1. Shoehorning Apache Onto Your Box
System Sizing tips
Sander Temme

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:
-/+ buffers/cache:
Swap:
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

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

8. Common Log Format Client IP 172.16.2.91 RFC 1413 ident - username
[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 Code
404
Content Bytes
283

9. SE Toolkit Solaris-specific Freely available monitoring toolkit
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 Multiple Listener Configuration (default)
Lock mutex
Loop: poll
listeners
Got conn?
Accept
connection
Unlock
mutex
Handle
connection
Multiple Listener Configuration (default)

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

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

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