Define Message Handlers

Our new actor already has one handler, the health check. Let’s add a new handler for an HTTP request that will perform the actor equivalent of “hello world”–return an HTTP response with that as the body. To make it a little bit more practical, let’s return the “hello world” string in a field of a JSON payload.

First, we’ll need to add a reference to the HTTP server actor interface and JSON serialization to our Cargo.toml file:

serde_json = "1.0.64"
wasmcloud-actor-http-server = { version = "0.1.2", features = ["guest"]}

In this case we’re using a git reference for the actor interface, but you’ll want to use the version for anything more than experimentation.

Now let’s add the handler to our (Rust) actor (src/

extern crate wapc_guest as guest;
use wasmcloud_actor_core as actorcore;
use wasmcloud_actor_http_server as http;
use serde_json::json;

use guest::prelude::*;

pub fn init() {

fn say_hello(_req: http::Request) -> HandlerResult<http::Response> {
  let result = json!({"greeting": "Hello world!" });
  Ok(http::Response::json(&result, 200, "OK"))

To make sure this actor is compiled and ready to run, we can simply run make in the project directory and cargo will compile it and generate a .wasm file and then the wash CLI will sign the module with a set of claims that includes access to the HTTP Server capability.