GlassFish Project - Load Balancer Administration

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Welcome to the Load Balancer Administration page. This page is dedicated to discussing the Clustering and Load Balancer Administration features in GlassFish. The source code for these features is part of this cvs repository.

Load Balancer Administration News

Load Balancer admin team is meeting every Friday 9 a.m. (U.S Pacific Time) to talk about the status and issues. Please participate. You can check out the weekly meeting agenda and mintues. . (October 06, 2006)
Check out Prashant's article on Setting up F5 Network's BIG-IP System with Application Server. (September 25, 2006)
A Instructions to setup SSL connection between DAS and Load Balancer, so that DAS can update loadbalancer whenever configuration is changed. This avoid manual export and copy of configuration from DAS to Load Balancer. Once this is setup, monitoring information can also be obtained from Load Balancer. (September 07, 2006)
A blog about using APS installer to setup LB plug-in is posted. It has less number of steps than the manual configuration of LB plug-in (August 25, 2006)
A presentation about clustering and steps to setup HTTP LB plug-in on Sun Web Server. It also covers user experience of Load Balancer administration. (August 24, 2006)

Overview

In order to scale for large amounts of load, it is typical to use multiple server instances in enterprise environments. Typically a load balancer is used in front of these cluster of instances. Please refer to EE quick start guide for more details on clustering. GlassFish does not any place special requirements on the load balancer. Any hardware or software load balancer can be used. GlassFish has documentation on configuring Sun HTTP LB plugin (works on Sun Web Server, Microsoft IIS and Apache), Apache mod_jk, Sun Secure Application Switch and F5 BIG-IP.

Sun HTTP LB plug-in has the following features:

Sticky RR Load Balancing
Can support multiple clusters
Rapid HTTP request failover (<30 ms)
Configurable Health checking to re-enlist server
Check for dynamic changes changes to Load Balancer configuration and re-load the changes
Support for Quiescence - enables rolling web service upgrade
Automatic retry of failed requests for idempotent URLs
Configurable error pages

The following picture shows Sun HTTP LB plug-in being used in 2 cluster (4 instances on 4 hosts) configuration.

Sun HTTP LB plug-in stores its configuration in loadbalancer.xml. Instead of asking users to manually edit this loadbalancer.xml, we can generate loadbalancer.xml. This reduces chances of manual errors. In Glassfish, a load balancer configuration is a named configuration in the domain.xml file. Load balancer configuration can contain clusters or stand alone instances. The following command generates the loadbalancer.xml for cluster by name cluster1.
asadmin configure-http-lb-config --target cluster1 "C:\loadbalancer.xml".

This command will do the following:

asadmin create-http-lb-config --target cluster1 cluster1-lb-config
asadmin enable-http-lb-server cluster1 (by default, all server instances are disabled in the load balancer)
asadmin enable-http-lb-application --name clusterjsp cluster1 (by default, all applications are disabled in the load balancer)
asadmin export-http-lb-config --config cluster1-lb-config "C:\loadbalancer.xml"

The sample generated xml file can be viewed here: loadbalacer.xml. GUI can alse be used to export the LB configuration file. From GUI select HTTP Load Balancers, select New, choose name and targets of the load balancer. You can skip step 2 screen. It is optional and click finish. To export click on the newly created load balancer, choose export tab and click on Export Now button. GUI shows the location where the loadbalancer.xml is generated. Screenshots can be viewed here - creating a load balancer configuration and exporting a load balancer configuration. Once this loadbalancer.xml is copied to Sun HTTP LB installation directory, this configuration is reloaded and the load balancer is ready to forward clusterjsp application requests to the cluster (cluster1).

Load balancer configuration is extremely flexible:

Each load balancer configuration can have multiple load balancers associated with it, though each load balancer has only one load balancer configuration.
A load balancer services only one domain, though a domain can have multiple load balancers associated with it.

The Configuration Model

New element called policy and attributes called policy-module and weight are added. For the complete load balancer configuration model, please refer to sun-loadbalancer_1_2.dtd

CLI Commands

Please refer to CLI command reference page for the list of commands available for Load Balancer Administration.

Code-Walkthrough

The GlassFish Load Balancer Administration code is located in lb-admin sub module in the repository. The following describes all the sub packages in this module.

The Mbeans sub-package, contains the MBean interface and implementation to manage Load Balancer configuration. CLI and GUI talks to these MBeans.

Reader sub-package contains the code that reads the config elements in domain.xml. These class file use Reader pattern. api package contains the API for the readers and impl package contains the implementation.

Transform contains the code the implements the Visitors, which visit the above readers and populate the elements in loadbalancer.xml.

We read information from loadbalancer.xml using schema2beans. These generated schema2beans are in Beans directory.

The logic to the configuration to loadbalancer.xml is in Writer.

Unit/Acceptance Tests

Running the Quicklook tests is required in this section. In addition to the Quicklook tests the Load Balancer Administration module has unit tests developed which need to pass prior to checking in any code. The setup for running unit tests is the same as the Quicklook tests. To run just the Load Balancer Administration unit tests do the following:

Go to glassfish/admin-ee/lb-admin
ant run-all-tests

This will build and run all the all the Load Balancer Administration unit tests including the tests in tests/com/sun/enterprise/ee/admin/lbadmin .

Supporting Documentation

This section will be updated with useful documents and information about the Load Balancer Administration - Tutorials, Blogs and other useful links.

ToDo List

The following is non-comprehensive list of developer friendly Load Balancer Administration ToDo features. Please email us if you have questions about current implementation or would like to contribute towards future ToDo list.

From GUI, we should provide feature to enable/disable applications and instances in LB.
Last export time should be displayed in GUI
Disable "Apply Changes Now" button, when Application Server can not communicate with LB or When is LB host information is not configured.
Auto Apply should not be enabled by default.