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Maximizing Web Performance Through Effective Caching Strategies

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Presentation Transcript

  1. Web Caching By Neeraj Agrawal

  2. Caching • Caching is widely used for improving performance in many context( e.g processor caches in hardware, buffer pool in DBMS etc). • Where and what to cache in web context? • Many points and many kind of objects! • Focus is on Transactional/Database apps.

  3. What Where When and How Considerations for caching in web context are: • What, when and where to cache • Granularity of caching: web pages, fragments of pages, servlet execution result, SQL query results etc • Location of cache: client, proxy, edge of the net, internet service provider (ISP), edge of enterprise, application server (EJBs etc), web server, database server.

  4. What Where When and How • Caching and Invalidating policies: Pull vs Push, freshness maintenance, triggers. • Related DB Technologies: • Replication • Materialized views • Mediator systems • Buffer management.

  5. Common Points of Caching • Browser • Proxy (Forward proxy cache) • Enterprise/ISP Edge Servers • Web Server • Application Server • Databases

  6. Front End Cache Caches data + markup Cache can be app independent Static pages easily cached Cache Models • Data Cache • Cache Data • Effectiveness depends on app design

  7. Cache Models • Distributed Applications • Multiple copies distributed around net • Turns caching into content management problem.

  8. HTTP Caching Today • Multiple cache between browser and server • HTTP header control • Whether a page can be cached • Cache expiration time. • Full pages and images can be cached. • Unable to cache html fragments

  9. Dynamically Generated Pages • Increased due to • Database centric e-commerce application • Frequently update contents • Personalization • Proxy caching is ineffective for such pages

  10. Caching Data-intensive Web Sites • Relies on the declarative spec of web sites • Data content is extracted from DBMS • Website structure and content is separate from graphical representation XSLT. • The mapping between raw data and logical model of web is described by declarative language (WeaveL) • HTML page is generated from XML and XSLT

  11. Materialization Strategies • What kind of data must be materialized? • When must materialization must be performed? • Where should the materialized intermediate result must be placed for effective performance improvements? • How are updates are propagated to the materialized data? • Which particular data must be materialized and which must be computed upon request?

  12. Approaches • Materialization (HTML) • Good response time • High space overhead • Propagating update to materialization difficult • Not always possible (forms) • Materialization granularity is not always appropriate

  13. Approaches • Cache DBMS query results • Significant performance improvement • Simple update propagation • Granularity • Cache intermediate XML • Complex update propagation • Granularity • Eliminate cost of database connection

  14. WeaveL

  15. XML Fragment

  16. Weave Web Site Management System

  17. Runtime Policies

  18. Conclusion • Results • Better performance with mixed caching

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