Crate redis

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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.

  • acl: enables acl support (enabled 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-comp: enables support for tokio (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://[<username>][:<passwd>@]<hostname>[:port][/<db>]

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

redis+unix:///<path>[?db=<db>[&pass=<password>][&user=<username>]]

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

unix:///<path>[?db=<db>][&pass=<password>][&user=<username>]]

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 ().

Note that commands with a sub-command (like “MEMORY USAGE”, “ACL WHOAMI”, “LATENCY HISTORY”, etc) must specify the sub-command as a separate arg:

fn do_something(con: &mut redis::Connection) -> redis::RedisResult<usize> {
    // This will result in a server error: "unknown command `MEMORY USAGE`"
    // because "USAGE" is technically a sub-command of "MEMORY".
    redis::cmd("MEMORY USAGE").arg("my_key").query(con)?;

    // However, this will work as you'd expect
    redis::cmd("MEMORY").arg("USAGE").arg("my_key").query(con)
}

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, 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);
}

Scripts

Lua scripts are supported through the Script type in a convenient way (it does not support pipelining currently). It will automatically load the script if it does not exist and invoke it.

Example:

let script = redis::Script::new(r"
    return tonumber(ARGV[1]) + tonumber(ARGV[2]);
");
let result : isize = script.arg(1).arg(2).invoke(&mut con)?;
assert_eq!(result, 3);

Async

In addition to the synchronous interface that’s been explained above there also exists an asynchronous interface based on futures and tokio.

This interface exists under the aio (async io) module and largely mirrors the synchronous with a few concessions to make it fit the constraints of futures.

use futures::prelude::*;
use redis::AsyncCommands;

let client = redis::Client::open("redis://127.0.0.1/").unwrap();
let mut con = client.get_async_connection().await?;

con.set("key1", b"foo").await?;

redis::cmd("SET").arg(&["key2", "bar"]).query_async(&mut con).await?;

let result = redis::cmd("MGET")
 .arg(&["key1", "key2"])
 .query_async(&mut con)
 .await;
assert_eq!(result, Ok(("foo".to_string(), b"bar".to_vec())));

Modules

acl

Defines types to use with the ACL commands.

aio

Adds experimental async IO support to redis.

geo

Defines types to use with the geospatial commands.

streams

Defines types to use with the streams commands.

Structs

AsyncIter

Represents a redis iterator that can be used with async connections.

Client

The client type.

Cmd

Represents redis commands.

Connection

Represents a stateful redis TCP connection.

ConnectionInfo

Holds the connection information that redis should use for connecting.

InfoDict

An info dictionary type.

Iter

Represents a redis iterator.

LposOptions

Options for the [LPOS] command

Msg

Represents a pubsub message.

Parser

The internal redis response parser.

Pipeline

Represents a redis command pipeline.

PubSub

Represents a pubsub connection.

RedisError

Represents a redis error. For the most part you should be using the Error trait to interact with this rather than the actual struct.

Script

Represents a lua script.

ScriptInvocation

Represents a prepared script call.

Enums

Arg

An argument to a redis command

ConnectionAddr

Defines the connection address.

ControlFlow

Allows pubsub callbacks to stop receiving messages.

ErrorKind

An enum of all error kinds.

NumericBehavior

Helper enum that is used in some situations to describe the behavior of arguments in a numeric context.

Value

Internal low-level redis value enum.

Traits

AsyncCommands

Implements common redis commands over asynchronous connections. This allows you to send commands straight to a connection or client.

Commands

Implements common redis commands for connection like objects. This allows you to send commands straight to a connection or client. It is also implemented for redis results of clients which makes for very convenient access in some basic cases.

ConnectionLike

Implements the “stateless” part of the connection interface that is used by the different objects in redis-rs. Primarily it obviously applies to Connection object but also some other objects implement the interface (for instance whole clients or certain redis results).

FromRedisValue

This trait is used to convert a redis value into a more appropriate type. While a redis Value can represent any response that comes back from the redis server, usually you want to map this into something that works better in rust. For instance you might want to convert the return value into a String or an integer.

IntoConnectionInfo

Converts an object into a connection info struct. This allows the constructor of the client to accept connection information in a range of different formats.

PubSubCommands

The PubSub trait allows subscribing to one or more channels and receiving a callback whenever a message arrives.

RedisWrite

Abstraction trait for redis command abstractions.

ToRedisArgs

Used to convert a value into one or multiple redis argument strings. Most values will produce exactly one item but in some cases it might make sense to produce more than one.

Functions

cmd

Shortcut function to creating a command with a single argument.

from_redis_value

A shortcut function to invoke FromRedisValue::from_redis_value to make the API slightly nicer.

pack_command

Packs a bunch of commands into a request. This is generally a quite useless function as this functionality is nicely wrapped through the Cmd object, but in some cases it can be useful. The return value of this can then be send to the low level ConnectionLike methods.

parse_redis_url

This function takes a redis URL string and parses it into a URL as used by rust-url. This is necessary as the default parser does not understand how redis URLs function.

parse_redis_value

Parses bytes into a redis value.

parse_redis_value_async

Parses a redis value asynchronously.

pipe

Shortcut for creating a new pipeline.

transaction

This function simplifies transaction management slightly. What it does is automatically watching keys and then going into a transaction loop util it succeeds. Once it goes through the results are returned.

Type Definitions

RedisFuture

Library generic future type.

RedisResult

Library generic result type.