just addressing the problem

misc/server/CHANGELOG.md

@@ -4,8 +4,6 @@
 
 - Use periodic and automatic bootstrap of Kademlia.
   See [PR 4838](https://github.com/libp2p/rust-libp2p/pull/4838).
-- Integrate Kademlia bootstrap function breaking change.
-  See [PR 5349](https://github.com/libp2p/rust-libp2p/pull/5349).
 
 ## 0.12.6
 

misc/server/src/behaviour.rs

@@ -49,7 +49,7 @@ impl Behaviour {
             for peer in &BOOTNODES {
                 kademlia.add_address(&PeerId::from_str(peer).unwrap(), bootaddr.clone());
             }
-            kademlia.bootstrap();
+            kademlia.bootstrap().unwrap();
             Some(kademlia)
         } else {
             None

protocols/kad/CHANGELOG.md

@@ -19,7 +19,7 @@
   See [PR 5317](https://github.com/libp2p/rust-libp2p/pull/5317).
 - Use `web-time` instead of `instant`.
   See [PR 5347](https://github.com/libp2p/rust-libp2p/pull/5347).
-- Always trigger a query when bootstrapping.
+- Correctly handle the `NoKnownPeers` error on automatic bootstrap.
   See [PR 5349](https://github.com/libp2p/rust-libp2p/pull/5349).
 
 ## 0.45.3

protocols/kad/src/behaviour.rs

@@ -914,10 +914,13 @@ where
     /// refreshed by initiating an additional bootstrapping query for each such
     /// bucket with random keys.
     ///
-    /// Returns the `QueryId` for the entire bootstrapping process. The progress of bootstrapping is
+    /// Returns `Ok` if bootstrapping has been initiated with a self-lookup, providing the
+    /// `QueryId` for the entire bootstrapping process. The progress of bootstrapping is
     /// reported via [`Event::OutboundQueryProgressed{QueryResult::Bootstrap}`] events,
     /// with one such event per bootstrapping query.
     ///
+    /// Returns `Err` if bootstrapping is impossible due an empty routing table.
+    ///
     /// > **Note**: Bootstrapping requires at least one node of the DHT to be known.
     /// > See [`Behaviour::add_address`].
     ///
@@ -928,15 +931,21 @@ where
     /// > This parameter is used to call [`Behaviour::bootstrap`] periodically and automatically
     /// > to ensure a healthy routing table.
     pub fn bootstrap(&mut self) -> Result<QueryId, NoKnownPeers> {
+        self.bootstrap_status.on_started();
         let local_key = *self.kbuckets.local_key();
         let info = QueryInfo::Bootstrap {
             peer: *local_key.preimage(),
             remaining: None,
             step: ProgressStep::first(),
         };
         let peers = self.kbuckets.closest_keys(&local_key).collect::<Vec<_>>();
-        let inner = QueryInner::new(info);
-        self.queries.add_iter_closest(local_key, peers, inner)
+        if peers.is_empty() {
+            self.bootstrap_status.on_finish();
+            Err(NoKnownPeers())
+        } else {
+            let inner = QueryInner::new(info);
+            Ok(self.queries.add_iter_closest(local_key, peers, inner))
+        }
     }
 
     /// Establishes the local node as a provider of a value for the given key.
@@ -2519,7 +2528,9 @@ where
 
         // Poll bootstrap periodically and automatically.
         if let Poll::Ready(()) = self.bootstrap_status.poll_next_bootstrap(cx) {
-            self.bootstrap();
+            if let Err(e) = self.bootstrap() {
+                tracing::warn!("Failed to trigger bootstrap: {e}");
+            }
         }
 
         loop {

protocols/kad/src/behaviour/test.rs

@@ -178,7 +178,7 @@ fn bootstrap() {
 
         let swarm_ids: Vec<_> = swarms.iter().map(Swarm::local_peer_id).cloned().collect();
 
-        let qid = swarms[0].behaviour_mut().bootstrap();
+        let qid = swarms[0].behaviour_mut().bootstrap().unwrap();
 
         // Expected known peers
         let expected_known = swarm_ids.iter().skip(1).cloned().collect::<HashSet<_>>();