Wednesday, November 3, 2010

Rediscover SOA with WSO2 Carbon & WS-Discovery

Written by Hiranya Jayathilaka

One of the hottest features of new WSO2 Carbon 3.0 based releases is the out-of-the-box WS-Discovery support. WS-Discovery is a standard protocol for discovering services and service endpoints. This enables service clients to search for services based on a given criteria and bind with the discovered services. The WS-Discovery specification defines two modes of operation:
1. Adhoc mode
In the adhoc mode, servers advertise the services they have using a UDP multicast protocol. Similarly client applications can search for available services by sending out probe requests over UDP multicast. Servers listening for such probe requests can then send the service information to the client over a unicast channel.
2. Managed mode
In the managed mode, servers and clients use an intermediary known as the discovery proxy for all service discovery purposes. Servers will register the available services with the discovery proxy by sending notifications over HTTP. Then clients can directly probe the discovery proxy to discover the registered services. This mode of operation does not use UDP multicast for any sort of communication. All interactions take place over regular HTTP channels and if needed, HTTPS can be used to provide transport level security.
Starting from version 3.0, WSO2 Carbon framework has full support for WS-Discovery managed mode. The following products ship the necessary WS-Discovery libraries with them by default:
WSO2 G-Reg has the ability to act as a discovery proxy. This mode is enabled by default and user doesn't have to configure anything in the G-Reg side. In products like WSAS and DSS, WS-Discovery support should be manually enabled by pointing them to an already existing discovery proxy. Once configured, these server applications will automatically register the services they have with the discovery proxy. Service information will be synchronized with the discovery proxy at server start up, shutdown and service level updates. This ensures that the information in the discovery proxy are always up-to-date. WSO2 ESB can query one or more discovery proxy instances to find the necessary services and service endpoints. The ESB UI also enables creating proxy services and mediation endpoints using the discovered endpoints.
There are lot of other cool things you can do in Carbon platform with WS-Discovery. There are several plug-ins and extensions available to download and try out as well. I'm planning to post a series of blogs addressing various aspects of WS-Discovery in the next few months. So stay tuned! In the meantime read this article to learn how Jos Dirksen integrated Mule with WSO2 G-Reg using the WS-Discovery capabilities of Carbon framework.

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