture allows Enhydra applications to distribute processing load among one or more instances, both on the same and separate machines. Trough additional modules (Connectors) Enhydra Director also includes 'native' (without Enhydra) load balancing support to several other application servers: Tomcat5.xx (Tomcat prior v5.5x) since release v6.0.1, Tomcat5.5x since release 6.2-1. and Jetty since Enhydra Director 6.2.2 release.

The Enhydra Director supports load balancing managers on several popular Web servers and operating systems, including Apache (on Linux/Unix and Windows), Netscape Enterprise Server (on Linux/UNIX and Windows), and Microsoft Internet Information Server (on Windows). The source code for the Enhydra Director web server interface is designed to be portable, so it won't be long before other Web servers and/or operating systems are supported.

Enhydra Director understands Session Affinity and can be configured to ensure that a client connects back to the same application server instance (if available) where the session is in memory. Modifing this configuration and the choice of Session Manger allows for various levels of fault tolerant architectures.

An additional benefit of Enhydra Director is that it provides a common method of connecting web servers to application servers. No longer will administrators have to struggle with the difficulty of setting up the Apache connector, nor will they have to settle for the poor performance of the single-threaded Netscape CORBA/WAI connector. Using the high performance interface of the Web server, Enhydra Director provides a direct connection between the front end content and load balancing server, and the backend application workhorses.


Enhydra Director is a collection of application connector modules that allows Web servers to easily connect to Application servers (Enhydra, Tomcat, Jetty) and make use of its powerful features, including:

  • Common connection method on the Application server, independent of which Web server is used.

  • Simple configuration on both the web server and application server.

  • Support for load sharing and balancing among multiple instances on multiple server machines.

  • Fail-over support when an application instance becomes unreachable by the Enhydra Director Web server module.

  • Use of high performance Web server interfaces such as NSAPI, ISAPI, and the Apache module interface.

  • Session history tracking and resource caching.

  • Dynamically (in run-time) applications servers re-balancing and priority changing.

  • A CGI module will be available for systems on which other higher performance methods are not yet available.

We look forward to you participation!

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