Web Services Reliability Specification (WS-Reliability)

Sunil KunisettyOracle Corp.

Jacques DurandFujitsu Software

What is WS-Reliability?

Transport agnostic SOAP-basedmessage 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

Request Response PollRequest

wsrm:SequenceNum

wsrm:MessageId

wsrm:AckRequested

wsrm:ReplyPattern

wsrm:ExpiryTime

wsrm:DuplicateElimination

any

wsrm:ReplyRange

any

wsrm:NonSequenceReplies

wsrm:SequenceReplieswsrm:SequenceNumRange

wsrm:RefToMessageIds

wsrm: http://www.oasis-open.org/committees/wsrm/schema/1.1/{SOAP1.1|SOAP1.2}

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 (@last=‘true’, 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<fnp:compositor uri=“

http://www.oasis-open.org/committees/wsrm/schema/1.1/fnp/compositor/all“>

<fmp:feature uri=“http://www.oasis-open.org/committees/wsrm/schema/1.1/fnp/feature/rel”>

<fnp:compositor uri=“http://www.oasis-open.org/committees/wsrm/schema/1.1/fnp/compositor/one-or-more”>

<fnp:property name=“wsrm:NoDuplicateDelivery”> <value>true</value> </fnp:property> <fnp:property name=“wsrm:GuaranteedDelivery”> <value>true</value> </fnp:property> </fnp:compositor> </fnp:feature></fnp:compositor>

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