Proxy-Based Acceleration of Proxy-Based Acceleration of Dynamically Generated Content Dynamically Generated Content

on the World Wide Web: An on the World Wide Web: An Approach and ImplementationApproach and Implementation

Anindya Dutta et alAnindya Dutta et al

WEB CACHING SOLUTIONS WEB CACHING SOLUTIONS BACKGROUNDBACKGROUND

BACK-END CACHING BACK-END CACHING PROXY-BASED CACHINGPROXY-BASED CACHING

BACK-END CACHINGBACK-END CACHING

DATABASE CACHING(OR RESULTS OF DATABASE CACHING(OR RESULTS OF QUERIES)QUERIES)

PRESENTATION LAYER CACHING PRESENTATION LAYER CACHING (CACHE HTML FRAGMENTS)(CACHE HTML FRAGMENTS)

COMPONENT LEVEL CACHING(CACHE COMPONENT LEVEL CACHING(CACHE ARBITRARY OBJECTS)ARBITRARY OBJECTS)

PROXY-BASED CACHINGPROXY-BASED CACHING

Page Level CachingPage Level Caching

Both at forward and backward proxyBoth at forward and backward proxy

ImprovesImproves– Delays associated with generation of contentDelays associated with generation of content– Packet filtering Packet filtering – BandwidthBandwidth

DRAWBACKSDRAWBACKS

URL BASED CACHING INCORRECT URL BASED CACHING INCORRECT PAGES.PAGES.

VERY LITTLE REUSABILITY OF FULL VERY LITTLE REUSABILITY OF FULL HTML PAGES(PERSONIZATION)HTML PAGES(PERSONIZATION)

INVALIDATIONINVALIDATION

DYNAMIC PAGE ASSEMBLYDYNAMIC PAGE ASSEMBLY

DYNAMIC WEB PAGE APPROACHDYNAMIC WEB PAGE APPROACH

ESTABLISH A TEMPLATE FOR EACH ESTABLISH A TEMPLATE FOR EACH DYNAMICALLY GENERATED PAGEDYNAMICALLY GENERATED PAGE

EACH PAGE IS FACTORED INTO A EACH PAGE IS FACTORED INTO A NUMBER OF FRAGMENTSNUMBER OF FRAGMENTS

ASSEMBLE FRAGMENT HTML AT ASSEMBLE FRAGMENT HTML AT PROXYPROXY

DRAWBACKSDRAWBACKS

CHANGE THE DESIGN OF CHANGE THE DESIGN OF WEBSITE(USE ONLY TEMPLATES)WEBSITE(USE ONLY TEMPLATES)

NO SEMANTIC INTERDEPENCE NO SEMANTIC INTERDEPENCE BETWEEN FRAGMENTSBETWEEN FRAGMENTS

AIMAIM

““Holy GRALE” of content caching has beingHoly GRALE” of content caching has being

a solution that can provide both bandwidtha solution that can provide both bandwidth

Saving, like proxy-based approaches and Saving, like proxy-based approaches and

as well as server-side acceleration.as well as server-side acceleration.

DYNAMIC PROXY CACHEDYNAMIC PROXY CACHE

OUTSIDE SITE’S INFRA (reverse-OUTSIDE SITE’S INFRA (reverse-PROXY) OR AT NETWORK EDGEPROXY) OR AT NETWORK EDGE

STORES CONTENT FRAGMENTSSTORES CONTENT FRAGMENTS

BEM(BACK END MONITOR) BEM(BACK END MONITOR) GENERATES THE LAYOUTGENERATES THE LAYOUT

FORWARD-PROXYFORWARD-PROXY– Request routingRequest routing– Cache coherencyCache coherency

GRANULAR PROXY BASED CACHINGGRANULAR PROXY BASED CACHING

CACHE DYNAMIC CONTENT CACHE DYNAMIC CONTENT FRAGMENT ON THE PROXY CACHEFRAGMENT ON THE PROXY CACHE

LAYOUT INFORMATION FROM LAYOUT INFORMATION FROM SOURCE SITESOURCE SITE

QUERY TO DYNAMIC PROXY QUERY TO DYNAMIC PROXY

PUSH INTO SERVER PUSH INTO SERVER

SERVER RESPONDS WITH LAYOUT SERVER RESPONDS WITH LAYOUT

Technical DetailsTechnical Details

SYSTEM INITIALIZATIONSYSTEM INITIALIZATION– Identify fragments and Tag themIdentify fragments and Tag them

RUN-TIME OPERATIONRUN-TIME OPERATION– ExampleExample– http://.../catalog.jsp?categoryID=fictionhttp://.../catalog.jsp?categoryID=fiction– Lookup fragID in BEMs cache dirLookup fragID in BEMs cache dir– Insert GET /SET in the codeInsert GET /SET in the code

Back End MonitorBack End Monitor

MANAGE DPC CACHEMANAGE DPC CACHE– cache directorycache directory– Frags of DPC and metadata(ID,Key,valid,ttl)Frags of DPC and metadata(ID,Key,valid,ttl)– Invalid fragment??Invalid fragment??

CACHE INTERMEDIATE OBJECTSCACHE INTERMEDIATE OBJECTS

ANALYTICAL RESULTSANALYTICAL RESULTS

Comparing average bytes served = BComparing average bytes served = B

B = sum(Sci x n(t))B = sum(Sci x n(t))

ncSci = sum(Sei) + fncSci = sum(Sei) + f

cSci = sum(Xj[(hxg) + (1-h)(sei + 2g)] + (1-cSci = sum(Xj[(hxg) + (1-h)(sei + 2g)] + (1-Xj)(sei) + f]Xj)(sei) + f]

Plot ratio cB/ncB with fragment sizePlot ratio cB/ncB with fragment size

Vary hit ratio and observeVary hit ratio and observe

Hit Ratio V/s Saving in Bytes Hit Ratio V/s Saving in Bytes

Cost Due to CacheCost Due to Cache

No cache scan cost = ncB * yNo cache scan cost = ncB * y

Cache Scan cost = cB*2yCache Scan cost = cB*2y

ncB > 2cBncB > 2cB

““It is preferable to dynamic proxy cache It is preferable to dynamic proxy cache when the expected bytes served with no when the expected bytes served with no cache are more than the twice the cache are more than the twice the expected bytes served with cache”expected bytes served with cache”

LIMITATIONSLIMITATIONS

For forward proxy cacheFor forward proxy cache– Request RoutingRequest Routing– Cache CoherencyCache Coherency– Cache ManagementCache Management– ScalabilityScalability