Fix

relay-threading/Cargo.toml

@@ -4,19 +4,21 @@ authors = ["Sentry <[email protected]>"]
 description = "Threading code that is used by Relay"
 homepage = "https://getsentry.github.io/relay/"
 repository = "https://github.com/getsentry/relay"
-version = "25.1.0"
+version = "25.2.0"
 edition = "2021"
 license-file = "../LICENSE.md"
 publish = false
 
 [dependencies]
-flume = { workspace = true }
-futures = { workspace = true, features = ["executor"] }
-tokio = { workspace = true, features = ["rt", "rt-multi-thread", "time", "sync", "macros"] }
+flume = { workspace = true, default-features = false }
+futures = { workspace = true, default-features = false }
+tokio = { workspace = true }
 pin-project-lite = { workspace = true }
 
 [dev-dependencies]
 criterion = { workspace = true, features = ["async_tokio"] }
+futures = { workspace = true, default-features = false, features = ["executor"] }
+tokio = { workspace = true, features = ["rt", "rt-multi-thread", "time", "sync", "macros"] }
 
 [[bench]]
 name = "pool"

relay-threading/src/builder.rs

@@ -6,6 +6,9 @@ use std::sync::Arc;
 use crate::pool::{AsyncPool, Thread};
 use crate::pool::{CustomSpawn, DefaultSpawn, ThreadSpawn};
 
+/// Type alias for a thread safe closure that is used for panic handling across the code.
+pub(crate) type PanicHandler = dyn Fn(Box<dyn Any + Send>) + Send + Sync;
+
 /// [`AsyncPoolBuilder`] provides a flexible way to configure and build an [`AsyncPool`] for executing
 /// asynchronous tasks concurrently on dedicated threads.
 ///
@@ -14,10 +17,8 @@ use crate::pool::{CustomSpawn, DefaultSpawn, ThreadSpawn};
 pub struct AsyncPoolBuilder<S = DefaultSpawn> {
     pub(crate) runtime: tokio::runtime::Handle,
     pub(crate) thread_name: Option<Box<dyn FnMut(usize) -> String>>,
-    #[allow(clippy::type_complexity)]
-    pub(crate) thread_panic_handler: Option<Arc<dyn Fn(Box<dyn Any + Send>) + Send + Sync>>,
-    #[allow(clippy::type_complexity)]
-    pub(crate) task_panic_handler: Option<Arc<dyn Fn(Box<dyn Any + Send>) + Send + Sync>>,
+    pub(crate) thread_panic_handler: Option<Arc<PanicHandler>>,
+    pub(crate) task_panic_handler: Option<Arc<PanicHandler>>,
     pub(crate) spawn_handler: S,
     pub(crate) num_threads: usize,
     pub(crate) max_concurrency: usize,

relay-threading/src/multiplexing.rs

@@ -1,10 +1,10 @@
-use std::any::Any;
 use std::future::Future;
 use std::panic::AssertUnwindSafe;
 use std::pin::Pin;
 use std::sync::Arc;
 use std::task::{Context, Poll};
 
+use crate::PanicHandler;
 use futures::future::CatchUnwind;
 use futures::stream::{FusedStream, FuturesUnordered, Stream};
 use futures::FutureExt;
@@ -19,16 +19,15 @@ pin_project! {
     struct Tasks<F> {
         #[pin]
         futures: FuturesUnordered<Unconstrained<CatchUnwind<AssertUnwindSafe<F>>>>,
-        panic_handler: Option<Arc<dyn Fn(Box<dyn Any + Send>) + Send + Sync>>,
+        panic_handler: Option<Arc<PanicHandler>>,
     }
 }
 
 impl<F> Tasks<F> {
     /// Creates a new task manager.
     ///
     /// This internal constructor initializes a new collection for tracking asynchronous tasks.
-    #[allow(clippy::type_complexity)]
-    fn new(panic_handler: Option<Arc<dyn Fn(Box<dyn Any + Send>) + Send + Sync>>) -> Self {
+    fn new(panic_handler: Option<Arc<PanicHandler>>) -> Self {
         Self {
             futures: FuturesUnordered::new(),
             panic_handler,
@@ -118,12 +117,8 @@ where
     ///
     /// Tasks from the stream will be scheduled for execution concurrently, and an optional panic handler
     /// can be provided to manage errors during task execution.
-    #[allow(clippy::type_complexity)]
-    pub fn new(
-        max_concurrency: usize,
-        rx: S,
-        panic_handler: Option<Arc<dyn Fn(Box<dyn Any + Send>) + Send + Sync>>,
-    ) -> Self {
+
+    pub fn new(max_concurrency: usize, rx: S, panic_handler: Option<Arc<PanicHandler>>) -> Self {
         Self {
             max_concurrency,
             rx,

relay-threading/src/pool.rs

@@ -1,4 +1,3 @@
-use std::any::Any;
 use std::future::Future;
 use std::io;
 use std::panic::AssertUnwindSafe;
@@ -9,6 +8,7 @@ use futures::FutureExt;
 
 use crate::builder::AsyncPoolBuilder;
 use crate::multiplexing::Multiplexed;
+use crate::PanicHandler;
 
 /// [`AsyncPool`] is a thread-based executor that runs asynchronous tasks on dedicated worker threads.
 ///
@@ -67,11 +67,12 @@ where
     ///
     /// # Panics
     ///
-    /// This method panics if the internal task channel is unexpectedly closed.
+    /// This method panics if all receivers have been dropped which can happen when all threads of
+    /// the pool panicked.
     pub fn spawn(&self, future: F) {
         assert!(
             self.tx.send(future).is_ok(),
-            "receiver never exits before sender"
+            "failed to schedule task: all worker threads have terminated (either none were spawned or all have panicked)"
         );
     }
 
@@ -81,11 +82,12 @@ where
     ///
     /// # Panics
     ///
-    /// This method panics if the internal task channel is unexpectedly closed.
+    /// This method panics if all receivers have been dropped which can happen when all threads of
+    /// the pool panicked.
     pub async fn spawn_async(&self, future: F) {
         assert!(
             self.tx.send_async(future).await.is_ok(),
-            "receiver never exits before sender"
+            "failed to schedule task: all worker threads have terminated (either none were spawned or all have panicked)"
         );
     }
 }
@@ -96,8 +98,7 @@ pub struct Thread {
     max_concurrency: usize,
     name: Option<String>,
     runtime: tokio::runtime::Handle,
-    #[allow(clippy::type_complexity)]
-    panic_handler: Option<Arc<dyn Fn(Box<dyn Any + Send>) + Send + Sync>>,
+    panic_handler: Option<Arc<PanicHandler>>,
     task: BoxFuture<'static, ()>,
 }
 
@@ -206,6 +207,7 @@ where
 #[cfg(test)]
 mod tests {
     use std::future::Future;
+    use std::panic::AssertUnwindSafe;
     use std::sync::atomic::AtomicBool;
     use std::sync::{
         atomic::{AtomicUsize, Ordering},
@@ -368,4 +370,19 @@ mod tests {
 
         assert!(has_panicked.load(Ordering::SeqCst));
     }
+
+    #[tokio::test]
+    async fn test_spawn_panics_if_no_threads_are_available() {
+        let pool = AsyncPoolBuilder::new(Handle::current())
+            .num_threads(0)
+            .max_concurrency(1)
+            .build()
+            .unwrap();
+
+        let result = std::panic::catch_unwind(AssertUnwindSafe(|| {
+            pool.spawn(async move {});
+        }));
+
+        assert!(result.is_err());
+    }
 }

relay/src/main.rs

@@ -63,6 +63,7 @@
 //!  - [`relay-statsd`]: High-level StatsD metric client for internal measurements.
 //!  - [`relay-system`]: Foundational system components for Relay's services.
 //!  - [`relay-test`]: Helpers for testing the web server and services.
+//!  - [`relay-threading`]: Threading code that is used by Relay.
 //!  - [`relay-ua`]: User agent parser with built-in rules.
 //!
 //! # Tools