WASI HTTP

This WASI HTTP example uses the Rust sample-wasi-http-rust component. It implements a complete WASI HTTP server that handles GET, POST, and header inspection using the wasi:http/proxy world.

Source Code

The source code is available in the Propeller examples directory. The sample-wasi-http-rust example is a Git submodule from bytecodealliance/sample-wasi-http-rust.

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Build Wasm

Initialize the Git submodule and build the example:

cd propeller
git submodule update --init --remote
cd examples/sample-wasi-http-rust

Install the required Rust target and dependencies:

rustup target add wasm32-wasip2
cargo install wkg
wkg wit fetch

Build the example:

cargo build --target wasm32-wasip2

Your output should look like this:

Compiling sample-wasi-http-rust v0.0.0 (/home/user/propeller/examples/sample-wasi-http-rust)
 Finished `dev` profile [unoptimized + debuginfo] target(s) in 5.65s

Docker Setup

The wasi-http example requires specific proplet configuration. Before running, configure your docker/.env file:

PROPLET_EXTERNAL_WASM_RUNTIME=""
PROPLET_HTTP_ENABLED=true
PROPLET_HTTP_PROXY_PORT=8081

These settings are required because:

PROPLET_EXTERNAL_WASM_RUNTIME="" — Must be empty. When set to wasmtime, the proplet spawns wasmtime run, which cannot serve a wasi:http/proxy component. The internal WasmtimeRuntime (used when unset) handles HTTP proxy components natively.
PROPLET_HTTP_ENABLED=true — Enables the HTTP proxy capability, which is disabled by default.
PROPLET_HTTP_PROXY_PORT=8081 — Sets the HTTP proxy port to match the exposed container port.

Then restart the proplet to apply the changes:

cd docker
docker compose up -d proplet

You should see the following in the proplet startup logs, confirming the correct configuration:

Using Wasmtime runtime
http_enabled: true, http_proxy_port: 8081

Create Task

Create a daemon task for the HTTP server:

curl -X POST "http://localhost:7070/tasks" \
-H "Content-Type: application/json" \
-d '{"name": "_start", "daemon": true}'

Your output should look like this:

{
  "id": "62fc5c37-da87-4d01-846d-713f885f3447",
  "name": "_start",
  "kind": "standard",
  "state": 0,
  "cli_args": null,
  "daemon": true,
  "encrypted": false,
  "start_time": "0001-01-01T00:00:00Z",
  "finish_time": "0001-01-01T00:00:00Z",
  "created_at": "2026-03-03T10:55:48.013225031Z",
  "updated_at": "0001-01-01T00:00:00Z",
  "next_run": "0001-01-01T00:00:00Z",
  "priority": 50
}

Upload Wasm

Upload the compiled wasm file (replace task ID with yours):

curl -X PUT "http://localhost:7070/tasks/62fc5c37-da87-4d01-846d-713f885f3447/upload" \
-F "file=@$(pwd)/target/wasm32-wasip2/debug/sample_wasi_http_rust.wasm"

Your output should look like this:

{
  "id": "62fc5c37-da87-4d01-846d-713f885f3447",
  "name": "_start",
  "kind": "standard",
  "state": 0,
  "file": "...<redacted>...",
  "cli_args": null,
  "daemon": true,
  "encrypted": false,
  "start_time": "0001-01-01T00:00:00Z",
  "finish_time": "0001-01-01T00:00:00Z",
  "created_at": "2026-03-03T10:55:48.013225031Z",
  "updated_at": "2026-03-03T10:56:07.314125682Z",
  "next_run": "0001-01-01T00:00:00Z",
  "priority": 50
}

Start Task

Start the HTTP server task:

curl -X POST "http://localhost:7070/tasks/62fc5c37-da87-4d01-846d-713f885f3447/start"

Your output should look like this:

{"started":true}

Query Task Status

Query the task status:

curl -X GET "http://localhost:7070/tasks/62fc5c37-da87-4d01-846d-713f885f3447"

Your output should look like this:

{
  "id": "62fc5c37-da87-4d01-846d-713f885f3447",
  "name": "_start",
  "kind": "standard",
  "state": 2,
  "cli_args": null,
  "daemon": true,
  "encrypted": false,
  "proplet_id": "d66600de-8827-4096-bc6f-ce1b5a0b2482",
  "results": "",
  "start_time": "2026-03-03T10:56:15.959761675Z",
  "finish_time": "0001-01-01T00:00:00Z",
  "created_at": "2026-03-03T10:55:48.013225031Z",
  "updated_at": "2026-03-03T10:56:15.959761909Z",
  "next_run": "0001-01-01T00:00:00Z",
  "priority": 50
}

The "state": 2 indicates the task is Running. For daemon tasks like this HTTP server, state 2 is the expected state — the task keeps running indefinitely to serve HTTP requests. Task states are: 0 (Pending), 1 (Dispatched), 2 (Running), 3 (Completed), 4 (Failed).

Test Endpoints

Test the HTTP endpoints on the proplet's HTTP port (8081):

curl http://localhost:8081/

Your output should look like this:

Hello, wasi:http/proxy world!

Test the wait endpoint:

curl http://localhost:8081/wait

Your output should look like this:

slept for 1000 millis

Test the echo endpoint:

curl http://localhost:8081/echo -d 'hello from propeller'

Your output should look like this:

hello from propeller

Test the headers endpoint:

curl -v http://localhost:8081/echo-headers -H 'X-Test: 123' -H 'X-Foo: bar'

The request headers are echoed back as response headers:

< HTTP/1.1 200 OK
< x-foo: bar
< user-agent: curl/8.5.0
< accept: */*
< x-test: 123

Running Standalone with WasmTime

You can also run the component standalone using wasmtime (without Propeller):

wasmtime serve -Scli -Shttp target/wasm32-wasip2/debug/sample_wasi_http_rust.wasm

Your output should look like this:

Serving HTTP on http://0.0.0.0:8080/

Test the endpoints:

# Root endpoint
curl http://localhost:8080/

# Wait endpoint (sleeps for ~1 second)
curl http://localhost:8080/wait

# Echo endpoint (returns the request body)
curl http://localhost:8080/echo -d 'hello from propeller'

# Echo headers endpoint (returns request headers as response headers)
curl -v http://localhost:8080/echo-headers -H 'X-Test: 123' -H 'X-Foo: bar'

The output should be the same as shown in the Test Endpoints section above.

When you are done: Go back to the terminal running wasmtime serve and press Ctrl+C to stop the server.

WASI HTTP

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