Brando (codename)

A Redis client written with the Akka IO package introduced in Akka 2.2.

Using

In your build.sbt

resolvers += "http://chrisdinn.github.com/snapshots/"

libraryDependencies += "com.digital-achiever" %% "brando" % "0.0.3"

Getting started

To use talk to Redis, create a Brando actor and send it requests and be prepared to handle the response.

  import brando._

  val brando = system.actorOf(Brando("localhost",6379))

  brando ! Request("SET", "some-key", "this-value")

  // Response: Some(Ok)

  brando ! Request("GET", "some-key")

  // Response: Some(ByteString("this-value"))

  brando ! Request("SADD", "some-set", "one", "two", "three")

  // Response: Some(3)

  brando ! Request("GET", "some-set")

  // Response: Some(List(Some("one"), Some("two"), Some("three")))

  brando ! Request("GET", "non-existent-key")

  // Response: None

Use Response extractors

Brando actor forwards the reply as redis send it back. However, some extractors are provided to help mapping the responses to scala types.

  for{ Response.AsString(value) ← brando ? Request("GET", "key") } yield value
  
  //value: String
  
  for{ Response.AsStrings(values) ← brando ? Request("KEYS", "*") } yield values
  
  //values: Seq[String]
  
  for{ Response.AsByteSeqs(value) ← brando ? Request("GET", "key") } yield value
  
  //value: Seq[Byte]
  
  for{ Response.AsStringsHash(fields) ← brando ? Request("HGETALL", "hash-key") } yield fields
  
  //value: Map[String,String]

Presharding

Brando now provides preliminary support for sharding (AKA "Presharding"), as outlined in the Redis documentation and in this blog post from antirez.

To use it, simply create an instance of ShardManager, passing it a list of Redis shards you'd like it to connect to. From there, we simply create a pool of Brando instances - one for each shard.

val shards = Seq(Shard("redis1", "10.0.0.1", 6379),
				 Shard("redis2", "10.0.0.2", 6379),
				 Shard("redis3", "10.0.0.3", 6379))
				 
val shardManager = context.actorOf(Props(new ShardManager(shards)))

Once an instance of ShardManager has been created, send it commands via the ShardRequest class.

shardManager ! ShardRequest(ByteString("GET"), ByteString(mykey))

Note that ShardRequest explicitly requires a key for all operations. This is because the key is used to determined which shard each request should be forwarded to. In this context, operations which operate on multiple keys (e.g. MSET, MGET) or no keys at all (e.g. SELECT, FLUSHDB) should be avoided, as they break the Redis sharding model.

Individual shards can have their configuration updated on the fly. To do this, send a Shard message to ShardManager.

shardManager ! Shard("redis1", "10.0.0.4", 6379)

This is intended to support failover via Redis Sentinel. Note that the id of the shard MUST match one of the original shards configured when the ShardManager instance was created. Adding new shards is not supported.