yam-redis-with-retries

redis-rb

A Ruby client library for the Redis key-value store.

A note about versions

Versions 1.0.x target all versions of Redis. You have to use this one if you are using Redis < 1.2.

Version 2.0 is a big refactoring of the previous version and makes little effort to be backwards-compatible when it shouldn't. It does not support Redis' original protocol, favoring the new, binary-safe one. You should be using this version if you're running Redis 1.2+.

Information about Redis

Redis is a key-value store with some interesting features:

1. It's fast.
2. Keys are strings but values are typed. Currently Redis supports strings, lists, sets, sorted sets and hashes. Atomic operations can be done on all of these types.

See the Redis homepage for more information.

Getting started

You can connect to Redis by instantiating the Redis class:

require "redis"

redis = Redis.new

This assumes Redis was started with default values listening on localhost, port 6379. If you need to connect to a remote server or a different port, try:

redis = Redis.new(:host => "10.0.1.1", :port => 6380)

To connect to Redis listening on a unix socket, try:

redis = Redis.new(:path => "/tmp/redis.sock")

Once connected, you can start running commands against Redis:

>> redis.set "foo", "bar"
=> "OK"

>> redis.get "foo"
=> "bar"

>> redis.sadd "users", "albert"
=> true

>> redis.sadd "users", "bernard"
=> true

>> redis.sadd "users", "charles"
=> true

How many users?

>> redis.scard "users"
=> 3

Is albert a user?

>> redis.sismember "users", "albert"
=> true

Is isabel a user?

>> redis.sismember "users", "isabel"
=> false

Handle groups:

>> redis.sadd "admins", "albert"
=> true

>> redis.sadd "admins", "isabel"
=> true

Users who are also admins:

>> redis.sinter "users", "admins"
=> ["albert"]

Users who are not admins:

>> redis.sdiff "users", "admins"
=> ["bernard", "charles"]

Admins who are not users:

>> redis.sdiff "admins", "users"
=> ["isabel"]

All users and admins:

>> redis.sunion "admins", "users"
=> ["albert", "bernard", "charles", "isabel"]

Storing objects

Redis only stores strings as values. If you want to store an object inside a key, you can use a serialization/deseralization mechanism like JSON:

>> redis.set "foo", [1, 2, 3].to_json
=> OK

>> JSON.parse(redis.get("foo"))
=> [1, 2, 3]

Executing multiple commands atomically

You can use MULTI/EXEC to run arbitrary commands in an atomic fashion:

redis.multi do
  redis.set "foo", "bar"
  redis.incr "baz"
end

Multithreaded Operation

Starting with redis-rb 2.2.0, the client is thread-safe by default. To use earlier versions safely in a multithreaded environment, be sure to initialize the client with :thread_safe => true. Thread-safety can be explicitly disabled for versions 2.2 and up by initializing the client with :thread_safe => false.

See the tests and benchmarks for examples.

Alternate drivers

Non-default connection drivers are only used when they are explicitly required. By default, redis-rb uses Ruby's socket library to talk with Redis.

hiredis

Using redis-rb with hiredis-rb (v0.3 or higher) as backend is done by requiring redis/connection/hiredis before requiring redis. This will make redis-rb pick up hiredis as default driver automatically. This driver optimizes for speed, at the cost of portability. Since hiredis is a C extension, JRuby is not supported (by default). Use hiredis when you have large array replies (think LRANGE, SMEMBERS, ZRANGE, etc.) and/or large pipelines of commands.

Using redis-rb with hiredis from a Gemfile:

gem "hiredis", "~> 0.3.1"
gem "redis", "~> 2.2.0", :require => ["redis/connection/hiredis", "redis"]

synchrony

This driver adds support for em-synchrony. Using the synchrony backend from redis-rb is done by requiring redis/connection/synchrony before requiring redis. This driver makes redis-rb work with EventMachine's asynchronous I/O, while not changing the exposed API. The hiredis gem needs to be available as well, because the synchrony driver uses hiredis for parsing the Redis protocol.

Using redis-rb with synchrony from a Gemfile:

gem "hiredis", "~> 0.3.1"
gem "em-synchrony"
gem "redis", "~> 2.2.0", :require => ["redis/connection/synchrony", "redis"]

Testing

This library (v2.2) is tested against the following interpreters:

• MRI 1.8.7 (drivers: Ruby, hiredis)
• MRI 1.9.2 (drivers: Ruby, hiredis, em-synchrony)
• JRuby 1.6 (drivers: Ruby)
• Rubinius 1.2 (drivers: Ruby, hiredis)

Known issues

• Ruby 1.9 doesn't raise on socket timeouts in IO#read but rather retries the read operation. This means socket timeouts don't work on 1.9 when using the pure Ruby I/O code. Use hiredis when you want use socket timeouts on 1.9.

• Ruby 1.8 does raise on socket timeouts in IO#read, but prints a warning that using IO#read for non blocking reads is obsolete. This is wrong, since the read is in fact blocking, but EAGAIN (which is returned on socket timeouts) is interpreted as if the read was non blocking. Use hiredis to prevent seeing this warning.

More info

Check the Redis Command Reference or check the tests to find out how to use this client.

Contributors

(ordered chronologically with more than 5 commits, see git shortlog -sn for all contributors)

• Ezra Zygmuntowicz
• Taylor Weibley
• Matthew Clark
• Brian McKinney
• Luca Guidi
• Salvatore Sanfillipo
• Chris Wanstrath
• Damian Janowski
• Michel Martens
• Nick Quaranto
• Pieter Noordhuis
• Ilya Grigorik

Contributing

Fork the project and send pull requests. You can also ask for help at #redis-rb on Freenode.