Switch back to the old sync version of HostOutputStream.

crates/factor-wasi/Cargo.toml

@@ -6,6 +6,7 @@ edition = { workspace = true }
 
 [dependencies]
 async-trait = "0.1"
+bytes = "1.0"
 cap-primitives = "3.0.0"
 spin-common = { path = "../common" }
 spin-factors = { path = "../factors" }

crates/factor-wasi/src/io.rs

@@ -0,0 +1,126 @@
+use std::io::{Read, Write};
+use std::sync::{Arc, Mutex};
+
+use async_trait::async_trait;
+use spin_factors::anyhow;
+use wasmtime_wasi::{
+    HostInputStream, HostOutputStream, StdinStream, StdoutStream, StreamError, Subscribe,
+};
+
+/// A [`HostOutputStream`] that writes to a `Write` type.
+///
+/// `StdinStream::stream` and `StdoutStream::new` can be called more than once in components
+/// which are composed of multiple subcomponents, since each subcomponent will potentially want
+/// its own handle. This means the streams need to be shareable. The easiest way to do that is
+/// provide cloneable implementations of streams which operate synchronously.
+///
+/// Note that this amounts to doing synchronous I/O in an asynchronous context, which we'd normally
+/// prefer to avoid, but the properly asynchronous implementations Host{In|Out}putStream based on
+/// `AsyncRead`/`AsyncWrite`` are quite hairy and probably not worth it for "normal" stdio streams in
+/// Spin. If this does prove to be a performance bottleneck, though, we can certainly revisit it.
+pub struct PipedWriteStream<T>(Arc<Mutex<T>>);
+
+impl<T> PipedWriteStream<T> {
+    pub fn new(inner: T) -> Self {
+        Self(Arc::new(Mutex::new(inner)))
+    }
+}
+
+impl<T> Clone for PipedWriteStream<T> {
+    fn clone(&self) -> Self {
+        Self(self.0.clone())
+    }
+}
+
+impl<T: Write + Send + Sync + 'static> HostOutputStream for PipedWriteStream<T> {
+    fn write(&mut self, bytes: bytes::Bytes) -> Result<(), StreamError> {
+        self.0
+            .lock()
+            .unwrap()
+            .write_all(&bytes)
+            .map_err(|e| StreamError::LastOperationFailed(anyhow::anyhow!(e)))
+    }
+
+    fn flush(&mut self) -> Result<(), StreamError> {
+        self.0
+            .lock()
+            .unwrap()
+            .flush()
+            .map_err(|e| StreamError::LastOperationFailed(anyhow::anyhow!(e)))
+    }
+
+    fn check_write(&mut self) -> Result<usize, StreamError> {
+        Ok(1024 * 1024)
+    }
+}
+
+impl<T: Write + Send + Sync + 'static> StdoutStream for PipedWriteStream<T> {
+    fn stream(&self) -> Box<dyn HostOutputStream> {
+        Box::new(self.clone())
+    }
+
+    fn isatty(&self) -> bool {
+        false
+    }
+}
+
+#[async_trait]
+impl<T: Write + Send + Sync + 'static> Subscribe for PipedWriteStream<T> {
+    async fn ready(&mut self) {}
+}
+
+/// A [`HostInputStream`] that reads to a `Read` type.
+///
+/// See [`PipedWriteStream`] for more information on why this is synchronous.
+pub struct PipeReadStream<T> {
+    buffer: Vec<u8>,
+    inner: Arc<Mutex<T>>,
+}
+
+impl<T> PipeReadStream<T> {
+    pub fn new(inner: T) -> Self {
+        Self {
+            buffer: vec![0_u8; 64 * 1024],
+            inner: Arc::new(Mutex::new(inner)),
+        }
+    }
+}
+
+impl<T> Clone for PipeReadStream<T> {
+    fn clone(&self) -> Self {
+        Self {
+            buffer: vec![0_u8; 64 * 1024],
+            inner: self.inner.clone(),
+        }
+    }
+}
+
+impl<T: Read + Send + Sync + 'static> HostInputStream for PipeReadStream<T> {
+    fn read(&mut self, size: usize) -> wasmtime_wasi::StreamResult<bytes::Bytes> {
+        let size = size.min(self.buffer.len());
+
+        let count = self
+            .inner
+            .lock()
+            .unwrap()
+            .read(&mut self.buffer[..size])
+            .map_err(|e| StreamError::LastOperationFailed(anyhow::anyhow!(e)))?;
+
+        Ok(bytes::Bytes::copy_from_slice(&self.buffer[..count]))
+    }
+}
+
+#[async_trait]
+impl<T: Read + Send + Sync + 'static> Subscribe for PipeReadStream<T> {
+    async fn ready(&mut self) {}
+}
+
+impl<T: Read + Send + Sync + 'static> StdinStream for PipeReadStream<T> {
+    fn stream(&self) -> Box<dyn HostInputStream> {
+        Box::new(self.clone())
+    }
+
+    fn isatty(&self) -> bool {
+        false
+    }
+}

crates/factor-wasi/src/lib.rs

@@ -1,18 +1,23 @@
+mod io;
 pub mod spin;
 mod wasi_2023_10_18;
 mod wasi_2023_11_10;
 
-use std::{future::Future, net::SocketAddr, path::Path};
+use std::{
+    future::Future,
+    io::{Read, Write},
+    net::SocketAddr,
+    path::Path,
+};
 
+use io::{PipeReadStream, PipedWriteStream};
 use spin_factors::{
     anyhow, AppComponent, Factor, FactorInstanceBuilder, InitContext, InstanceBuilders,
     PrepareContext, RuntimeFactors, RuntimeFactorsInstanceState,
 };
-use tokio::io::{AsyncRead, AsyncWrite};
 use wasmtime_wasi::{
-    pipe::{AsyncReadStream, AsyncWriteStream},
-    AsyncStdinStream, AsyncStdoutStream, DirPerms, FilePerms, ResourceTable, StdinStream,
-    StdoutStream, WasiCtx, WasiCtxBuilder, WasiImpl, WasiView,
+    DirPerms, FilePerms, ResourceTable, StdinStream, StdoutStream, WasiCtx, WasiCtxBuilder,
+    WasiImpl, WasiView,
 };
 
 pub use wasmtime_wasi::SocketAddrUse;
@@ -179,35 +184,29 @@ impl InstanceBuilder {
         self.ctx.stdin(stdin);
     }
 
-    /// Sets the WASI `stdin` descriptor to the given [`AsyncRead`]er.
-    pub fn stdin_pipe(&mut self, r: impl AsyncRead + Send + Unpin + 'static) {
-        self.stdin(AsyncStdinStream::new(AsyncReadStream::new(r)));
+    /// Sets the WASI `stdin` descriptor to the given [`Read`]er.
+    pub fn stdin_pipe(&mut self, r: impl Read + Send + Sync + Unpin + 'static) {
+        self.stdin(PipeReadStream::new(r));
     }
 
     /// Sets the WASI `stdout` descriptor to the given [`StdoutStream`].
     pub fn stdout(&mut self, stdout: impl StdoutStream + 'static) {
         self.ctx.stdout(stdout);
     }
 
-    /// Sets the WASI `stdout` descriptor to the given [`AsyncWrite`]r.
-    pub fn stdout_pipe(&mut self, w: impl AsyncWrite + Send + Unpin + 'static) {
-        self.stdout(AsyncStdoutStream::new(AsyncWriteStream::new(
-            1024 * 1024,
-            w,
-        )));
+    /// Sets the WASI `stdout` descriptor to the given [`Write`]r.
+    pub fn stdout_pipe(&mut self, w: impl Write + Send + Sync + Unpin + 'static) {
+        self.stdout(PipedWriteStream::new(w));
     }
 
     /// Sets the WASI `stderr` descriptor to the given [`StdoutStream`].
     pub fn stderr(&mut self, stderr: impl StdoutStream + 'static) {
         self.ctx.stderr(stderr);
     }
 
-    /// Sets the WASI `stderr` descriptor to the given [`AsyncWrite`]r.
-    pub fn stderr_pipe(&mut self, w: impl AsyncWrite + Send + Unpin + 'static) {
-        self.stderr(AsyncStdoutStream::new(AsyncWriteStream::new(
-            1024 * 1024,
-            w,
-        )));
+    /// Sets the WASI `stderr` descriptor to the given [`Write`]r.
+    pub fn stderr_pipe(&mut self, w: impl Write + Send + Sync + Unpin + 'static) {
+        self.stderr(PipedWriteStream::new(w));
     }
 
     /// Appends the given strings to the WASI 'args'.