Apache
  Home arrow Apache arrow Compressing Web Content with mod_gzip and ...
Dev Articles Forums 
ADO.NET  
Apache  
ASP  
ASP.NET  
C#  
C++  
ColdFusion  
COM/COM+  
Delphi-Kylix  
Design Usability  
Development Cycles  
DHTML  
Embedded Tools  
Flash  
Graphic Design  
HTML  
IIS  
Interviews  
Java  
JavaScript  
MySQL  
Oracle  
Photoshop  
PHP  
Reviews  
Ruby-on-Rails  
SQL  
SQL Server  
Style Sheets  
VB.Net  
Visual Basic  
Web Authoring  
Web Services  
Web Standards  
XML  
Mobile Linux 
App Generation ROI 
IBM® developerWorks 
Weekly Newsletter
 
Developer Updates  
Free Website Content 
 RSS  Articles
 RSS  Forums
 RSS  All Feeds
Write For Us Get Paid 
Request Media Kit
Contact Us 
Site Map 
Privacy Policy 
Support 
 USERNAME
 
 PASSWORD
 
 
  >>> SIGN UP!  
  Lost Password? 
APACHE

Compressing Web Content with mod_gzip and mod_deflate
By: Stephen Pierzchala
  • Search For More Articles!
  • Disclaimer
  • Author Terms
  • Rating: 4 stars4 stars4 stars4 stars4 stars / 5
    2003-05-30

    Table of Contents:

    Rate this Article: Poor Best 
      ADD THIS ARTICLE TO:
      Del.ici.ous Digg
      Blink Simpy
      Google Spurl
      Y! MyWeb Furl
    Email Me Similar Content When Posted
    Add Developer Shed Article Feed To Your Site
    Email Article To Friend
    Print Version Of Article
    PDF Version Of Article
     
     
    ADVERTISEMENT


    It simply makes sense. Compress your files with mod_gzip and save money with less bandwidth transmissions. Read this article to find out more.

    In a previous paper, the use of mod_gzip to dynamically compress the output from an Apache server. With the growing use of the Apache 2.0.x family of Web servers, the question arises of how to perform a similar GZIP-encoding function within this server. The developers of the Apache 2.0.x servers have included a module in the codebase for the server to perform just this task.

    mod_deflate is included in the Apache 2.0.x source package, and compiling it in is a simple matter of adding it to the configure command.

    ./configure --enable-modules=all --enable-mods-shared=all --enable-deflate

    When the server is made and installed, the GZIP-encoding of documents can be enabled in one of two ways: explicit exclusion of files by extension; or by explicit inclusion of files by MIME type. These methods are specified in the httpd.conf file.

    Explicit Exclusion

     SetOutputFilter DEFLATE
    DeflateFilterNote ratio
    SetEnvIfNoCase Request_URI \.(?:gif|jpe?g|png)$ no-gzip dont-vary
    SetEnvIfNoCase Request_URI \.(?:exe|t?gz|zip|bz2|sit|rar)$ no-gzip dont-vary
    SetEnvIfNoCase Request_URI \.pdf$ no-gzip dont-vary

    Explicit Inclusion

     DeflateFilterNote ratio
    AddOutputFilterByType DEFLATE text/*
    AddOutputFilterByType DEFLATE application/ms*
    application/vnd* application/postscript

    Both methods enable the automatic GZIP-encoding of all MIME-types, except image and PDF files, as they leave the server. Image files and PDF files are excluded as they are already in a highly compressed format. In fact, PDFs become unreadable by Adobe's Acrobat Reader if they are further compressed by mod_deflate or mod_gzip.

    On the server used for testing mod_deflate for this article, no Windows executables or compressed files are served to visitors. However, for safety's sake, please ensure that compressed files and binaries are not GZIP-encoded by your Web server application.

    For the file-types indicated in the exclude statements, the server is told explicitly not to send the Vary header. The Vary header indicates to any proxy or cache server which particular condition(s) will cause this response to Vary from other responses to the same request.

    If a client sends a request which does not include the Accept-Encoding: gzip header, then the item which is stored in the cache cannot be returned to the requesting client if the Accept-Encoding headers do not match. The request must then be passed directly to the origin server to obtain a non-encoded version. In effect, proxy servers may store 2 or more copies of the same file, depending on the client request conditions which cause the server response to Vary.

    Removing the Vary response requirement for objects not handled means that if the objects do not vary due to any other directives on the server (browser type, for example), then the cached object can be served up without any additional requests until the Time-To-Live (TTL) of the cached object has expired.

    In examining the performance of mod_deflate against mod_gzip, the one item that distinguished mod_deflate from mod_gzip in versions of Apache prior to 2.0.45 was the amount of compression that occurred. The examples below demonstrate that the compression algorithm for mod_gzip produces between 4-6% more compression than mod_deflate for the same file.[1]

    Table 1 — Large HTML Document

    CompressionSizeCompression %
    No compression56380 bytesn/a
    Apache 1.3.x/mod_gzip16333 bytes29% of original
    Apache 2.0.x/mod_deflate19898 bytes35% of original

    Table 2 — Postscript File

    CompressionSizeCompression %
    No Compression63451 bytesn/a
    Apache 1.3.x/mod_gzip19758 bytes31% of original
    Apache 2.0.x/mod_deflate23407 bytes37% of original

    Attempts to increase the compression ratio of mod_deflate in Apache 2.044 and lower using the directives provided for this module produced no further decrease in transferred file size. A comment from one of the authors of the mod_deflate module stated that the module was written specifically to ensure that server performance was not degraded by using this compression method. The module was, by default, performing the fastest compression possible, rather than a mid-range compromise between speed and final file size.

    Starting with Apache 2.0.45, the compression level of mod_deflate is configurable using the DeflateCompressionLevel directive. This directive accepts values between 1 (fastest compression speed; lowest compression ratio) and 9 (slowest compression speed; highest compression ratio), with the default value being 6. This simple change makes the compression in mod_deflate comparable to mod_gzip out of the box.

    Using mod_deflate for Apache 2.0.x is a quick and effective way to decrease the size of the files that are sent to clients. Anything that can produce between 50% and 80% in bandwidth savings with so little effort should definitely be considered for any and all Apache 2.0.x deployments wishing to use the default Apache codebase.


    [1] A note on the compression in mod_deflate for Apache 2.044 and lower:

    The level of compression can be modified by changing the ZLIB compression setting in mod_deflate.c from Z_BEST_SPEED (equivalent to "gzip -1") to Z_BEST_COMPRESSION (equivalent to "gzip -9").

    These defaults can also be replaced with a numeric value between 1 and 9. A "hacked" version of the mod_deflate.c code is available here; the compression level has been set to "6", which is regarded as a good balance between speed and compression.

    More info on hacking mod_deflate for Apache 2.0.44 and lower can be found here.


    DISCLAIMER: The content provided in this article is not warranted or guaranteed by Developer Shed, Inc. The content provided is intended for entertainment and/or educational purposes in order to introduce to the reader key ideas, concepts, and/or product reviews. As such it is incumbent upon the reader to employ real-world tactics for security and implementation of best practices. We are not liable for any negative consequences that may result from implementing any information covered in our articles or tutorials. If this is a hardware review, it is not recommended to open and/or modify your hardware.

    More Apache Articles
    More By Stephen Pierzchala

     

    IBM® developerWorks developerWorks - FREE Tools!


    NEW! Best Practices: The Integrated Project and Portfolio Management Platform.

    Hear how IBM Rational Project and Portfolio Management integrated solutions help teams put the right tools and processes in place to maximize the effectiveness and efficiency of project teams and ensure that the business vision is being executed correctly. Learn how to automate and integrate requirements prioritization, top-down project planning, communications and controls, and methodology deployment to keep your scope, costs, and schedules under control. Tackle with an end-to-end approach the management of scope and scope changes, usage of methodology to control and empower project teams, and optimization of resources to align activity costs with the overall project plan.
    FREE! Go There Now!


    NEW! Evaluate IBM Lotus Sametime Standard V8.0

    Visit IBM developerWorks to download a free trial of the latest release of IBM Lotus Sametime Standard V8.0. Lotus Sametime Standard V8.0 is a platform for unified communications and collaboration that combines security features with an extensible, open solution including integrated Voice over IP, geographic location awareness, mobile clients, and a robust Business Partner community offering telephony and video integration.
    FREE! Go There Now!


    NEW! Harnessing the power of SQL and Java for high performance data access

    Join this webcast to see how IBM Data Studio Developer and pureQuery can take the pain out of Java data access. uApplications developed using both Java and SQL have become a common requirement. Database connectivity using Java Database Connectivity (JDBC) to create an application is a multi-step tedious process, and tooling that covers both SQL and Java has been unavailable, until now. IBM Data Studio introduces the pureQuery platform: a high-performance, Java data access platform focused on simplifying the tasks of developing, managing, and optimizing database applications and services.
    FREE! Go There Now!


    NEW! IBM Enterprise Modernization Sandbox for System z: Architecture

    Analysts, architects, and developers who have existing COBOL or PL/I skills and want to extend those skills to deploy new workloads on the mainframe can use the IBM Enterprise Modernization Sandbox for System z to find hands-on walkthroughs of common real world scenarios. The scenarios provide examples of how to rapidly design, create, assemble, test, and deploy high-quality Web, Web services, portal, and SOA applications for IBM CICS, IBM IMS, and IBM WebSphere Application Server.
    FREE! Go There Now!


    NEW! IBM Rational Systems Development e-Kit

    As systems increase in complexity, communication between systems and software teams becomes more and more difficult. Now, there’s a way to improve product quality and communication.<br />Read the “Model Driven Systems Development” white paper to see how. Also included in this kit are more educational white papers, customer examples, tutorials, informative Webcasts, and best practices for designing, building and managing systems.<br />
    FREE! Go There Now!


    NEW! Section 508 of the U.S. Rehabilitation Act: Web accessibility compliance

    Because access to government information continues to be an area of concern for many U.S. citizens with disabilities, the U.S. government enacted Section 508 of the Rehabilitation Act in 2001 to ensure that government agencies create accessible Web content, enabling all citizens to access the information they need. A fully accessible Web site makes Web content accessible to all individuals, including those with disabilities, who may be accessing Web content via a variety of user agents. Common user agents include standard Web browsers, text-only browsers, assistive devices and mobile devices such as cell phones or personal digital assistants (PDAs).
    FREE! Go There Now!


    NEW! Trial download: IBM Rational Method Composer V7.2

    Get a free trial download of the latest version of IBM Rational Method Composer V7.2 which helps you deliver customized yet consistent process guidance to your project teams and IT organization, and includes the latest version of IBM Rational Unified Process (RUP), which has provided process guidance to teams since 1996.
    FREE! Go There Now!


    NEW! Trial download: IBM Rational Performance Tester V7.0.1

    Get a free trial download of the latest version of IBM Rational Performance Tester V7.0.1, a load and performance testing solution for teams concerned about the scalability of their Web-based applications. Combining multiple ease-of-use features with granular detail, Rational Performance Tester simplifies the test-creation, load-generation and data-collection processes that help teams ensure the ability of their applications to accommodate required user loads.
    FREE! Go There Now!


    NEW! Using Rational Business Developer to enhance your developer productivity

    Join this Rational Talks to You teleconference, to hear how Enterprise Generation Language (EGL) eliminates the need for tedious and error-prone low level coding, so developers can focus on business requirements. EGL extends the Rational software development platform with a simplified programming language that enables developers who have little or no experience with Java, Web technologies or Service Oriented Architecture, to create enterprise-class applications and services quickly and easily. It also allows developers who may have little or no mainframe programming experience to quickly create traditional mainframe components.
    FREE! Go There Now!


    NEW! Webcast: Introducing the new Information Server and Solutions community: LeverageInformation

    User communities play an important role in communication and collaboration around products, solutions and other areas of special interest to members. Successful communities are able to provide the right mix of content and services to deliver a value proposition that resonates with each audience. Join Tom Inman, VP of Marketing for Information and Platform Solutions as he introduces the new LeverageINFORMATION community. During this webcast, learn about the value provided by the community and how customers and partners derive value from the community in addressing their own technical and business challenges.
    FREE! Go There Now!



    All FREE IBM® developerWorks Tools!

    APACHE ARTICLES

    - Programmatically Manipulating Microsoft Exce...
    - Installing PHP under Windows
    - Compressing Web Content with mod_gzip and mo...
    - Compressing Web Output Using mod_deflate and...
    - Setting Up Apache 2.0.45 to Parse PHP Pages
    - Custom Error 404 Documents with PHP
    - Using Apache and PHP on Mac OS X
    - ASP: Active Sessions, Active Logins and Tota...
    - Working With Oracle on Windows: Part 1
    - The Quick-n-Dirty Guide to Setting Up Apache...
    - Installing Apache With SSL: The Complete Gui...
    - 7 Powerful .htaccess Customization Tips
    - Trap And Get Notified: A Practical Solution ...
    - One Way To Use Server Side Includes
    - Using ForceType For Nicer Page URLs







    © 2003-2010 by Developer Shed. All rights reserved. DS Cluster 12 Hosted by Hostway
    For more Enterprise Application Development news, visit eWeek