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Add support for external Tokio runtimes in TokioAdapter #665

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Add support for external Tokio runtimes in TokioAdapter
riederm Mar 19, 2026
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riederm Mar 19, 2026
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49 changes: 40 additions & 9 deletions src/experimental.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -121,31 +121,62 @@ impl GetAttrResponse {
}
}

#[derive(Debug)]
enum Runtime {
/// Use the runtime provided by the user
External(tokio::runtime::Handle),
/// Use an internal runtime
Internal(tokio::runtime::Runtime),
}

/// Adapter to allow running an [`AsyncFilesystem`] with tokio's runtime.
#[derive(Debug)]
pub struct TokioAdapter<T: AsyncFilesystem> {
inner: Arc<T>,
runtime: tokio::runtime::Runtime,
runtime: Runtime,
}

impl<T: AsyncFilesystem> TokioAdapter<T> {

/// Create a new adapter with an internal tokio runtime.
pub fn new(inner: T) -> Self {
Self {
inner: Arc::new(inner),
runtime: tokio::runtime::Builder::new_multi_thread()
.enable_all()
.build()
.unwrap(),
runtime: Runtime::Internal(
tokio::runtime::Builder::new_multi_thread()
.enable_all()
.build()
.unwrap(),
),
}
}

/// Use an existing tokio runtime. This is useful if you want to run the filesystem
/// in an existing application that already uses a tokio runtime.
pub fn with_runtime(inner: T, runtime_handle: tokio::runtime::Handle) -> Self {
Self {
inner: Arc::new(inner),
runtime: Runtime::External(runtime_handle),
Comment on lines +156 to +159
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@chatgpt-codex-connector chatgpt-codex-connector Bot Mar 19, 2026

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P1 Badge Keep the external Tokio runtime alive for the mount

TokioAdapter::with_runtime stores only a tokio::runtime::Handle, which can spawn onto a runtime but does not own it. That means a caller can mount successfully and still end up with an adapter whose executor disappears as soon as the original Runtime value is dropped or shut down—for example with spawn_mount(...) after setup code exits, or with a temporary Runtime::new()?.handle().clone(). In that state new FUSE requests are still accepted, but there is no longer a guaranteed live executor to run the async handlers, so the mount can stop servicing operations unexpectedly.

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}
}

fn spawn<F>(&self, fut: F)
where
F: std::future::Future<Output = ()> + Send + 'static,
{
match &self.runtime {
Runtime::External(handle) => handle.spawn(fut),
Runtime::Internal(rt) => rt.spawn(fut),
};
}
}

impl<T: AsyncFilesystem + Send + Sync + 'static> Filesystem for TokioAdapter<T> {
fn lookup(&self, req: &Request, parent: INodeNo, name: &OsStr, reply: ReplyEntry) {
let context: RequestContext = req.into();
let name = name.to_os_string();
let inner = self.inner.clone();
self.runtime.spawn(async move {
self.spawn(async move {
match inner.lookup(&context, parent, &name).await {
Ok(LookupResponse {
ttl,
Expand All @@ -160,7 +191,7 @@ impl<T: AsyncFilesystem + Send + Sync + 'static> Filesystem for TokioAdapter<T>
fn getattr(&self, req: &Request, ino: INodeNo, fh: Option<FileHandle>, reply: ReplyAttr) {
let context: RequestContext = req.into();
let inner = self.inner.clone();
self.runtime.spawn(async move {
self.spawn(async move {
match inner.getattr(&context, ino, fh).await {
Ok(GetAttrResponse { ttl, attr }) => reply.attr(&ttl, &attr),
Err(e) => reply.error(e),
Expand All @@ -181,7 +212,7 @@ impl<T: AsyncFilesystem + Send + Sync + 'static> Filesystem for TokioAdapter<T>
) {
let context: RequestContext = req.into();
let inner = self.inner.clone();
self.runtime.spawn(async move {
self.spawn(async move {
let mut buf = vec![];
match inner
.read(&context, ino, fh, offset, size, flags, lock_owner, &mut buf)
Expand All @@ -203,7 +234,7 @@ impl<T: AsyncFilesystem + Send + Sync + 'static> Filesystem for TokioAdapter<T>
) {
let context: RequestContext = req.into();
let inner = self.inner.clone();
self.runtime.spawn(async move {
self.spawn(async move {
let builder = DirEntListBuilder {
entries: &mut reply,
};
Expand Down