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feat: manual shutdown of client #4492

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Mar 15, 2024
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feat: manual shutdown of client #4492

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feat: manual shutdown of client
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@maan2003
maan2003 committed Mar 15, 2024
commit 3ee4640aa2149fa47fa9f60cd42cbfc7d46335d7
119 changes: 64 additions & 55 deletions fedimint-client/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -553,24 553,51 @@ impl ClientHandle {
self.as_inner().start_executor().await
}

/// Block for the `client` to no longer contain any strong references.
/// Shutdown the client.
///
/// Some parts of the code can temporarily clone client to perform some
/// actions. No further strong references guarantees that the `client`
/// is no longer used inside the system.
pub async fn wait_until_fully_dropped(self) {
let weak = self.downgrade();
drop(self);

for attempt in 0u64.. {
if Weak::strong_count(&weak.inner) == 0 {
break;
}
// we want to retry fast, give feedback, but not spam
if attempt % 100 == 0 {
info!("Waiting for ArcClient to stop being used");
/// Returns Err if there are other clones of [`ClientHandle`].
pub async fn shutdown(self) -> Result<(), ClientHandle> {
match Arc::try_unwrap(self.inner) {
Ok(mut inner) => {
inner.shutdown().await;
Ok(())
}
fedimint_core::task::sleep(Duration::from_millis(10)).await;
Err(inner) => Err(Self { inner }),
}
}
}

impl ClientHandleShared {
async fn shutdown(&mut self) {
let Some(inner) = self.inner.take() else {
error!("ClientHandleShared::shutdown called twice");
return;
};
inner.executor.stop_executor();
let db = inner.db.clone();
debug!(target: LOG_CLIENT, "Waiting for client task group to shut down");
if let Err(err) = inner
.task_group
.clone()
.shutdown_join_all(Some(Duration::from_secs(30)))
.await
{
warn!(target: LOG_CLIENT, %err, "Error waiting for client task group to shut down");
}

let client_strong_count = Arc::strong_count(&inner);
debug!(target: LOG_CLIENT, "Dropping last handle to Client");
// We are sure that no background tasks are running in the client anymore, so we
// can drop the (usually) last inner reference.
drop(inner);

if client_strong_count != 1 {
debug!(target: LOG_CLIENT, count = client_strong_count - 1, LOG_CLIENT, "External Client references remaining after last handle dropped");
}

let db_strong_count = db.strong_count();
if db_strong_count != 1 {
debug!(target: LOG_CLIENT, count = db_strong_count - 1, "External DB references remaining after last handle dropped");
}
}
}
Expand Down Expand Up @@ -629,49 656,31 @@ impl ClientWeak {
/// `Arc<Client>`s such that at least one `Executor` never gets dropped.
impl Drop for ClientHandleShared {
fn drop(&mut self) {
debug!(target: LOG_CLIENT, "Shutting down the Client on last handle drop");
let inner = self.inner.take().expect("Must have inner client set");
inner.executor.stop_executor();
if self.inner.is_none() {
return;
}

// We can't use block_on in single-threaded mode or wasm
#[cfg(target_family = "wasm")]
let can_block = false;
#[cfg(not(target_family = "wasm"))]
{
if RuntimeHandle::current().runtime_flavor() == RuntimeFlavor::CurrentThread {
// We can't use block_on in single-threaded mode
return;
}

let db = inner.db.clone();

tokio::task::block_in_place(|| {
tokio::runtime::Handle::current().block_on(async {
// futures::executor::block_on(async {
debug!(target: LOG_CLIENT, "Waiting for client task group to shut down");
if let Err(err) = inner
.task_group
.clone()
.shutdown_join_all(Some(Duration::from_secs(30)))
.await
{
warn!(target: LOG_CLIENT, %err, "Error waiting for client task group to shut down");
}
});
});

let client_strong_count = Arc::strong_count(&inner);
debug!(target: LOG_CLIENT, "Dropping last handle to Client");
// We are sure that no background tasks are running in the client anymore, so we
// can drop the (usually) last inner reference.
drop(inner);

if client_strong_count != 1 {
debug!(target: LOG_CLIENT, count = client_strong_count - 1, LOG_CLIENT, "External Client references remaining after last handle dropped");
}

let db_strong_count = db.strong_count();
if db_strong_count != 1 {
debug!(target: LOG_CLIENT, count = db_strong_count - 1, "External DB references remaining after last handle dropped");
let can_block = RuntimeHandle::current().runtime_flavor() != RuntimeFlavor::CurrentThread;
if !can_block {
let inner = self.inner.take().expect("Must have inner client set");
inner.executor.stop_executor();
if cfg!(target_family = "wasm") {
error!(target: LOG_CLIENT, "Automatic client shutdown is not possible on wasm, call ClientHandle::shutdown manually.");
} else {
error!(target: LOG_CLIENT, "Automatic client shutdown is not possible on current thread runtime, call ClientHandle::shutdown manually.");
}
return;
}

debug!(target: LOG_CLIENT, "Shutting down the Client on last handle drop");
#[cfg(not(target_family = "wasm"))]
tokio::task::block_in_place(|| {
RuntimeHandle::current().block_on(self.shutdown());
});
}
}

Expand Down
4 changes: 3 additions & 1 deletion gateway/ln-gateway/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1272,7 1272,9 @@ impl Gateway {
)))?
.into_value();

client.wait_until_fully_dropped().await;
if client.shutdown().await.is_err() {
warn!("failed to shutdown client");
}

// Remove previously assigned scid from `scid_to_federation` map
self.scid_to_federation
Expand Down
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