Scalable Web Architectures and Infrastructure

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    Scalable Web Architectures and Infrastructure - Presentation Transcript

    1. Scalable Web Architectures and Infrastructure Chris Munt M/Gateway Developments Ltd
    2. Topics
      • Web Servers
        • Microsoft IIS, Apache, Sun JSWS
        • Development trends
      • Web application development/run-time environments
        • CSP, WebLink
        • Dedicated: JSP, ASP.NET, PHP etc …
        • Pre-existing: Perl, Python, Ruby etc …
      • Creating high-performance and scalable web infrastructure
    3. Evolution
      • “ Since 1999, the web has grown from a document retrieval system into an application delivery system. ”
        • Douglas Crockford at AjaxWorld 2008
      • Implications for:
        • Web Server extensibility
        • Resilience
        • Performance and scalability
        • Architecture
    4. Web Servers: Market Share
      • 2005:
        • Apache 71%
        • IIS 20%
      • 2008:
        • Apache 50%
        • IIS 35%
      • Source: Netcraft
    5. Internet Information Services ( IIS)
      • v1.0 Introduced as free add-on for NT v3.51 (mid 1990s)
        • Single multi-threaded process
      • Extensibility
        • Common Gateway Interface (CGI)
        • Internet Server Application Programming Interface (ISAPI)
    6. IIS: CGI
      • Modules implemented as stand-alone scripts/executables
      • Application requests processed in separate server process
      • Non-optimal but secure
        • Overhead of starting new process to serve each request; Overhead of inter-process communication
        • Application crash does not impact hosting web server
      • Architecturally the same for all web servers
    7. IIS: ISAPI
      • Modules implemented as Windows DLLs
        • Can be a Filter (e.g. GZIP) or Extension (e.g. PHP, CSP)
      • Application requests serviced in process space of IIS host
      • Optimal but there are risks
        • No overhead in process management and inter-process communication
        • Application crash does impact hosting web server
      • Supported for all versions of IIS
        • The only web server API (excluding CGI) that’s completely backwards (and forwards) compatible!
    8. IIS v5.0 & Windows 2000
      • Concept of isolation levels (or application protection levels).
        • Low
          • All in same process
        • Medium
          • ISAPI extensions run in a separate process
        • High
          • ISAPI extensions run in a separate process per application
          • An application is broadly defined in terms of its path
    9. IIS v6.0 & Windows 2003
      • Concept of Worker Process Isolation and Application pools
        • Application pool
          • Applications associated with one or more worker processes
        • Web Gardens
          • Multiple worker processes supporting an application
          • Not to be confused with web farms where multiple web server installations manage the work load
        • Process recycling
        • Process idle-time timeout
    10. IIS v7.0 & Windows 2008
      • Major upgrade
        • Previewed in Vista: A good reason to get Vista
        • Modular architecture
          • Administrators choose the modules required
        • Improved security
        • Application pools
        • New configuration schema. XML based.
      • New API
        • ISAPI still supported (as a supplied module)
        • Third-party modules can be added
    11. IIS Resources
      • www.microsoft.com
      • www.iis.net
        • IIS developers participate
    12. Apache
      • v1.0 Consolidated in mid-90s
        • Robert McCool
        • Successor to NCSA HTTPd ( National Center for Supercomputing Application)
      • Modular architecture
      • Multi-threaded for Windows; Multi-process for UNIX
      • Extensibility
        • Common Gateway Interface (CGI)
        • Apache API
    13. Apache: API
      • Modules implemented as Dynamic Shared Objects (DSOs)
        • DLLS for Windows, Shared Objects/Libraries for UNIX, Shareable Images for OpenVMS
      • Modules can process any phase of request/response cycle
        • Request handling (e.g. mod_csp, mod_weblink)
        • Authentication (e.g. mod_auth)
        • Security (e.g. mod_ssl)
        • Filters (e.g. mod_deflate)
        • Miscellaneous (e.g. mod_rewrite)
    14. Apache: v2.0 - 2002
      • Substantial rewrite of core with improved modularization
      • Multi-threaded for Windows and OpenVMS
      • Support for UNIX threading
        • Multi-process/Multi-threaded hybrid server
      • New API
        • Use mod_csp2.so instead of mod_csp.so
    15. Apache: v2.2 - 2005
      • Improved Modules – particularly for authorization
      • Same API but binary incompatibilities
        • Use mod_csp22.so instead of mod_csp2.so
    16. Web Servers based on Apache
      • HP Secure Web Server (HPSWS)
        • For OpenVMS
        • v1.3-1 based on Apache v1.3.26
        • v2.1-1 based on Apache v2.0.52
        • Tomcat (Java/JSP), Perl, PHP
        • CSP
      • Many others
    17. Apache: Resources
      • www.apache.org
    18. Sun JSWS
      • Netscape Enterprise (mid 1990s)
        • FastTrack – lightweight offering
      • iPlanet (late 1990s)
        • America Online, Sun
      • Sun ONE (early 2000s)
      • Sun Java System Web Server (mid 2000s)
        • Resources: www.sun.com
    19. Sun JSWS
      • Multi-threaded for Windows
      • Multi-process/Multi-threaded hybrid for UNIX
      • Extensibility
        • Common Gateway Interface (CGI)
        • Netscape Server Application Programming Interface (NSAPI)
          • Modules implemented as DLLS for Windows, Shared Objects/Libraries for UNIX
          • Binary incompatibility between Netscape Enterprise v2 and v3
    20. Trends: All web servers
      • Multi-process/Multi-threaded servers
      • Increased flexibility/extensibility through modularization
      • Better security
    21. Trends: Implications for WebLink and CSP
      • State-aware mode (preserve mode 1 for CSP) increasingly non-optimal
        • Connection pool distributed amongst multiple process with no control over the relationship between requests and processes
        • Using Network Service Daemon (NSD) in single process mode becomes essential
          • Channel load into single multi-threaded process
          • Maintain single process pool
    22. Web Standards?
      • Applications using AJAX techniques generate much more HTTP traffic than conventional web applications.
        • Poor performance unless connection between client and server is kept open between requests.
      • HTTP v1.0: Asymmetric protocol by default
        • Client opens connection to server then sends request
        • Server sends response then closes connection to server
    23. HTTP Keep-Alive
      • Connection kept open between requests
        • HTTP v1.0: Default off
          • Connection: Keep-Alive (switch on)
        • HTTP v1.1: Default on
          • Connection: Close (switch off)
      • Must send response size notification
        • Content-Length
        • Chunked transfer (HTTP v1.1)
          • Transfer-Encoding: chunked
        • WebLink/CSP Gateway will do this automatically
    24. HTTP Connections: The current status
      • Standard specifies the maximum number of simultaneous connections to a given server
        • HTTP v1.0: usually 4
        • HTTP v1.1: always 2 (Section 8.1.4 RFC2616)
      • Objective: to improve response times and avoid congestion.
      • Can change setting in browser configuration
        • Inappropriate for web based applications
        • Proxys will implement standard
    25. HTTP Connections: The future
      • Now recognised that high-bandwidth connections are now commonplace
        • Key development since HTTP v1.1 which was drafted in January 1997.
        • Client-side bandwidth no longer gating factor in connection speed.
      • IE v8 will almost certainly increase the number of connections to 6
        • Direct response to needs of AJAX applications
    26. Application Development CSP & WebLink
      • WebLink (1996); CSP (~2000)
      • Implemented over CGI and Web Server APIs
      • Proxy to Caché
        • Responses generated entirely in Caché
      • Support for state-aware sessions
        • Migration of legacy M/Caché code to the web
      • WebLink Event Broker (1998)
        • Early incarnation of AJAX-like techniques
        • In-form scriptable communication with server
          • Initially Java applet based; then XMLHTTP
        • CSP equivalent: Hyperevents
    27. Application Development JSP
      • Specified by Sun
      • Apache Tomcat
        • web container or application server
        • Implements Java Servlet and JSP
        • Apache mod_jk (Jakarta) manages communication between Apache and Tomcat
      • Database access
        • JDBC, web services
    28. Application Development ASP & ASP.NET
      • Microsoft IIS
      • Classic ASP (~1996)
        • script based and interpretive
      • ASP.NET (~2002)
        • Compiled, dependent on .Net framework
      • Database access
        • ADO.Net (base class library)
        • ODBC data provider
        • Web Services
    29. Application Development PHP
      • PHP ( Hypertext Preprocessor)
      • Created 1994
      • Used for over 20 million web sites
      • Most popular Apache module
      • M-like associative arrays
      • Increasing OO capability
      • Interfaces to numerous SQL-based databases
        • MySQL popular choice
    30. Application Development Perl
      • Created 1987
      • General purpose scripting language
      • Emphasis on text processing
        • Suited to the needs of web programming
      • DBI (Database Interface) modules
    31. Application Development Python
      • Created 1991
      • General purpose scripting environment
        • Some implementations include compiler
      • Multi-paradigm programming environment
        • Functional
        • Object Oriented
      • Large standard library
        • Modules for processing web requests
        • Modules for database access
    32. Application Development Ruby (on Rails)
      • Created mid 1990s
      • General purpose
      • Multi-paradigm programming environment
        • Functional
        • Object Oriented (Many ideas from Perl and Smalltalk)
      • Ruby On Rails: Created 2004
        • Complete web application development framework
        • Consists of several packages
          • ActiveRecord – Object Relational mapping
    33. MGWSI Gateway
      • Uniform/Normalized interface to Cach é
      • Underpins Enterprise Web Developer (EWD)
      • Currently supported:
        • PHP (m_php)
        • JSP (m_jsp)
        • ASP.NET (m_aspx)
      • Future support anticipated:
        • Ruby (m_ruby)
        • Python (m_python)
        • Perl (m_perl)
      • www.mgateway.com
    34. Application Development Scalability I
      • Non CSP/WebLink environments
        • Requests processed and responses generated on web server host
        • Possible multiple round trips to database
        • Will need to increase capacity of web server tier sooner
          • Load-Balancing techniques
    35. Application Development Scalability II
      • CSP/WebLink
        • Web server extension as intelligent proxy/router
        • Requests and complete response generated in Caché
        • Single round trip to database per request/response cycle
        • Integrated scripting environment and database ideal for web application run-time environment
        • Better performance/throughput per web server
    36. Scalable Web Applications Conclusion
      • Keep web servers updated
      • Keep eye on developments in standards
      • Use HTTP Keep-alive for applications using AJAX techniques
      • Don’t use state-aware mode in WebLink or CSP
      • Follow these guidelines and future scalability options will remain open
        • Server clusters/farms
        • Load-balancing/Fail-Over

    + george.jamesgeorge.james, 2 years ago

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