Fred

A high level async Redis client for Rust built on Tokio and Futures.

Example

use fred::prelude::*;

#[tokio::main]
async fn main() -> Result<(), RedisError> {
  let config = RedisConfig::default();
  let policy = ReconnectPolicy::default();
  let client = RedisClient::new(config);
  
  // connect to the server, returning a handle to the task that drives the connection
  let _ = client.connect(Some(policy));
  let _ = client.wait_for_connect().await?;
  let _ = client.flushall(false).await?;
 
  // convert responses to many common Rust types
  let foo: Option<String> = client.get("foo").await?;
  assert!(foo.is_none());
  
  let _: () = client.set("foo", "bar", None, None, false).await?;
  // or use turbofish to declare response types
  println!("Foo: {:?}", client.get<String, _>("foo").await?);
  
  // or use a lower level interface for responses to defer parsing, etc
  let foo: RedisValue = client.get("foo").await?;
  assert_eq!(foo.as_str().unwrap(), "bar");
  
  let _ = client.quit().await?;
  Ok(())
}

See the examples for more.

Install

With cargo edit.

cargo add fred

Features

• Flexible and generic client interfaces.
• Supports clustered, centralized, and sentinel Redis deployments.
• Optional built-in reconnection logic with multiple backoff policies.
• Publish-Subscribe and keyspace events interfaces.
• Supports transactions.
• Supports Lua scripts.
• Supports streaming results from the MONITOR command.
• Supports custom commands provided by third party modules.
• Supports TLS connections.
• Handles cluster rebalancing operations without downtime or errors.
• Supports streaming interfaces for scanning functions.
• Options to automatically pipeline requests when possible.
• Automatically retry requests under bad network conditions.
• Support for configuring global settings that can affect performance under different network conditions. Callers can configure backpressure settings, when and how the underlying socket is flushed, and how many times requests are attempted.
• Built-in tracking for network latency and payload size metrics.
• A client pooling interface to round-robin requests among a pool of clients.
• Built in support for tracing.

Tracing

This crate supports tracing via the tracing crate. See the tracing info for more information.

This feature is disabled by default, but callers can opt-in via the full-tracing or partial-tracing features.

Logging

To enable logs use the environment variable RUST_LOG with a value of trace, debug, warn, error, or info. See the documentation for env_logger for more information.

When a client is initialized it will generate a unique client name with a prefix of fred-. This name will appear in all logging statements on the client in order to associate client and server operations if logging is enabled on both.

Compile Time Features

Environment Variables

These are environment variables because they're dangerous in production and callers should be forced to surface them in a loud and obvious way.

Pipelining

The caller can toggle pipelining via flags on the RedisConfig provided to a client to enable automatic pipelining for commands whenever possible. These settings can drastically affect performance on both the server and client, but further performance tuning may be necessary to avoid issues such as using too much memory on the client or server while buffering commands.

See the global performance tuning functions for more information on how to tune backpressure or other relevant settings related to pipelining.

This module also contains a separate test application that can be used to demonstrate the effects of pipelining. This test application also contains some helpful information on how to use the tracing features.

ACL & Authentication

Prior to the introduction of ACL commands in Redis version 6 clients would authenticate with a single password. If callers are not using the ACL interface, or using Redis version <=5.x, they should configure the client to automatically authenticate by using the password field on the RedisConfig and leaving the username field as None.

If callers are using ACLs and Redis version >=6.x they can configure the client to automatically authenticate by using the username and password fields on the provided RedisConfig.

It is required that the authentication information provided to the RedisConfig allows the client to run CLIENT SETNAME and CLUSTER NODES. Callers can still change users via the auth command later, but it recommended to instead use the username and password provided to the RedisConfig so that the client can automatically authenticate after reconnecting.

If this is not possible callers need to ensure that the default user can run the two commands above. Additionally, it is recommended to move any calls to the auth command inside the on_reconnect block.

Redis Sentinel

To use the Redis Sentinel interface callers should provide a ServerConfig::Sentinel variant when creating the client's RedisConfig. This should contain the host/port tuples for the known sentinel nodes when first creating the client.

The client will automatically update these values in place as sentinel nodes change whenever connections to the primary Redis server close. Callers can inspect these changes with the client_config function on any RedisClient that uses the sentinel interface.

Note: Sentinel connections will use the same authentication and TLS configuration options as the connections to the Redis servers.

Callers can also use the sentinel-client feature to communicate directly with Sentinel nodes.

Customizing Error Handling

The custom-reconnect-errors feature enables an interface on the globals to customize the list of errors that should automatically trigger reconnection logic (if configured).

In many cases applications respond to Redis errors by logging the error, maybe waiting and reconnecting, and then trying again. Whether to do this often depends on the prefix in the error message, and this interface allows callers to specify which errors should be handled this way.

Errors that trigger this can be seen with the on_error function.

Tests

To run the unit and integration tests:

cargo test -- --test-threads=1

OR

# run the tests with default features
./tests/run.sh

OR

# run the tests 3 times, once with default features, once with no features, and once with all features (except chaos monkey)
./tests/run_all.sh

Note: a local Redis server must be running on port 6379, and a clustered deployment must be running on ports 30001 - 30006 for the integration tests to pass.

Scripts are included to download and run centralized and clustered redis servers at any Redis version. These scripts will not make any modifications to your system outside the tests/tmp folder.

export REDIS_VERSION=6.2.2
./tests/scripts/install_redis_centralized.sh
./tests/scripts/install_redis_clustered.sh

Beware: the tests will periodically run flushall.

Contributing

See the contributing documentation for info on adding new commands.