1.
EFFECTIVE CACHING
WITH PHP & MEMCACHED
by Justin Carmony

2.
ABOUT ME
• Full Time Web Developer & Consultant
• Worked with LAMP & .NET Solutions
• Blog - http://www.justincarmony.com/blog/
• Current Projects:

3.
ABOUT PRESENTATION
On-Topic Questions During Presentation
Q & A Session After Presentation
Feel Free to Email Me Questions: justin@justincarmony.com

4.
WHAT IS MEMCACHED?

5.
ABOUT MEMCACHED

6.
ABOUT MEMCACHED
Developed by LiveJournal’s Developers

7.
ABOUT MEMCACHED
Developed by LiveJournal’s Developers
Primary Function: Relieve Database Load (Mainly Reads)

8.
ABOUT MEMCACHED
Developed by LiveJournal’s Developers
Primary Function: Relieve Database Load (Mainly Reads)
Can Scale Across Multiple Servers

9.
ABOUT MEMCACHED
Developed by LiveJournal’s Developers
Primary Function: Relieve Database Load (Mainly Reads)
Can Scale Across Multiple Servers
Giant “Hash Table” or “Array”

10.
ABOUT MEMCACHED
Developed by LiveJournal’s Developers
Primary Function: Relieve Database Load (Mainly Reads)
Can Scale Across Multiple Servers
Giant “Hash Table” or “Array”
Stores Data in Memory - Extremely Fast

11.
WHY WE CACHE

12.
CONCEPT OF CACHING

13.
CONCEPT OF CACHING
• Resource that is Struggling
Website
Resource
Application

14.
CONCEPT OF CACHING
• Resource that is Struggling
Website
• Introduce Cache to Help Resource
Application
Cache

15.
CONCEPT OF CACHING
• Resource that is Struggling
Website
• Introduce Cache to Help Resource
Application
• Store “Reliable” Data in Cache
Cache

16.
CONCEPT OF CACHING
• Resource that is Struggling
Website
• Introduce Cache to Help Resource
Application
• Store “Reliable” Data in Cache
• Check Cache Before Hitting Resource
Cache

17.
CONCEPT OF CACHING
• Resource that is Struggling
Website
• Introduce Cache to Help Resource
Application
• Store “Reliable” Data in Cache
• Check Cache Before Hitting Resource
Cache
• Resource Types: DB, Web Service, XML,
Files, Etc.

18.
THE DATABASE

19.
THE DATABASE
• Scaling is Complicated

20.
THE DATABASE
• Scaling is Complicated
• Its
because what makes
databases great: ACID.

21.
THE DATABASE
• Scaling is Complicated
• Its
because what makes
databases great: ACID.
• What about SQL’s Internal
Caching?

22.
THE DATABASE
• Scaling is Complicated
• Its
because what makes
databases great: ACID.
• What about SQL’s Internal
Caching?
• Less Load on DB is Good

23.
HOW DOES IT IMPROVE
PERFORMANCE?

24.
DATING DNA PERFORMANCE BOOST
Before After
Daily New Registrations 100 500
HTTP Requests Per Second ~ 36 r/s ~150 r/s
AVG Database CPU ~ 73% ~32%
# Queries Per Second ~ 2,200 ~1,700
AVG Page Load Time 2 - 5 seconds 0.01 - 0.4 seconds
* Note - Several Performance Changes Made, Not 100% Due to Memcached

25.
LIVE MEMCACHED STATS

26.
INSTALLING & RUNNING
MEMCACHED

27.
INSTALLING
• Linux - Aptitude, Yum, RPM, Compile from Source, etc...
• Mac OS X - Compile Only
• Windows - Downloadable Binaries
• Its pretty simple!

28.
RUNNING
• No Configuration Files
• Just a few command line options:
memcached -d -m 2048 -l 127.0.0.1 -p 11211

29.
BASIC CACHE FLOW

30.
CONNECT
<?php
// Create New Memcache Instance
$memcache = new Memcache();
// Add Memcache Server to Connection Pool
$memcache->addServer('127.0.0.1', 11211);
// ... continue code ...

31.
GET & SET DATA
// Try to Get the
$my_name = $memcache->get('my_name');
if($my_name === false)
{
$my_name = 'Justin Carmony';
$memcache->set('my_name', $my_name, false, 60);
}
echo $my_name; // output: Justin Carmony

32.
“DELETING” DATA
// Lets say we don't like Justin anymore...
$memcache->delete('my_name');
$value = $memcache->get('my_name'); // returns false

33.
CACHING THEORY
( WHERE, WHAT, WHEN, & HOW)

34.
WHERE TO CACHE

35.
IDENTIFYING WHAT TO CACHE

36.
IDENTIFYING WHAT TO CACHE
‣ High Demand

37.
IDENTIFYING WHAT TO CACHE
‣ High Demand
‣ Expensive

38.
IDENTIFYING WHAT TO CACHE
‣ High Demand
‣ Expensive
‣ Large in Size

39.
IDENTIFYING WHAT TO CACHE
‣ High Demand
‣ Expensive
‣ Large in Size
‣ Common

40.
IDENTIFYING WHAT TO CACHE
‣ High Demand
‣ Expensive
‣ Large in Size
‣ Common
The Best Cacheable Data with Highest
Performance ROI Fits Multiple Characteristics

41.
TIPS FOR FINDING CACHEABLE DATA

42.
TIPS FOR FINDING CACHEABLE DATA
‣ Monitor Queries

43.
TIPS FOR FINDING CACHEABLE DATA
‣ Monitor Queries
‣ Output Queries

44.
TIPS FOR FINDING CACHEABLE DATA
‣ Monitor Queries
‣ Output Queries
‣ Monitor Page Loads

45.
TIPS FOR FINDING CACHEABLE DATA
‣ Monitor Queries
‣ Output Queries
‣ Monitor Page Loads
‣ Monitor Web Analytics

46.
TIPS FOR FINDING CACHEABLE DATA
‣ Monitor Queries
‣ Output Queries
‣ Monitor Page Loads
‣ Monitor Web Analytics
‣ Brainstorming

47.
WHAT TO CACHE

48.
OUTPUT CACHING
Capture Output Buffer
When to Use Output Caching:
- Page Has High Load
- Expensive to Generate
- Easier to Cache over Data

49.
OUTPUT CACHING
Capture Output Buffer
When to Use Output Caching:
- Page Has High Load
- Expensive to Generate
- Easier to Cache over Data

50.
OUTPUT BUFFER EXAMPLE
// Output Buffer Cache
$output = $memcache->get('my_html');
if(!$output)
{
ob_start(); // Start Capture
?>
<div id="main">Hello World!</div>
<!-- Insert Some Crazy HTML Code -->
<?php
$output = ob_get_contents();
ob_end_clean();
$memcache->set('my_html', $output, false, 15 * 60);
}
echo $output;

51.
DATA CACHING
Create a Class to Cache
Use Factory Methods to Retrieve
Use When Use:
- Data Used Frequently
- Displayed Different
- Easier from Cache than other Sources

52.
WHEN TO EXPIRE

53.
TIMEOUT EXPIRATION
Settings a Lower Timeout
Great for Summaries
Okay to be Kinda Out of Date
“Quick & Dirty” Optimizations
Output + Timeout Common

54.
EVENT EXPIRATION
Data is Infrequently Updated
Data is Time Critical
- Cannot Be Out of Date
Data + Event Common

55.
HOW TO CACHE

56.
IT’S ALL ABOUT YOUR KEYS
Keys MUST Be Unique
Prefix Cache Types (i.e. prflinfo_ for ProfileInfo)
SHA256 / MD5 Identifiers
Example: ProfileInfo for User ID 1337:
prflinfo_e48e13207341b6bffb7fb1622282247b

57.
WRAP YOUR CACHE W/ CLASS
Pick a Cacheable Piece of Information
Create a Class For That Cache
Create Methods For:
‣ Generate Key Name
‣ Get & Set
‣ Destroy / Delete

58.
class ProfileInformation
{
public $user_id = null;
public $first_name = null;
public $email_address = null;
public $profile_img
= null;
public $city = null;
public $state = null;
public $age = null;
private function __construct($user_id)
{
$this->user_id = $user_id;
$sql = "SELECT * FROM users WHERE user_id = '$user_id'";
$p_data = DBI::fetchObject($sql);
$this->first_name = $p_data->first_name;
$this->email_address = $p_data->email_address;
$this->age = xDate::GetAge($p_data->birthdate);
// .. Set More Information ..
}
// .. more ..
}

59.
class ProfileInformation
{
// .. more ..
static public function GetProfile($user_id)
{
// Try to get it from the cache
$profile = null;
$profile = self::GetCache($user_id);
if(!$profile)
{
$profile = new ProfileInformation($user_id);
self::SetCache($user_id, $profile);
}
return $profile;
}
// ... more ...
}

60.
class ProfileInformation
{
// .. more ..
static protected function GetCacheName($user_id)
{
return 'profile_'.hash('sha256',"user_".$user_id."_".$user_id);
}
// ... more ...
}

61.
class ProfileInformation
{
// .. more ..
static protected function GetCache($user_id)
{
$name = self::GetCacheName($user_id);
$profile = null;
$memcache = MemcacheCluster::GetInstance();
$profile = $memcache->get($name);
if(!$profile)
{
return null;
}
return $profile;
}
// ... more ...
}

62.
class ProfileInformation
{
// .. more ..
static protected function SetCache($user_id, $data)
{
$name = self::GetCacheName($user_id);
$memcache = MemcacheCluster::GetInstance();
$profile = $memcache->set($name, $data, false, 24 * 60 * 60);
}
public static function DestroyCache($user_id)
{
$name = self::GetCacheName($user_id);
$memcache = MemcacheCluster::GetInstance();
$profile = $memcache->delete($name);
}
// End Of Class
}

63.
require_once 'ProfileInformation.class.php';
$user_id = 1337;
// Incorrect Method
$profile = new ProfileInformation($user_id); // Throws Error
// Correct Method
$profile = ProfileInformation::GetProfile($user_id);
echo $profile->first_name;

64.
FINAL THOUGHTS

65.
COMMON PITFALLS
• Caching Only Optimization - Ignoring Other Inefficiencies
• Cache Offline == Catastrophic Failure
• Poor Key Choices
• Inability to easily invalidate specific Cache Entries
• Caching SQL Queries

66.
PITFALL: QUERY CACHE
<?php
$sql = "SELECT * FROM users WHERE id = 5";
$result = $mem->get(md5($sql));
if(!$result)
{
// Execute and get the result of the query in an array
$result = Database::FetchArray($sql);
// set the timeout to 4 hours
$mem->set(md5($sql), $result, 0, 4 * 60 * 60);
}
?>

67.
SECURITY
No Real Security for Memcached
--listen Not Super Secure / Configurable
Limit Access at Network Level
IPTables / Firewalls / Internal Network

68.
MISCELLANEOUS THINGS
Memcache Library vs Memcached Library
Where can I find out More?
- My Blog: Search Memcached
- Google Memcached
- PHP Documentation

69.
QUESTIONS?

70.
SHAMELESS PLUG:
October 8-10, 2009 | www.utosc.com

71.
THANK YOU
Website www.justincarmony.com
Email justin@justincarmony.com
Twitter JustinCarmony
Skype JustinCarmony
IRC irc.freenode.net #uphpu