1 / 16

Prof. Gio Wiederhold, Dr. Dorothea Beringer, several Ph.D. and master students

CHAIMS. Cost Estimation in CPAM, an Access Protocol for Remote and Autonomous Services. Prof. Gio Wiederhold, Dr. Dorothea Beringer, several Ph.D. and master students Stanford University http://www-db.stanford.edu/CHAIMS/.

williamslinda
Download Presentation

Prof. Gio Wiederhold, Dr. Dorothea Beringer, several Ph.D. and master students

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. CHAIMS Cost Estimation in CPAM, an Access Protocol for Remote and Autonomous Services Prof. Gio Wiederhold, Dr. Dorothea Beringer, several Ph.D. and master students Stanford University http://www-db.stanford.edu/CHAIMS/ Objective: Investigate new approaches to large-scale software composition. Approach: Develop and validate a composition-only language, a protocol for large, distributed, heterogeneous and autonomous megamodules, and a supporting system. CHAIMS

  2. Composition of Services... • versus composition of Components • reusing small components via copy/paste or shared libraries locally installed • large distributed components within same “domain” as composition, e.g. within one bank or airline • versus composition and integration of Data • data-warehouses • wrapping data available on web CPAM/CHAIMS:»composing processes »composing services of remote, autonomous, large megamodules CHAIMS

  3. Assumption Composition of services that are remote, autonomous, heterogeneous, computation intensive ==> specific requirements Domain expert Client workstation c l i e n t IO module IO module CPAM and distribution systems data control s e r v e r s at provider's sites e b Megamodules a d c CHAIMS

  4. Challenge: Autonomy Megamodule C at site NewCom provided by BestCalc Megamodules are autonomous: • responsibility for maintenance is with provider • client has no direct control over availability of services and resources provided • heterogeneity concerning implementation languages, server platforms, distribution systems, and interface definitions (ontologies, ==> SKC project) • yet client might be able to choose from several providers Megamodule A at site Stanford provided by InfoLab Megamodule B at site SLAC provided by Admin CHAIMS

  5. Challenge: Heavy-weight Services What we would like: ==>monitoring progress of a service ==> possibility to choose cheapest or fastest service ==>exploitingparallelism among services Services are not free for a client: • execution time of a service • transfer time and fee for data • fees for services CHAIMS

  6. Parallelism, Invocation Scheduling Distributed services ==> potential parallel execution • focus is on parallelism of remote (long) services, not on parallelism of local operations i1 a e1 i2 i1 b i3 a i4 c d e1 e2 i2 i3 b c e4 time time e2 e3 i5 e e3 e5 i4 d e4 i5 e e5 dataflow dependency CHAIMS

  7. Cost Estimation for Scheduling (1) Scheduling of invocations: • defer shorter invocations so results will be extractable from all services at about the same time i3 c (>a+b) i1 a i4 e1 i2 d (<c) b time e4 e3 e2 i5 e e5 ==>ESTIMATE ( methodname), returns estimated execution time, fee, and datavolume of results CHAIMS

  8. Cost Estimation for Scheduling (2) Scheduling of invocations: • control-flow dependency (conditional block), yet no data-flow dependency i1 a e1 i2 a d b e2 i3 b c condi- tional time e3 c i4 d e e4 i5 e control flow dependency: results of c only needed under certain conditions, determined by b e5 dataflow dependency CHAIMS

  9. Cost Estimation for Scheduling (3) ==>cost-function based on cost information from a, b, and c i1 a i4 d e1 i3 i2 i1 c i4 b a d e4 e1 i2 e2 b time i3 e4 c e3 time e2 i5 e e5 e3 i5 e e5 Risk: waste of resources and money Risk: waste of time CHAIMS

  10. SETUP () SETPARAM (attributes essential for cost estimation) (f1=fee, t1=time) = ESTIMATE (“Optimum”) SETUP () SETPARAM (attributes essential for cost estimation) (f2=fee, t2=time) = ESTIMATE (“BestRoute”) time BestPick.INVOKE (“BestRoute”, …) Cost Estimation for Selection Choosing megamodules: C H A I M S c l i e n t RouteChoose - Optimum - … BestPick - BestRoute - ... calculate cost function ==> today BestPick is better CHAIMS

  11. Why Run-time Cost Estimation? Static cost information in repository or catalog: • upper bound? average? • fluctuation in resources and load of server • dependence on specific input data Run-time cost information from megamodule: • reflects actual load and resources • takes into account autonomy, no out-of-date cost information in a central repository, no daily updates • easily fits into CPAM and the concept of having several primitives for remote execution • yet: requires in megamodule either statistics of costs over typical loads and input data gained by previous invocations, or special functionality in (wrapped) server software CHAIMS

  12. Monitoring: Incremental Extraction CPAM primitive EXTRACT: • Partial extract: all results are ready, but results are extracted step by step (always available) • Partial extract: only some of the results are ready and can be extracted before rest of results is ready • Progressive extract: preliminary version of a result is ready and can be extracted EXTRACT: takes list of result attributes to be returned, returns values of these attributes CHAIMS

  13. Monitoring: Progress Information CPAM primitive EXAMINE: • EXAMINE allows to ask for the completion of: • an invocation: DONE, NOT_DONE, PARTIAL, ERROR • EXAMINE allows to ask for the progress of: • a result attribute: returns current accuracy • an invocation: returns current progress Progress information is optional, not provided by every megamodule. ==> partial and progressive extraction ==> rescheduling of invocations, stopping slow invocations ==> getting preliminary results which influence program flow (e.g. invocation parameters) CHAIMS

  14. Primitives in CPAM Pre-invocation: SETUP: set up a connection to a megamodule SET-, GETPARAM: preset / get attributes in a megamodule ESTIMATE: get cost estimation for optimization Invocation and result gathering: INVOKE: start a specific method EXAMINE: test status and progress of an invoked method EXTRACT: extract results from an invoked method Termination: TERMINATE: terminate a method invocation TERMINATEALL: terminate the connection to a megamodule All primitives are procedure calls ==> asynchrony in method invocation CHAIMS

  15. Megamodule Provider Composer provides megamodules client side server side writes Wrapper Templates CLAM program adds information to CHAIMS Compiler CHAIMS Repository b d generates e a Client Side Run Time c MEGA Modules CPAM protocol Distribution Systems (CORBA, RMI…) CHAIMS Architecture CHAIMS

  16. CPAM and WfMS • Composing services of autonomous, computation ==> intensive servers • Issues like cost-estimation also important for WfMS Managing workflow across organizations computation-intensive, autonomous services run-time cost estimation, progress monitoring CHAIMS

More Related