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Shoehorning Apache Onto Your Box

System Sizing Tips

Sander Temme <sander@temme.net>

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So, your web server machine may not be the fastest, shiniest

machine,but it can still take a few hits

without going down.

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Assumptions

• Limited Resources

• Work With What You Have

• You’re probably running Linux

• No Compiling or Recompiling!

• You can find httpd.conf

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Purposes of Monitoring

• Observation

• Extrapolation

• Signals/Alerts

• Testing

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Monitoring Your Server

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Monitoring Apache

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Monitoring Solaris: SE Toolkit

• Lightweight• Programmable• Alive

http://www.wundermoosen.com/default.aspx?f=2&p=setoolkit

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Other Monitoring Tools

• vmstat

• top

• free

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Web Server Logs

• ErrorLog– LogLevel: debug, info, notice, warn, error, crit

• Access Log: TransferLog or CustomLog– Common Log Format

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Common Log Format172.16.2.91 - - [16/Nov/2003:15:23:27 -0800] "GET /~sctemme/ HTTP/1.1" 200 1446172.16.2.91 - - [16/Nov/2003:15:23:28 -0800] "GET /~sctemme/css/doc.css HTTP/1.1" 200 167172.16.2.91 - - [16/Nov/2003:15:23:28 -0800] "GET /~sctemme/css/menu.css HTTP/1.1" 200 623172.16.2.91 - - [16/Nov/2003:15:23:29 -0800] "GET /favicon.ico HTTP/1.1" 404 283172.16.2.91 - - [16/Nov/2003:15:23:34 -0800] "GET /~sctemme/index.html HTTP/1.1" 200 1446

Client IP 172.16.2.91

RFC 1413 ident -

username -

timestamp [16/Nov/2003:15:23:29 -0800]

Request "GET /favicon.ico HTTP/1.1"

Status Code 404

Content Bytes 283

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Configuring for Performance

• Configuring Apache

• Tuning the Operating System

• Scaling Your Site

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Apache Configuration

• Process/Thread Management

• DNS Lookups

• Avoid .htaccess Files

• Disable unused modules

• Tune your App Tier

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DNS Lookups

• HostnameLookups

• Access Control– Bad: Deny from example.com– Good: Deny from 172.160.234.5

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.htaccess Files

• Per-directory configuration files

• Accessed for every request

• Best performance: AllowOverride none

GET /dir1/dir2/restricted.html HTTP/1.0

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MaxClients

• Configuration file directive

• Maximum number of workers

• Apache 1.3, 2.0 Prefork: processes

• Apache 2.0 Worker: threads * processes

• Limit according to resources (memory)

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Sizing MaxClients

• Take total RAM

• Subtract OS allowance– look at free value without Apache, etc.

• Subtract external program allowance– JVM, cgi programs, MySQL?

• Divide by httpd process size– Read process size from top

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Top

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Selecting Your MPM

• Apache 2.0 only!

• Processes and Threads

• Differences between platforms

• Thread-safety issues

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Processes and Threads

• Process:– Own copy of data structures– Shares: program code, shared memory– Context switches expensive

• Thread:– Runs within process– Shares process environment– No context switch

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Platforms and Threading

• Context switches expensive on Solaris, AIX• Context switches cheaper on Linux• Solaris uses M:N threading• Linux uses 1 process per thread• LinuxThreads implementation is old

– Replaced by Native Posix Thread Library (NPTL) in 2.6

– NTPL already in RH 9, RHAS 3

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Thread-safety

• Third-party modules and libraries– mod_perl: experimental threading in Perl 5.6;

more mature in Perl 5.8– PHP: uses many third-party libraries

• FreeBSD: threading not reliable until 5.x– Use KSE threading in 5.x– Still not endorsed by ASF

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Tune your App Tier

• Tomcat– Edit server.xml, tune minProcessors,

maxProcessors– Tune JVM (Heap, Garbage Collection)

• MySQL– Ships with various scenarios in support-files:

• my-{small,medium,large,huge}.conf

– PHP & prefork: every child makes a connection

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System Tuning Tips

• RAM and swap space

• ulimit: files and processes

• Turn off unused services and modules

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RAM and Swap

• Swap is disk-based Extension of RAM

• Excessive swapping kills performance

• Tune MaxClients

• Never have more memory than swap– Upgrade RAM -> add more swap space

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ulimit

• Per-process resource limits• Built-in command of sh, bash• Important limits:

– processes (-u)– open files (-n)

• Set in invoking shell• Code in Apache 2.0 startup script

– ulimit -S -n `ulimit -H -n`

• Linux: /etc/security/limits.conf

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Scaling Your Site

• Vertically– Tiered Model

• Horizontally– Load Balancing

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Scaling Vertically

ClientTCP/IP

TCP/IP

TCP/IP

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Scaling Vertically

• Move Services to Other Hosts• Pros:

– Less resource contention– Specialized hardware– Scale tiers individually

• Cons:– Development/Deployment harder– More hosts to manage

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Scaling Horizontally

Client

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Tips

• Observe Before You Act

• Act on Monitoring Results

• Don’t Overload Your System

• Use A Staging Server

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Q&A

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Further Reading

• Ryan B. Bloom, Apache Server 2.0: The Complete Reference, 2002 McGraw Hill Osborne; ISBN 0-07-222344-8

• Ben Laurie and Peter Laurie, Apache: The Definitive Guide (3rd Edition), 2002 O’Reilly & Associates; ISBN 0596002033

• Patrick Killelea, Web Performance Tuning, 2nd Edition, 2002 O’Reilly & Associates; ISBN 0-596-00172-X

• http://httpd.apache.org/docs-2.0/misc/perf-tuning.html• http://httpd.apache.org/docs/misc/perf-tuning.html• Adrian Cockcroft, Richard Pettit and Sun Microsystems Press, Sun

Performance and Tuning: Java and the Internet (2nd Edition), 1998 Prentice Hall PTR; ISBN 0130952494

• Ken Coar and Rich Bowen, Apache Cookbook, 2003 O’Reilly & Associates; ISBN 0596001916

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Conference Roadmap

• T11: Scalable Internet Architectures• MO04: Advanced Topics in Module Design• TU02: Apache as a Reverse Proxy• TU05: Building Scalable Websites with Perl• TU13: Feedster at 18 Months Old• TU17: Migrating the BBC website to Apache • WE08: Apache Performance• WE19: Powering High-volume web sites with

Lenya/Cocoon and mod_cache

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Current Version

http://apache.org/~sctemme/Apcon2004/MO14/

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Thank You