Using Real-Time Scheduling Principles in Web Service Clusters to Achieve Predictability of Service Execution Vidura Gamini Abhaya Prof. Zahir Tari and Assoc. Prof. Peter Bertok Distributed Systems and Networking Group School of Computer Science and IT RMIT University Melbourne, Australia December 8, 2010
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Using Real-Time Scheduling Principles in Web Service Clusters to Achieve Predictability of Execution
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Using Real-Time Scheduling Principles in Web
Service Clusters to Achieve Predictability of
Service Execution
Vidura Gamini AbhayaProf. Zahir Tari and Assoc. Prof. Peter Bertok
Distributed Systems and Networking GroupSchool of Computer Science and IT
RMIT UniversityMelbourne, Australia
December 8, 2010
Intro. Prev. Work Solution Results Conclusion
Presentation Structure
1 Introduction
2 Previous Work
3 Solution
4 Empirical Results
5 Conclusion
V. Gamini Abhaya et. al. ICSOC 2010 - pages 197-212 in proceedings
Intro. Prev. Work Solution Results Conclusion Motivation
Motivation
Web Services enable communication between DistributedHeterogeneous Systems.
V. Gamini Abhaya et. al. ICSOC 2010 - pages 197-212 in proceedings
Intro. Prev. Work Solution Results Conclusion Motivation
Motivation
Web Services enable communication between DistributedHeterogeneous Systems. It is the foundation for...
V. Gamini Abhaya et. al. ICSOC 2010 - pages 197-212 in proceedings
Intro. Prev. Work Solution Results Conclusion Motivation
Motivation
Web Services enable communication between DistributedHeterogeneous Systems. It is the foundation for...
V. Gamini Abhaya et. al. ICSOC 2010 - pages 197-212 in proceedings
Intro. Prev. Work Solution Results Conclusion Motivation
Motivation
Web Services enable communication between DistributedHeterogeneous Systems. It is the foundation for...
V. Gamini Abhaya et. al. ICSOC 2010 - pages 197-212 in proceedings
Intro. Prev. Work Solution Results Conclusion Motivation
Motivation
V. Gamini Abhaya et. al. ICSOC 2010 - pages 197-212 in proceedings
Intro. Prev. Work Solution Results Conclusion Motivation
Motivation
Scalability Issues...
Quality of Service ?
Performance ?
Predictability ?
V. Gamini Abhaya et. al. ICSOC 2010 - pages 197-212 in proceedings
Intro. Prev. Work Solution Results Conclusion Single Host
1 Introduction
2 Previous Work
3 Solution
4 Empirical Results
5 Conclusion
V. Gamini Abhaya et. al. ICSOC 2010 - pages 197-212 in proceedings
Intro. Prev. Work Solution Results Conclusion Single Host
Our Previous Work [5,6,*]...
Achievement
Achieve Predictability and Service Differentiation in WS execution(in a single server)
* Building Web Service Middleware with Predictable Service Execution, WISE 2010, LNCS, vol. 6488 pp. 23-37.
V. Gamini Abhaya et. al. ICSOC 2010 - pages 197-212 in proceedings
Intro. Prev. Work Solution Results Conclusion Single Host
Our Previous Work [5,6,*]...
Achievement
Achieve Predictability and Service Differentiation in WS execution(in a single server)
Highlights...
Introduced the notion of a deadline
Use Real-time scheduling principles
Select tasks with achievable deadlines, reject the rest
Selected tasks scheduled in the order of increasing deadlines
Implementation based on Apache Axis2
Tested for various request size, arrival rate combinations
* Building Web Service Middleware with Predictable Service Execution, WISE 2010, LNCS, vol. 6488 pp. 23-37.
V. Gamini Abhaya et. al. ICSOC 2010 - pages 197-212 in proceedings
Intro. Prev. Work Solution Results Conclusion Single Host
Task Execution with a Deadline
V. Gamini Abhaya et. al. ICSOC 2010 - pages 197-212 in proceedings
Intro. Prev. Work Solution Results Conclusion Single Host
Task Execution with a Deadline
Laxity of a Task
Laxity =Deadline
ExecutionTime
V. Gamini Abhaya et. al. ICSOC 2010 - pages 197-212 in proceedings
Intro. Prev. Work Solution Results Conclusion Single Host
Single Host Implementation
Task selection based on a ‘Schedulability Check’
Deadline based scheduling
Implementation on a single server
V. Gamini Abhaya et. al. ICSOC 2010 - pages 197-212 in proceedings
Intro. Prev. Work Solution Results Conclusion Single Host
Deadline based Task Schedule
EDF based task schedule
Larger laxities allow requests to be executed in staggeredmanner
Enable timely completion of requests with earlier deadlines
V. Gamini Abhaya et. al. ICSOC 2010 - pages 197-212 in proceedings
Intro. Prev. Work Solution Results Conclusion Overview Dispatching Algo Details
1 Introduction
2 Previous Work
3 Solution
4 Empirical Results
5 Conclusion
V. Gamini Abhaya et. al. ICSOC 2010 - pages 197-212 in proceedings
Intro. Prev. Work Solution Results Conclusion Overview Dispatching Algo Details
Solution Overview
V. Gamini Abhaya et. al. ICSOC 2010 - pages 197-212 in proceedings
Intro. Prev. Work Solution Results Conclusion Overview Dispatching Algo Details
Solution Overview
Sun Real-time Java Specification used asdevelopment platform
Sun Solaris 10 08/05 used as RT-OS
V. Gamini Abhaya et. al. ICSOC 2010 - pages 197-212 in proceedings
Intro. Prev. Work Solution Results Conclusion Overview Dispatching Algo Details
Solution Overview
Sun Real-time Java Specification used asdevelopment platform
Sun Solaris 10 08/05 used as RT-OS
Apache Synapse based dispatcher implementation
Apache Axis2 based executor implementation
V. Gamini Abhaya et. al. ICSOC 2010 - pages 197-212 in proceedings
Intro. Prev. Work Solution Results Conclusion Overview Dispatching Algo Details
Solution Overview
Sun Real-time Java Specification used asdevelopment platform
Sun Solaris 10 08/05 used as RT-OS
Apache Synapse based dispatcher implementation
Apache Axis2 based executor implementation
All Thread-pools replaced with custom-designedReal-time Thread pools
Introduction of Real-time scheduler component
V. Gamini Abhaya et. al. ICSOC 2010 - pages 197-212 in proceedings
Intro. Prev. Work Solution Results Conclusion Overview Dispatching Algo Details
Cluster Design
Request processing at the dispatcher
Requests are dispatched based on algorithm used
Requests are ‘mostly’ queued at dispatcher
Results are sent back to clients via dispatcher
V. Gamini Abhaya et. al. ICSOC 2010 - pages 197-212 in proceedings
Intro. Prev. Work Solution Results Conclusion Overview Dispatching Algo Details
Dispatching Algorithms
Objectives
*Ensures deadline requirement of tasks could be met*Distribute requests evenly among executors based on a condition*Avoids executors going into overload conditions
4 algorithms used
RT-RoundRobin
RT-Sequential
RT-ClassBased
RT-LaxityBased
V. Gamini Abhaya et. al. ICSOC 2010 - pages 197-212 in proceedings
Intro. Prev. Work Solution Results Conclusion Overview Dispatching Algo Details
RT-RoundRobin
Details
Requests assignment cyclesthrough all executors in RRfashion
Sched. check is done only onceper request
If sched. check fails on selectedserver → request rejected
V. Gamini Abhaya et. al. ICSOC 2010 - pages 197-212 in proceedings
Intro. Prev. Work Solution Results Conclusion Overview Dispatching Algo Details
RT-RoundRobin
Details
Requests assignment cyclesthrough all executors in RRfashion
Sched. check is done only onceper request
If sched. check fails on selectedserver → request rejected
Hightlights
POC for how a simple dispatching algorithm could be made real-time ready
Processing overhead is minimum
V. Gamini Abhaya et. al. ICSOC 2010 - pages 197-212 in proceedings
Intro. Prev. Work Solution Results Conclusion Overview Dispatching Algo Details
RT-Sequential
Details
Requests are assigned in asequential manner
Req’s sent to one executor tillsched. check fails, then assignedto the second and so on
Sched. check happens againstmultiple executors till a requestcan be assigned
V. Gamini Abhaya et. al. ICSOC 2010 - pages 197-212 in proceedings
Intro. Prev. Work Solution Results Conclusion Overview Dispatching Algo Details
RT-Sequential
Details
Requests are assigned in asequential manner
Req’s sent to one executor tillsched. check fails, then assignedto the second and so on
Sched. check happens againstmultiple executors till a requestcan be assigned
Highlights
If it’s possible to schedule a job within the cluster, it will be guaranteed
V. Gamini Abhaya et. al. ICSOC 2010 - pages 197-212 in proceedings
Intro. Prev. Work Solution Results Conclusion Overview Dispatching Algo Details
RT-ClassBased
Details
Requests are divided into classesbased on a priority scheme
Mapping of requests to executorsis pre-determined and definedoffline
Sched. check is only consideredwith the assigned executor
Reference implementation usespriorities based on task sizes
V. Gamini Abhaya et. al. ICSOC 2010 - pages 197-212 in proceedings
Intro. Prev. Work Solution Results Conclusion Overview Dispatching Algo Details
RT-ClassBased
Details
Requests are divided into classesbased on a priority scheme
Mapping of requests to executorsis pre-determined and definedoffline
Sched. check is only consideredwith the assigned executor
Reference implementation usespriorities based on task sizes
Highlights
Results in the reduction of variance of task sizes at each executor
Pre-defined mapping of request sizes to executors could be done usingpre-profiled execution times or execution time history
V. Gamini Abhaya et. al. ICSOC 2010 - pages 197-212 in proceedings
Intro. Prev. Work Solution Results Conclusion Overview Dispatching Algo Details
RT-LaxityBased
Details
Laxity = Ability of delaying arequest whilst still meeting itsdeadline
Higher the laxity the morerequests an executor could service
Sched. check is done only againstthe assigned executor
V. Gamini Abhaya et. al. ICSOC 2010 - pages 197-212 in proceedings
Intro. Prev. Work Solution Results Conclusion Overview Dispatching Algo Details
RT-LaxityBased
Details
Laxity = Ability of delaying arequest whilst still meeting itsdeadline
Higher the laxity the morerequests an executor could service
Sched. check is done only againstthe assigned executor
Highlights
Distribution of requests results in a broad range of laxities at each executor
Keeps track of the last two laxities assigned and prevents them being assignedfor the same executor consecutively
V. Gamini Abhaya et. al. ICSOC 2010 - pages 197-212 in proceedings
Intro. Prev. Work Solution Results Conclusion RT-RR RT-CB Others
1 Introduction
2 Previous Work
3 Solution
4 Empirical Results
5 Conclusion
V. Gamini Abhaya et. al. ICSOC 2010 - pages 197-212 in proceedings
Intro. Prev. Work Solution Results Conclusion RT-RR RT-CB Others