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Dynamic-Content Web Caching with Cooperative Proxy Scheme

Dynamic-Content Web Caching with Cooperative Proxy Scheme. Βελισκάκης Μανώλης. Εθνικό Μετσόβιο Πολυτεχνείο Dept. of Electrical & Computer Engineering Knowledge and Database Systems Laboratory. Συνάντηση DBLAB Τρίτη, 20 Ιανουαρίου 2004. Outline. Problem Definition

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Dynamic-Content Web Caching with Cooperative Proxy Scheme

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  1. Dynamic-Content Web Caching with Cooperative Proxy Scheme Βελισκάκης Μανώλης Εθνικό Μετσόβιο Πολυτεχνείο Dept. of Electrical & Computer Engineering Knowledge and Database Systems Laboratory Συνάντηση DBLABΤρίτη, 20 Ιανουαρίου 2004

  2. Outline • Problem Definition • Dynamic-Data Web Caching vs Cooperative Schemes • Proposed Web Caching Algorithm • Current and Future Work • Discussion

  3. Problem Definition – What? • Query Results • Dynamic Data for personalization purposes

  4. Problem Definition – Where? • Client • Proxy • Edge-of-net • Internet Service Provider • Edge-of-Enterprise • Application Server • Web Server • DBMS

  5. Problem Definition – How? Nowadays Approaches • Exact matching query • Materialized Views • DB Characteristics to Proxies

  6. Problem Definition – Topology Scheme • Broadcast queries • Hierarchical Caching • URL Hashing • Directory based Cooperation

  7. Problem Definition - Issues • Replacement Policy • Cache Consistency • Proxy Communication • Web objects placement

  8. Exact matching query Materialized Views DB Characteristics to Proxies Broadcast queries Hierarchical Caching URL Hashing Directory based Cooperation Dynamic-Data Web Caching vs Cooperative Schemes • Replacement Policy • Proxy Communication • Web objects placement

  9. Dynamic-Data Web Caching vs Cooperative Schemes Conclusions (?) • Exact Matching Query • Common Web Caching Issues • Not interesting • DB Characteristics to Proxies • Common DB Replication Issues • Interesting Issue: Create Cache Tables knowing that there is a cooperative proxy Scheme

  10. Dynamic-Data Web Caching vs Cooperative Schemes Conclusions (?) • Materialized Views • Many interesting issues • Query rewriting • Replacement Algorithm • Appropriate Cooperative Scheme • Web Objects exchange between Proxies • Consideration of DBMS structure • Dynamic or a priori definition of Materialized Views • Giving DB capabilities to Proxies (queries on Materialized Views) • Communication between Proxies

  11. CL I ENTS PROXY 1a CLIENTS PROXY 2a Q.M Q.M CACHE CACHE DIRECTORY DIRECTORY PROXY 1b PROXY 1c PROXY 2b PROXY 2c Q.M Q.M Q.M Q.M CACHE CACHE CACHE CACHE DIRECTORY DIRECTORY DIRECTORY DIRECTORY WEB SERVER WEB SERVER DATABASE SERVER DATABASE SERVER Proposed Web Caching Algorithm – Hybrid Topology (Hierarchical-Directory Based)

  12. Proposed Web Caching Algorithm – Web Objects description • There are 3 different ways to refer to a Web Object • URL • QTag • QTag+Query Result (Whole Web Object)

  13. Proposed Web Caching Algorithm – Web Objects description QTAG <QTag ID:Number, //Unique identifier for every QTag Query:String, //Contains the query that has been asked to the Back-End Database LocationOfWebServer:URL, //Contains the URL Location of the Web Server that stands in front of the Database DatabaseID:Number, //Contains the ID of the Database where the query was asked TimeToLive:Number (sec), //Determines the period in which the query is valid and can satisfy Requests Weight:Number, //Determines the significance (Weight) of the query. Relationships:List of QTag.ID //Determines a list of Web Objects that are frequently used with the current Web Object in order to satisfy query requests />

  14. Proposed Web Caching Algorithm – Web Objects description QTAG + Query Results <QTag ID=1029384, Query=”Select name, surname, age from Customers where Name=’John’”, LocationOfWebServer =”http://www.dblab.ece.ntua.gr/siteNo1”, DatabaseID =1, TimeToLive=1000, Weight=0.65 Relationships=”15433456, 15433766, 15682456, 15432456 /> John, Manolopoulos, 28 John, Nikolaidis,35 . . . John,Fissas,40 Query Result

  15. PROXY STRUCTURE REST OF COOPERATIVE SCHEME URL/QTag TRANSFORMER COOPERATIVE-SCHEME DIRECTORY QUERY REWRITER WEIGHT CALCULATOR CACHE DIRECTORY MAIN CACHE Proposed Web Caching Algorithm – Proxy Structure

  16. Proposed Web Caching Algorithm – Proxy Structure – URL/QTag Transformer • Proxies manipulates Web-Objects (Query Results) through their <QTags> • Extract from a Web Object’s URL the • Query (Knowing the CGI that produces the Query Result) • LocationOfWebServer • DatabaseID • 1-1 correspondence between URLs and QTags

  17. Proposed Web Caching Algorithm – Proxy Structure – Query Rewriter • Rewriting the requested Web Objects (Queries) in case there is not an exact match of the requested query cached but it can be satisfied from other already cached web objects (queries). • Query rewriter will follow standard query-rewriting methods and techniques that are already used to database system and environments

  18. Proposed Web Caching Algorithm – Proxy Structure – Weight Calculator Every web object will be characterized from a Weight W which will be determined from the following factors: S (Determined from the web-object’s size) Πs  (Determined from the influence percentage of Factor S to the Weight) CS   (Determined from the web-object’s cost-retrieval) Πcs    (Determined from the influence percentage of factor CSto the Weight) Ρ (Determined from the web-object’s popularity) Πp   (Determined from the influence percentage of Factor Ρto the Weight) R     (Determined from the web-object’s significance as far as its relationships concerns) Πr  (Determined from the influence percentage of Factor R to the Weight)

  19. The Request arrives to a Proxy The URL/QTag Transformer Finds the QTag that best describes the incoming URL The QTag is sent to Query Rewriter Query Rewriter Rewrites the Query and produces Sub-QTags Some of the Sub-QTags are cached The Query Rewriter asks the Cache Directory if any of these Sub-QTags is already cached in the Main Cache None of the Sub-QTags are cached The Query Rewriter asks the Cooperative-scheme Directory if the rest Sub-QTags cached in other Proxies Send request to Web Server and Caches the response ALL of the rest of the Sub-Qtags are cached in other Proxies All the Sub-QTags are cached Not all of the rest of the Sub-Qtags are cached in other Proxies Query Rewriter retrieves the locally cached Web Objects Proxy retrieves the Cached Web Objects from the other Proxies and sends them to Query Rewriter Query Rewriter combines the Sub QTags and the proxy sends the response The Proxy Caches locally the retrieved Web Objects Weight Calculator Refreshes Weight Value and Parameters of the Sub-Tags Proposed Web Caching Algorithm

  20. Current and Future Work • Study and Testing the proposed new approaches • Definition of Workload • Better Definition and Testing of the proposed Algorithm

  21. Discussion • Efficiency of Testing Tools (Simulator) • Ideas for efficient Web Caching for Dynamic-Data • Comments

  22. Thank You

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