WS Coordination

1. WS Coordination Nurhak Karakaya & Murat Çavdar

2. Why WS Coordination? • Web services bind a large number of participants that forms large distributed computational units , we call these units as activities. • These activities are often complex in structure, and the execution of such activities often takes a long time to complete their tasks. • WS Coordination specification defines an extensible framework for coordinating activities to reduce complexity of web services.

3. What is WS Coordination • WS-Coordination is a proposed IT industry standard for how individual Web Services can interact to accomplish an application task • WS-Coordination is one of a series of specifications from an industry group that includes IBM, Microsoft, and BEA Systems • WS-Coordination provides standard mechanisms to create and register services.

5. WS Coordination Model • The Coordination Framework supports the following services : • Activation Service to create an activity. • Registration Service to coordinate protocol selection and register participants. • Coordination Service for activity completion processing.

6. Illustration of Framework

7. Illustration of Framework (2) • Applications use the Activation service to create the coordination context. • The context contains the necessary information to register into the activity specifying the coordination behavior that the application will follow. • An application that receives a coordination context may use the Registration service of the original application or may use another coordinator’s service.

8. An overview of WS-Coordination

9. Activation Service • The Activation service creates a new activity and returns its coordination context. • An application sends: • CreateCoordinationContext • An activation service returns • CreateCoordinationContextResponse

10. CreateCoordinationContext

11. CreateCoordinationContext(2) • CoordinationType: This provides the unique identifier for the desired coordination type for the activity. • Expires: The expiration for the returned CoordinationContext expressed as an unsigned integer in milliseconds.This is optional. • CurrentContext: This may be used for variety of purposes including recovery. • We can declare any attribute or elements to convey additional information.This option increases our flexibility.

12. CreateCoordinationContextResponse

13. CreateCoordinationContextResponse(2) • CoordinationContext: This is the created coordination context. • We can declare any attribute or elements to convey additional information.This option increases our flexibility.

14. Response Example:

15. Registration service • Defines a Register operation that allows a Web service to register to participate in a coordination protocol. • The registration process identifies the specific protocol used for activity coordination.

16. The usage of Endpoint Reference

17. The usage of Endpoint Reference(2) • 1. The Register message targets this Endpoint reference and includes the participant protocol service Endpoint reference as a parameter • 2. The RegisterResponse includes the coordinator’s protocol service Endpoint reference • 3. & 4. At this point both sides have the end point references of the other’s protocol service, so the protocol messages can target the other side.

18. Coordination service • The coordination service controls the activity completion processing for the registered Web services using the selected coordination protocol

19. Coordination Faults • WS-Coordination faults must include as the property the following fault action URI: http://schemas.xmlsoap.org/ws/2004/10/wscoor/fault • The definitions of faults in this section use the following properties: • [Code] The fault code. • [Subcode] The fault subcode. • [Reason] The English language reason element. • [Detail] The detail element. If absent, no detail element is defined for the fault.

20. Fault Example

21. Fault Types • Invalid State: This fault is sent by either the coordinator or a participant to indicate that the endpoint that generates the fault has received a message that is not valid for its current state. This is an unrecoverable condition. • Invalid Protocol: This fault is sent by either the coordinator or a participant to indicate that the endpoint that generates the fault received a message from an invalid protocol. This is an unrecoverable condition.

22. Fault Types(2) • Invalid Parameters: This fault is sent by either the coordinator or a participant to indicate that the endpoint that generated the fault received invalid parameters on or within a message. This is an unrecoverable condition. • No Activity: This fault is sent by the coordinator if the participant has been quiet for too long and is presumed to have ended.

23. Fault Types(3) • Context Refused: This fault is sent to a coordinator to indicate that the endpoint cannot accept a context which it was passed: • Already Registered: This fault is sent to a participant if the coordinator detects that the participant attempted to register for the same protocol of the same activity more than once.

24. References • http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnglobspec/html/ws-coordination.asp • http://www.ibm.com/developerworks/library/ws-coor/ • http://ftpna2.bea.com/pub/downloads/ws-standards-coordination.pdf • http://www.serviceoriented.org/ws-coordination.html

25. Questions?