feat(iroh): remove Arc requirements from ProtocolHandler (#3010)

## Breaking Changes

- `iroh::protocol::ProtocolHandler::accept` now takes `&self` instead of
`Arc<Self>`
- `iroh::protocol::ProtocolHandler::shutdown` now takes `&self` instead
of `Arc<Self>`
- `iroh::protocol::RouterBuilder::accept` now takes `T: ProtocolHandler`
instead of `Arc<dyn ProtocolHandler>`
- `iroh::protocol::ProtocolMap` is now private

iroh/examples/echo.rs

@@ -6,8 +6,6 @@
 //!
 //!     cargo run --example echo --features=examples
 
-use std::sync::Arc;
-
 use anyhow::Result;
 use futures_lite::future::Boxed as BoxedFuture;
 use iroh::{
@@ -60,10 +58,7 @@ async fn accept_side() -> Result<Router> {
     let endpoint = Endpoint::builder().discovery_n0().bind().await?;
 
     // Build our protocol handler and add our protocol, identified by its ALPN, and spawn the node.
-    let router = Router::builder(endpoint)
-        .accept(ALPN, Arc::new(Echo))
-        .spawn()
-        .await?;
+    let router = Router::builder(endpoint).accept(ALPN, Echo).spawn().await?;
 
     Ok(router)
 }
@@ -76,7 +71,7 @@ impl ProtocolHandler for Echo {
     ///
     /// The returned future runs on a newly spawned tokio task, so it can run as long as
     /// the connection lasts.
-    fn accept(self: Arc<Self>, connecting: Connecting) -> BoxedFuture<Result<()>> {
+    fn accept(&self, connecting: Connecting) -> BoxedFuture<Result<()>> {
         // We have to return a boxed future from the handler.
         Box::pin(async move {
             // Wait for the connection to be fully established.

iroh/examples/search.rs

@@ -127,7 +127,8 @@ impl ProtocolHandler for BlobSearch {
     ///
     /// The returned future runs on a newly spawned tokio task, so it can run as long as
     /// the connection lasts.
-    fn accept(self: Arc<Self>, connecting: Connecting) -> BoxedFuture<Result<()>> {
+    fn accept(&self, connecting: Connecting) -> BoxedFuture<Result<()>> {
+        let this = self.clone();
         // We have to return a boxed future from the handler.
         Box::pin(async move {
             // Wait for the connection to be fully established.
@@ -145,7 +146,7 @@ impl ProtocolHandler for BlobSearch {
 
             // Now, we can perform the actual query on our local database.
             let query = String::from_utf8(query_bytes)?;
-            let num_matches = self.query_local(&query).await;
+            let num_matches = this.query_local(&query).await;
 
             // We want to return a list of hashes. We do the simplest thing possible, and just send
             // one hash after the other. Because the hashes have a fixed size of 32 bytes, this is
@@ -167,11 +168,11 @@ impl ProtocolHandler for BlobSearch {
 
 impl BlobSearch {
     /// Create a new protocol handler.
-    pub fn new(endpoint: Endpoint) -> Arc<Self> {
-        Arc::new(Self {
+    pub fn new(endpoint: Endpoint) -> Self {
+        Self {
             endpoint,
             blobs: Default::default(),
-        })
+        }
     }
 
     /// Query a remote node, download all matching blobs and print the results.

iroh/src/protocol.rs

@@ -3,17 +3,15 @@
 //! ## Example
 //!
 //! ```no_run
-//! # use std::sync::Arc;
 //! # use anyhow::Result;
 //! # use futures_lite::future::Boxed as BoxedFuture;
 //! # use iroh::{endpoint::Connecting, protocol::{ProtocolHandler, Router}, Endpoint, NodeAddr};
 //! #
 //! # async fn test_compile() -> Result<()> {
 //! let endpoint = Endpoint::builder().discovery_n0().bind().await?;
 //!
-//! const ALPN: &[u8] = b"/my/alpn";
 //! let router = Router::builder(endpoint)
-//!     .accept(&ALPN, Arc::new(Echo))
+//!     .accept(b"/my/alpn", Echo)
 //!     .spawn()
 //!     .await?;
 //! # Ok(())
@@ -24,7 +22,7 @@
 //! struct Echo;
 //!
 //! impl ProtocolHandler for Echo {
-//!     fn accept(self: Arc<Self>, connecting: Connecting) -> BoxedFuture<Result<()>> {
+//!     fn accept(&self, connecting: Connecting) -> BoxedFuture<Result<()>> {
 //!         Box::pin(async move {
 //!             let connection = connecting.await?;
 //!             let (mut send, mut recv) = connection.accept_bi().await?;
@@ -111,39 +109,59 @@ pub trait ProtocolHandler: Send + Sync + std::fmt::Debug + 'static {
     /// Handle an incoming connection.
     ///
     /// This runs on a freshly spawned tokio task so this can be long-running.
-    fn accept(self: Arc<Self>, conn: Connecting) -> BoxedFuture<Result<()>>;
+    fn accept(&self, conn: Connecting) -> BoxedFuture<Result<()>>;
 
     /// Called when the node shuts down.
-    fn shutdown(self: Arc<Self>) -> BoxedFuture<()> {
+    fn shutdown(&self) -> BoxedFuture<()> {
         Box::pin(async move {})
     }
 }
 
+impl<T: ProtocolHandler> ProtocolHandler for Arc<T> {
+    fn accept(&self, conn: Connecting) -> BoxedFuture<Result<()>> {
+        self.as_ref().accept(conn)
+    }
+
+    fn shutdown(&self) -> BoxedFuture<()> {
+        self.as_ref().shutdown()
+    }
+}
+
+impl<T: ProtocolHandler> ProtocolHandler for Box<T> {
+    fn accept(&self, conn: Connecting) -> BoxedFuture<Result<()>> {
+        self.as_ref().accept(conn)
+    }
+
+    fn shutdown(&self) -> BoxedFuture<()> {
+        self.as_ref().shutdown()
+    }
+}
+
 /// A typed map of protocol handlers, mapping them from ALPNs.
-#[derive(Debug, Clone, Default)]
-pub struct ProtocolMap(BTreeMap<Vec<u8>, Arc<dyn ProtocolHandler>>);
+#[derive(Debug, Default)]
+pub(crate) struct ProtocolMap(BTreeMap<Vec<u8>, Box<dyn ProtocolHandler>>);
 
 impl ProtocolMap {
     /// Returns the registered protocol handler for an ALPN as a [`Arc<dyn ProtocolHandler>`].
-    pub fn get(&self, alpn: &[u8]) -> Option<Arc<dyn ProtocolHandler>> {
-        self.0.get(alpn).cloned()
+    pub(crate) fn get(&self, alpn: &[u8]) -> Option<&dyn ProtocolHandler> {
+        self.0.get(alpn).map(|p| &**p)
     }
 
     /// Inserts a protocol handler.
-    pub fn insert(&mut self, alpn: Vec<u8>, handler: Arc<dyn ProtocolHandler>) {
+    pub(crate) fn insert(&mut self, alpn: Vec<u8>, handler: Box<dyn ProtocolHandler>) {
         self.0.insert(alpn, handler);
     }
 
     /// Returns an iterator of all registered ALPN protocol identifiers.
-    pub fn alpns(&self) -> impl Iterator<Item = &Vec<u8>> {
+    pub(crate) fn alpns(&self) -> impl Iterator<Item = &Vec<u8>> {
         self.0.keys()
     }
 
     /// Shuts down all protocol handlers.
     ///
     /// Calls and awaits [`ProtocolHandler::shutdown`] for all registered handlers concurrently.
-    pub async fn shutdown(&self) {
-        let handlers = self.0.values().cloned().map(ProtocolHandler::shutdown);
+    pub(crate) async fn shutdown(&self) {
+        let handlers = self.0.values().map(|p| p.shutdown());
         join_all(handlers).await;
     }
 }
@@ -201,7 +219,8 @@ impl RouterBuilder {
 
     /// Configures the router to accept the [`ProtocolHandler`] when receiving a connection
     /// with this `alpn`.
-    pub fn accept(mut self, alpn: impl AsRef<[u8]>, handler: Arc<dyn ProtocolHandler>) -> Self {
+    pub fn accept<T: ProtocolHandler>(mut self, alpn: impl AsRef<[u8]>, handler: T) -> Self {
+        let handler = Box::new(handler);
         self.protocols.insert(alpn.as_ref().to_vec(), handler);
         self
     }