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Shoehorning Apache Onto Your Box

Shoehorning Apache Onto Your Box. System Sizing tips. Sander Temme <sander@temme.net>. Agenda. The Problem Monitoring Your Server How Many Processes? Selecting Your MPM Spinning Locks Tuning Tips Further Reading. The Problem. 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. Agenda • The Problem • Monitoring Your Server • How Many Processes? • Selecting Your MPM • Spinning Locks • Tuning Tips • Further Reading

  3. The Problem • Limited Resources • Work with what you have • How to get the most out of existing infrastructure

  4. Monitoring Your Server • top • free • vmstat • Web server logs • SE Toolkit • mod_status • Generating Load

  5. Top

  6. free and vmstat [sctemme@eartha sctemme]$ free total used free shared buffers cached Mem: 635080 601288 33792 0 110824 301084 -/+ buffers/cache: 189380 445700 Swap: 1315400 76 1315324 [sctemme@eartha sctemme]$ vmstat 3 5 procs memory swap io system cpu r b w swpd free buff cache si so bi bo in cs us sy id 1 0 0 76 32704 110876 301092 0 0 14 17 117 254 4 3 92 11 0 1 76 29672 110876 301092 0 0 0 32 118 1717 52 48 0 16 0 1 76 24564 110876 301092 0 0 0 0 119 2529 51 49 0 28 0 0 76 19740 110876 301092 0 0 0 8 119 4194 58 42 0 0 0 0 76 25188 110880 301092 0 0 0 8 182 5707 56 39 5

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

  8. 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

  9. SE Toolkit • Solaris-specific • Freely available monitoring toolkit • http://www.setoolkit.com/ • Scriptable with own language

  10. zoom.se

  11. zoom.se: trouble

  12. mod_status • Apache module • Outputs internal status of web server • Part of standard installation • Not turned on by default

  13. Generating Load • For testing and sizing purposes • Not necessarily realistic • Several free programs available • ab • http_load • Flood • JMeter • OpenSTA • Commercial offerings • Load Runner

  14. How Many Processes? • MaxClients • Spinning Threads • Sizing MaxClients

  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 • 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 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. Spinning Locks • Accept mutex locking • Why Apache locks • When it doesn’t • How to manipulate

  23. Accept Mutex Locking Lock mutex Got conn? Loop: poll listeners Accept connection Unlock mutex Handle connection Multiple Listener Configuration (default)

  24. Accept Mutex Locking Lock mutex Accept connection Unlock mutex Handle connection Single Listener Configuration

  25. Accept Mutex Locking Accept connection Handle connection Single Listener Unserialized Accept (SLUA)

  26. Tuning Tips • RAM and swap space • ulimit: files and processes • Turn off unused services and modules • Spread the load around

  27. ulimit • Per-process resource limits • Built-in command of sh, bash • Important limits: • processes (-u) • open files (-n) • Set in invoking shell • Add to Apache startup script • ulimit -S -n `ulimit -H -n` • Linux: /etc/security/limits.conf

  28. Spread the Load • Move to tiered model • Off-load services to other boxes • Images • SSL • Database • Application server • Development/Deployment schism

  29. Tiered Model Database Tomcat Net Apache

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

  31. Session Roadmap • TU02 – Advanced Topics in Module Design: Threadsafety and Portability • TU05 – Apache Performance • TU18 – Scalable Apache for Beginners • WE04 – Parallel Development and Hosting using Apache, Tomcat and MySQL

  32. Current Version http://apache.org/~sctemme/Apcon2003/MO12/

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