wasm-compose: update the example for latest tooling. (#941)

This commit updates the `wasm-compose` example to the latest tooling.

It updates the examples for the latest `cargo-component` and updates Wasmtime
and dependencies to latest.

The server also has been updated to use the `bindgen` macro from Wasmtime for
generating the server's bindings.

Fixes #937.

Author: Peter Huene

crates/wasm-compose/example/README.md

@@ -19,31 +19,33 @@ The server will listen for `POST` requests at `http://localhost:8080`.
 When it receives a request, the server will instantiate a service component
 and forward it the request.
 
-Each component implements a `service` interface defined in `service.wit` as:
+Each service implements a `handler` interface defined in `service.wit` as:
 
 ```wit
-record request {
-    headers: list<tuple<list<u8>, list<u8>>>,
-    body: list<u8>,
+interface handler {
+    record request {
+        headers: list<tuple<list<u8>, list<u8>>>,
+        body: list<u8>,
+    }
+
+    record response {
+        headers: list<tuple<list<u8>, list<u8>>>,
+        body: list<u8>
+    }
+
+    enum error {
+        bad-request,
+    }
+
+    execute: func(req: request) -> result<response, error>
 }
-
-record response {
-    headers: list<tuple<list<u8>, list<u8>>>,
-    body: list<u8>
-}
-
-enum error {
-    bad-request,
-}
-
-execute: func(req: request) -> expected<response, error>
 ```
 
-A service will be passed a `request` containing only the headers and body and
-respond with a `response` containing only the headers and body.
+A service handler will be passed a `request` containing only the headers and 
+body and respond with a `response` containing only the headers and body.
 
-Note that this is an overly-simplistic (and inefficient) interface for describing
-HTTP request processing.
+Note that this is an overly-simplistic (and inefficient) interface for 
+describing HTTP request processing.
 
 ### Execution flow
 
@@ -154,9 +156,9 @@ compressed.
 
 ## Composing with a middleware
 
-If we want to instead compress the response bodies for the service, we can easily
-compose a new component that sends requests through the `middleware` component
-without rebuilding any of the previously built components.
+If we want to instead compress the response bodies for the service, we can 
+easily compose a new component that sends requests through the `middleware` 
+component without rebuilding any of the previously built components.
 
 The `server/config.yml` file contains the configuration needed to compose a new
 component from the `service` and `middleware` components.

crates/wasm-compose/example/middleware/Cargo-component.lock

@@ -0,0 +1,3 @@
+# This file is automatically generated by cargo-component.
+# It is not intended for manual editing.
+version = 1

crates/wasm-compose/example/middleware/Cargo.toml

@@ -6,18 +6,12 @@ publish = false
 
 [dependencies]
 flate2 = "1.0.24"
-wit-bindgen-guest-rust = { git = "https://github.com/bytecodealliance/wit-bindgen", default_features = false }
+wit-bindgen = { version = "0.3.0", default_features = false }
 
 [lib]
 crate-type = ["cdylib"]
 
 [package.metadata.component]
-direct-export = "service"
-
-[package.metadata.component.imports]
-backend = "../service.wit"
-
-[package.metadata.component.exports]
-service = "../service.wit"
+target = { path = "../service.wit", world = "service.middleware" }
 
 [workspace]

crates/wasm-compose/example/middleware/src/lib.rs

@@ -1,22 +1,22 @@
 use bindings::{
-    backend,
-    service::{Error, Request, Response, Service},
+    downstream,
+    handler::{Error, Handler, Request, Response},
 };
 use flate2::{write::GzEncoder, Compression};
 use std::io::Write;
 
 struct Component;
 
-impl Service for Component {
+impl Handler for Component {
     fn execute(req: Request) -> Result<Response, Error> {
         let headers: Vec<_> = req
             .headers
             .iter()
             .map(|(k, v)| (k.as_slice(), v.as_slice()))
             .collect();
 
-        // Send the request to the backend
-        let mut response = backend::execute(backend::Request {
+        // Send the request to the downstream service
+        let mut response = downstream::execute(downstream::Request {
             headers: &headers,
             body: &req.body,
         })
@@ -25,7 +25,7 @@ impl Service for Component {
             body: r.body,
         })
         .map_err(|e| match e {
-            backend::Error::BadRequest => Error::BadRequest,
+            downstream::Error::BadRequest => Error::BadRequest,
         })?;
 
         // If the response is already encoded, leave it alone

crates/wasm-compose/example/server/Cargo.toml

@@ -6,9 +6,10 @@ publish = false
 
 [dependencies]
 async-std = { version = "1.12.0", features = ["attributes"] }
-clap = { version = "3.2.16", features = ["derive"] }
+clap = { version = "3.2.23", features = ["derive"] }
 driftwood = "0.0.6"
 tide = "0.16.0"
-wasmtime = { git = "https://github.com/bytecodealliance/wasmtime", rev = "b61e678", features = ["component-model"] }
+wasmtime = { version = "6.0.0", features = ["component-model"] }
+wasmtime-component-macro = "6.0.0"
 
 [workspace]

crates/wasm-compose/example/server/config.yml

@@ -4,4 +4,4 @@ search-paths:
 instantiations:
   $input:
     arguments:
-      backend: svc
+      downstream: svc

crates/wasm-compose/example/server/src/main.rs

@@ -10,6 +10,11 @@ use tide::{
 };
 use wasmtime::{component::*, Config, Engine, Store};
 
+wasmtime_component_macro::bindgen!({
+    path: "../service.wit",
+    world: "service"
+});
+
 /// Represents state stored in the tide application context.
 ///
 /// This is so that a component is only parsed and compiled once.
@@ -33,42 +38,10 @@ impl State {
     }
 }
 
-#[derive(ComponentType, Lower)]
-#[component(record)]
-struct ServiceRequest {
-    headers: Vec<(Vec<u8>, Vec<u8>)>,
-    body: Vec<u8>,
-}
-
-impl ServiceRequest {
-    async fn new(mut req: Request<State>) -> tide::Result<Self> {
-        // Convert the tide request to a service request.
-        let headers = req
-            .iter()
-            .map(|(n, v)| {
-                (
-                    n.as_str().as_bytes().to_vec(),
-                    v.as_str().as_bytes().to_vec(),
-                )
-            })
-            .collect();
-        let body = req.take_body().into_bytes().await?;
-
-        Ok(Self { headers, body })
-    }
-}
-
-#[derive(ComponentType, Lift)]
-#[component(record)]
-struct ServiceResponse {
-    headers: Vec<(Vec<u8>, Vec<u8>)>,
-    body: Vec<u8>,
-}
-
-impl TryFrom<ServiceResponse> for tide::Response {
+impl TryFrom<handler::Response> for tide::Response {
     type Error = tide::Error;
 
-    fn try_from(r: ServiceResponse) -> Result<Self, Self::Error> {
+    fn try_from(r: handler::Response) -> Result<Self, Self::Error> {
         // Convert the service response to a tide response
         let mut builder = tide::Response::builder(StatusCode::Ok);
         for (name, value) in r.headers {
@@ -82,25 +55,16 @@ impl TryFrom<ServiceResponse> for tide::Response {
     }
 }
 
-#[derive(ComponentType, Lift)]
-#[component(enum)]
-enum ServiceError {
-    #[component(name = "bad-request")]
-    BadRequest,
-}
-
-impl From<ServiceError> for tide::Error {
-    fn from(e: ServiceError) -> Self {
-        match e {
-            ServiceError::BadRequest => {
+impl handler::Error {
+    fn into_tide(self) -> tide::Error {
+        match self {
+            Self::BadRequest => {
                 tide::Error::from_str(StatusCode::BadRequest, "bad service request")
             }
         }
     }
 }
 
-type ServiceResult = Result<ServiceResponse, ServiceError>;
-
 /// WebAssembly component server.
 ///
 /// A demonstration server that executes WebAssembly components.
@@ -144,24 +108,29 @@ impl ServerApp {
         app.listen(address).await.map_err(Into::into)
     }
 
-    async fn process_request(req: Request<State>) -> tide::Result {
-        let state = req.state();
+    async fn process_request(mut req: Request<State>) -> tide::Result {
+        let body = req.body_bytes().await?;
+        let headers = req
+            .iter()
+            .map(|(n, v)| (n.as_str().as_bytes(), v.as_str().as_bytes()))
+            .collect::<Vec<_>>();
 
         // Create a new store for the request
-        let mut store = Store::new(&state.engine, ());
+        let state = req.state();
         let linker: Linker<()> = Linker::new(&state.engine);
-
-        // Instantiate the service component and get its `execute` export
-        let instance = linker.instantiate(&mut store, &state.component)?;
-        let execute = instance
-            .get_typed_func::<(ServiceRequest,), (ServiceResult,), _>(&mut store, "execute")?;
-
-        // Call the `execute` export with the request and translate the response
-        execute
-            .call(&mut store, (ServiceRequest::new(req).await?,))?
-            .0
-            .map_err(Into::into)
-            .and_then(TryInto::try_into)
+        let mut store = Store::new(&state.engine, ());
+        let (service, _) = Service::instantiate(&mut store, &state.component, &linker)?;
+        service
+            .handler
+            .call_execute(
+                &mut store,
+                handler::Request {
+                    headers: &headers,
+                    body: &body,
+                },
+            )?
+            .map(TryInto::try_into)
+            .map_err(handler::Error::into_tide)?
     }
 }
 

crates/wasm-compose/example/service.wit

@@ -1,15 +1,26 @@
-record request {
-    headers: list<tuple<list<u8>, list<u8>>>,
-    body: list<u8>,
-}
+interface handler {
+    record request {
+        headers: list<tuple<list<u8>, list<u8>>>,
+        body: list<u8>,
+    }
+
+    record response {
+        headers: list<tuple<list<u8>, list<u8>>>,
+        body: list<u8>
+    }
 
-record response {
-    headers: list<tuple<list<u8>, list<u8>>>,
-    body: list<u8>
+    enum error {
+        bad-request,
+    }
+
+    execute: func(req: request) -> result<response, error>
 }
 
-enum error {
-    bad-request,
+default world service {
+    export handler: self.handler
 }
 
-execute: func(req: request) -> result<response, error>
+world middleware {
+    import downstream: self.handler
+    export handler: self.handler
+}

crates/wasm-compose/example/service/Cargo-component.lock

@@ -0,0 +1,3 @@
+# This file is automatically generated by cargo-component.
+# It is not intended for manual editing.
+version = 1

crates/wasm-compose/example/service/Cargo.toml

@@ -5,15 +5,12 @@ edition = "2021"
 publish = false
 
 [dependencies]
-wit-bindgen-guest-rust = { git = "https://github.com/bytecodealliance/wit-bindgen", default_features = false }
+wit-bindgen = { version = "0.3.0", default_features = false }
 
 [lib]
 crate-type = ["cdylib"]
 
 [package.metadata.component]
-direct-export = "service"
-
-[package.metadata.component.exports]
-service = "../service.wit"
+target = { path = "../service.wit" }
 
 [workspace]