fix(examples): Fix tower examples (#624)

Doing ```rust let clone = self.inner.clone(); Box::pin(async move { let response = clone.call(request).await?; Ok(response) }) ``` If `self.inner` is (or contains) a `tower::buffer::Buffer` might panic. That is because cloning a `Buffer` drops the permit that was acquired in `poll_ready`, meaning it is no longer ready and panic in `call`. The solution is to use `mem::replace` to take the ready service and pass that into the async block. Fixes #545
hyperium · May 7, 2021 · 4a917a3 · 4a917a3
1 parent 4b26e78
commit 4a917a3
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diff --git a/examples/src/tower/client.rs b/examples/src/tower/client.rs
@@ -56,12 +56,17 @@ mod service {
         }
 
         fn call(&mut self, req: Request<BoxBody>) -> Self::Future {
-            let mut channel = self.inner.clone();
+            // This is necessary because tonic internally uses `tower::buffer::Buffer`.
+            // See https://github.com/tower-rs/tower/issues/547#issuecomment-767629149
+            // for details on why this is necessary
+            let clone = self.inner.clone();
+            let mut inner = std::mem::replace(&mut self.inner, clone);
 
             Box::pin(async move {
                 // Do extra async work here...
+                let response = inner.call(req).await?;
 
-                channel.call(req).await.map_err(Into::into)
+                Ok(response)
             })
         }
     }

diff --git a/examples/src/tower/server.rs b/examples/src/tower/server.rs
@@ -71,12 +71,17 @@ where
     }
 
     fn call(&mut self, req: HyperRequest<Body>) -> Self::Future {
-        let mut svc = self.inner.clone();
+        // This is necessary because tonic internally uses `tower::buffer::Buffer`.
+        // See https://github.com/tower-rs/tower/issues/547#issuecomment-767629149
+        // for details on why this is necessary
+        let clone = self.inner.clone();
+        let mut inner = std::mem::replace(&mut self.inner, clone);
 
         Box::pin(async move {
-            // Do async work here....
+            // Do extra async work here...
+            let response = inner.call(req).await?;
 
-            svc.call(req).await
+            Ok(response)
         })
     }
 }