Launch with Confidence
Improving Website
Performance and Scalability
with Memcached
Presented by: Shawn Smiley [Lead Architect]
About Me
LinkedIn: www.linkedin.com/in/shawnsmiley/
Twitter: @shawnsmiley
3
•
Shawn S. Smiley
•
Lead Architect at
Achieve Internet
•
15+ years experience
in Internet software
and hosting
•
5+ years with Drupal
•
Recently married
Agenda
About Achieve

At a Glance

Key Clients

Achieve Services
Intro to Caching

How it Works?
What is Memcached?
When and Why You Should Use It?

Performance and Stats
Minimal Setup

Components of a Memcache Solution

PECL Memcache vs Memcached

Commands
Verifying and Troubleshooting

Minimal Install Verification
Distributed Configurations

When to Use It

Types

Configuration

Tuning Tips
Are There Alternatives?
Conclusion
Q&A
4
Achieve at a Glance
legal name
founded
headquarters
leadership
mission
primary
contact info
Achieve Internet, Inc.
1998
1767 Grand Avenue, Suite #2 | San Diego, CA 92109 | U.S.A.
Ron Huber, Chief Executive Officer
Achieve leverages best-in-class Open Source web application development experience, and tools to create
optimized platforms for enterprise clients.
800.618.8777 | info@achieveinternet.com
Achieve is a leading software development company that leverages Drupal to develop advanced
enterprise web and mobile solutions for an array of clients in varying verticals. Achieve has a singular
goal: To help you launch your advanced digital platforms with confidence.
Our ethos is “it’s not magic, it’s excellence,” and our all-star developers deliver on that promise
with every new project we take on by consistently exceeding client expectations.
5
Key Clients: Media & Entertainment
clients
6
Additional Key Clients
clients
7
Achieve Services
Achieve builds custom enterprise IT management systems to solve the most complex business challenges.
Application
Development
Achieve makes integration easy so you can focus on what is most important to your business – your customers.
Platform
Integration
Optimize the performance of your web site or application to increase productivity and streamline operations.
Infrastructure
Services
Achieve has vast experience in creating global web solutions that far out perform the competition.
Globalization
Services
‘Going Mobile’ is no longer an option. With Achieve you won’t have to compromise design for utility.
Mobility & End User
Services
8
Intro to Caching
9
Intro to Caching
• A cache is a system that stores the results of some
processing for repeated later use.
• Example in Drupal is the page cache.
• Utilized via the cache_set() and cache_get() Drupal API
calls.
• Caches in Drupal are Key/Value pairs.
10
Intro to Caching: How it Works?
REQUEST
CACHE_
GET()
CHECK CACHE
RETURN
CACHED
DATA
11
QUERY CACHE
Intro to Caching: How it Works?
REQUEST
CACHE_
GET()
CHECK CACHE
QUERY CACHE
GENERAT
E DATA
RETURN
CACHED
DATA
CACHE_SET()
12
SAVE CACHE
What is Memcached?
13
What is Memcached?
• “Memcached is an in-memory key-value store for small
chunks of arbitrary data (strings, objects) from results of
database calls, API calls, or page rendering.” –
memcached.org
• A system to cache data in RAM rather than in database.
• Replaces Drupal’s default database cache.
• Just one component of your high performance scalable
architecture.
14
When & Why Should You Use
It?
15
Why Use Memcached?
• Improves cache read/write performance
• Reduces the number of database queries
• Reduces database load
• Can improve page load performance*
• Allows distributing the cache load to separate servers
• Moves the threshold for performance degradation to a higher
number of concurrent users.
* By itself, Memcache.d won’t provide a significant performance improve on low traffic sites. The page load performance
boost comes mostly from offloading work from your database server so that the system can handle more requests.
16
Performance Stats
• Performance & Scalability
• Cache read performance: 4X Faster
• Cache write performance: 60X Faster
• Actual statistics* (Drupal core vs. Memcached)
• 1000 Cache write operations: 12 seconds vs. 0.2 seconds
• 1000 Cache read operations: 0.4 seconds vs. 0.1 seconds
• DB queries: 3028 vs. 13
* Cache Read/Write stats are for performing 2,000 operations (1,000 write, 1,000 read)
* Your results will vary, tests performed on a single AWS instance with default D7 install
17
Performance Stats
Caching Performance Comparison: 2,000 Operations
Execution time (seconds)
12
Core DB
Memcache
1
0.0833333
Cache Set
Cache Get
18
Performance Degradation Threshold
NOTE: This is an idealized graph of the average change in response time across
several projecs.
19
When to (or not) use Memcached
• Use Memcached when:
• Significant portion of site traffic is authenticated users or when
static page caching isn’t an option.
• Have adequate server resources to allocate to Memcached
without negatively impacting other services.
• Have enough traffic to make a difference.
• Don’t use Memcached when:
• Site is completely anonymous traffic
•
Static caching is better for this (such as Varnish or Boost)
• Low traffic sites that are not straining server resources
•
Probably won’t see any noticeable benefit and have increased the
complexity of the system.
• Severely resource constrained single server hosting
•
Can negatively impact performance/scalability in this case.
20
Setup
21
Components of Memcached Solution
• Memcached Daemon (v 1.4.x)
• PHP Extension
• PECL Memcache (> 3.x)
• PECL Memcached (> 2.x)
• TIP: Use the setting “memcache_extension” to select
which library to use if you have both installed.
• Memcache Module
• Drupal 8, Drupal 7.9+, Pressflow 6, or Drupal
6 with core patch
22
PECL Memcache vs. Memcached
PECL Memcache
PECL Memcached
Stable, not as frequently updated
Newer, more features
Easy to install
More complicated install with multiple
dependencies
Lower PHP memory footprint in some
cases.
Can be slightly faster in some cases
Slightly better for single server
Memcached daemon installations.
Slightly better for distributed or
clustered Memcached daemon
installations.
igbinary support
* Generally, we default to PECL Memcache unless a project can take
advantage of the additional features provided by PECL Memcached.
23
Minimal Install: Commands (Ubuntu)
• Enable apt multiverse repositories
• sudo apt-get install php-pear build-essential
• sudo apt-get install memcached
• sudo apt-get install php5-memcache
• drush dl memcache devel
24
Minimal Install: Daemon Configuration
/etc/memcached.conf (or /etc/default/memcached)
• Configuration file for the memcached daemon
• Important settings:
• -m 64
•
Amount of memory in MB to allocate.
• -p 11211
•
TCP/IP Port to listen for cache requests on.
• -l 127.0.0.1
•
IP Address to listen for cache requests on.
25
Determining Memcached size
• Look at the data size of all cache* tables in your DB.
• Use this handy query to get the total size:
SELECT count(*) TABLES,
sum(table_rows) ROWS,
concat(round(sum(data_length)/(1024*1024),2),'MB') DATA,
concat(round(sum(index_length)/(1024*1024),2),'MB') idx,
concat(round(sum(data_length+index_length)/(1024*1024),2),'MB') total_size
FROM information_schema.TABLES
WHERE TABLE_SCHEMA=’dbname' AND TABLE_NAME LIKE "cache%"
• Total memory allocated to Memcached should be at least
the size returned in the “DATA” column.
• I usually like to add at least 50% to this size to start with.
26
Note about Memcached security
• Basically there are no security controls in Memcached.
• Any user or application that can establish a TCP
connection to the Memcached daemon can access all
data stored within Memcached.
• Security Best Practices:
• Always set the daemon to listen on a specific IP
address/network interface.
• Use 127.0.0.1 if there is only 1 Memcached server and it is
running on the same server as the web server.
• Use iptables or other firewall to restrict access to the
Memcached TCP/IP Port(s).
27
Minimal Install: Drupal Settings.php
// Required minimum settings.
$conf['cache_backends'][] = 'sites/all/modules/contrib/memcache/memcache.inc';
$conf['cache_default_class'] = 'MemCacheDrupal';
$conf['cache_class_cache_form'] = 'DrupalDatabaseCache';
// Optional, but recommended settings.
$conf['memcache_key_prefix'] = 'ai_'; // Remember about 250 byte key size limit.
$conf['lock_inc'] = 'sites/all/modules/contrib/memcache/memcache-lock.inc';
$conf['memcache_stampede_protection'] = TRUE;
// The following are required only if Memcached is on a different server.
$conf['memcache_servers’] = array(’10.11.12.13:11211' => 'default');
$conf['memcache_bins’] = array('cache' => 'default');
// Only if both PECL Memcache and Memcached are installed.
$conf['memcache_extension'] = 'Memcache';
28
Minimal Install: Drupal Configuration
Drupal Performance Settings
29
Verifying & Troubleshooting
30
Minimal Install: Verifying
• Memcache Admin Module
• Adds configuration page at Configuration => Memcached
• Enable the option “Show Memcache statistics” to see a log of
all Memcached calls on each page.
• Devel Module
• Enable the Query Logging option.
• Memcache Admin UIs:
• http://livebookmark.net/journal/2008/05/21/memcachephpstats-like-apcphp/
• https://code.google.com/p/phpmemcacheadmin/
31
Minimal Install: Verifying - Memcache
• Enable the module “Memcache Admin”
• Config page at Configuration => Memcache
• Enable the option “Show Memcache statistics” to see a log of
all Memcached calls on each page.
32
Minimal Install: Verifying - Devel
• In Devel Settings, enable “Display query log”
• Reload pages, you’ll see a list of all queries executed
• Ensure there are no calls to any “cache*” tables (other than
cache_form)
• Ensure there are no calls to the “semaphore” table (lock.inc)
33
Minimal Install: Verifying – Admin UIs
Demo
• Drupal Memcache Statistics
• memcache.php
• Memcache Admin
34
Distributed Configurations
35
Distributed Install: Overview
• When to use
• Types of distributed installs
• Configuration Steps
36
Distributed Install: When To Use It
• High traffic sites making more cache requests than a
single instance can efficiently handle.
• The default config of a Memcached daemon will support up to
1,024 simultaneous connection requests.
• Large caches where it makes sense to separate out cache
data by type or update frequency (e.g. cache_menu is
usually pretty static whereas the default cache could be
constantly changing)
• I start looking at this as an option when the memory allocation
for Memcached starts getting over 128MB.
37
Distributed Install: Types
• Multi-server/Clustered
• Distributes cache load across multiple Memcached servers.
• Allows for handling larger numbers of cache operations.
Useful for high traffic sites.
• NOTE: Caches are not replicated between multiple servers by
default.
• Multi-bin
• Segments different types of caches to different servers.
• Useful for very large caches with varying characteristics (e.g.
segmenting mostly read-only caches from caches that are
frequently updated)
• Hybrid
• You can combine both of the above approaches (e.g. have
multiple bins with each bin spread across multiple servers).
38
Distributed Install: Configuration
• Server configuration is same as the basic install, just on
multiple servers.
• Make sure the Memcached daemon is configured to listen on
each servers external IP address (not 127.0.0.1).
• All daemons within a cluster should be configured with the
same memory allocation.
• You can have multiple Memcached daemons running on a
single server. Just use different ports.
39
Distributed Install: Configuration
Additional settings needed in the site settings.php file
// Must be exactly the same on all web servers.
$conf['memcache_servers' = array(
'10.11.12.13:11211' => 'default',
'10.11.12.14:11211' => 'default',
'10.11.12.15:11211' => 'my_readonly_bin',
);
$conf['memcache_bins’] = array(
'cache' => 'default', // must specify if setting this variable.
'cache_bootstrap' => 'my_readonly_bin',
'cache_menu' => 'my_readonly_bin',
'cache_path' => 'my_readonly_bin',
);
// If using PECL Memcached.
$conf['memcache_options'] = array(
Memcached::OPT_DISTRIBUTION => Memcached::DISTRIBUTION_CONSISTENT,
);
40
Tuning Tips
• Watch the “Available Memory”, “Evictions” (==0), and
“reclaimed” (==0) stats to determine if memory allocation
needs to be adjusted.
• Watch “Max Connection Errors” (==0), “Accepting
Connections” (==1), “Connection Yields” (==0), and
“Listen Disabled Number” (==0) to determine when you
need to move from a single memcached server to
multiple servers.
Tip: See this page for a description of various stat counters:
http://www.pal-blog.de/entwicklung/perl/memcached-statistics-statscommand.html
41
Alternatives
42
Are There Alternatives?
Redis (https://drupal.org/project/redis)
• Great for persistent or replicated caches.
• Supports additional caching options such as structured data
caching.
• More efficient support for selective cache delete/expiration.
• Nice comparison to Memcache:
http://noblogdeffound.blogspot.com/2013/04/memcached-vsredis-comparison-name.html
MongoDB Cache (https://drupal.org/project/mongodb)
• Great for extremely large caches or when a large amount of
data must be stored in a single cache key.
43
Conclusion
By adding Memcached to our hosting solution we:
• Reduced the number of database queries.
• Reduced the load on our database servers.
• Reduced the amount of time the site spends accessing
cached data.
• Reduced the rendering time for page requests.
• Improved the overall scalability of the site.
44
Thank You
Shawn Smiley
 Lead Engineer
 shawn.smiley@achieveinternet.com
 Drupal: shawn_smiley
 800.618.8777
Connect with Achieve
If you have any further questions or would like to get in touch with
Achieve you can do so on these various channels:
info@achieveinternet.com
linkedin.com/company/Achieve-Internet
plus.google.com/101805819007866218919
@AchieveInternet
facebook.com/pages/Achieve-Internet
46
Q&A
47