feat(kad): configurable OUTBOUND_SUBSTREAMS_TIMEOUT

Author: maqi

protocols/kad/CHANGELOG.md

@@ -16,6 +16,8 @@
   See [PR 5774](https://github.com/libp2p/rust-libp2p/pull/5774).
 - Add lazy cleanup for expired provider records in `Behavior::get_providers` and `Behavior::provider_peers`.
   See [PR 5980](https://github.com/libp2p/rust-libp2p/pull/5980)
+- Configurable OUTBOUND_SUBSTREAMS_TIMEOUT.
+  See [PR 6015](https://github.com/libp2p/rust-libp2p/pull/6015).
 
 <!-- Update to libp2p-core v0.43.0 -->
 

protocols/kad/src/handler.rs

@@ -23,6 +23,7 @@ use std::{
     error, fmt, io,
     marker::PhantomData,
     pin::Pin,
+    sync::LazyLock,
     task::{Context, Poll, Waker},
     time::Duration,
 };
@@ -48,6 +49,16 @@ use crate::{
 
 const MAX_NUM_STREAMS: usize = 32;
 
+/// Specifies the outbound_substreams timeout.
+///
+/// Can be overridden by the `OUTBOUND_STREAMS_TIMEOUT` environment variable.
+static OUTBOUND_STREAMS_TIMEOUT: LazyLock<u64> = LazyLock::new(|| {
+    std::env::var("OUTBOUND_STREAMS_TIMEOUT")
+        .ok()
+        .and_then(|s| s.parse().ok())
+        .unwrap_or(10)
+});
+
 /// Protocol handler that manages substreams for the Kademlia protocol
 /// on a single connection with a peer.
 ///
@@ -462,7 +473,7 @@ impl Handler {
             next_connec_unique_id: UniqueConnecId(0),
             inbound_substreams: Default::default(),
             outbound_substreams: futures_bounded::FuturesTupleSet::new(
-                Duration::from_secs(10),
+                Duration::from_secs(*OUTBOUND_STREAMS_TIMEOUT),
                 MAX_NUM_STREAMS,
             ),
             pending_streams: Default::default(),