MySQL Scaling with Memcached
Presented by: Bill Takacs
Director, Product Management
July 9th 2009

Agenda
• M SQL overview
MySQL i
• Memcached overview
• What’s Memcached good for – and
how does it help me scale MySQL?
• Example architectures
• Customer examples
2 : Copyright 2009 Gear6 Inc.

About MySQL
• 12 years old
• 400+ employees
00 e p oyees
• 750 partners
p
• 60K downloads/day
• Customers across every major operating system,
hardware vendor, geography, industry, and application
h d d h i d t d li ti
type
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Cache is King
Browser cache
Web
W b server cache
h
Memcached cache
MySQL database cache – query cache
Disk
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Memcached
“A high performance, distributed memory object caching
g p , y j g
system, generic in nature, but intended for use in
speeding up dynamic web applications by alleviating
database load”
Ref: http://www.danga.com/memcached/
• Big hash table
• Created by Danga Interactive for Live Journal
• Significantly reduced database load
• Perfect for web sites with high database load
• In use by Facebook, Twitter, MyYearBook, others
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More on Memcached
• Takes advantage of available DRAM
• Open source
Ope sou ce
• Distributed under BSD license
• Server - Current version is 1.2.8
» http://www.danga.com/memcached/download.bml
• M
Many Clients
Cli t
» http://code.google.com/p/memcached/wiki/Clients
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Why Memcached with MySQL?
• Scale-out of dynamic web sites
y
• Page loads
• Efficient resource utilization
• Support for dozens
to hundreds of nodes
• Open source
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How Does Memcached Work?
• Client - Server
• H h Function
Hash F ti
• Memcached
» Two stage
» Key / value p
y pair
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Memcached Server
• Slab allocator
• Libevent based
• Simple Protocol (no xml)
• Server has internal hash table
• Servers are dumb – they don’t know about each other
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Memcached Server
• Limits
» Key size = (250 bytes)
» 1MB Limit
» 32bit/64bit (maximum size of process)
• LRU
» Least recently accessed items are cycled out
» One LRU exists per “slab class”
slab class
» LRU “evictions” need not be common
• Threads? Yes
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Memcached Clients
• Client hashes key to server list
• Serializes t e object
Se a es the
• Many client libraries
y
• Authentication
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What about…..
• Redundancy
• Failover
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Consistent Hashing
• Why?
• How does it work?
» Libk t
Libketama
» http://www.last.fm/user/RJ/journal/2007/04/10/rz_libketama_-
_a_consistent_hashing_algo_for_memcache_clients
• Reference:
http://www.lexemetech.com/2007/11/consistent-hashing.html
p g
http://www8.org/w8-papers/2a-
webserver/caching/paper2.htmlhttp://www.last.fm/user/RJ/jo
urnal/2007/04/10/rz_libketama_-
_a_consistent_hashing_algo_for_memcache_clients
a consistent hashing algo for memcache clients
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Commands
• Storage commands:
» Set / Add / Replace /
Append / Prepend / CAS
• Retrieval commands:
» Get / Gets
• Delete / increment /
decrement
• Stats
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Memcached UDFs for MySQL
• Suite of functions that work
with Memcached and MySQL
• Leverage power of SQL Engine
• Combine tasks
• O
Open source
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Putting it all together
Client 1
Client-1 Client 2
Client-2 Client 3
Client-3
C
Server X Server Y Server Z
Key = value
y
Foo = seattle
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Some Architectures

Memcached and Single MySQL
Read Write
Web Servers
Application Servers
Memcached Clients
Memcached Servers
Cache Update
MySQL
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MySQL Replication Scale-Out
Web / Application Servers MySQL
+ +
Memached Clients Memcached Servers
Writes
MySQL
Replication
Reads
Reads
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Memcached and MySQL Replication
Read from cache Write Read from slave
Application Severs
+
Memcached Clients
Memcached Servers
Cache Update
MySQL Master
MySQL Slaves
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Memcached and MySQL Replication
Read from cache Write Read from slave
Application Severs
+
Memcached Clients
Shard1 Cust_id 0-999 Shard1 Cust_id 1000 -1999
Cache Update Cache Update
MySQL MySQL
Replication Replication
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About Gear6
• First and leading provider
of Memcached solutions
• Memcached solution including
• High density
• High Availability
• Advanced memory
management
• Enhanced reporting
capabilities
biliti
• Support for multi-tenancy
• Disruption free
software upgrades
• 100% c e t co pat b e
00% client compatible
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Credits and References
• Designing and Implementing Scalable Applications with Memcached and MySQL, Monty
Taylor
http://www.mysql.com/why-mysql/white-papers/mysql_wp_memcached.php
• Memcached Study, Brian Acker
http://download.tangent.org/talks/Memcached%20Study.pdf
htt //d l dt t /t lk /M h d%20St d df
• A Bunch of Great Strategies for Using Memcached and MySQL Better Together, Todd Hoff
http://highscalability.com/bunch great strategies using memcached and mysql better together
http://highscalability.com/bunch-great-strategies-using-memcached-and-mysql-better-together
• Memcached Functions for MySQL: Seamless Caching for MySQL, Patrick Galbraith
http://www.scribd.com/doc/15014678/memcached-Functions-for-MySQL-Seemless-Caching-in-
MySQL
• Memcached Protocol
http://code.sixapart.com/svn/memcached/trunk/server/doc/protocol.txt
http://code sixapart com/svn/memcached/trunk/server/doc/protocol txt
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Thank You!
For more information
information:
www.gear6.com
www gear6 com
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