By Tom Evans


A few of you more intrepid Openfire fans may have noticed a bit of recent activity in one of the branches of the Openfire SVN repository. Well, some of your fellow developers have been working behind the scenes to provide clustering support for PubSub, perhaps one of the lesser-known modules of our beloved real-time collaboration server. PubSub is an implementation of the XEP-0060 specification which extends the XMPP standard to add publish-subscribe functionality to the XMPP Core. However, if you have ever tried to use this module in Openfire, you may have been disappointed to discover that it was not designed to work in a clustered deployment. In fact, PubSub was forcibly disabled when deployed in a cluster! The main focus of the development effort was to address OF-205 and implement clustering support for the PubSub module. This work is now complete and the PubSub module is cluster-enabled and ready for action.


My Kingdom for  a Cluster!


However, during the course of this development effort, the team also took a critical look at the current clustering implementation itself (the "clustering" plugin). This solution is currently the only way to run Openfire in a clustered configuration (where multiple servers share the load). Unfortunately this plugin is inextricably tied to Oracle Coherence, an enterprise class (and enterprise priced) middleware component. A recent quote from Oracle put the price of Coherence (EE) at well over $300K for a smallish deployment ... clearly an untenable solution and incompatible partnership with the Openfire project.


We looked around for clustering alternatives that would have better affinity with Openfire, and landed with Hazelcast (Community Edition). Hazelcast is an open source clustering and highly scalable data distribution platform for Java. It enjoys a large deployment base and is licensed under the community-friendly Apache 2.0 license. There are also commercial licensing options available for deployments where professional support and enterprise security (among other features) are must-haves. This looked like a perfect fit for our needs, and likely for the Openfire community as well.


Where Two or Three are Gathered...


We are pleased to annouce the immediate availabilty of a new Hazelcast-based clustering plugin for Openfire. Starting today in the trunk of the Openfire SVN repository you will find the new plugin (/src/plugins/hazelcast/). Note that you will need to also setup the latest version of the Openfire core (currently 3.7.2-Beta) to use the new plugin.


We are looking for a few brave Openfire afficionados who can take the latest build and give it a whirl with your various deployment scenarios:

  • How many users and/or cluster member nodes do you have?
  • Which modules/components of Openfire are you using?
  • What is your typical JVM configuration? Preferred OS? Network topology (load balancer, LAN/WAN, etc.)?

Your feedback is very important and will help ensure that this new clustering solution will be a robust and stable component in the next Openfire release.


Those who have wrestled with the existing clustering plugin will hopefully find the new solution to be much simpler to configure and deploy ... and certainly much lower cost! There is a README file included with the new Hazelcast plugin that documents the basic steps for setting up an Openfire cluster, including links to the supporting Hazelcast documentation (if needed).


Testing ... Testing ... Is this thing on?


Please take the new build for a spin and report your feedback here. We will be posting an article to the main community page before long, but would love to have some initial feedback from the core developers before engaging a wider audience. No doubt there will be some bugs and configuration glitches ... can you help us find and fix them?


Thanks in advance for your consideration and assistance.


Cross posted from




I have added a slighlty modified version of hazelcast that is backwards compatible with Openfire 3.6.4 and Openfire 3.7.1. Unzip and copy the clustering.jar file to your plugins folder.


Please test and post your results at