Custom Bindings

You can write custom bindings by using the bindings protocol.

Rust

In Rust, there’s already an official client library you can use. You can add it to your dependencies.

Cargo.toml

[dependencies]
# The client library
svld-ipc-client = { git = "https://github.com/AWeirdDev/serverlessd" }

# JSON support
serde_json = "1"

First, connect to the socket and perform a handshake.

use std::path::PathBuf;

let mut client = svld_ipc_client::connect()
    .binding_type("my_binding".into()) // your binding type
    .path(PathBuf::new())
    .call()
    .await?
    .perform_handshake()
    .await?;

Then, within a loop, receive server-side messages and reply:

use svld_ipc_client::ServerMessage;

while let Ok(ServerMessage {
    id,
    function_name,
    worker_name,
    args,
}) = client.recv_message::<Vec<serde_json::Value>>().await {
    // echo back
    client
        .send_ok(
            id, 
            format!(
                "{} called {}, with args: {:?}", 
                worker_name, 
                function_name, 
                args
            )
        )
        .await?;
}

^C Safety

You can make the program safely exit on ^C.

let ctrl_c = tokio::signal::ctrl_c();
tokio::pin!(ctrl_c);

loop {
  let server_message = tokio::select! {
    _ = &mut ctrl_c => {
        break;
    }
    msg = client.recv_message::<Vec<serde_json::IValue>>() => msg
  };

 let ServerMessage {
    id,
    function_name,
    worker_name,
    args,
 } = match server_message {
    Ok(t) => t,
    Err(err) => {
      eprintln!("error while receiving message: {err:?}");
      break;
    }
  };

  // ... other tasks
}

Testing your bindings

After you’re done making your bindings, test them out!

Add bindings your configuration file:

wrangler.toml

[my-binding-1]
binding = "MY_BINDING_ONE"

[my-binding-2]
binding = "MY_BINDING_TWO"

And the JavaScript worker script:

main.js

export default {
  async fetch(request, env) {
    await env.MY_BINDING_ONE.foo();
    await env.MY_BINDING_TWO.bar(123, 4.56);

    return "foo";
  }
}

serverlessd one \
    ./wrangler.toml \
    --bindings my-binding-1 \
    --bindings my-binding-2

The --bindings flag specifies what bindings the worker has access to.

After starting a serverlessd instance, you can start your bindings to make them connect to the IPC server.

KV Protocol