Web Services Reliability Specification (WS-Reliability)

1
Web Services Reliability Specification
(WS-Reliability)

• Sunil Kunisetty
• Oracle Corp.
• Jacques Durand
• Fujitsu Software

2
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

3
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

4
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)

5
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)

6
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

7
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

8
RM Elements
Request
Response
PollRequest
wsrmMessageId
wsrmRefToMessageIds
wsrmNonSequenceReplies
wsrmSequenceNum
wsrmSequenceNumRange
wsrmSequenceReplies
wsrmExpiryTime
wsrmReplyRange
any
wsrmReplyPattern
any
wsrmAckRequested
wsrmDuplicateElimination
wsrmMessageOrder
any
wsrm http//www.oasis-open.org/committees/wsrm/sc
hema/1.1/SOAP1.1SOAP1.2
9
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

10
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

11
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 (_at_lasttrue, max sequence
  number)

12
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

13
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

14
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

15
An Example

• ltfnpcompositor urihttp//www.oasis-open.org/com
  mittees/wsrm/schema/1.1/fnp/compositor/allgt
• ltfmpfeature urihttp//www.oasis-open.org/comm
  ittees/wsrm/schema/1.1/fnp/feature/relgt
• ltfnpcompositor urihttp//www.oasis-open.org
  /committees/wsrm/schema/1.1/fnp/compositor/one-or-
  moregt
• ltfnpproperty namewsrmNoDuplicateDeliver
  ygt
• ltvaluegttruelt/valuegt
• lt/fnppropertygt
• ltfnpproperty namewsrmGuaranteedDeliver
  ygt
• ltvaluegttruelt/valuegt
• lt/fnppropertygt
• lt/fnpcompositorgt
• lt/fnpfeaturegt
• lt/fnpcompositorgt

16
Summary

• Public Royalty Free specification
• Doesnt depend on proprietary private
  specifications.
• Protocol is extensible and can work with other
  public specifications such as WS-Security
• Interoperable Proof of Concept implementations

17
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

18

• Q A