Generate Dynamic Content On Cache Server

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Generate Dynamic Content On Cache Server

• Masters Project Proposal by
• Aparna Yeddula

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Introduction

• Caching
• fetching document.
• pass to the browser.
• save copies.
• Referred to as a web proxy server.
• Subsequent requests from other users of the cache
  get the saved copy.
• Advantage Faster and does not consume Internet
  bandwidth over the often-congested network links.
  

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Intro

• With out caching generating dynamic web page
  imposes heavy burden on the original web server.
  To alleviate that, the generation of dynamic web
  pages can be done at the cache servers.
• One of the content delivery network providers
  Akamai had proposed Edge Side Include (ESI)
  language for specifying how a web page can be
  dynamically generated.

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Edge side include Test Server (ETS)

• The ESI assembly model is comprised of a template
  containing fragments.
• The template is the container for assembly.
• Each fragment of the page need to be retrieved
  from the origin server.
• Each fragment has its own time-to-live (TTL)
  attribute, which specifies how long the cache
  server maintains the copies.
• Fragments are separate resources, they can be
  assigned their own cacheability and handling
  information.

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ESI Example

• ltesiincludegt tag example
• The include element specifies a fragment for
  assembly.
• ltesiinclude src"URI" ttl1hr" /gt
• For example,
• ltesiinclude src"http//example.com/1.html"
  ttl1hr/gt
• ltesichoosegt tag example
• The conditional elements add the ability
  to perform logic based on expressions.
• For example,
• ltesichoosegt
• ltesiwhen test"(HTTP_HOST)128.198.192.174'"gt
  
• ltesiinclude src"http//www.example.com/advance
  d.html"/gt lt/esiwhengt
• ltesiotherwisegt
• ltesiinclude src"http//www.example.com/newuser
  .html"/gt lt/esiotherwisegt
• lt/esichoosegt

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Web services specifications

• The web services model is independent of
  languages, platforms, and object models.
• Each time a service request is received, a new
  object is created. The request for the method
  call, and the object is destroyed after the
  method call is returned.

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DOTNET Models

• Direct client model
• The client browser issues a GET HTTP request
  .asmx page directly to the web service.
• When we call a web service from a browser, we
  access the description page, which lists the
  methods that are included in the Web service. The
  protocol that is used in this case is HTTP, and
  the data is returned as XML.
• Web server or the proxy client model
• The client browser issues a GET HTTP request
  .aspx page to the web server. The server parses
  and compiles the page. The code invokes the proxy
  to call the web service. Here the request and
  response between the servers is using XMLP. And
  the web server sends the response to the client
  in HTTP 6.

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JSP (Java Server Pages) custom tag specifications

• JSP custom tag can be used to implement XML
  languages including ESI.
• To use the JSP custom tags, we need to define
  three separate components
• JSP file that uses the tag library.
• tag library descriptor (tld) file that maps the
  XML elements names to the tag implementations.
• tag handler class that defines the tags behavior.

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The JSP file

• lt!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0
  Transitional//EN"gt
• lthtmlgt ltheadgt
• lt_at_ taglib uri"simple-taglib.tld prefix"jspx"
  gt
• lttitlegtltjspxhello /gtlt/titlegt
• lt/headgtltbodygt
• ltH1 align"center"gt JSP Custom Tag Test Page
• lt/H1gt
• ltH2gtFirst JSP Custom Tag
• ltjspxhello /gt
• lt/H2gt
• lt/bodygtlt/htmlgt

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Tag library descriptor file

• lt!DOCTYPE taglib
• PUBLIC "-//Sun Microsystems, Inc.//DTD
  JSP Tag Library 1.1//EN"
• "http//java.sun.com/j2ee/dtd/web-jsptaglibrary_1
  _1.dtd"gt
• lttaglibgt
• lttlibversiongt1.0lt/tlibversiongt
• ltjspversiongt1.1lt/jspversiongt
• lturigt simple-taglib.tldlt/urigt
• lttaggt
• ltnamegthellolt/namegt
• lttagclassgtcwp.tags.HelloWorldTaglt/tagclassgt
• lt/taggt
• lt/taglibgt

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Tag handler class

• import javax.servlet.jsp.
• import javax.servlet.jsp.tagext.TagSupport //
  tells system what to do when it sees the tag
  
  
• // This is a simple tag example to show how
  content is added to the output stream when a tag
  is encountered in a JSP page.
• public class HelloWorldTag extends TagSupport
•   // doStartTag is called by the JSP container
  when the tag is encountered
• public int doStartTag()
• JspWriter out pageContext.getOut()
• out.println("lttrgtlttdgt Hello World
  lt/tdgtlt/trgt")
• // Must return SKIP_BODY because we are
  not supporting a body for this tag
• return SKIP_BODY

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JSP Example

• JSP FILE
• ltbodygt
• lt_at_ taglib uri"include-taglib.tld"
  prefix"jspx" gt
• ltjspxinclude uri"http//uccs.edu/page.html"
  ttl"1"/gt
• lt/bodygt
• TLD FILE
• lttaggt
• ltnamegtincludelt/namegt lttagclassgtcwp.tags.In
  cludeTaglt/tagclassgt
• ltattributegt ltnamegturilt/namegt
  ltrequiredgttruelt/requiredgt
• lt/attributegt
• ltattributegt ltnamegtttllt/namegt
  ltrequiredgttruelt/requiredgt
• lt/attributegt
• lt/taggt

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JSP Example

• public int doStartTag() throws JspException
• public void setUri (String name) uriName
  name
• // Set Ttl called when set the Tag attribute
• public void setTtl (String name) ttlName
  name

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Tasks

• Already Complete
• 1.      Study how to change the date and time of
  the web page based on the Java Script.
• 2.      Study how to change the date and time
  using DOTNET on the server side with .asmx page.
• 3.      Study how to change the date and time
  using DOTNET on the server side with .aspx page.
• 4.      Study how to use Java socket library to
  process the http request and response.
• 5.      Study database access using Microsoft
  access and Active Server Page (ASP).
• 6.      Study how ESI works.
• 7.      Study how JSP custom tags to implement
  ESI.
• In Progress
• Testing the performance of my project
  with the ESI proposed by Akamai, using a simple
  PERL program to test the time taken to deliver
  the document.
• Deliverables
• My project report documenting the
  approach and code to the project, related work
  and the lessons learned in this project.

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References

• 1 Microsoft DOTNET sample training modules
  http//www.microsoft.com/traincert/training/develo
  per/dotnet.asp
• 2 Active Cache Caching Dynamic Contents on
  the Web http//www.cs.wisc.edu/cao/papers/ac
  tive-cache/SECTION00100000000000000000
• 3 ESI Resources http//www.esi.org/language_sp
  ec_1-0.html
• 4 Core Servlets and Java Server Pages by
  Marty Hall
• 5 Core Web Programming by Marty Hall and
  Larry Brown
• 6 DOTNET Training http//www.imguniversity.com/
  WebUPublic/default.asp?URL2E2E2FWebSyllabus2F
  wsStudentClassList2Easp