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Efficient Apache Monitoring and Sizing Tips

Learn how to monitor and size your Apache server for optimal performance. Find tips on configuration, performance, and scaling strategies. Discover useful tools and techniques to keep your server running smoothly.

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Efficient Apache Monitoring and Sizing Tips

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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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