Web Services Reliability Specification (WS-Reliability) Sunil Kunisetty Oracle Corp. Jacques Durand Fujitsu Software

What is WS-Reliability? Transport agnostic SOAP-based message protocol to send critical messages in a reliable way according to an agreed Quality of Service

Quality of Service (QoS) Guaranteed Delivery –Effort to deliver at least once, or notify failure No Duplicate Delivery –Guarantee to deliver at most once Exactly Once Delivery –Combining above two agreements Ordered Delivery –Messages delivered in the order they are sent

Why Reliable Messaging? Provide applications with “built in” reliability at the messaging layer, in the context of: –Multiple transports (reliable or not) –Loosely coupled services (SOA architecture) –One-way messages (MOM platforms)

Context and Status Open public standard process First version was announced in Jan 2003 –Oracle, Fujitsu, Sun, Sonic, Hitachi, NEC Submitted to OASIS WS Reliable Messaging TC (Feb 2003) –All major industry players were invited –SeeBeyond, HP, SAP, Nokia, Cyclone Commerce, webMethods, Choreology and few others joined Design validated by Implementations –5 companies implemented; 2 interop demos Working draft (v 0.51) in Sep 2003 Just wrapped up a Committee Draft (v 0.992)

Overview (1) Simple & Robust –Minimal set of ‘signals’ –Yet, supports varied use cases –Protocol survives ‘signal’ loss Deployment friendly –Accommodates Client firewall model –Works well with limited resource too Efficient persistence management model –Clear rules on Sender and Receiver sides

Overview (2) Open and Composable –Abstract “RM Agreement” can map to any policy representation. –WSDL extensions option for supported RM features –Supports SOAP 1.1 and SOAP 1.2 –Normative HTTP binding defined –Extensible for use with other public standards

RM Elements RequestResponse PollRequest wsrm : SequenceNum wsrm: MessageId wsrm : AckRequested wsrm:ReplyPattern wsrm : ExpiryTime wsrm : DuplicateElimination any wsrm : ReplyRange any wsrm : NonSequenceReplies wsrm : SequenceReplies wsrm:SequenceNumRange wsrm : RefToMessageIds wsrm: wsrm : MessageOrder any

Reply Patterns Response –RM-Reply (RM Acks and RM Faults) is sent back as a response in the same underlying connection –Primarily for WSDL 1.1 Request-Response Operations Callback –RM-Reply is sent as a request in a different connection –Primarily for WSDL 1.1 One-way Operations Poll –Scenarios: Behind the firewall Senders, Avoid retries, Thin client, Security constraints for Callback listeners –RM-Reply based on the a Poll Request

Fault Handling Robust fault handling mechanism –Mechanism to batch faults –Mechanism to send faults for Poll requests –Independent of SOAP Fault mechanism Fault Types –Message Format: Not well-formed headers –Message Processing: Processing errors Faults are non-critical signals –Loss of faults are not critical to the protocol

Message Management Messages: Either alone or in sequences (groups) Message Groups –Simple life-cycle mgmt. –No prior hand shaking & no extra ‘signals’ Group Termination options: –Timeouts (GroupMaxIdleDuration,GroupExpiryTime) –Message markers max sequence number)

RM Agreement (QoS) Defined abstractly, open to concrete representations by external policy or agreement mark-up Abstract Items: –GuaranteedDelivery, NoDuplicateDelivery, OrderedDelivery etc. Scopes –Per group, per message, per interaction Sender-side deployment only

Agreement Criteria Business requirements + Messaging constraints Who sets the RM Agreement parameters? –Business partners –RM Provider based on network conditions and load Parameters that affect the load / overhead –ReplyPattern –Resending Effort (number of retries, time interval) –Message ExpiryTime: date/time after which a message can be dropped

QoS Representation The Challenge –Representation of QoS features supported by a WS need be standardized for interoperability –Many proprietary choices, but none usable in an Royalty Free OASIS specification - TODAY Option: Define a simple & an efficient model using extensible mechanism in WSDL –Atomic QoS Properties –Plus basic composition All, Choice, One-or-More, & Zero-or-More

An Example open.org/committees/wsrm/schema/1.1/fnp/compositor/all open.org/committees/wsrm/schema/1.1/fnp/feature/rel true true

Summary Public Royalty Free specification Doesn’t depend on proprietary private specifications. Protocol is extensible and can work with other public specifications such as WS- Security Interoperable Proof of Concept implementations

Stand-out Features Simple, flexible, and fundamental persistence storage management model ‘Reply Patterns’ accommodating different deployment constraints & use cases Comprehensive Polling support Abstract RM Agreement –Sender-side deployment only –Simple and convenient WSDL representation option

Q & A