1 Shoehorning Apache Onto Your Box System Sizing Tips Sander Temme

2 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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4 Assumptions Limited Resources Work With What You Have You’re probably running Linux No Compiling or Recompiling! You can find httpd.conf

5 Purposes of Monitoring Observation Extrapolation Signals/Alerts Testing

6 Monitoring Your Server

7 Monitoring Apache

8 Monitoring Solaris: SE Toolkit Lightweight Programmable Alive

9 Other Monitoring Tools vmstat top free

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

11 Common Log Format [16/Nov/2003:15:23: ] "GET /~sctemme/ HTTP/1.1" [16/Nov/2003:15:23: ] "GET /~sctemme/css/doc.css HTTP/1.1" [16/Nov/2003:15:23: ] "GET /~sctemme/css/menu.css HTTP/1.1" [16/Nov/2003:15:23: ] "GET /favicon.ico HTTP/1.1" [16/Nov/2003:15:23: ] "GET /~sctemme/index.html HTTP/1.1" Client IP RFC 1413 ident- username- timestamp[16/Nov/2003:15:23: ] Request"GET /favicon.ico HTTP/1.1" Status Code404 Content Bytes283

12 Configuring for Performance Configuring Apache Tuning the Operating System Scaling Your Site

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

14 DNS Lookups HostnameLookups Access Control –Bad: Deny from example.com –Good: Deny from

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

16 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)

17 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

18 Top

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

20 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

21 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

22 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

23 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

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

25 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

26 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

27 Scaling Your Site Vertically –Tiered Model Horizontally –Load Balancing

28 Scaling Vertically Client TCP/IP

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

30 Scaling Horizontally Client

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

32 Q&A

33 Further Reading Ryan B. Bloom, Apache Server 2.0: The Complete Reference, 2002 McGraw Hill Osborne; ISBN Ben Laurie and Peter Laurie, Apache: The Definitive Guide (3rd Edition), 2002 O’Reilly & Associates; ISBN Patrick Killelea, Web Performance Tuning, 2nd Edition, 2002 O’Reilly & Associates; ISBN X Adrian Cockcroft, Richard Pettit and Sun Microsystems Press, Sun Performance and Tuning: Java and the Internet (2nd Edition), 1998 Prentice Hall PTR; ISBN Ken Coar and Rich Bowen, Apache Cookbook, 2003 O’Reilly & Associates; ISBN

34 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

35 Current Version

36 Thank You