Shoehorning Apache Onto Your Box

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Shoehorning Apache Onto Your Box

• System Sizing tips

Sander Temme ltsander_at_temme.netgt
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Agenda

• The Problem
• Monitoring Your Server
• How Many Processes?
• Selecting Your MPM
• Spinning Locks
• Tuning Tips
• Further Reading

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The Problem

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

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Monitoring Your Server

• top
• free
• vmstat
• Web server logs
• SE Toolkit
• mod_status
• Generating Load

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Top
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free and vmstat
sctemme_at_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_at_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
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Web Server Logs

• ErrorLog
• LogLevel debug, info, notice, warn, error, crit
• Access Log TransferLog or CustomLog
• Common Log Format

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Common Log Format
172.16.2.91 - - 16/Nov/2003152327 -0800 "GET
/sctemme/ HTTP/1.1" 200 1446 172.16.2.91 - -
16/Nov/2003152328 -0800 "GET
/sctemme/css/doc.css HTTP/1.1" 200
167 172.16.2.91 - - 16/Nov/2003152328 -0800
"GET /sctemme/css/menu.css HTTP/1.1" 200
623 172.16.2.91 - - 16/Nov/2003152329 -0800
"GET /favicon.ico HTTP/1.1" 404 283 172.16.2.91 -
- 16/Nov/2003152334 -0800 "GET
/sctemme/index.html HTTP/1.1" 200 1446
Client IP 172.16.2.91
RFC 1413 ident -
username -
timestamp 16/Nov/2003152329 -0800
Request "GET /favicon.ico HTTP/1.1"
Status Code 404
Content Bytes 283
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SE Toolkit

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

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zoom.se
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zoom.se trouble
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mod_status

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

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Generating Load

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

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How Many Processes?

• MaxClients
• Spinning Threads
• Sizing MaxClients

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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)

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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

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Top
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Selecting Your MPM

• Apache 2.0 only!
• Processes and Threads
• Differences between platforms
• Thread-safety issues

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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

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Platforms and Threading

• Context switches expensive on Solaris, AIX
• Context switches cheaper on Linux
• Solaris uses MN threading
• Linux uses 1 process per thread
• LinuxThreads implementation is old
• Replaced by NPTL in 2.6
• NTPL already in RH 9, RHAS 3

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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

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Spinning Locks

• Accept mutex locking
• Why Apache locks
• When it doesnt
• How to manipulate

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Accept Mutex Locking
Lock mutex
Got conn?
Loop poll listeners
Accept connection
Unlock mutex
Handle connection
Multiple Listener Configuration (default)
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Accept Mutex Locking
Lock mutex
Accept connection
Unlock mutex
Handle connection
Single Listener Configuration
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Accept Mutex Locking
Accept connection
Handle connection
Single Listener Unserialized Accept (SLUA)
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Tuning Tips

• RAM and swap space
• ulimit files and processes
• Turn off unused services and modules
• Spread the load around

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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

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Spread the Load

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

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Tiered Model
Database
Tomcat
Net
Apache
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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 OReilly 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

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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

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Current Version

• http//apache.org/sctemme/Apcon2003/MO12/