Redis - Your Advanced In-Memory Key-Value Store

Jordi Boggiano
@seldaek
http://nelm.io/

Redis - Your Advanced
In-Memory Key-Value Store

About Me
Belgian living in Zürich, Switzerland
Weby stuff for 10 years
http://seld.be
Symfony2, Composer and other OSS contributions
http://github.com/Seldaek
Working at Nelmio
http://nelm.io
Symfony2 & frontend performance consulting

Jordi Boggiano Company nelm.io
Twitter @seldaek Blog seld.be

Agenda
Intro
Features
Use Cases
Using it with PHP


Redis
Wut?


Store
You put data in it


Key-Value Store
Like NoSQL?


Like Memcached?


Memory is fast, but ephemeral


Persist to Disk
Fast and lasting


Created by @antirez
Sponsored by VMWare


So how does it work?


Simple Text Protocol
Human Readable!


Example - Client Library
1 SET key value


1 SET key value
2 > OK


1 SET key value
2 > OK
3 GET key


1 SET key value
2 > OK
3 GET key
4 > "value"


Example - Low Level
1 *3
2 $3
3 SET
4 $3
5 key
6 $5
7 value
1 +OK
1 *2
2 $3
3 GET
4 $3
5 key
1 $5
2 value


Example - Low Level
1 *3rn
2 $3rn
3 SETrn
4 $3rn
5 keyrn
6 $5rn
7 valuern
1 +OKrn
1 *2rn
2 $3rn
3 GETrn
4 $3rn
5 keyrn
1 $5rn
2 valuern


Data Types


Strings
1 SET name Bob
2 SET age 20
3 MGET name age
4 > Bob
5 > 20
1 GETSET name Alice
2 > Bob


Strings
1 SETEX age 3 20
2 GET age
3 > 20
4 // .. 3 seconds later ..
5 GET age
6 > null


Integers
1 INCR count
2 > 1
3 INCR count
4 > 2
5 INCRBY count 3
6 > 5


Hashes
01 HMSET user name Alice email
alice@example.org
02 HGET user email
03 > alice@example.org
04 HKEYS user
05 > name
06 > email
07 HGETALL user
08 > name
09 > Alice
10 > email
11 > alice@example.org


Lists
01 RPUSH admins Alice
02 > 1
03 RPUSH admins Bob
04 > 2
05 LINDEX admins 0
06 > Alice
07 LLEN admins
08 > 2
09 RPOP admins
10 > Bob


Sets
01 SADD page:3:visitors 134
02 > 1
04 > 1
06 > 0
07 SCARD page:3:visitors
08 > 2
09 SMEMBERS page:3:visitors
10 > 134
11 > 253
12 SISMEMBER page:3:visitors 349
13 > 0


Sets
4 SINTER page:3:visitors page:6:visitors
5 > 253


Sorted Sets
1 ZADD highscores 2930 Alice
2 ZADD highscores 1546 Bob
3 ZREVRANGE highscores 0 10 WITHSCORES
4 > Alice
5 > 2930
6 > Bob
7 > 1546


Sort of Lists? Listed Sets?
Lists
1 array('foo', 'bar')

Sets
1 shuffle(array('foo', 'bar'))

Sorted Sets
1 ksort(array(3 => 'foo', 1 => 'bar'))


The basic datatypes of every
language exist in Redis


Process data in Redis
instead of PHP


A Few Features


Atomic Operations
1 SETNX name Alice
2 GET name
3 > Alice
4 SETNX name Bob
5 GET name
6 > Alice
1 INCR foo
2 GET foo
3 > 1
4 INCRBY foo 3
5 GET foo
6 > 4


EXPIRE / EXPIREAT / PERSIST


Pipelining


SORT - SQL in your NoSQL
1 SORT key
2 SORT key LIMIT 0 10 DESC
3 SORT key ALPHA
4 SORT page:6:visitors BY user_*->rank GET
user_* DESC


Append-Only File & Snapshots


Pub/Sub
1 SUBSCRIBE foo1
2 PSUBSCRIBE foo*
3 PUBLISH foo0 message


Master/Slave Replication


Transactions: MULTI / EXEC /
DISCARD
Optimistic Locking with WATCH


Upcoming Features


Lua Scripting: EVAL / EVALSHA
This is great.


EVAL
1 EVAL <body> <num_keys_in_args> [<arg1> <arg2> ... <arg_N>]
1 GET A
2 EVAL "return redis.call('get', KEYS[1])" 1 A


EVAL
Example: Atomic Conditional Decrement, Client-Side
1 WATCH foo
2 $val = GET foo
3 $newVal = max(0, $val - 1); // decrement if foo > 0 client-side
4 MULTI
5 SET foo $newVal
6 EXEC

This may return -ERR, or will block.


EVAL
Example: Atomic Conditional Decrement, Server-Side
01 EVAL "local value = tonumber(redis.call('get', KEYS[1]))
02 if value == nil
03 then
04 return {err="Value at key is not integer"}
05 end
06 if value > tonumber(ARGV[1])
07 then
08 value = value - 1
09 redis.call('set', KEYS[1], value)
10 end
11 return value" 1 foo 0

This is instant and can not fail.


Redis Cluster
Almost as delayed as
Duke Nukem Forever


Speed
Redis is FAST.
CPU is unlikely to be the
bottleneck.
What do you do when
you run out of RAM?


Wait for Redis Cluster?
If you can. Cluster looks great.


Use sharding, most client
libraries can do it.


Use Edis, a protocol compatible
storage-oriented server.
http://inaka.github.com/edis/index.html


Use it without persistence,
store to disk/DB
and load hot data in memory.
A good example in these slides from Wooga


Ok, great. But..
What is it good for?


WEB SCALE
THE CLOUD
NOSQL
ELASTIC
HORIZONTAL SCALING
VERTICAL TOO


BULLSHIT


Get real
"If you do actually have to scale,
then your database isn't going to
magically do it for you."


Really.
What is it good for?


Storing Sessions
Caching Data
Other typical Memcached uses


Caching: Newspaper Site
Expensive reads
Fast-changing pages
Dynamic tracking of what's read for users


Caching: Newspaper Site
Cache generic results:
1 SETEX <pageid>:content 600 <data>
Store user read-state in sets
1 SADD <pageid>:views <userid>
Combine and render for each user
1 GET <pageid>:content
2 SISMEMBER <pageid>:views <userid>


Logging, games and other
write-heavy usages
1 LPUSH logs "Log message"
2 // keep the last 1000 entries
3 LTRIM logs 0 999


Highscore tables
1 ZADD scores 4290 <playerid>
2 ZADD scores 390 <playerid2>
3 // ...
4 ZREVRANK scores <playerid> // 0
5 ZREVRANGE scores 0 10 WITHSCORES
Note: players will only be listed once since it is a set.


Who's online now?
1 ZADD visits <unix> <userid>
2 ZADD visits 1327681399 52
3 ZADD visits 1327683245 18
4 ZRANGEBYSCORE visits <unix>-3600 <unix>
5 ZREMRANGEBYSCORE visits 0 <unix>-3600


Job Queues
Workers:
1 BRPOP queue
Application:
1 LPUSH queue "job description"

e.g. the Resque lib from GitHub


Behavior Tracking
1 SETBIT click:<item>:<date> <userid> 1
2 GETBIT click:3:2012-01-28 55239


Last but not least, it puts the
fun back in Datafunbases


Usage with PHP


Extension: phpredis


Extension: phpredis
Comes with a session handler, sharding, up to date.
1 $redis = new Redis();
2 $redis->connect('127.0.0.1', 6379);
3 $redis->watch('x');
4 $val = $redis->get('x');
5 $newVal = max(0, $val - 1);
6 $result = $redis->multi()
7 ->set('x', $newVal)
8 ->exec();
9 echo $result !== false ? 'Success' : 'Race lost, try again';

http://github.com/nicolasff/phpredis


Extension: phpiredis


Extension: phpiredis
Basic hiredis bindings, protocol parsing, low level.
1 $redis = phpiredis_connect('127.0.0.1', 6379);
2 phpiredis_command($redis, 'WATCH x');
3 $val = phpiredis_command($redis, 'GET x');
5 phpiredis_command($redis, 'MULTI');
6 phpiredis_command($redis, 'SET x '.$newVal);
7 $result = phpiredis_command($redis, 'EXEC');
8 echo $result !== false ? 'Success' : 'Race lost, try again';

http://github.com/seppo0010/phpiredis


Plain PHP: Predis


Plain PHP: Predis
Very complete, sharding, master/slave auto-select,
can use phpiredis for parsing.
01 $redis = new PredisClient('tcp://10.0.0.1:6379');
02
03 $options = array(
04 'cas' => true, // enable Check-and-Set
05 'watch' => 'x',
06 'retry' => 10, // automatic retries
07 );
08
09 $result = $redis->multiExec($options, function($transaction) {
10 $val = $transaction->get('x');
12 $transaction->multi();
13 $transaction->set('x', $newVal);
14 });
15
16 echo $result !== false ? 'Success' : 'Race lost 10 times, giving up';

http://github.com/nrk/predis
http://github.com/snc/SncRedisBundle (Symfony2
integration)

It's fast. It's fun. Try it.
try.redis-db.com


Thank you.
Slides: http://slides.seld.be


Find Out More
Redis.io
Try Redis
The Little Redis Book
Redis Cluster Specification


Questions?
jordi@nelm.io
@seldaek

Feedback:
http://joind.in/4764


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