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!


    IBM DB2 Deep Compression ROI Tool

    The IBM DB2 Deep Compression ROI tool is designed for DBA’s and IT management personnel to perform a clinical analysis of the cost savings gained from the Storage Optimization feature of DB2 9 for Linux, UNIX and Windows. The feature, also known as Deep Compression, compresses data that lies within a database by up to 80% at times.
    FREE! Go There Now!


    NEW! Cook up Web sites fast with CakePHP, Part 4: Use CakePHP's Session and Request Handler components

    CakePHP is a stable production-ready, rapid-development aid for building Web sites in PHP. This "Cook up Web sites fast with CakePHP" series shows you how to build an online product catalog using CakePHP.
    FREE! Go There Now!


    NEW! Download IBM Data Studio V1.1

    Visit IBM developerWorks to download the latest trial version of IBM Data Studio V1.1 at no cost. IBM Data Studio is a comprehensive data management solution that helps you effectively design, develop, deploy and manage your data, databases, and database applications throughout the data management life cycle utilizing a consistent and integrated user interface. Unlike other client-side data management solutions that focus on only one aspect of the application lifecycle or database administration, Data Studio complements the Rational Software Delivery platform, providing unparalleled flexibility for a heterogeneous data server environment across platforms.
    FREE! Go There Now!


    NEW! Hello World: Learn how to install and use the Rational Asset Manager Eclipse client

    In this tutorial, you can learn how to install and configure the IBM Rational Asset Manager Eclipse client, explore the different views in the Asset Management perspective, learn various search techniques, work with existing assets, and submit a new asset.
    FREE! Go There Now!


    NEW! IBM Enterprise Modernization Sandbox for System z

    IBM Enterprise Modernization solutions help organizations evolve core IT systems towards modern architectures and technologies—reducing the burden of maintenance and freeing up resources to develop new business requirements and capabilities. With the IBM Enterprise Modernization Sandbox for System z you can evaluate IBM Enterprise Modernization solutions focused on five key areas: Assets, Architectures, Skills, Processes and Infrastructures, and Investment. Each solution is based upon real customer experiences and offers a proven path to get you started with your modernization projects.
    FREE! Go There Now!


    NEW! IBM Rational AppScan Standard Edition V7.7

    Secure your Web applications with IBM Rational AppScan Standard Edition V7.7, previously known as Watchfire AppScan. This Web application security testing tool automates vulnerability assessments and scans and tests for common Web application vulnerabilities. Visit IBM developerWorks to download a free trial of IBM Rational AppScan Standard Edition V7.7.
    FREE! Go There Now!


    NEW! Info 2.0: Harnessing the power of Web 2.0 and Enterprise Mashups

    Listen to this webcast to get an overview of Info 2.0 and a technical demo of how to quickly build an enterprise mashup. IBM's Info 2.0 technology leverages emerging Web 2.0 technologies such as mashups, feeds, AJAX, and JSON in order to simplify assembly of information using feeds and services. Come learn about the technical elements of Info 2.0 including the Feed Generation framework, Mashup Engine, and mashup assembly components. Learn how to pull information from databases, departmental information, and the Web to create mashups critical to your company’s success. We will also discuss best practices to help you get started.
    FREE! Go There Now!


    NEW! Rational Asset Manager eKit

    Learn how to do more with your reusable assets with the free Rational Asset Manager eKit. The eKit includes demos on how Rational Asset Manager tracks and audits your assets in order to utilize them for reuse. Plus you’ll find white papers and a Webcast that discuss the challenges of a Service Oriented Architecture and how Rational Asset Manager can provide quick and effective solutions.
    FREE! Go There Now!


    NEW! Software Change and Configuration Management Solution Guidelines

    This whitepaper provides areas to consider when evaluating any software configuration management solution. It addresses how the IBM solutions (Rational ClearCase and Rational ClearQuest) meet the needs and requirements of both project leaders and developers to provide successful Software Change and Configuration Management.
    FREE! Go There Now!


    NEW! Webcast: Accelerating Software Innovation with System z

    Attend this launch webcast with Scott Hebner, Vice President of IBM Rational Marketing and Strategy, where he will overview Rational’s new offerings and programs to help customers accelerate software innovation on System z. He will discuss how these solutions help organizations extend their core business processes toward modern architectures such as SOA and web technologies to deliver business improvements that stand the test of time.
    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 2 Hosted by Hostway
    For more Enterprise Application Development news, visit eWeek