Binding- and Port-Agnostic Service Composition using a P2P SOA

Abstract

The assumption of the availability of port information at design time of service compositions in Service-Oriented Architectures (SOAs) is not valid for an increasing number of hosts on the Internet that do not have a public, static IP address. Existing workflow engines do not support services deployed on such hosts, as service invocations require the availability of port information defined either in concrete WSDL definitions or within a deployment descriptor of the BPEL workflow engine. This paper presents a workflow engine that supports runtime look-up of service endpoints based on a P2P middleware. Using a service identifier based on a DHT identifier, Service Proxy objects that encapsulate port information are downloaded over the structured P2P network from the host where the service is deployed. A Service Proxy delegates service invocations to an abstract protocol adaptor framework that uses dynamic invocation mechanisms to provide a protocol-independent execution of remote services, e.g., over GIOP/IIOP or SOAP. This allows us to specify binding- and port-agnostic service compositions in BPEL using abstract WSDL and our service identifiers. To validate our approach, we extended the ActiveBPEL workflow engine to support the discovery and consumption of services using our P2P middleware and the abstract protocol adaptor.