diff --git a/opentelemetry-sdk/CHANGELOG.md b/opentelemetry-sdk/CHANGELOG.md
index 4837e6e11b..b409a65b99 100644
--- a/opentelemetry-sdk/CHANGELOG.md
+++ b/opentelemetry-sdk/CHANGELOG.md
@@ -217,6 +217,14 @@ metadata, a feature introduced in version 0.1.40. [#2418](https://github.com/ope
- Update `EnvResourceDetector` to allow resource attribute values containing
equal signs (`"="`). [#2120](https://github.com/open-telemetry/opentelemetry-rust/pull/2120)
+- **Breaking** Introduced `experimental_async_runtime` feature for runtime-specific traits.
+ - Runtime-specific features (`rt-tokio`, `rt-tokio-current-thread`, and `rt-async-std`)
+ now depend on the `experimental_async_runtime` feature.
+ - For most users, no action is required. Enabling runtime features such as `rt-tokio`, `rt-tokio-current-thread`,
+ or `rt-async-std` will automatically enable the `experimental_async_runtime` feature.
+ - If you're implementing a custom runtime, you must explicitly enable the experimental_async_runtime` feature in your
+ Cargo.toml and implement the required `Runtime` traits.
+
## 0.27.1
Released 2024-Nov-27
diff --git a/opentelemetry-sdk/Cargo.toml b/opentelemetry-sdk/Cargo.toml
index 167846dce1..ca21fd55dd 100644
--- a/opentelemetry-sdk/Cargo.toml
+++ b/opentelemetry-sdk/Cargo.toml
@@ -49,9 +49,10 @@ logs = ["opentelemetry/logs", "serde_json"]
spec_unstable_logs_enabled = ["logs", "opentelemetry/spec_unstable_logs_enabled"]
metrics = ["opentelemetry/metrics", "glob", "async-trait"]
testing = ["opentelemetry/testing", "trace", "metrics", "logs", "rt-async-std", "rt-tokio", "rt-tokio-current-thread", "tokio/macros", "tokio/rt-multi-thread"]
-rt-tokio = ["tokio", "tokio-stream"]
-rt-tokio-current-thread = ["tokio", "tokio-stream"]
-rt-async-std = ["async-std"]
+experimental_async_runtime = []
+rt-tokio = ["tokio", "tokio-stream", "experimental_async_runtime"]
+rt-tokio-current-thread = ["tokio", "tokio-stream", "experimental_async_runtime"]
+rt-async-std = ["async-std", "experimental_async_runtime"]
internal-logs = ["tracing"]
experimental_metrics_periodicreader_with_async_runtime = ["metrics"]
spec_unstable_metrics_views = ["metrics"]
diff --git a/opentelemetry-sdk/src/lib.rs b/opentelemetry-sdk/src/lib.rs
index 4afda7deb7..4e2ef47ba7 100644
--- a/opentelemetry-sdk/src/lib.rs
+++ b/opentelemetry-sdk/src/lib.rs
@@ -94,6 +94,7 @@
//! Support for recording and exporting telemetry asynchronously and perform
//! metrics aggregation can be added via the following flags:
//!
+//! * `experimental_async_runtime`: Enables the experimental `Runtime` trait and related functionality.
//! * `rt-tokio`: Spawn telemetry tasks using [tokio]'s multi-thread runtime.
//! * `rt-tokio-current-thread`: Spawn telemetry tasks on a separate runtime so that the main runtime won't be blocked.
//! * `rt-async-std`: Spawn telemetry tasks using [async-std]'s runtime.
@@ -133,6 +134,7 @@ pub mod metrics;
#[cfg_attr(docsrs, doc(cfg(feature = "trace")))]
pub mod propagation;
pub mod resource;
+#[cfg(feature = "experimental_async_runtime")]
pub mod runtime;
#[cfg(any(feature = "testing", test))]
#[cfg_attr(docsrs, doc(cfg(any(feature = "testing", test))))]
diff --git a/opentelemetry-sdk/src/runtime.rs b/opentelemetry-sdk/src/runtime.rs
index 7705c10e91..00720e0892 100644
--- a/opentelemetry-sdk/src/runtime.rs
+++ b/opentelemetry-sdk/src/runtime.rs
@@ -15,6 +15,7 @@ use thiserror::Error;
///
/// [Tokio]: https://crates.io/crates/tokio
/// [async-std]: https://crates.io/crates/async-std
+#[cfg(feature = "experimental_async_runtime")]
pub trait Runtime: Clone + Send + Sync + 'static {
/// A future stream, which returns items in a previously specified interval. The item type is
/// not important.
@@ -44,13 +45,19 @@ pub trait Runtime: Clone + Send + Sync + 'static {
}
/// Runtime implementation, which works with Tokio's multi thread runtime.
-#[cfg(feature = "rt-tokio")]
-#[cfg_attr(docsrs, doc(cfg(feature = "rt-tokio")))]
+#[cfg(all(feature = "experimental_async_runtime", feature = "rt-tokio"))]
+#[cfg_attr(
+ docsrs,
+ doc(cfg(all(feature = "experimental_async_runtime", feature = "rt-tokio")))
+)]
#[derive(Debug, Clone)]
pub struct Tokio;
-#[cfg(feature = "rt-tokio")]
-#[cfg_attr(docsrs, doc(cfg(feature = "rt-tokio")))]
+#[cfg(all(feature = "experimental_async_runtime", feature = "rt-tokio"))]
+#[cfg_attr(
+ docsrs,
+ doc(cfg(all(feature = "experimental_async_runtime", feature = "rt-tokio")))
+)]
impl Runtime for Tokio {
type Interval = tokio_stream::wrappers::IntervalStream;
type Delay = ::std::pin::Pin<Box<tokio::time::Sleep>>;
@@ -71,13 +78,31 @@ impl Runtime for Tokio {
}
/// Runtime implementation, which works with Tokio's current thread runtime.
-#[cfg(feature = "rt-tokio-current-thread")]
-#[cfg_attr(docsrs, doc(cfg(feature = "rt-tokio-current-thread")))]
+#[cfg(all(
+ feature = "experimental_async_runtime",
+ feature = "rt-tokio-current-thread"
+))]
+#[cfg_attr(
+ docsrs,
+ doc(cfg(all(
+ feature = "experimental_async_runtime",
+ feature = "rt-tokio-current-thread"
+ )))
+)]
#[derive(Debug, Clone)]
pub struct TokioCurrentThread;
-#[cfg(feature = "rt-tokio-current-thread")]
-#[cfg_attr(docsrs, doc(cfg(feature = "rt-tokio-current-thread")))]
+#[cfg(all(
+ feature = "experimental_async_runtime",
+ feature = "rt-tokio-current-thread"
+))]
+#[cfg_attr(
+ docsrs,
+ doc(cfg(all(
+ feature = "experimental_async_runtime",
+ feature = "rt-tokio-current-thread"
+ )))
+)]
impl Runtime for TokioCurrentThread {
type Interval = tokio_stream::wrappers::IntervalStream;
type Delay = ::std::pin::Pin<Box<tokio::time::Sleep>>;
@@ -108,13 +133,19 @@ impl Runtime for TokioCurrentThread {
}
/// Runtime implementation, which works with async-std.
-#[cfg(feature = "rt-async-std")]
-#[cfg_attr(docsrs, doc(cfg(feature = "rt-async-std")))]
+#[cfg(all(feature = "experimental_async_runtime", feature = "rt-async-std"))]
+#[cfg_attr(
+ docsrs,
+ doc(cfg(all(feature = "experimental_async_runtime", feature = "rt-async-std")))
+)]
#[derive(Debug, Clone)]
pub struct AsyncStd;
-#[cfg(feature = "rt-async-std")]
-#[cfg_attr(docsrs, doc(cfg(feature = "rt-async-std")))]
+#[cfg(all(feature = "experimental_async_runtime", feature = "rt-async-std"))]
+#[cfg_attr(
+ docsrs,
+ doc(cfg(all(feature = "experimental_async_runtime", feature = "rt-async-std")))
+)]
impl Runtime for AsyncStd {
type Interval = async_std::stream::Interval;
type Delay = BoxFuture<'static, ()>;
@@ -138,6 +169,7 @@ impl Runtime for AsyncStd {
///
/// [log]: crate::logs::BatchLogProcessor
/// [span]: crate::trace::BatchSpanProcessor
+#[cfg(feature = "experimental_async_runtime")]
pub trait RuntimeChannel: Runtime {
/// A future stream to receive batch messages from channels.
type Receiver<T: Debug + Send>: Stream<Item = T> + Send;
@@ -152,6 +184,7 @@ pub trait RuntimeChannel: Runtime {
}
/// Error returned by a [`TrySend`] implementation.
+#[cfg(feature = "experimental_async_runtime")]
#[derive(Debug, Error)]
pub enum TrySendError {
/// Send failed due to the channel being full.
@@ -166,6 +199,7 @@ pub enum TrySendError {
}
/// TrySend is an abstraction of `Sender` that is capable of sending messages through a reference.
+#[cfg(feature = "experimental_async_runtime")]
pub trait TrySend: Sync + Send {
/// The message that will be sent.
type Message;
@@ -176,7 +210,10 @@ pub trait TrySend: Sync + Send {
fn try_send(&self, item: Self::Message) -> Result<(), TrySendError>;
}
-#[cfg(any(feature = "rt-tokio", feature = "rt-tokio-current-thread"))]
+#[cfg(all(
+ feature = "experimental_async_runtime",
+ any(feature = "rt-tokio", feature = "rt-tokio-current-thread")
+))]
impl<T: Send> TrySend for tokio::sync::mpsc::Sender<T> {
type Message = T;
@@ -188,8 +225,11 @@ impl<T: Send> TrySend for tokio::sync::mpsc::Sender<T> {
}
}
-#[cfg(feature = "rt-tokio")]
-#[cfg_attr(docsrs, doc(cfg(feature = "rt-tokio")))]
+#[cfg(all(feature = "experimental_async_runtime", feature = "rt-tokio"))]
+#[cfg_attr(
+ docsrs,
+ doc(cfg(all(feature = "experimental_async_runtime", feature = "rt-tokio")))
+)]
impl RuntimeChannel for Tokio {
type Receiver<T: Debug + Send> = tokio_stream::wrappers::ReceiverStream<T>;
type Sender<T: Debug + Send> = tokio::sync::mpsc::Sender<T>;
@@ -206,8 +246,17 @@ impl RuntimeChannel for Tokio {
}
}
-#[cfg(feature = "rt-tokio-current-thread")]
-#[cfg_attr(docsrs, doc(cfg(feature = "rt-tokio-current-thread")))]
+#[cfg(all(
+ feature = "experimental_async_runtime",
+ feature = "rt-tokio-current-thread"
+))]
+#[cfg_attr(
+ docsrs,
+ doc(cfg(all(
+ feature = "experimental_async_runtime",
+ feature = "rt-tokio-current-thread"
+ )))
+)]
impl RuntimeChannel for TokioCurrentThread {
type Receiver<T: Debug + Send> = tokio_stream::wrappers::ReceiverStream<T>;
type Sender<T: Debug + Send> = tokio::sync::mpsc::Sender<T>;
@@ -224,7 +273,7 @@ impl RuntimeChannel for TokioCurrentThread {
}
}
-#[cfg(feature = "rt-async-std")]
+#[cfg(all(feature = "experimental_async_runtime", feature = "rt-async-std"))]
impl<T: Send> TrySend for async_std::channel::Sender<T> {
type Message = T;
@@ -236,8 +285,11 @@ impl<T: Send> TrySend for async_std::channel::Sender<T> {
}
}
-#[cfg(feature = "rt-async-std")]
-#[cfg_attr(docsrs, doc(cfg(feature = "rt-async-std")))]
+#[cfg(all(feature = "experimental_async_runtime", feature = "rt-async-std"))]
+#[cfg_attr(
+ docsrs,
+ doc(cfg(all(feature = "experimental_async_runtime", feature = "rt-async-std")))
+)]
impl RuntimeChannel for AsyncStd {
type Receiver<T: Debug + Send> = async_std::channel::Receiver<T>;
type Sender<T: Debug + Send> = async_std::channel::Sender<T>;