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Showing posts from 2011

WS-Notification implementation

Since the early days, Apache ServiceMix has had an implementation of the Oasis WS-Notification specifications. This implementation was built on top of Apache ActiveMQ and available inside the JBI bus as a service. Now that JBI is being put aside in ServiceMix, some questions arose about the future of this component.

So last week, I took a stab at rewriting the component using pure JAX-WS services. For those that are not familiar with WS-Notification, this specification, unlike most other WS-* specifications defines a service described by a WSDL, so there's no low level protocol implementation to write. I took most of the code from ServiceMix implementation and just rewrote the JBI specific bits to leverage JAX-WS instead.

The results have been committed into Apache CXF and should be part of the upcoming 2.5 release. Note that the implementation itself does not require CXF, though it can very well use it as the JAXWS provider.

If you want to give it a try, you need to build CX…

Distributed OSGi in Fabric

The Remote Services OSGi specification describes how services registered in an OSGi framework can be transparently accessed from another OSGi framework. This is in essence a remoting capability for OSGi services. Fabric has a very fast implementation of this specification, leveraging ZooKeeper for the discovery of services.

From the user point of view, registering a service with a property service.exported.interfaces (with a value of ‘*’ or a list of classes to expose) is the only thing to do to make a service available from the outside. The Fabric DOSGi implementation will automatically detect which services have to be imported and will automatically create a proxy in the OSGi registry for those needed. This services to be imported are found through the use of Service Hooks which enable the implementation to be aware of which services are required by existing bundles. For example, if a bundle registers a ServiceListener (directly or indirectly by using Blueprint for example), t…

Provisionning with Fabric

Already, one month since my last blog entry, but time as been flying with the birth of my son Arthur a few weeks ago. I'd like to talk about the provisioning mechanism of Fabric a bit.

In my last post, I explained how configuration was done through the use of ZooKeeper as the repository for configurations and profiles, propagated to various bundles using the OSGi ConfigurationAdmin service. The provisioning mechanism in Fabric is based on this mechanism: the fabric-agent bundle receives its configuration through the org.fusesource.fabric.agent pid and will automatically update bundles as needed. The nice thing is that the configurations are computed using an overlay mechanism which means that the list of bundles or features to deploy will come from the various profiles a give node has been assigned.

The agent itself supports several kinds of informations:
bundles that need to be installedkaraf features that need to be installedrepositories for karaf featuresa url pointing to the…

Configuration with FuseSource Fabric

From a high level, ZooKeeper can be seen as a replicated tree, and Fabric uses this tree to store the configuration of the various agents (we call Agent, any Karaf instance connected to the same Fabric cluster).

Fabric defines a notion of profile, which is a "kind" of agent. We can define different profiles for various applications we want to deploy in Karaf, for example an ActiveMQ broker or a web server. A given agent can be assigned multiple profiles, allowing a single Karaf instance to serve multiple purposes.

To configure a Karaf instance, Fabric uses the ConfigAdmin OSGi service which is the standard way to push configurations to OSGi applications. An agent will have a bundle deployed which will monitor the ZooKeeper tree and update the configurations according to the profiles it has been assigned. Each bundle will then automatically be notified of the changes through the ConfigAdmin service.

It is often the case that configurations are mostly the same between several …

Introducing FuseSource Fabric

I'm very pleased to introduce FuseSource Fabric, a distributed configuration, management and provisioning system for the products supported by FuseSource: Apache ServiceMix, Apache Camel, Apache ActiveMQ and Apache CXF.

The user's guide contains lots of informations, so I won't rewrite it all again, but I instead invite you to have a quick look at it. The core Fabric is deployed on top of Apache Karaf and heavily reuses the very mature Apache ZooKeeper project.

I'm really excited about Fabric. I've been working on it since Apache Karaf 2.2.0 has been released and I'm glad to share this work. I won't add much more for now, but stay tuned as I plan to write a number of posts explaining the various parts of Fabric.

CamelOne conference

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I just want to point out the great conference FuseSource is sponsoring around open source integration and especially Apache Camel. Unfortunately, I won't be able to attend the event as my wife is expecting our sixth child in the coming weeks :-). That would have been a great opportunity to have my copy of the EIP book signed by Gregor though.
You should definitely go there and listen to all the great speakers. Click on the image below for more informations.