Redis driver

WasmEdge provides a Redis driver for Rust developers, enabling developers to build database applications in Rust and then running in WasmEdge.

note

Before we start, you need to have Rust and WasmEdge installed. Make sure that you read the special notes on networking apps especially if you are compiling Rust programs on a Mac.

Run the example

The wasmedge-db-example/redis is a Redis connector example written in Rust.

git clone https://github.com/WasmEdge/wasmedge-db-examples
cd wasmedge-db-examples/redis

# Compile the rust code into WASM
RUSTFLAGS="--cfg wasmedge --cfg tokio_unstable" cargo build --target wasm32-wasi --release

# Execute Redis command against a Redis instance at redis://localhost/
wasmedge --env "REDIS_URL=redis://localhost/" target/wasm32-wasi/release/wasmedge-redis-client-examples.wasm

Configuration

In order to compile the redis and tokio crates, we will need to apply patches to add WasmEdge-specific socket APIs to those crates in Cargo.toml.

[patch.crates-io]
tokio = { git = "https://github.com/second-state/wasi_tokio.git", branch = "v1.36.x" }

[dependencies]
anyhow = "1.0"
chrono = { version = "0.4", features = ["serde"] }
tokio = { version = "1", features = ["full"] }
redis = { version = "0.25.4", default-features = false, features = [
    "tokio-comp",
] }

Code explanation

The following program uses the redis crate to access a Redis server through its connection URL. It gets the current time, saves the timestamp object to the Redis server, and then reads it back for display on the console.

#[tokio::main(flavor = "current_thread")]
async fn main() -> Result<()> {
    // connect to redis
    let client = redis::Client::open(&*get_url()).unwrap();
    let mut con = client.get_multiplexed_async_connection().await.unwrap();

    let time = format!("{}", chrono::Utc::now());
    // throw away the result, just make sure it does not fail
    let _: () = con.set("current_time", time).await.unwrap();

    // read back the key and return it.  Because the return value
    // from the function is a result for String, this will automatically
    // convert into one.
    let value: String = con.get("current_time").await.unwrap();
    println!("Successfully GET `time`: {}", value);

    Ok(())
}