cache: add grpc read-only response caching

crates/crank-adapter-grpc/src/test_support.rs

@@ -1,5 +1,9 @@
 use base64::{Engine as _, engine::general_purpose::STANDARD};
 use futures_util::stream;
+use std::sync::{
+    Arc,
+    atomic::{AtomicUsize, Ordering},
+};
 use tokio::net::TcpListener;
 use tonic::{Request, Response, Status, transport::Server};
 
@@ -121,6 +125,54 @@ pub async fn spawn_metadata_echo_server() -> String {
     format!("http://{}", address)
 }
 
+pub async fn spawn_counting_unary_echo_server(request_count: Arc<AtomicUsize>) -> String {
+    struct CountingEchoServiceImpl {
+        request_count: Arc<AtomicUsize>,
+    }
+
+    #[tonic::async_trait]
+    impl echo::echo_service_server::EchoService for CountingEchoServiceImpl {
+        async fn unary_echo(
+            &self,
+            request: Request<echo::EchoRequest>,
+        ) -> Result<Response<echo::EchoResponse>, Status> {
+            let message = request.into_inner().message;
+            let count = self.request_count.fetch_add(1, Ordering::SeqCst) + 1;
+
+            Ok(Response::new(echo::EchoResponse {
+                message: format!("{message}-{count}"),
+            }))
+        }
+
+        type ServerEchoStream = std::pin::Pin<
+            Box<dyn futures_util::Stream<Item = Result<echo::EchoResponse, Status>> + Send>,
+        >;
+
+        async fn server_echo(
+            &self,
+            _request: Request<echo::EchoRequest>,
+        ) -> Result<Response<Self::ServerEchoStream>, Status> {
+            Ok(Response::new(Box::pin(stream::empty())))
+        }
+    }
+
+    let listener = TcpListener::bind("127.0.0.1:0").await.unwrap();
+    let address = listener.local_addr().unwrap();
+    let incoming = tonic::transport::server::TcpIncoming::from(listener);
+
+    tokio::spawn(async move {
+        Server::builder()
+            .add_service(echo::echo_service_server::EchoServiceServer::new(
+                CountingEchoServiceImpl { request_count },
+            ))
+            .serve_with_incoming(incoming)
+            .await
+            .unwrap();
+    });
+
+    format!("http://{}", address)
+}
+
 pub fn descriptor_set_b64() -> String {
     STANDARD.encode(echo::FILE_DESCRIPTOR_SET)
 }