Launch with Confidence

Improving Website Performance and Scalability with Memcached

Presented by: Shawn Smiley [Lead Architect]

About Me

• Shawn S. Smiley

• Lead Architect at Achieve Internet

• 15+ years experience in Internet software and hosting

• 5+ years with Drupal

• Recently marriedLinkedIn: www.linkedin.com/in/shawnsmiley/Twitter: @shawnsmiley

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AgendaAbout 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 StatsMinimal 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?ConclusionQ&A

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Achieve at a Glancelegal 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.

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Key Clients: Media & Entertainment

clients

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Additional Key Clients

clients

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Achieve Services

Achieve builds custom enterprise IT management systems to solve the most complex business challenges.

Achieve makes integration easy so you can focus on what is most important to your business – your customers.

Optimize the performance of your web site or application to increase productivity and streamline operations. 

Achieve has vast experience in creating global web solutions that far out perform the competition.  

‘Going Mobile’ is no longer an option. With Achieve you won’t have to compromise design for utility.

Application Development

Platform Integration

Infrastructure Services

Globalization Services

Mobility & End User Services

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Intro to Caching

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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.

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Intro to Caching: How it Works?

REQUESTREQUEST CHECK CACHECHECK CACHE CACHE_GET()

CACHE_GET() QUERY CACHEQUERY CACHE

RETURN CACHED

DATA

RETURN CACHED

DATA

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Intro to Caching: How it Works?

REQUESTREQUEST CHECK CACHECHECK CACHE CACHE_GET()

CACHE_GET() QUERY CACHEQUERY CACHE

GENERATE DATA

GENERATE DATA

CACHE_SET()

CACHE_SET() SAVE CACHESAVE CACHE

RETURN CACHED

DATA

RETURN CACHED

DATA

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What is Memcached?

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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.

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When & Why Should You Use It?

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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.

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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

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Performance Stats

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Performance Degradation Threshold

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NOTE: This is an idealized graph of the average change in response time across several projecs.

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.

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Setup

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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

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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.

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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

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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.

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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.

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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).

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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';

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Minimal Install: Drupal Configuration

Drupal Performance Settings

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Verifying & Troubleshooting

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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/memcachephp-stats-like-apcphp/

• https://code.google.com/p/phpmemcacheadmin/

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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.

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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)

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Minimal Install: Verifying – Admin UIs

Demo

•Drupal Memcache Statistics

•memcache.php

•Memcache Admin

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Distributed Configurations

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Distributed Install: Overview

• When to use

• Types of distributed installs

• Configuration Steps

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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.

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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).

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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.

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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,);

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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-stats-command.html

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Alternatives

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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-vs-redis-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.

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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.

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Thank You

Shawn SmileyLead Engineer

shawn.smiley@achieveinternet.com

Drupal: shawn_smiley

800.618.8777

Connect with AchieveIf you have any further questions or would like to get in touch with Achieve you can do so on these various

channels:

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info@achieveinternet.com

linkedin.com/company/Achieve-Internet

plus.google.com/101805819007866218919

@AchieveInternet

facebook.com/pages/Achieve-Internet

Q & A

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