Redis 101: An Introduction to Caching with Redis

REDIS 101

Desert Code Camp
November, 2011

CardinalPath.com

Redis 101

About Me
• Geoffrey Hoffman
• Advertising MSU
• 20 yrs software dev
• Web Apps for 15 yrs
• MySQL Admin for 10 yrs
• Scalability, H.A. Sys
& Deployment for 5 yrs

Twitter: @m2guru Http://github.com/phpguru
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Redis 101

About Cardinal Path

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Redis 101

Think of Google Instant search. Showing
results with “as you type” latency enables
a whole new class of use cases.

Scaling Redis http://bit.ly/iSY04K

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Redis 101

Redis can perform >100k+ SETs per second,
and >80k+ GETs per second.

(You're lucky to get over 6kt/s from MySQL.)

Redis from the ground up http://bit.ly/cJfRov

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Redis 101

We use Redis in every single project now.
IMHO this is one of the most significant
pieces of software to come down the pipeline
in the last few years. Keep doing what you do
@antirez!

- kidvelop
Comment @ antirez.com

Everything about Redis 2.4 http://bit.ly/qZRYHw

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Redis 101

Instead of trying to keep track of text logs
spread across multiple machines we just push any
log line we are interested in onto a single Redis
queue. Then, we have one process pop from that
queue and write those log lines to disk. If that
process or the logging server goes down, no big
deal, events just queue up in Redis until the
logging service is back online.

How we use Redis at Bump http://bit.ly/gHJ89P

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Session Overview
• About Me & Cardinal Path
• Overview of Caching
• What is Redis?
• What makes Redis unique?
• Try Redis
• How to use Redis from PHP
• Use Cases & Examples
• Quotes, Links & Resources
• Questions

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Redis 101

Overview of Caching
• A cache (/ˈkæʃ/ kash) is a
component that transparently
stores data so that future
requests for that data can
be served faster.

http://en.wikipedia.org/wiki/Cache
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Redis 101

Overview of Caching
Types of caches
• Disk drive cache
Mechanical / component

• Browser cache
client-side / local

• Server cache
Server-side / remote

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Redis 101

Overview of Caching
Caching Methods
• SQL Cache
Run queries less often

• Cached files on disk
Process code less frequently

• In-Memory Cache
Store frequently-used data

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Redis 101

Overview of Caching
PHP Caching Software
• Smarty Templates
Creates parsed files on disk

• WordPress Caching Plugins
W3 Total Cache, SuperCache

• MVC Frameworks
Symfony, Kohana, CodeIgniter, Zend

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Redis 101

Overview of Caching
PHP Caching Extensions
• Memcache
Key-value store, in memory (volatile)

• APC The Alternative PHP Cache
Key-value store (memory) & opcode cache (disk)

• Redis Remote Dictionary Server
Data store, in memory (disk-backed)

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Redis 101

What is Redis?
Redis is an open source, advanced
key-value store. It is often
referred to as a data structure
server since keys can contain
strings, hashes, lists, sets and
sorted sets.

Http://redis.io
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Redis 101

What is Redis?
Originally written by
Salvatore Sanfilippo, he
now works full-time on
Redis, sponsored by VMWare.
@antirez on Twitter.

Http://redis.io
CardinalPath.com

Redis 101

What makes Redis Unique?
• simple to learn, lightweight
text-based tcp protocol
• very, very, very fast – in RAM
• hashes, list, sets and sorted sets
• widely supported (C, .NET, PHP, Java... more)

• Disk-backed, Background writes!
• Master-Slave configurations

Redis Cluster coming soon...
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Redis 101

What makes Redis Unique?
APC Memcache Redis
Strings ✔ ✔ ✔
Hashes ✔
Lists ✔
Sets ✔
Disk-backed ✔
Replication ✔
Op-code ✔
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Redis 101

Installation
Download, extract and compile Redis with:

$ wget http://redis.googlecode.com/files/redis-2.4.2.tar.gz
$ tar xzf redis-2.4.2.tar.gz
$ cd redis-2.4.2
$ make

Need Linux? VirtualBox

Change 2.4.2 to the latest version

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Redis 101

Check Installation

Start Redis like so: redis-server

MacbookPro: geoffh$ redis-server
[40306] 03 Nov 20:00:59 # Warning: no config file specified, using
the default config. In order to specify a config file use 'redis-
server /path/to/redis.conf'
[40306] 03 Nov 20:00:59 * Server started, Redis version 2.2.11
[40306] 03 Nov 20:00:59 * The server is now ready to accept
connections on port 6379
[40306] 03 Nov 20:00:59 - 0 clients connected (0 slaves), 922064
bytes in use
[40306] 03 Nov 20:01:04 - 0 clients connected (0 slaves), 922064
bytes in use

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Redis 101

Check Installation

You can interact with Redis using the built-in client:

$ src/redis-cli
redis> set foo bar
OK
redis> get foo
"bar"

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Redis 101

Basic Usage - Strings

$ src/redis-cli
redis> set foo bar
OK
redis> get foo
"bar"

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Redis 101


$ src/redis-cli <?php
redis> set foo bar $redis = new Redis();
OK $redis->connect('127.0.0.1',6379);
redis> get foo $redis->set('foo','bar');
"bar" $stored = $redis->get('foo');
echo $stored;

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Redis 101


$ src/redis-cli
redis> set bar "{"a":"1","b":"2"}"
OK
redis> get bar
"{"a":"1","b":"2"}"

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Redis 101


$ src/redis-cli
redis> set bar "{"a":"1","b":"2"}"
OK
redis> get bar <?php
"{"a":"1","b":"2"}" $redis = new Redis();
$redis->connect('127.0.0.1',6379);
$data = array('a'=>'1','b'=>'2');
$json = json_encode($data);
$redis->set('bar',$json);
$stored = $redis->get('bar');
echo $stored;

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Redis 101


$ src/redis-cli
redis> set baz "a=1&b=2&c=3&d=4"
OK
reds> get baz
"a=1&b=2&c=3&d=4"

You get the idea.

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Redis 101


At this point you now know
(basically) everything you need
to use Memcache and/or APC.

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Redis 101



$mc = new Memcache;
$mc->set('a','b');
$a = $mc->get('a');
// $a = "b"

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Redis 101



$mc = new Memcache; $b = 'b';
$mc->set('a','b'); apc_add('a', $b);
$a = $mc->get('a'); $a = apc_fetch('a');
// $a = "b" // $a == "b"

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Redis 101

But with Redis,
there's so much more you can do.

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Redis 101

Before we dive back into more Redis, check it out:
our redis-server process has already forked a bg save.

[40306] 03 Nov 21:00:59 - 0 clients connected (0 slaves), 922368 bytes in use
[40306] 03 Nov 21:01:00 * 1 changes in 3600 seconds. Saving...
[40306] 03 Nov 21:01:00 * Background saving started by pid 40865
[40865] 03 Nov 21:01:00 * DB saved on disk
[40306] 03 Nov 21:01:00 * Background saving terminated with success
[40306] 03 Nov 21:01:04 - DB 0: 3 keys (0 volatile) in 4 slots HT.

CardinalPath.com

Redis 101

Why are we excited about a bg save?

If you're using Memcache or APC, you may know what
a cache "warm up" is. You've implemented on-demand
in-memory caching, which means that your app really
hums... once a ton of stuff is in the cache.

BUT... if memcache goes down, your DB server is
about to get hammered, until the most frequently-
cached objects get rebuilt and recached.

Cache warm-up is the time it takes for your app to
rebuild its cache.

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Redis 101

Why are we excited about a bg save?

With Redis, you can restart your caching server(s)
periodically at opportune times.

Redis re-populates from the "Append Only File" on
disk in seconds.

You can also backup the AOF...

Or Replicate it...

CardinalPath.com

Redis 101

Yes, we added two million items into a
list in 1.28 seconds, with a
networking layer between us and the
server. Just saying...

- Salvatore Sanfilippo, Creator

Everything about Redis 2.4 http://bit.ly/qZRYHw
CardinalPath.com

Redis 101

Basic Usage – More with Strings

APPEND – Make a string longer
GET – Fetch a string at key
GETRANGE – Fetch a substring of key's value
GETSET – Get and Set in one operation
MGET – Multiple Gets
MSET – Multiple Sets
MSETNX – SET Multiple if Not eXists
SET – SET a value if not exists
SETEX – SET a value that EXpires
SETNX – Set if Not eXists
SETRANGE – Rewrite a substring
STRLEN – Integer length of string

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Redis 101


INCR, INCRBY, DECR, DECRBY,

Atomic Counters!

Atomic operation - prevents any
other processor or I/O device from
writing or reading memory until
the operation is complete.

CardinalPath.com

Redis 101


In fact, all of the built-in
commands of Redis are atomic.

And they can be chained together
(pipelined) to create complex
atomic transactions.

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Redis 101

Basic Usage - Keys

redis> keys b*
1) "baz"
2) "bar"

Memcache & APC don't have this feature!
You have to remember all your own keys!

(Use sparingly, though; keys is expensive.)

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Redis 101

Basic Usage - Lists

Lists are to Redis, as
arrays are to PHP.

Duplicates are OK.

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Redis 101

Basic Usage - Lists

arrays are to PHP.

redis> LPUSH mylist "world"
(integer) 1
redis> LPUSH mylist "hello"
(integer) 2
// [ 'world', 'hello' ]
redis> LRANGE mylist 0 -1
1) "hello"
2) "world"

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Redis 101

Basic Usage - Lists

arrays are to PHP.

<?php
$redis = new Redis();
$redis->connect('127.0.0.1',6379);
$redis->delete('key1');
$redis->rpush('key1', 'A'); // returns 1
$redis->rpush('key1', 'B'); // returns 2
$redis->rpush('key1', 'C'); // returns 3
$redis->rpush('key1', 'A'); // returns 4
/* key1 now points to the following list:
[ 'A', 'B', 'C', 'A' ] */

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Redis 101

Basic Usage – More with Lists

LINDEX – Return the list item at a certain position
LINSERT – Insert item into list BEFORE|AFTER item
LLEN – Number of list items (length)
LRANGE – Return some of the items
LREM – Remove one or more items
LSET – Sets the list element at index to value
LTRIM – Lop off some items
LPOP, LPUSH, LPUSHX – Left pop/push
RPOP, RPUSH, RPUSHX, RPOPLPUSH – Right pop/push
BLPOP, BRPOP, BRPOPLPUSH – Blocking pop/push

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Redis 101

Basic Usage - Sets

Sets are to Redis, as
arrays are to PHP.*

*
NO DUPLICATES ALLOWED!

CardinalPath.com

Redis 101

Basic Usage - Sets

Sets are to Redis, as
arrays are to PHP.

<?php
$redis->connect('127.0.0.1',6379);
$redis->delete('key2');
$redis->sadd('key2', 'A'); // returns 1
$redis->sadd('key2', 'B'); // returns 2
$redis->sadd('key2', 'C'); // returns 3
$redis->sadd('key2', 'A'); // returns false
/* key2 now points to the following list:
[ 'A', 'B', 'C' ] */

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Redis 101

Basic Usage - Sets

SADD – Add a member to a set
SCARD – Set CARDinality – Number of set members
SDIFF – Calculate difference between 2 sets
SDIFFSTORE – Store the Difference of 2 sets in a set
SINTER – Calculate the intersection between 2 sets
SINTERSTORE – Store the intersection of 2 sets in a set
SISMEMBER – Bool test whether X is a member of set S
SMEMBERS – list out all the members
SMOVE – Move a member from a set to another set
SPOP – Pop a member off from a set
SRANDMEMBER – Fetch a random set member
SREM – Remove a member from the set
SUNION – Merge two sets together
SUNIONSTORE – Store the merger of two sets in a set

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Redis 101

Basic Usage - Hashes
Hashes are to Redis, as
associative arrays are to PHP.

redis> hmset firsthash a "1" b "2" c "3" d "4"
OK
redis> hget firsthash c
"3"
redis> hset firsthash e "5"
(integer) 1
redis> hget firsthash e
"5"
redis> hget firsthash d
"4"

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Redis 101


<?php
$redis->connect('127.0.0.1',6379);
$redis->delete('user:1');
$redis->hmset('user:1',
array('name' => 'Joe', 'salary' => 2000)
);
// Give Joe a $100 Raise:
$redis->hincrby('user:1', 'salary', 100);

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Redis 101


Hashes are also great representations of
Database table rows, simple objects,
JSON packets... and you can use Redis to store JSON
encoded strings, or serialized objects, as simple
key-value pairs.

But with hashes, No de-serialization is
necessary to get one field from the hash map

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Redis 101


<?php
$redis->connect('127.0.0.1',6379);
array('name' => 'Sally', 'salary' => 5000));
array('name' => 'Bill', 'salary' => 6000));
$uid = 3;
$user = $redis->hgetall('user:'.$uid)
// {name:'Bill',salary:6000}
echo $user['salary']; // 6000

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Redis 101


HDEL – Delete a field & value from a hash
HEXISTS – Bool test whether field is in hash
HGET – fetch value stored under hash → field
HGETALL – fetch the whole hash
HINCRBY – Increment a value stored under a hash field
HKEYS – keys as a set → array_keys( )
HLEN – Integer – Number of fields stored in hash
HMGET – Array – Fetch multiple fields from hash
HMSET – Set multiple fields in a hash
HSET – Set one field in a hash
HSETNX – Set a hash field if it doesn't exist
HVALS – vals as a list → array_values( )

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Redis 101

Basic Usage – Pub/Sub

redis>

redis> subscribe vh1 redis> subscribe mtv
Reading messages... (press Reading messages... (press
Ctrl-C to quit) Ctrl-C to quit)
1) "subscribe" 1) "subscribe"
2) "vh1" 2) "mtv"
3) (integer) 1 3) (integer) 1

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Redis 101


redis> publish mtv "lady gaga"
(integer) 1
redis>

2) "vh1" 2) "mtv"
1) "message"
2) "mtv"
3) "lady gaga"

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Redis 101


redis> publish mtv "lady gaga"
(integer) 1
redis> publish vh1 "rihanna"
(integer) 1

2) "vh1" 2) "mtv"
1) "message" 1) "message"
2) "vh1" 2) "mtv"
3) "rihanna" 3) "lady gaga"

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Redis 101

Advanced Usage – Sorted Sets
ZADD – Add a member to a set with a score
ZCARD – Count how many members are in the sorted set
ZCOUNT – Count how many elemenents between 2 scores
ZINCRBY – Increase/Decrease a member's score
ZINTERSTORE – Intersect on scores and store it
ZRANGE – Return some members between 2 indexes
ZRANGEBYSCORE – Return some members between 2 scores
ZRANK – Returns a member index from Lo to Hi
ZREM – Remove a sorted set's member
ZREMRANGEBYRANK – Remove some members by rank
ZREMRANGEBYSCORE – Remove some members by score
ZREVRANGE – Fetch members by index in desc order
ZREVRANGEBYSCORE – Fetch members by score in desc order
ZREVRANK – Returns the index from Hi to Lo
ZSCORE – Fetch the score of a member
ZUNIONSTORE – Merge 2 sorted sets into a 3rd sorted set

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Redis 101

Advanced Usage – Transactions
MULTI, EXEC, DISCARD and WATCH are the foundation of
transactions in Redis. They allow the execution of a
group of commands in a single step, with two
important guarantees:

1) All the commands in a transaction are serialized
and executed sequentially. It can never happen that a
request issued by another client is served in the
middle of the execution of a Redis transaction. This
guarantees that the commands are executed as a single
atomic operation.

2) Either all or none of the commands are executed.

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Redis 101

Advanced Usage – Transactions

MULTI – Start a transaction
EXEC – Execute a transaction
DISCARD – Ditch a transaction
UNWATCH – Stop watching a key for changes
WATCH – Start watching a key for changes

Example:
> MULTI
OK
> INCR foo
QUEUED
> INCR bar
QUEUED
> EXEC
1) (integer) 1
2) (integer) 1

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Redis 101

Advanced Usage – Redis Admin
BGREWRITEAOF – Write backup Append-Only File
BGSAVE – Perform an on-demand save
CONFIG GET – Read configuration variable
CONFIG RESETSTAT – Reset the statistics reported
CONFIG SET – Set a configuration variable
DBSIZE – Return the size of the Redis DB
FLUSHALL – Erase everything! All databases
FLUSHDB – Erase the current Redis Database
INFO – General statistics
LASTSAVE – Unix Timestamp of last successful save
MONITOR – Watch Redis in real time (via telnet)
SAVE – Save (not in the background)
SHUTDOWN – Turn off the Redis Server
SLAVEOF – Slave to a master Redis Server
SLOWLOG – See where Redis is slowing down

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Redis 101

Redis Resources

Redis Sharding at Craigslist http://bit.ly/gVx0B4

Storing hundreds of millions of key value pairs in
Redis http://bit.ly/tayAXy

Redis-DB Google Group http://bit.ly/RBhvG

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Redis 101

Documentation
• http://redis.io/
• http://redis.io/commands

Try Redis – in real time
• http://try.redis-db.com

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Redis 101

Similar / Related

NoSQL MongoDB Cassandra
CouchDB LevelDB ZeroMQ
NodeJS ActiveMQ RabbitMQ

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Redis 101: An Introduction to Caching with Redis

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