The Apache Modules Book: Application Development with Apache (Prentice Hall Open Source Software Development Series)

589 Pages·2007·2.81 MB·English

by  Nick Kew

The Apache Modules Book
Prentice Hall
Open Source Software Development Series
Arnold Robbins, Series Editor
“Real world code from real world applications”
Open Source technology has revolutionized the computing world. Many large-scale projects are
in production use worldwide, such as Apache, MySQL, and Postgres, with programmers writing
applications in a variety of languages including Perl, Python, and PHP.These technologies are in
use on many different systems, ranging from proprietary systems, to Linux systems, to traditional
UNIX systems, to mainframes.
The Prentice Hall Open Source Software Development Series is designed to bring you the
best of these Open Source technologies. Not only will you learn how to use them for your
projects, but you will learn from them. By seeing real code from real applications, you will learn
the best practices of Open Source developers the world over.
Titles currently in the series include:
Linux® Debugging and Performance Tuning: Tips and Techniques
Steve Best
0131492470, Paper, ©2006
Understanding AJAX: Using JavaScript to Create Rich Internet Applications
Joshua Eichorn
0132216353, Paper, ©2007
Embedded Linux Primer
Christopher Hallinan
0131679848, Paper, ©2007
SELinux by Example
Frank Mayer, David Caplan, Karl MacMillan
0131963694, Paper, ©2007
UNIX to Linux® Porting
Alfredo Mendoza, Chakarat Skawratananond, Artis Walker
0131871099, Paper, ©2006
Linux Programming by Example: The Fundamentals
Arnold Robbins
0131429647, Paper, ©2004
The Linux® Kernel Primer: A Top-Down Approach for x86 and PowerPC Architectures
Claudia Salzberg, Gordon Fischer, Steven Smolski
0131181637, Paper, ©2006
The Apache Modules Book
Application Development
with Apache
Nick Kew
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Library of Congress Cataloging-in-Publication Data
Kew, Nick.
The Apache modules book : application development with Apache / Nick Kew.
p. cm.
Includes bibliographical references and index.
ISBN 0-13-240967-4 (pbk. : alk. paper)
1. Apache (Computer file : Apache Group) 2. Web servers—Computer programs. 3. Application software—
Development. I. Title.
TK5105.8885.A63K49 2007
005.7'1376—dc22
2006036623
Copyright © 2007 Pearson Education, Inc.
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Text printed in the United States on recycled paper at RR Donnelley in Crawfordsville, Indiana.
First printing, January 2007
To all who share my dream, and are working to help make it happen…
…the dream of a world where your work, your colleagues, and your opportunities
in life are not dictated by where you live or how far you commute. Where the
old-fashioned office of the nineteenth and twentieth centuries has passed into
history, along with its soul-destroying bums-on-seats culture and Dilbertian work
practices. A world inclusive of those who cannot work in a standard office. A world
inclusive of those who reject car-dependence, but embrace a full and active life.
A world inclusive of those who seek to fit study and learning into a busy life, yet
have no accessible library, let alone university. Of those who are housebound…
Our information infrastructure is poised to liberate us all. We who develop
with Apache are playing a small but exciting part in that. This work is
dedicated to all of us!
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Contents
Foreword. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxi
Preface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxiii
Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxvii
About the Author . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxix
Chapter 1 Applications Development with Apache . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 A Brief History of the Apache Web Server. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1.1 Apache 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1.2 Apache 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2 The Apache Software Foundation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2.1 Meritocracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2.2 Roles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2.3 Philosophy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.3 The Apache Development Process. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.3.1 The Apache Codebase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.3.2 Development Forums. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.3.3 Developers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
1.3.4 Participation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.4 Apache and Intellectual Property. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
1.4.1 The Apache License . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
1.4.2 Third-Party Intellectual Property . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
1.5 Further Reading. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
1.5.1 Interactive Online Forums. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
1.5.2 Conferences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
1.5.3 Websites. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
1.6 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
vii
viii Contents
Chapter 2 The Apache Platform and Architecture . . . . . . . . . . . . . . . . . . . . . . . 21
2.1 Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2.2 Two-Phase Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
2.2.1 Start-up Phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.2.2 Operational Phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
2.2.3 Shutdown. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
2.3 Multi-Processing Modules. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
2.3.1 Why MPMs? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
2.3.2 The UNIX-Family MPMs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
2.3.3 Working with MPMs and Operating Systems . . . . . . . . . . . . . . . . . . . . . . . . . 28
2.4 Basic Concepts and Structures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.4.1 request_rec. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
2.4.2 server_rec. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
2.4.3 conn_rec . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
2.4.4 process_rec. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
2.5 Other Key API Components. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
2.6 Apache Configuration Basics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
2.7 Request Processing in Apache . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
2.7.1 Content Generation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
2.7.2 Request Processing Phases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
2.7.3 Processing Hooks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
2.7.4 The Data Axis and Filters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
2.7.5 Order of Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
2.7.6 Processing Hooks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
2.8 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Chapter 3 The Apache Portable Runtime. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
3.1 APR. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
3.2 APR-UTIL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
3.3 Basic Conventions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
3.3.1 Reference Manual: API Documentation and Doxygen. . . . . . . . . . . . . . . . . . . 57
3.3.2 Namespacing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
3.3.3 Declaration Macros . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
3.3.4 apr_status_t and Return Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
3.3.5 Conditional Compilation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
Contents ix
3.4 Resource Management: APR Pools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
3.4.1 The Problem of Resource Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
3.4.2 APR Pools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
3.4.3 Resource Lifetime. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
3.4.4 Limitations of Pools. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
3.5 Selected APR Topics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
3.5.1 Strings and Formats. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
3.5.2 Internationalization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
3.5.3 Time and Date. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
3.5.4 Data Structs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
3.5.5 Buckets and Brigades . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
3.5.6 Filesystem. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
3.5.7 Network. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
3.5.8 Encoding and Cryptography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
3.5.9 URI Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
3.5.10 Processes and Threads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
3.5.11 Resource Pooling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
3.5.12 API Extensions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
3.6 Databases in APR/Apache. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
3.6.1 DBMs and apr_dbm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
3.6.2 SQL Databases and apr_dbd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
3.7 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
Chapter 4 Programming Techniques and Caveats. . . . . . . . . . . . . . . . . . . . . . . . 85
4.1 Apache Coding Conventions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
4.1.1 Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
4.1.2 Functions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
4.1.3 Blocks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
4.1.4 Flow Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
4.1.5 Declarations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
4.1.6 Comments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
4.2 Managing Module Data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
4.2.1 Configuration Vectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
4.2.2 Lifetime Scopes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
4.3 Communicating Between Modules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
4.4 Thread-Safe Programming Issues. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92