dependable web service compositions usng a semantic replication scheme laboratÓrio de sistemas...
TRANSCRIPT
Dependable Web Service Compositions usng a
Semantic Replication Scheme
LABORATÓRIO DE SISTEMAS DISTRIBUÍDOS – LASID
DEPARTAMENTO DE CIÊNCIA DA COMPUTAÇÃO - DCC
UNIVERSIDADE FEDERAL DA BAHIA - UFBA
SBRC 2008
Raimundo José de Araújo Macêdo2Daniela Barreiro Claro1
1. Dr. Daniela Barreiro Claro is supported by FAPESB (BOL2071/2006).2. Prof. Raimundo José de Araujo Macêdo is supported by FAPESB and CNPQ(Edital Universal).
Outline
MotivationDependability requirements for WSCThe SAREK approachExperimental testsPerformance evaluationComparison with related workConclusion and future directions
Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a [email protected] [email protected] Semantic Replication Scheme 2
Experimental TestsPerformance EvaluationComparison with Related WorkConclusion
OutlineMotivation
Properties for WSCSAREK approach
Motivation
Web services are autonomous applications that can be published, located and invoked over the Internet.
Due to their potential for heterogeneous integration, companies are implementing their business as a Web service format.
However, a single Web service cannot fulfill a user request and need to be combined.
Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a [email protected] [email protected] Semantic Replication Scheme 3
Experimental TestsPerformance EvaluationComparison with Related WorkConclusion
OutlineMotivation
Properties for WSCSAREK approach
Motivation
Whereas WS specifications cover dependable issues, no one handles the problem of dependable and automatic Web service compositions.
This raises another problem: a single WS failure, thus the failure of the whole composition.
Availability or continuity of service must be taken into account to apply WSC in critical applications.
Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a [email protected] [email protected] Semantic Replication Scheme 4
Experimental TestsPerformance EvaluationComparison with Related WorkConclusion
OutlineMotivation
Properties for WSCSAREK approach
Motivation
A commonly used technique for improving availability is to replicate services.
This work tackles the problem of dependability requirements of WSC, using ontologies to form a set of semantically alike replicas.
We propose a framework SAREK where a failure of a primary service can be masked by the execution of another service semantically compatible.
Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a [email protected] [email protected] Semantic Replication Scheme 5
Experimental TestsPerformance EvaluationComparison with Related WorkConclusion
OutlineMotivation
Properties for WSCSAREK approach
Required Properties for WSC
Some kinds of faults should be treated by a fault tolerant mechanism in order to reach the goal of a WSC.unavailability of a Web servicepartially operational WS Internet disconnections
Some mechanisms have been introducedFT-SOAP, WS-Reliability, WS-Replication, etc
Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a [email protected] [email protected] Semantic Replication Scheme 6
Experimental TestsPerformance EvaluationComparison with Related WorkConclusion
OutlineMotivation
Properties for WSCSAREK approach
Required Properties for WSC
Data ConsistencyWSC should guarantee the integrity of data in its
executionComputation Availability
It is not possible to assume that all WS in a composition are reliable. A WSC should guarantee availability without knowing the reliability level of single WS
ScalabilityWSC ability to handle a growing amount of WS
TransparencyWS is included and removed from a composition in
a transparent way
Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a [email protected] [email protected] Semantic Replication Scheme 7
Experimental TestsPerformance EvaluationComparison with Related WorkConclusion
OutlineMotivation
Properties for WSCSAREK approach
The SAREK approach
System model and assumptions A set of activities m is the
number of activities. A set of services n is the number
of services. Candidate services is a subset of Service for a
specific activity A composition C is a sequence of activities
performed by a set of services
WS are implemented as processes Channels are assumed to be reliable
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Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a [email protected] [email protected] Semantic Replication Scheme 8
Experimental TestsPerformance EvaluationComparison with Related WorkConclusion
OutlineMotivation
Properties for WSCSAREK approach
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The SAREK Approach
SAREK is a modified and enhanced version of SPOC1
SAREK is divided into two modulesThe Planner Module
Aims to automatically determine the activities for a given composition
The Executor ModuleAims to execute the composition defined by the Planner
Both modules are replicated using a passive replication mechanism.
Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a [email protected] [email protected] Semantic Replication Scheme 9
Experimental TestsPerformance EvaluationComparison with Related WorkConclusion
OutlineMotivation
Properties for WSCSAREK approach
1. Claro D.B, Albers P. And Hao, J-K. A framework for automatic composition of RFQ Web services. In IEEE SCW/ WSCA-ICWS, Salt Lake City, USA. 2007
Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a [email protected] [email protected] Semantic Replication Scheme 10
Experimental TestsPerformance EvaluationComparison with Related WorkConclusion
OutlineMotivation
Properties for WSCSAREK approach
The Planner Module
The Planner is divided into two main phases: Planning and Optimization
The Planning phase It uses an AI Planning algorithm based on preconditions
and effects Interacts with OPS (an OWL ontology) to discover
services Each WS is described using an OWL-S format This phase aims to determine which activity belongs to
the composition in order to fulfill the user request It main issue is the set of activities A that can reach the
given requestDaniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a
[email protected] [email protected] Semantic Replication Scheme 11
Experimental TestsPerformance EvaluationComparison with Related WorkConclusion
OutlineMotivation
Properties for WSCSAREK approach
The Planner Module
The Optimization phaseOptimizes the combination of WS and activitiesThe values used to optimize are based on estimated
values retrieved from each candidate Web service It seems a quotation systemProduces a set of semantic similar compositionsWe used a genetic algorithm called NSGA-II to get
the Pareto optimal solutions, i.e. the compositions
Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a [email protected] [email protected] Semantic Replication Scheme 12
Experimental TestsPerformance EvaluationComparison with Related WorkConclusion
OutlineMotivation
Properties for WSCSAREK approach
The Executor Module
This module executes the composition using the prefix mechanism
In order to provide fault tolerance both a transactional approach and a replication mechanism are applied.Semantic replication schemeTransactional Level
Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a [email protected] [email protected] Semantic Replication Scheme 13
Experimental TestsPerformance EvaluationComparison with Related WorkConclusion
OutlineMotivation
Properties for WSCSAREK approach
The Executor Module
Semantic replication schemeFaulty Web service can be replaced by a
semantically similar service (transparency property)
Kind of spatial redundancy, because there is a set of compositions that achieve the same goal.
The prefix approach increases performanceOnly the failed partition of the composition is re-
executed
and the prefix . It saves recovery time supposing that the service s3 failed.
321 ,, sssC
Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a [email protected] [email protected] Semantic Replication Scheme 14
Experimental TestsPerformance EvaluationComparison with Related WorkConclusion
OutlineMotivation
Properties for WSCSAREK approach
21, ss
The Executor Module
Transactional LevelTemporal redundancy mechanism, SAREK tries
one more time to recover from a possible transient fault
If the problem persists, and no other semantic similar composition can be replaced, SAREK roll back the previous executed Web serviceUsing ACID or a compensation technique
Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a [email protected] [email protected] Semantic Replication Scheme 15
Experimental TestsPerformance EvaluationComparison with Related WorkConclusion
OutlineMotivation
Properties for WSCSAREK approach
Experimental Tests
Case StudySAREK was applied to a bidding process for
repairing public buildings.
Prototype implementation of SAREK Java 1.5, Apache Tomcat 5.0, Axis 1.3, Jena API
2.3, OWL-S API 1.1.0 and MySQL Database 4.1Experiments were carried out in single computer
Inter motherboard Core Duo, processor T2300 1.66 Ghz and 1Gb of RAM.
Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a [email protected] [email protected] Semantic Replication Scheme 16
Experimental TestsPerformance EvaluationComparison with Related WorkConclusion
OutlineMotivation
Properties for WSCSAREK approach
Simulated scenario
4 activitiessupplyWood, supplyConcrete, supplyIron and
buildStaircase
Each activity can be performed by 2 candidate services
Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a [email protected] [email protected] Semantic Replication Scheme 17
OutlineMotivation
Properties for WSCSAREK approach
Experimental TestsPerformance EvaluationComparison with Related WorkConclusion
Simulated scenario
There is one WSDL operations for executionString executeWS()
Results were produced by 2 runsWithout failures
Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a [email protected] [email protected] Semantic Replication Scheme 18
Experimental TestsPerformance EvaluationComparison with Related WorkConclusion
OutlineMotivation
Properties for WSCSAREK approach
Simulated scenario
With failures (services 5, 3, 6 failed)
Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a [email protected] [email protected] Semantic Replication Scheme 19
Experimental TestsPerformance EvaluationComparison with Related WorkConclusion
OutlineMotivation
Properties for WSCSAREK approach
Performance Evaluation
Each experiment was run 400 times for calculating the average time and standard deviation
Two kinds of experimentsA composition is fixedA composition is randomly chosen
Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a [email protected] [email protected] Semantic Replication Scheme 20
Experimental TestsPerformance EvaluationComparison with Related WorkConclusion
OutlineMotivation
Properties for WSCSAREK approach
Performance Evaluation
The overhead caused by faults for an increasing the number of forced Web services failures.
Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a [email protected] [email protected] Semantic Replication Scheme 21
OutlineMotivation
Properties for WSCSAREK approach
Experimental TestsPerformance EvaluationComparison with Related WorkConclusion
Related Work
Comparison in the light of the required dependability properties for automatic WSC
Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a [email protected] [email protected] Semantic Replication Scheme 22
Experimental TestsPerformance EvaluationComparison with Related WorkConclusion
OutlineMotivation
Properties for WSCSAREK approach
Conclusion and future directions
Challenges for achieving Dependable Web service compositionsSuggesting a set of required dependability
properties.
To the best of our knowledge, SAREK is the first framework that provides such fault tolerant guarantees in WSC
Future worksEvaluate the fault tolerant mechanism in real
scenarios
Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a [email protected] [email protected] Semantic Replication Scheme 23
Experimental TestsPerformance EvaluationComparison with Related WorkConclusion
OutlineMotivation
Properties for WSCSAREK approach
Experimental TestsPerformance EvaluationComparison with Related WorkConclusion
Thank you!
Daniela Barreiro [email protected]
Raimundo Macêdo [email protected]
http://www.lasid.ufba.br
LaSiD/DCC/UFBa
24Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a
[email protected] [email protected] Semantic Replication Scheme
OutlineMotivation
Properties for WSCSAREK approach