Render content off the request handler's thread.

src/content/body.rs

@@ -6,7 +6,7 @@ use super::StreamError;
 use crate::bug_message;
 use bytes::Bytes;
 use futures::Stream;
-use futures::future::{Future, FutureExt, LocalBoxFuture};
+use futures::future::{BoxFuture, Future, FutureExt};
 use std::cmp;
 use std::fs::File;
 use std::io::ErrorKind::Interrupted;
@@ -21,7 +21,7 @@ use actix_web::error::BlockingError;
 use actix_web::web;
 
 type ChunkResult<T> = Result<Result<T, StreamError>, BlockingError>;
-type ChunkOperation<'a, T> = LocalBoxFuture<'a, ChunkResult<T>>;
+type ChunkOperation<'a, T> = BoxFuture<'a, ChunkResult<T>>;
 
 fn flatten_chunk_result<T>(result: ChunkResult<T>) -> Result<T, StreamError> {
     match result {
@@ -106,7 +106,7 @@ impl Stream for FileBody {
                     file.by_ref().take(max_bytes).read_to_end(&mut buffer)?;
                     Ok((file, Bytes::from(buffer)))
                 })
-                .boxed_local(),
+                .boxed(),
             );
             self.poll_next(context)
         }
@@ -200,7 +200,7 @@ impl Stream for ProcessBody {
                 }
             }
         })
-        .boxed_local();
+        .boxed();
 
         self.next = Some(next);
         self.poll_next(context)

src/content/handlebars_helpers/get.rs

@@ -176,11 +176,10 @@ where
                 Ok(all_bytes)
             },
         );
-        // `FileBody`/`ProcessBody` rely on `actix_web::web::block`, which needs
-        // a Tokio runtime. When called from an HTTP handler one is already
-        // active, so `futures::executor::block_on` can drive the future to
-        // completion. From sync contexts (e.g. unit tests, the `eval`/`get`
-        // CLI subcommands) we spin up a fresh runtime to wait for the future.
+        // `block_on`, needs an active future runtime. When this is called from
+        // an HTTP handler one's already active, but in sync contexts (e.g. unit
+        // tests, the `eval`/`get` CLI subcommands) we spin up a fresh runtime
+        // to wait for the future.
         let bytes = match tokio::runtime::Handle::try_current() {
             Ok(_) => executor::block_on(bytes_future),
             Err(_) => actix_rt::System::new().block_on(bytes_future),

src/content/mod.rs

@@ -29,12 +29,12 @@ pub use content_registry::{ContentRepresentations, RegisteredContent};
 pub use route::Route;
 
 // This is just a trait alias to help make type signatures a bit saner.
-pub trait ByteStream: Stream<Item = Result<Bytes, StreamError>>
+pub trait ByteStream: Stream<Item = Result<Bytes, StreamError>> + Send
 where
     Self: Unpin,
 {
 }
-impl<T> ByteStream for T where T: Stream<Item = Result<Bytes, StreamError>> + Unpin {}
+impl<T> ByteStream for T where T: Stream<Item = Result<Bytes, StreamError>> + Unpin + Send {}
 
 /// A piece of rendered content along with its media type.
 pub struct Media<Content: ByteStream> {