redis-rs

*NOTE: THIS IS NOT THE BEST VERSION OF REDIS-RS -- THIS IS A VERSION THAT WAS FORKED IN ORDER TO PUBLISH SINCE DEVELOPMENT SEEMED TO TEMPORARILY HALT IN THE MAIN BRANCH. GO HERE FOR THE ORIGINAL: redis-rs.

To install, this is trezm-redis on crates.io.

lib.rs:

redis-rs is a rust implementation of a Redis client library. It exposes a general purpose interface to Redis and also provides specific helpers for commonly used functionality.

The crate is called redis and you can depend on it via cargo:

[dependencies.redis]
version = "*"

If you want to use the git version:

[dependencies.redis]
git = "https://github.com/mitsuhiko/redis-rs.git"

Basic Operation

redis-rs exposes two API levels: a low- and a high-level part. The high-level part does not expose all the functionality of redis and might take some liberties in how it speaks the protocol. The low-level part of the API allows you to express any request on the redis level. You can fluently switch between both API levels at any point.

Connection Handling

For connecting to redis you can use a client object which then can produce actual connections. Connections and clients as well as results of connections and clients are considered ConnectionLike objects and can be used anywhere a request is made.

The full canonical way to get a connection is to create a client and to ask for a connection from it:

extern crate redis;

fn do_something() -> redis::RedisResult<()> {
    let client = redis::Client::open("redis://127.0.0.1/")?;
    let mut con = client.get_connection()?;

    /* do something here */

    Ok(())
}

Optional Features

There are a few features defined that can enable additional functionality if so desired. Some of them are turned on by default.

• aio: enables async IO support (enabled by default)
• geospatial: enables geospatial support (enabled by default)
• script: enables script support (enabled by default)
• r2d2: enables r2d2 connection pool support (optional)
• cluster: enables redis cluster support (optional)
• tokio-rt-core: enables support for tokio-rt (optional)
• connection-manager: enables support for automatic reconnection (optional)

Connection Parameters

redis-rs knows different ways to define where a connection should go. The parameter to Client::open needs to implement the IntoConnectionInfo trait of which there are three implementations:

• string slices in redis:// URL format.
• URL objects from the redis-url crate.
• ConnectionInfo objects.

The URL format is redis://[:<passwd>@]<hostname>[:port][/<db>]

If Unix socket support is available you can use a unix URL in this format:

redis+unix:///[:<passwd>@]<path>[?db=<db>]

For compatibility with some other redis libraries, the "unix" scheme is also supported:

unix:///[:<passwd>@]<path>[?db=<db>]

Executing Low-Level Commands

To execute low-level commands you can use the cmd function which allows you to build redis requests. Once you have configured a command object to your liking you can send a query into any ConnectionLike object:

fn do_something(con: &mut redis::Connection) -> redis::RedisResult<()> {
    let _ : () = redis::cmd("SET").arg("my_key").arg(42).query(con)?;
    Ok(())
}

Upon querying the return value is a result object. If you do not care about the actual return value (other than that it is not a failure) you can always type annotate it to the unit type ().

Executing High-Level Commands

The high-level interface is similar. For it to become available you need to use the Commands trait in which case all ConnectionLike objects the library provides will also have high-level methods which make working with the protocol easier:

extern crate redis;
use redis::Commands;

fn do_something(con: &mut redis::Connection) -> redis::RedisResult<()> {
    let _ : () = con.set("my_key", 42)?;
    Ok(())
}

Note that high-level commands are work in progress and many are still missing!

Type Conversions

Because redis inherently is mostly type-less and the protocol is not exactly friendly to developers, this library provides flexible support for casting values to the intended results. This is driven through the FromRedisValue and ToRedisArgs traits.

The arg method of the command will accept a wide range of types through the ToRedisArgs trait and the query method of a command can convert the value to what you expect the function to return through the FromRedisValue trait. This is quite flexible and allows vectors, tuples, hashsets, hashmaps as well as optional values:

let count : i32 = con.get("my_counter")?;
let count = con.get("my_counter").unwrap_or(0i32);
let k : Option<String> = con.get("missing_key")?;
let name : String = con.get("my_name")?;
let bin : Vec<u8> = con.get("my_binary")?;
let map : HashMap<String, i32> = con.hgetall("my_hash")?;
let keys : Vec<String> = con.hkeys("my_hash")?;
let mems : HashSet<i32> = con.smembers("my_set")?;
let (k1, k2) : (String, String) = con.get(&["k1", "k2"])?;

Iteration Protocol

In addition to sending a single query you iterators are also supported. When used with regular bulk responses they don't give you much over querying and converting into a vector (both use a vector internally) but they can also be used with SCAN like commands in which case iteration will send more queries until the cursor is exhausted:

let mut iter : redis::Iter<isize> = redis::cmd("SSCAN").arg("my_set")
    .cursor_arg(0).clone().iter(&mut con)?;
for x in iter {
    // do something with the item
}

As you can see the cursor argument needs to be defined with cursor_arg instead of arg so that the library knows which argument needs updating as the query is run for more items.

Pipelining

In addition to simple queries you can also send command pipelines. This is provided through the pipe function. It works very similar to sending individual commands but you can send more than one in one go. This also allows you to ignore individual results so that matching on the end result is easier:

let (k1, k2) : (i32, i32) = redis::pipe()
    .cmd("SET").arg("key_1").arg(42).ignore()
    .cmd("SET").arg("key_2").arg(43).ignore()
    .cmd("GET").arg("key_1")
    .cmd("GET").arg("key_2").query(&mut con)?;

If you want the pipeline to be wrapped in a MULTI/EXEC block you can easily do that by switching the pipeline into atomic mode. From the caller's point of view nothing changes, the pipeline itself will take care of the rest for you:

let (k1, k2) : (i32, i32) = redis::pipe()
    .atomic()
    .cmd("SET").arg("key_1").arg(42).ignore()
    .cmd("SET").arg("key_2").arg(43).ignore()
    .cmd("GET").arg("key_1")
    .cmd("GET").arg("key_2").query(&mut con)?;

You can also use high-level commands on pipelines:

let (k1, k2) : (i32, i32) = redis::pipe()
    .atomic()
    .set("key_1", 42).ignore()
    .set("key_2", 43).ignore()
    .get("key_1")
    .get("key_2").query(&mut con)?;

Transactions

Transactions are available through atomic pipelines. In order to use them in a more simple way you can use the transaction function of a connection:

use redis::Commands;
let key = "the_key";
let (new_val,) : (isize,) = redis::transaction(&mut con, &[key], |con, pipe| {
    let old_val : isize = con.get(key)?;
    pipe
        .set(key, old_val + 1).ignore()
        .get(key).query(con)
})?;
println!("The incremented number is: {}", new_val);

For more information see the transaction function.

PubSub

Pubsub is currently work in progress but provided through the PubSub connection object. Due to the fact that Rust does not have support for async IO in libnative yet, the API does not provide a way to read messages with any form of timeout yet.

Example usage:

let client = redis::Client::open("redis://127.0.0.1/")?;
let mut con = client.get_connection()?;
let mut pubsub = con.as_pubsub();
pubsub.subscribe("channel_1")?;
pubsub.subscribe("channel_2")?;

loop {
    let msg = pubsub.get_message()?;
    let payload : String = msg.get_payload()?;
    println!("channel '{}': {}", msg.get_channel_name(), payload);
}