Report RPC Errors to the application on peer disconnections (#5680)

Squashed commit of the following:

commit 02f1b2d
Author: dapplion <[email protected]>
Date:   Fri May 3 10:17:42 2024 +0900

    Drop lookups after peer disconnect and not awaiting events

commit f5dc1a3
Author: dapplion <[email protected]>
Date:   Wed May 1 17:14:50 2024 +0900

    Expect RPCError::Disconnect to fail ongoing requests

commit 888f129
Author: dapplion <[email protected]>
Date:   Wed May 1 14:14:22 2024 +0900

    Report RPC Errors to the application on peer disconnections

    Co-authored-by: Age Manning <[email protected]>

beacon_node/lighthouse_network/src/rpc/handler.rs

@@ -352,6 +352,31 @@ where
         !matches!(self.state, HandlerState::Deactivated)
     }
 
+    // NOTE: This function gets polled to completion upon a connection close.
+    fn poll_close(&mut self, _: &mut Context<'_>) -> Poll<Option<Self::ToBehaviour>> {
+        // Inform the network behaviour of any failed requests
+
+        while let Some(substream_id) = self.outbound_substreams.keys().next().cloned() {
+            let outbound_info = self
+                .outbound_substreams
+                .remove(&substream_id)
+                .expect("The value must exist for a key");
+            // If the state of the connection is closing, we do not need to report this case to
+            // the behaviour, as the connection has just closed non-gracefully
+            if matches!(outbound_info.state, OutboundSubstreamState::Closing(_)) {
+                continue;
+            }
+
+            // Register this request as an RPC Error
+            return Poll::Ready(Some(HandlerEvent::Err(HandlerErr::Outbound {
+                error: RPCError::Disconnected,
+                proto: outbound_info.proto,
+                id: outbound_info.req_id,
+            })));
+        }
+        Poll::Ready(None)
+    }
+
     fn poll(
         &mut self,
         cx: &mut Context<'_>,

beacon_node/lighthouse_network/src/service/mod.rs

@@ -972,6 +972,12 @@ impl<AppReqId: ReqId, E: EthSpec> Network<AppReqId, E> {
             .goodbye_peer(peer_id, reason, source);
     }
 
+    /// Hard (ungraceful) disconnect for testing purposes only
+    /// Use goodbye_peer for disconnections, do not use this function.
+    pub fn __hard_disconnect_testing_only(&mut self, peer_id: PeerId) {
+        let _ = self.swarm.disconnect_peer_id(peer_id);
+    }
+
     /// Returns an iterator over all enr entries in the DHT.
     pub fn enr_entries(&self) -> Vec<Enr> {
         self.discovery().table_entries_enr()

beacon_node/lighthouse_network/tests/rpc_tests.rs

@@ -3,7 +3,7 @@
 mod common;
 
 use common::Protocol;
-use lighthouse_network::rpc::methods::*;
+use lighthouse_network::rpc::{methods::*, RPCError};
 use lighthouse_network::{rpc::max_rpc_size, NetworkEvent, ReportSource, Request, Response};
 use slog::{debug, warn, Level};
 use ssz::Encode;
@@ -996,6 +996,96 @@ fn test_tcp_blocks_by_root_chunked_rpc_terminates_correctly() {
     })
 }
 
+#[test]
+fn test_disconnect_triggers_rpc_error() {
+    // set up the logging. The level and enabled logging or not
+    let log_level = Level::Debug;
+    let enable_logging = false;
+
+    let log = common::build_log(log_level, enable_logging);
+    let spec = E::default_spec();
+
+    let rt = Arc::new(Runtime::new().unwrap());
+    // get sender/receiver
+    rt.block_on(async {
+        let (mut sender, mut receiver) = common::build_node_pair(
+            Arc::downgrade(&rt),
+            &log,
+            ForkName::Base,
+            &spec,
+            Protocol::Tcp,
+        )
+        .await;
+
+        // BlocksByRoot Request
+        let rpc_request = Request::BlocksByRoot(BlocksByRootRequest::new(
+            // Must have at least one root for the request to create a stream
+            vec![Hash256::from_low_u64_be(0)],
+            &spec,
+        ));
+
+        // build the sender future
+        let sender_future = async {
+            loop {
+                match sender.next_event().await {
+                    NetworkEvent::PeerConnectedOutgoing(peer_id) => {
+                        // Send a STATUS message
+                        debug!(log, "Sending RPC");
+                        sender.send_request(peer_id, 42, rpc_request.clone());
+                    }
+                    NetworkEvent::RPCFailed { error, id: 42, .. } => match error {
+                        RPCError::Disconnected => return,
+                        other => panic!("received unexpected error {:?}", other),
+                    },
+                    other => {
+                        warn!(log, "Ignoring other event {:?}", other);
+                    }
+                }
+            }
+        };
+
+        // determine messages to send (PeerId, RequestId). If some, indicates we still need to send
+        // messages
+        let mut sending_peer = None;
+        let receiver_future = async {
+            loop {
+                // this future either drives the sending/receiving or times out allowing messages to be
+                // sent in the timeout
+                match futures::future::select(
+                    Box::pin(receiver.next_event()),
+                    Box::pin(tokio::time::sleep(Duration::from_secs(1))),
+                )
+                .await
+                {
+                    futures::future::Either::Left((ev, _)) => match ev {
+                        NetworkEvent::RequestReceived { peer_id, .. } => {
+                            sending_peer = Some(peer_id);
+                        }
+                        other => {
+                            warn!(log, "Ignoring other event {:?}", other);
+                        }
+                    },
+                    futures::future::Either::Right((_, _)) => {} // The timeout hit, send messages if required
+                }
+
+                // if we need to send messages send them here. This will happen after a delay
+                if let Some(peer_id) = sending_peer.take() {
+                    warn!(log, "Receiver got request, disconnecting peer");
+                    receiver.__hard_disconnect_testing_only(peer_id);
+                }
+            }
+        };
+
+        tokio::select! {
+            _ = sender_future => {}
+            _ = receiver_future => {}
+            _ = sleep(Duration::from_secs(30)) => {
+                panic!("Future timed out");
+            }
+        }
+    })
+}
+
 /// Establishes a pair of nodes and disconnects the pair based on the selected protocol via an RPC
 /// Goodbye message.
 fn goodbye_test(log_level: Level, enable_logging: bool, protocol: Protocol) {

beacon_node/network/src/sync/backfill_sync/mod.rs

@@ -307,49 +307,15 @@ impl<T: BeaconChainTypes> BackFillSync<T> {
     /// A peer has disconnected.
     /// If the peer has active batches, those are considered failed and re-requested.
     #[must_use = "A failure here indicates the backfill sync has failed and the global sync state should be updated"]
-    pub fn peer_disconnected(
-        &mut self,
-        peer_id: &PeerId,
-        network: &mut SyncNetworkContext<T>,
-    ) -> Result<(), BackFillError> {
+    pub fn peer_disconnected(&mut self, peer_id: &PeerId) -> Result<(), BackFillError> {
         if matches!(
             self.state(),
             BackFillState::Failed | BackFillState::NotRequired
         ) {
             return Ok(());
         }
 
-        if let Some(batch_ids) = self.active_requests.remove(peer_id) {
-            // fail the batches
-            for id in batch_ids {
-                if let Some(batch) = self.batches.get_mut(&id) {
-                    match batch.download_failed(false) {
-                        Ok(BatchOperationOutcome::Failed { blacklist: _ }) => {
-                            self.fail_sync(BackFillError::BatchDownloadFailed(id))?;
-                        }
-                        Ok(BatchOperationOutcome::Continue) => {}
-                        Err(e) => {
-                            self.fail_sync(BackFillError::BatchInvalidState(id, e.0))?;
-                        }
-                    }
-                    // If we have run out of peers in which to retry this batch, the backfill state
-                    // transitions to a paused state.
-                    // We still need to reset the state for all the affected batches, so we should not
-                    // short circuit early
-                    if self.retry_batch_download(network, id).is_err() {
-                        debug!(
-                            self.log,
-                            "Batch could not be retried";
-                            "batch_id" => id,
-                            "error" => "no synced peers"
-                        );
-                    }
-                } else {
-                    debug!(self.log, "Batch not found while removing peer";
-                        "peer" => %peer_id, "batch" => id)
-                }
-            }
-        }
+        self.active_requests.remove(peer_id);
 
         // Remove the peer from the participation list
         self.participating_peers.remove(peer_id);

beacon_node/network/src/sync/block_lookups/mod.rs

@@ -374,16 +374,13 @@ impl<T: BeaconChainTypes> BlockLookups<T> {
     /* Error responses */
 
     pub fn peer_disconnected(&mut self, peer_id: &PeerId) {
-        /* Check disconnection for single lookups */
-        self.single_block_lookups.retain(|_, req| {
-            let should_drop_lookup =
-                req.should_drop_lookup_on_disconnected_peer(peer_id );
-
-            if should_drop_lookup {
-                debug!(self.log, "Dropping single lookup after peer disconnection"; "block_root" => %req.block_root());
+        self.single_block_lookups.retain(|_, lookup| {
+            if lookup.remove_peer(peer_id) {
+                debug!(self.log, "Dropping single lookup after peer disconnection"; "block_root" => ?lookup.block_root());
+                false
+            } else {
+                true
             }
-
-            !should_drop_lookup
         });
     }
 

beacon_node/network/src/sync/block_lookups/single_block_lookup.rs

@@ -191,21 +191,11 @@ impl<T: BeaconChainTypes> SingleBlockLookup<T> {
             && self.blob_request_state.state.is_processed()
     }
 
-    /// Checks both the block and blob request states to see if the peer is disconnected.
-    ///
-    /// Returns true if the lookup should be dropped.
-    pub fn should_drop_lookup_on_disconnected_peer(&mut self, peer_id: &PeerId) -> bool {
-        self.block_request_state.state.remove_peer(peer_id);
-        self.blob_request_state.state.remove_peer(peer_id);
-
-        if self.all_available_peers().count() == 0 {
-            return true;
-        }
-
-        // Note: if the peer disconnected happens to have an on-going request associated with this
-        // lookup we will receive an RPCError and the lookup will fail. No need to manually retry
-        // now.
-        false
+    /// Remove peer from available peers. Return true if there are no more available peers and all
+    /// requests are not expecting any future event (AwaitingDownload).
+    pub fn remove_peer(&mut self, peer_id: &PeerId) -> bool {
+        self.block_request_state.state.remove_peer(peer_id)
+            && self.blob_request_state.state.remove_peer(peer_id)
     }
 }
 
@@ -469,9 +459,11 @@ impl<T: Clone> SingleLookupRequestState<T> {
         self.available_peers.insert(*peer_id);
     }
 
-    /// If a peer disconnects, this request could be failed. If so, an error is returned
-    pub fn remove_peer(&mut self, disconnected_peer_id: &PeerId) {
+    /// Remove peer from available peers. Return true if there are no more available peers and the
+    /// request is not expecting any future event (AwaitingDownload).
+    pub fn remove_peer(&mut self, disconnected_peer_id: &PeerId) -> bool {
         self.available_peers.remove(disconnected_peer_id);
+        self.available_peers.is_empty() && self.is_awaiting_download()
     }
 
     pub fn get_used_peers(&self) -> impl Iterator<Item = &PeerId> {

beacon_node/network/src/sync/block_lookups/tests.rs

@@ -450,8 +450,25 @@ impl TestRig {
         })
     }
 
-    fn peer_disconnected(&mut self, peer_id: PeerId) {
-        self.send_sync_message(SyncMessage::Disconnect(peer_id));
+    fn peer_disconnected(&mut self, disconnected_peer_id: PeerId) {
+        self.send_sync_message(SyncMessage::Disconnect(disconnected_peer_id));
+
+        // Return RPCErrors for all active requests of peer
+        self.drain_network_rx();
+        while let Ok(request_id) = self.pop_received_network_event(|ev| match ev {
+            NetworkMessage::SendRequest {
+                peer_id,
+                request_id: RequestId::Sync(id),
+                ..
+            } if *peer_id == disconnected_peer_id => Some(*id),
+            _ => None,
+        }) {
+            self.send_sync_message(SyncMessage::RpcError {
+                peer_id: disconnected_peer_id,
+                request_id,
+                error: RPCError::Disconnected,
+            });
+        }
     }
 
     fn drain_network_rx(&mut self) {

beacon_node/network/src/sync/manager.rs

@@ -366,9 +366,7 @@ impl<T: BeaconChainTypes> SyncManager<T> {
         self.range_sync.peer_disconnect(&mut self.network, peer_id);
         self.block_lookups.peer_disconnected(peer_id);
         // Regardless of the outcome, we update the sync status.
-        let _ = self
-            .backfill_sync
-            .peer_disconnected(peer_id, &mut self.network);
+        let _ = self.backfill_sync.peer_disconnected(peer_id);
         self.update_sync_state();
     }
 

beacon_node/network/src/sync/range_sync/chain.rs

@@ -174,30 +174,8 @@ impl<T: BeaconChainTypes> SyncingChain<T> {
 
     /// Removes a peer from the chain.
     /// If the peer has active batches, those are considered failed and re-requested.
-    pub fn remove_peer(
-        &mut self,
-        peer_id: &PeerId,
-        network: &mut SyncNetworkContext<T>,
-    ) -> ProcessingResult {
-        if let Some(batch_ids) = self.peers.remove(peer_id) {
-            // fail the batches
-            for id in batch_ids {
-                if let Some(batch) = self.batches.get_mut(&id) {
-                    if let BatchOperationOutcome::Failed { blacklist } =
-                        batch.download_failed(true)?
-                    {
-                        return Err(RemoveChain::ChainFailed {
-                            blacklist,
-                            failing_batch: id,
-                        });
-                    }
-                    self.retry_batch_download(network, id)?;
-                } else {
-                    debug!(self.log, "Batch not found while removing peer";
-                        "peer" => %peer_id, "batch" => id)
-                }
-            }
-        }
+    pub fn remove_peer(&mut self, peer_id: &PeerId) -> ProcessingResult {
+        self.peers.remove(peer_id);
 
         if self.peers.is_empty() {
             Err(RemoveChain::EmptyPeerPool)

beacon_node/network/src/sync/range_sync/range.rs

@@ -278,9 +278,8 @@ where
     /// for this peer. If so we mark the batch as failed. The batch may then hit it's maximum
     /// retries. In this case, we need to remove the chain.
     fn remove_peer(&mut self, network: &mut SyncNetworkContext<T>, peer_id: &PeerId) {
-        for (removed_chain, sync_type, remove_reason) in self
-            .chains
-            .call_all(|chain| chain.remove_peer(peer_id, network))
+        for (removed_chain, sync_type, remove_reason) in
+            self.chains.call_all(|chain| chain.remove_peer(peer_id))
         {
             self.on_chain_removed(
                 removed_chain,