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), the Fabric DOSGi implementation will check if there is a local service satisfying the listener and if there’s none, it will look into the ZooKeeper registry and import a matching service.

The Fabric implementation is based on the insanely fast HawtDispatch library which has a very nice support for NIO. The result is a very fast remoting mechanism for OSGi with more than 25.000 requests per second on my laptop. This remoting mechanism is actually not dependant on OSGi and external clients can also connect to a remote OSGi service provided they can find the service identifier from ZooKeeper or some other place.

A complete example can be found in the Fabric source tree at on github.

Comments

ML said…
The example is now at:

https://github.com/fusesource/fuse/tree/master/fabric/fabric-examples/fabric-camel-dosgi

Popular posts from this blog

SSH Server in Java

ServiceMix Kernel is a small container based on OSGi. The latest release allows external clients to connect to it and issue commands using a simple protocol implemented on top of TCP or SSL. However, this remoting protocol has some drawbacks as the internals makes it unable to do another remote login from a remote session. In addition to that, completion and history do not really work great. So I've been thinking about using the SSH protocol, which is widely used, secured, with tons of different clients available. Unfortunately, no SSH server is available in Java. Over the past weeks, I've been working on implementing this SSH server, based on the IEFT specifications, the JSch SSH client library, and the OpenSSH server source code. The server itself is based on Apache Mina which is a great framework for using NIO. The project is available at http://code.google.com/p/sshd/ and although there are lots of limitations right now, the basics of the SSH protocol work. I plan t...

Apache Karaf

ApacheCon was really interesting this year! Recently, a lot of people have expressed a real interest in ServiceMix Kernel , our generic OSGi distribution for server side applications. We've been discussing moving this subproject into Apache Felix for several reasons: raise the visibility and awareness on ServiceMix Kernel attract a broader community Several Apache projects are planning to use ServiceMix Kernel as their container: this includes Apache James , Apache Directory and Apache ActiveMQ . The Apache Sling community is also willing to contribute to this effort along with some other groups like the OPS4J project. During this discussion, a name as been proposed by Jamie Goodyear: Apache Karaf . A carafe is a small container used for serving wine and other drinks (http://en.wikipedia.org/wiki/Carafe). In similarity to the name the Kernel allows applications to be more easily handled, and improves their characteristics (much like a bottle of wine left to breath in a dec...

Camel Endpoint DSL

Camel Endpoint DSL One of the new features of Camel 3.0  is an Endpoint DSL.  This new API aims to provide a type safe replacement for the URLs that are used in Camel to designate the consumer or producer endpoints.  These URLs provide 3 things: the scheme of the URL identifies the component to use, a unique name or id for the endpoint, and a set of parameters to customize the endpoint behavior. Here is an example of an FTP consumer endpoint definition: from( "ftp://foo@myserver?password=secret& recursive=true& ftpClient.dataTimeout=30000& ftpClientConfig.serverLanguageCode=fr" ) .to( "bean:doSomething" ); There are several drawbacks with such constructs : no type safety, bad readability and no simple completion. So we now use the meta model, which is currently extracted from the source using an annotation processor and written in various JSON files, to generate a fluent DSL for each endpoint.  The same...