UKOUG 2011 - Effective Fault Handling in Oracle SOA Suite 11g

WELCOME Effective Fault Handling in Oracle SOA Suite 11g Guido Schmutz (Trivadis) Ronald van Luttikhuizen (Vennster) UKOUG Conference 2011 6.12.2011BASEL BERN LAUSANNE ZÜRICH DÜSSELDORF FRANKFURT A.M. FREIBURG I.BR. HAMBURG MÜNCHEN STUTTGART WIEN 2011 © Trivadis, Vennster 1 Effective Fault Handling in Oracle SOA Suite 11g 06.12.2011

Guido Schmutz• Working for Trivadis for more than 15 years• Oracle ACE Director for Fusion Middleware and SOA• Co-Author of different books• Consultant, Trainer Software Architect for Java, Oracle, SOA and EDA• Member of Trivadis Architecture Board• Technology Manager @ Trivadis• More than 20 years of software development experience• Contact: guido.schmutz@trivadis.com• Blog: http://guidoschmutz.wordpress.com• Twitter: gschmutz 2011 © Trivadis, Vennster

Ronald van Luttikhuizen• Managing Partner at Vennster• Oracle ACE Director for Fusion Middleware and SOA• Author of different articles, co-author Oracle SOA Book 11g book• Upcoming book SOA Made Simple• Architect, consultant, trainer for Oracle, SOA, EDA, Java• More than 10 years of software development and architecture experience• Contact: ronald.van.luttikhuizen@vennster.nl• Blog: blog.vennster.nl• Twitter: rluttikhuizen 2011 © Trivadis, Vennster

Agenda1. What is Fault Handling2. Fault Handling in SOA vs. traditional systems3. Scenario and Patterns4. Implementation of Scenario5. Summary and Best Practices 2011 © Trivadis, Vennster4 Effective Fault Handling in Oracle SOA Suite 11g 06.12.2011

Error/Fault Handling• The goal of every programmer should be to write unbreakable software• Extent of achievement depends on how good expected and unexpected exception conditions are handled and managed• Object-oriented languages such as C++ and Java provide an efficient way for handling exceptions using constructs such as try, catch, and finally.• With a SOA, most of what is available at language level is still valid and usable• SOA raises different challenges once starting orchestrating services and creating composite applications• Prevention vs. handling 2011 © Trivadis, Vennster5 Effective Fault Handling in Oracle SOA Suite 11g 06.12.2011

What is a Fault ? Something outside normal operational activity or “happy flow” happened  Technical error  Programming error  Faulty operation by user  Exceptional business behavior 2011 © Trivadis, Vennster Effective Fault Handling in Oracle SOA Suite 11g 06.12.2011

Two Types of FaultsBusiness faults Faults that service clients can expect and recover from Failure to meet a particular business requirement Often: expected, business value, contractual and recoverableTechnical faults Faults that service clients do not expect and cannot (easily) recover from Results of unexpected errors during runtime, e.g. null pointer errors, resources not available, and so on Often: unexpected, technical, implementation and non-recoverable 2011 © Trivadis, Vennster Effective Fault Handling in Oracle SOA Suite 11g 06.12.2011

Business Fault<wsdl:operation name=“orderProduct”> <wsdl:input message=“order:OrderProductRequestMessage"/> <wsdl:output message=“order:OrderProductResponseMessage"/> <wsdl:fault message=“order:ProductNotInStockFaultMessage" 1. Service contract including fault name=“ProductNotInStockFault"/> <wsdl:fault message=“order:CustomerNotFoundFaultMessage" name=“CustomerNotFoundFault"/></wsdl:operation><xsd:element name=“CustomerNotFoundFaultMessage”> <xsd:complexType> <xsd:sequence> 2. Fault message payload <xsd:element name=“CustName” type=“xsd:string”/> <xsd:element name=“City” type=“xsd:string”/> </xsd:sequence> </xsd:complexType></xsd:element> 2011 © Trivadis, Vennster Effective Fault Handling in Oracle SOA Suite 11g 06.12.2011

Business Fault (II) <soap:Envelope> 3. Actual service response <soap:Header/> <soap:Body> <soap:Fault> <faultcode>CST-1234</faultcode> <faultstring>Customer not found</faultstring> <detail> <CustomerNotFoundFault> <CustName>John Doe</CustName> <City>Long Beach</City> </CustomerNotFoundFault> </detail> </soap:Fault> </soap:Body> </soap:Envelope> 2011 © Trivadis, Vennster Effective Fault Handling in Oracle SOA Suite 11g 06.12.2011

Technical Fault<wsdl:operation name=“orderProduct”> <wsdl:input message=“order:OrderProductMessage"/> <wsdl:output message=“order:OrderProductResponseMessage"/> <wsdl:fault message=“order:ProductNotInStockFaultMessage" name=“ProductNotInStockFault"/> 1. Service contract <wsdl:fault message=“order:CustomerNotFoundFaultMessage" including fault name=“CustomerNotFoundFault"/></wsdl:operation> 2. Actual service response<soap:Envelope> <soap:Header/> <soap:Body> <soap:Fault> <faultcode>S:Server</faultcode> <faultstring>Could not connect to URL 127.0.0.1 on port 8001</faultstring> </soap:Fault> </soap:Body></soap:Envelope> 2011 © Trivadis, Vennster Effective Fault Handling in Oracle SOA Suite 11g 06.12.2011

Fault Handling SOA vs. traditional Higher degree of complexity BPM/BPEL User Interface Multiple service consumers Services part of larger unit Heterogeneous & external ESB components Long running processes Implemen- Implemen- Implemen- Asynchronous tation tation tation Timed events Often enterprise-wide Transactions 2011 © Trivadis, Vennster Effective Fault Handling in Oracle SOA Suite 11g 06.12.2011

Scenario (Areas of Problems/Faults) Old System with limited scalability Short Network interruptions No 7*24 avail. for single instance ofSync vs Async visa Processing Only reachable by queuing Response sometimes get lost Fault if product is no longer avail Not always available 2011 © Trivadis, Vennster Effective Fault Handling in Oracle SOA Suite 11g 06.12.2011

Fault Recovery StrategiesInaction – ignore the requestBalk – admit failureGuarded suspension – suspend execution until conditions for correctexecution are establishedProvisional action – pretend to perform the request, but do not commituntil success is grantedRecovery – perform an acceptable alternative 2011 © Trivadis, Vennster Effective Fault Handling in Oracle SOA Suite 11g 06.12.2011

Fault Recovery StrategiesRollback – try to proceed, but on failure, undo the effects of a failedactionRetry – repeatedly attempt a failed action after recovering from failedattemptsAppeal to higher authority – ask someone to apply judgment andsteer the software to an acceptable resolutionResign – Minimize damage, write log information, then signal definite andsafe failure 2011 © Trivadis, Vennster Effective Fault Handling in Oracle SOA Suite 11g 06.12.2011

Patterns for Fault Tolerant SoftwareCompensationException shielding(Limit) RetryShare the loadAlternativeException handlerHeartbeatThrottling 2011 © Trivadis, Vennster Effective Fault Handling in Oracle SOA Suite 11g 06.12.2011

Implementation of Scenario 2011 © Trivadis, Vennster Effective Fault Handling in Oracle SOA Suite 11g 06.12.2011

Product ManagementResult Caching Result CacheProblem Not to overload the old, non-scalable product system with the new demandSolution Use Result Caching to cache the product information (read-only operation) Use Service Throttling to limit the number of concurrent requests 2011 © Trivadis, Vennster Effective Fault Handling in Oracle SOA Suite 11g 06.12.2011

Product ManagementResult CachingResults are returned from cache rather than invoking alwaysthe external service Product data is rather static, so ideal candidate for caching Proxy Business 1 Product DB Service Service 2 3 Result Cache OSB 2011 © Trivadis, Vennster Effective Fault Handling in Oracle SOA Suite 11g 06.12.2011

Product ManagementService Throttlingrestricts the number of messages on the message flow to abusiness service Message Buffer Proxy Business Product Service Service DBOSB Set from Operational Settings on the OSB console 2011 © Trivadis, Vennster Effective Fault Handling in Oracle SOA Suite 11g 06.12.2011

Credit Card BookingRetry Configuration RetryProblem Unstable network between us and the external servicesSolution Use Retry mechanism of OSB to try many times No Fault Management necessary for service consumer if network interruption is only for a short time 2011 © Trivadis, Vennster Effective Fault Handling in Oracle SOA Suite 11g 06.12.2011

Credit Card BookingRetry ConfigurationConfigured on the business service in OSB 1 Proxy Business after 2s Visa Service Service Service 2OSB 5x 2011 © Trivadis, Vennster Effective Fault Handling in Oracle SOA Suite 11g 06.12.2011

Credit Card BookingService Pooling Service PoolingProblem Visa Service does not guarantee 7*24 availability for one single instanceSolution Use the multiple instances (endpoints) visa provides and use service pooling feature of OSB No Fault Management for the service consumer if at least one endpoint is available 2011 © Trivadis, Vennster Effective Fault Handling in Oracle SOA Suite 11g 06.12.2011

Credit Card BookingService Pooling Visa Service 1 Proxy Business Visa Service 2 Service ServiceOSB Visa Service 3 2011 © Trivadis, Vennster Effective Fault Handling in Oracle SOA Suite 11g 06.12.2011

Order ManagementTransaction configuration Transaction of OSB Service Consumer Transaction of OSB Service ConsumerProblem Guarantee that the message will be delivered to the order management systemSolution Make sure that queues are available, even if the Handle Order system is not Make sure that queuing run‟s in the same transaction as the service consumer 2011 © Trivadis, Vennster Effective Fault Handling in Oracle SOA Suite 11g 06.12.2011

Order Management (II) Fault Message on Callback ContractFault Message onCallback Contract Problem  Need to return a Product No Longer Available Business Fault over an Asynchronous MEP Solution  Design a separate Fault Message and Operation on the Callback contract (WSDL) and use that 2011 © Trivadis, Vennster Effective Fault Handling in Oracle SOA Suite 11g 06.12.2011

Order Management (II)Fault Message on Callback Contract“Business Fault” modeled as another operation on the Callback WSDL 2011 © Trivadis, Vennster Effective Fault Handling in Oracle SOA Suite 11g 06.12.2011

Order HistoryFault Management Framework Use Fault Policy Management In Mediator to configure retryProblem Order History System not available should have no impact on Business ProcessSolution Use Mediator with Fault Management Framework to configure retry independent of availability of Order History Web Service 2011 © Trivadis, Vennster Effective Fault Handling in Oracle SOA Suite 11g 06.12.2011

Order HistoryFault Management Framework<faultPolicyBindings version="2.0.1" <composite faultPolicy=“OrdderProcessingFaults"/></faultPolicyBindings><faultPolicies> <faultPolicy version="2.0.1" id=“OrderProcessingFaults“...> <Conditions> <action ref=“ora-retry”/> </Conditions> <Actions> <Action id="ora-retry"> <Retry> <retryCount>3</retryCount> <retryInterval>2</retryInterval> <exponentialBackoff/> <retryFailureAction ref="ora-java"/> <retrySuccessAction ref="ora-java"/> </Retry> </Action> </Actions> </faultPolicy></faultPolicies> © Trivadis, Vennster 2011 Effective Fault Handling in Oracle SOA Suite 11g 06.12.2011

Order Handling ProcessReturn Errors as synchronous response Problem  Both Product Management and Credit Card Booking Fault Handling can return Business Faults Solution Fault Handling  Handle errors and map them to errors returned to theReply with Fault service consumer (i.e. the caller of the process)  After that process changes from synchronous to asynchronous 2011 © Trivadis, Vennster Effective Fault Handling in Oracle SOA Suite 11g 06.12.2011

Order Handling ProcessReturn Errors as synchronous responseHandle Business Faults in BPEL error handler and reply with anerror 2011 © Trivadis, Vennster Effective Fault Handling in Oracle SOA Suite 11g 06.12.2011

Order Handling Process (II)Handle missing callback message with timeout Problem  Order Processing Response Message can get lost in the Order Processing system, i.e. the callback message will never arrive in BPEL Solution  Timeout on the Wait For Answer with a BPEL pick activity with a timeout Pick with timeout  Undo the process by doing compensation  Use the BPEL compensate activity together with Compensate compensation handler to undo the Booking of the Credit Card 2011 © Trivadis, Vennster Effective Fault Handling in Oracle SOA Suite 11g 06.12.2011

Order Handling Process (II)Handle missing callback message with timeoutPick Activity for handling callbackmessage with timeout branch c 2011 © Trivadis, Vennster Effective Fault Handling in Oracle SOA Suite 11g 06.12.2011

Order Handling Process (III)Compensation Handling Problem  Order Processing Callback Message can be a Product No Longer Available Business Fault Compensation Handler Solution  Undo the process by doing compensation  Use the BPEL compensate activity together with compensation handler to undo the Booking of the Credit Card Handle Business Fault and Compensate 2011 © Trivadis, Vennster Effective Fault Handling in Oracle SOA Suite 11g 06.12.2011

Order Handling Process (III)Compensation HandlingCompensate activity invokes compensationhandling on the inner scope• Can only be invoked from within a fault handler or another compensation handler 2011 © Trivadis, Vennster Effective Fault Handling in Oracle SOA Suite 11g 06.12.2011

Order Handling Process (V)Generic Error Handler w. Fault Policy Framework Problem  Unexpected (technical) fault  Multiple processes deal with unexpected faults in their own wayUnexpected (technical) error Solution  Use fault handler mechanism to enqueue on error queue without adding process logic  Create one process to listen to error queue and handle faults  Retrieve process information by using (composite) sensors 2011 © Trivadis, Vennster Effective Fault Handling in Oracle SOA Suite 11g 06.12.2011

Order Handling Process (V)Generic Error Handler w. Fault Policy FrameworkExplanation and demo of generic fault handler 2011 © Trivadis, Vennster Effective Fault Handling in Oracle SOA Suite 11g 06.12.2011

SummaryIssue Solution ProductOverloading product management system ThrottlingResult cache OSBVisa Service does not guarantee 7*24 uptime Muliple endpoints OSBdue to e.g. network problems Service poolingGuarantee message delivery to order Availability of queues OSB (and SOA Suitemanagement system Enqueue and dequeue in for XA propagation to service consumer transaction OSB)Returning business fault over async MEP from Separate operation and fault OSB and SOA Suiteorder management system message (callback contract between the two)Order history service not available Retry in Mediator using fault SOA Suite policy frameworkBusiness fault handling from service to process Catch faults in process and OSB and SOA Suiteto consumer reply fault to consumer (correct contracts)Detect missing response message Timeout in pick activity SOA SuiteHandle product no longer available Compensation SOA SuiteAvoid calling credit card booking twice Set non-idempotent property SOA SuiteProcesses needing to deal with unexpected Fault policy frameworks, error SOA Suitetechnical faults. All processes solving it in their queue, generic error handler &own way using process logic. (composite sensors. 2011 © Trivadis, Vennster Effective Fault Handling in Oracle SOA Suite 11g 06.12.2011

Summary & Best PracticesDifferentiate between business and technical faultsDesign service contracts with faults in mind: formally describe businessfaults in service contractsDon„t use exceptions as goto‟sDesign with criticality, likeliness to fail, and cost in mindDifferentiate fault patterns in OSB and BPM/BPEL: OSB: Retry, Throttling, transactions BPM/BPEL: Compensation, business fault handling, generic fault handler, timeoutHandle unexpected errors genericallyMake services autonomousFault-handling on scope of services and in wider perspective 2011 © Trivadis, Vennster Effective Fault Handling in Oracle SOA Suite 11g 06.12.2011

Thank You! Trivadis AG Guido Schmutz guido.schmutz@trivadis.com Vennster Ronald van Luttikhuizen ronald.van.luttikhuizen@vennster.nlBASEL BERN LAUSANNE ZÜRICH DÜSSELDORF FRANKFURT A.M. FREIBURG I.BR. HAMBURG MÜNCHEN STUTTGART WIEN 2011 © Trivadis, Vennster 46 Effective Fault Handling in Oracle SOA Suite 11g 06.12.2011

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UKOUG 2011 - Effective Fault Handling in Oracle SOA Suite 11g

by Ronald van Luttikhuizen

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