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Shoehorning Apache Onto Your Box

Shoehorning Apache Onto Your Box. System Sizing Tips. Sander Temme <sander@temme.net>. So, your web server machine may not be the fastest, shiniest machine, but it can still take a few hits without going down. Assumptions. Limited Resources Work With What You Have

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Shoehorning Apache Onto Your Box

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  1. Shoehorning Apache Onto Your Box System Sizing Tips Sander Temme <sander@temme.net>

  2. So, your web server machine may not be the fastest, shiniest machine,but it can still take a few hits without going down.

  3. Assumptions • Limited Resources • Work With What You Have • You’re probably running Linux • No Compiling or Recompiling! • You can find httpd.conf

  4. Purposes of Monitoring • Observation • Extrapolation • Signals/Alerts • Testing

  5. Monitoring Your Server

  6. Monitoring Apache

  7. Monitoring Solaris: SE Toolkit • Lightweight • Programmable • Alive http://www.wundermoosen.com/default.aspx?f=2&p=setoolkit

  8. Other Monitoring Tools • vmstat • top • free

  9. Web Server Logs • ErrorLog • LogLevel: debug, info, notice, warn, error, crit • Access Log: TransferLog or CustomLog • Common Log Format

  10. Common Log Format 172.16.2.91 - - [16/Nov/2003:15:23:27 -0800] "GET /~sctemme/ HTTP/1.1" 200 1446 172.16.2.91 - - [16/Nov/2003:15:23:28 -0800] "GET /~sctemme/css/doc.css HTTP/1.1" 200 167 172.16.2.91 - - [16/Nov/2003:15:23:28 -0800] "GET /~sctemme/css/menu.css HTTP/1.1" 200 623 172.16.2.91 - - [16/Nov/2003:15:23:29 -0800] "GET /favicon.ico HTTP/1.1" 404 283 172.16.2.91 - - [16/Nov/2003:15:23:34 -0800] "GET /~sctemme/index.html HTTP/1.1" 200 1446

  11. Configuring for Performance • Configuring Apache • Tuning the Operating System • Scaling Your Site

  12. Apache Configuration • Process/Thread Management • DNS Lookups • Avoid .htaccess Files • Disable unused modules • Tune your App Tier

  13. DNS Lookups • HostnameLookups • Access Control • Bad: Deny from example.com • Good: Deny from 172.160.234.5

  14. .htaccess Files • Per-directory configuration files • Accessed for every request • Best performance: AllowOverride none GET /dir1/dir2/restricted.html HTTP/1.0

  15. 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)

  16. 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

  17. Top

  18. Selecting Your MPM • Apache 2.0 only! • Processes and Threads • Differences between platforms • Thread-safety issues

  19. 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

  20. 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

  21. 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

  22. 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

  23. System Tuning Tips • RAM and swap space • ulimit: files and processes • Turn off unused services and modules

  24. 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

  25. 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

  26. Scaling Your Site • Vertically • Tiered Model • Horizontally • Load Balancing

  27. Scaling Vertically TCP/IP Client TCP/IP TCP/IP

  28. Scaling Vertically • Move Services to Other Hosts • Pros: • Less resource contention • Specialized hardware • Scale tiers individually • Cons: • Development/Deployment harder • More hosts to manage

  29. Scaling Horizontally Client

  30. Tips • Observe Before You Act • Act on Monitoring Results • Don’t Overload Your System • Use A Staging Server

  31. Q&A

  32. 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

  33. 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

  34. Current Version http://apache.org/~sctemme/Apcon2004/MO14/

  35. Thank You

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