Squid: The Definitive Guide (Paperback)

Squid is the most popular Web caching software in use today, and it works on a variety of platforms including Linux, FreeBSD, and Windows. Squid improves network performance by reducing the amount of bandwidth used when surfing the Web. It makes web pages load faster and can even reduce the load on your web server. By caching and reusing popular web content, Squid allows you to get by with smaller network connections. It also protects the host on your internal network by acting as a firewall and proxying your internal web traffic. You can use Squid to collect statistics about the traffic on your network, prevent users from visiting inappropriate web sites at work or school, ensure that only authorized users can surf the Internet, and enhance your privacy by filtering sensitive information from web requests. Companies, schools, libraries, and organizations that use web-caching proxies can look forward to a multitude of benefits.

Written by Duane Wessels, the creator of Squid, Squid: The Definitive Guide will help you configure and tune Squid for your particular situation. Newcomers to Squid will learn how to download, compile, and install code. Seasoned users of Squid will be interested in the later chapters, which tackle advanced topics such as high-performance storage options, rewriting requests, HTTP server acceleration, monitoring, debugging, and troubleshooting Squid.

Topics covered include:

• Compiling and installing Squid
  
• Running Squid
  
• Using Squid's sophisticated access controls
  
• Tuning disk storage for optimal performance
  
• Configuring your operating system for HTTP interception
  
• Forwarding Requests to other web caches
  
• Using redirectors to rewrite user requests
  
• Monitoring Squid with the cache manager and SNMP
  
• Using Squid to accelerate and protect HTTP servers
  
• Managing bandwidth consumption with Delay Pools

Table of Contents

Preface 

1. Introduction

      Web Caching 

      A Brief History of Squid 

      Hardware and Operating System Requirements 

      Squid Is Open Source 

      Squid's Home on the Web 

      Getting Help 

      Getting Started with Squid 

      Exercises 

2. Getting Squid

      Versions and Releases 

      Use the Source, Luke 

      Precompiled Binaries 

      Anonymous CVS 

      devel.squid-cache.org 

      Exercises 

3. Compiling and Installing

      Before You Start 

      Unpacking the Source 

      Pretuning Your Kernel 

      The configure Script 

      make 

      make Install 

      Applying a Patch 

      Running configure Later 

      Exercises 

4. Configuration Guide for the Eager

      The squid.conf Syntax 

      User IDs 

      Port Numbers 

      Log File Pathnames 

      Access Controls 

      Visible Hostname 

      Administrative Contact Information 

      Next Steps 

      Exercises 

5. Running Squid

      Squid Command-Line Options 

      Check Your Configuration File for Errors 

      Initializing Cache Directories 

      Testing Squid in a Terminal Window 

      Running Squid as a Daemon Process 

      Boot Scripts 

      A chroot Environment 

      Stopping Squid 

      Reconfiguring a Running Squid Process 

      Rotating the Log Files 

      Exercises 

6. All About Access Controls

      Access Control Elements 

      Access Control Rules 

      Common Scenarios 

      Testing Access Controls 

      Exercises 

7. Disk Cache Basics

      The cache_dir Directive 

      Disk Space Watermarks 

      Object Size Limits 

      Allocating Objects to Cache Directories 

      Replacement Policies 

      Removing Cached Objects 

      refresh_pattern 

      Exercises 

8. Advanced Disk Cache Topics

      Do I Have a Disk I/O Bottleneck? 

      Filesystem Tuning Options 

      Alternative Filesystems 

      The aufs Storage Scheme 

      The diskd Storage Scheme 

      The coss Storage Scheme 

      The null Storage Scheme 

      Which Is Best for Me? 

      Exercises 

9. Interception Caching

      How It Works 

      Why (Not) Intercept? 

      The Network Device 

      Operating System Tweaks 

      Configure Squid 

      Debugging Problems 

      Exercises 

10. Talking to Other Squids

      Some Terminology 

      Why (Not) Use a Hierarchy? 

      Telling Squid About Your Neighbors 

      Restricting Requests to Neighbors 

      The Network Measurement Database 

      Internet Cache Protocol 

      Cache Digests 

      Hypertext Caching Protocol 

      Cache Array Routing Protocol 

      Putting It All Together 

      How Do I ... 

      Exercises 

11. Redirectors

      The Redirector Interface 

      Some Sample Redirectors 

      The Redirector Pool 

      Configuring Squid 

      Popular Redirectors 

      Exercises 

12. Authentication Helpers

      Configuring Squid 

      HTTP Basic Authentication 

      HTTP Digest Authentication 

      Microsoft NTLM Authentication 

      External ACLs 

      Exercises 

13. Log Files

      cache.log 

      access.log 

      store.log 

      referer.log 

      useragent.log 

      swap.state 

      Rotating the Log Files 

      Privacy and Security 

      Exercises 

14. Monitoring Squid

      cache.log Warnings 

      The Cache Manager 

      Using SNMP 

      Exercises 

15. Server Accelerator Mode

      Overview 

      Configuring Squid 

      Gee, That Was Confusing! 

      Access Controls 

      Content Negotiation 

      Gotchas 

      Exercises 

16. Debugging and Troubleshooting

      Some Common Problems 

      Debugging via cache.log 

      Core Dumps, Assertions, and Stack Traces 

      Replicating Problems 

      Reporting a Bug 

      Exercises 

A. Config File Reference

B. The Memory Cache

C. Delay Pools

D. Filesystem Performance Benchmarks

E. Squid on Windows

F. Configuring Squid Clients

Index