blockchain/v2: make the removal of an already removed peer a noop (#5553)

also, since multiple StopPeerForError calls may be executed in parallel,
only execute StopPeerForError once

Closes #5541

CHANGELOG_PENDING.md

@@ -31,4 +31,5 @@ Friendly reminder, we have a [bug bounty program](https://hackerone.com/tendermi
 - [types] \#5523 Change json naming of `PartSetHeader` within `BlockID` from `parts` to `part_set_header` (@marbar3778)
 - [blockchain/v2] \#5530 Fix "processed height 4541 but expected height 4540" panic (@melekes)
 - [consensus/wal] Fix WAL autorepair by opening target WAL in read/write mode (@erikgrinaker)
+- [blockchain/v2] \#5553 Make the removal of an already removed peer a noop (@melekes)
 - [evidence] \#5574 Fix bug where node sends committed evidence to peer (@cmwaters)

blockchain/v2/scheduler.go

@@ -238,14 +238,13 @@ func (sc *scheduler) touchPeer(peerID p2p.ID, time time.Time) error {
 	return nil
 }
 
-func (sc *scheduler) removePeer(peerID p2p.ID) error {
+func (sc *scheduler) removePeer(peerID p2p.ID) {
 	peer, ok := sc.peers[peerID]
 	if !ok {
-		return nil
+		return
 	}
-
 	if peer.state == peerStateRemoved {
-		return fmt.Errorf("tried to remove peer %s in peerStateRemoved", peerID)
+		return
 	}
 
 	for height, pendingPeerID := range sc.pendingBlocks {
@@ -279,8 +278,6 @@ func (sc *scheduler) removePeer(peerID p2p.ID) error {
 			delete(sc.blockStates, h)
 		}
 	}
-
-	return nil
 }
 
 // check if the blockPool is running low and add new blocks in New state to be requested.
@@ -309,16 +306,12 @@ func (sc *scheduler) setPeerRange(peerID p2p.ID, base int64, height int64) error
 	}
 
 	if height < peer.height {
-		if err := sc.removePeer(peerID); err != nil {
-			return err
-		}
+		sc.removePeer(peerID)
 		return fmt.Errorf("cannot move peer height lower. from %d to %d", peer.height, height)
 	}
 
 	if base > height {
-		if err := sc.removePeer(peerID); err != nil {
-			return err
-		}
+		sc.removePeer(peerID)
 		return fmt.Errorf("cannot set peer base higher than its height")
 	}
 
@@ -372,15 +365,9 @@ func (sc *scheduler) setStateAtHeight(height int64, state blockState) {
 	sc.blockStates[height] = state
 }
 
+// CONTRACT: peer exists and in Ready state.
 func (sc *scheduler) markReceived(peerID p2p.ID, height int64, size int64, now time.Time) error {
-	peer, ok := sc.peers[peerID]
-	if !ok {
-		return fmt.Errorf("received block from unknown peer %s", peerID)
-	}
-
-	if peer.state != peerStateReady {
-		return fmt.Errorf("cannot receive blocks from not ready peer %s", peerID)
-	}
+	peer := sc.peers[peerID]
 
 	if state := sc.getStateAtHeight(height); state != blockStatePending || sc.pendingBlocks[height] != peerID {
 		return fmt.Errorf("received block %d from peer %s without being requested", height, peerID)
@@ -541,12 +528,13 @@ func (peers PeerByID) Swap(i, j int) {
 func (sc *scheduler) handleBlockResponse(event bcBlockResponse) (Event, error) {
 	err := sc.touchPeer(event.peerID, event.time)
 	if err != nil {
-		return scPeerError{peerID: event.peerID, reason: err}, nil
+		// peer does not exist OR not ready
+		return noOp, nil
 	}
 
 	err = sc.markReceived(event.peerID, event.block.Height, event.size, event.time)
 	if err != nil {
-		_ = sc.removePeer(event.peerID)
+		sc.removePeer(event.peerID)
 		return scPeerError{peerID: event.peerID, reason: err}, nil
 	}
 
@@ -561,7 +549,7 @@ func (sc *scheduler) handleNoBlockResponse(event bcNoBlockResponse) (Event, erro
 	}
 
 	// The peer may have been just removed due to errors, low speed or timeouts.
-	_ = sc.removePeer(event.peerID)
+	sc.removePeer(event.peerID)
 
 	return scPeerError{peerID: event.peerID,
 		reason: fmt.Errorf("peer %v with base %d height %d claims no block for %d",
@@ -588,13 +576,10 @@ func (sc *scheduler) handleBlockProcessed(event pcBlockProcessed) (Event, error)
 // Handles an error from the processor. The processor had already cleaned the blocks from
 // the peers included in this event. Just attempt to remove the peers.
 func (sc *scheduler) handleBlockProcessError(event pcBlockVerificationFailure) (Event, error) {
-	if len(sc.peers) == 0 {
-		return noOp, nil
-	}
 	// The peers may have been just removed due to errors, low speed or timeouts.
-	_ = sc.removePeer(event.firstPeerID)
+	sc.removePeer(event.firstPeerID)
 	if event.firstPeerID != event.secondPeerID {
-		_ = sc.removePeer(event.secondPeerID)
+		sc.removePeer(event.secondPeerID)
 	}
 
 	if sc.allBlocksProcessed() {
@@ -610,12 +595,8 @@ func (sc *scheduler) handleAddNewPeer(event bcAddNewPeer) (Event, error) {
 }
 
 func (sc *scheduler) handleRemovePeer(event bcRemovePeer) (Event, error) {
-	err := sc.removePeer(event.peerID)
-	if err != nil {
-		// XXX - It is possible that the removePeer fails here for legitimate reasons
-		// for example if a peer timeout or error was handled just before this.
-		return scSchedulerFail{reason: err}, nil
-	}
+	sc.removePeer(event.peerID)
+
 	if sc.allBlocksProcessed() {
 		return scFinishedEv{reason: "removed peer"}, nil
 	}
@@ -633,9 +614,7 @@ func (sc *scheduler) handleTryPrunePeer(event rTryPrunePeer) (Event, error) {
 		// from that peer within sc.peerTimeout. Remove the peer. This is to ensure that a peer
 		// will be timed out even if it sends blocks at higher heights but prevents progress by
 		// not sending the block at current height.
-		if err := sc.removePeer(sc.pendingBlocks[sc.height]); err != nil {
-			return nil, err
-		}
+		sc.removePeer(sc.pendingBlocks[sc.height])
 	}
 
 	prunablePeers := sc.prunablePeers(sc.peerTimeout, sc.minRecvRate, event.time)
@@ -643,11 +622,7 @@ func (sc *scheduler) handleTryPrunePeer(event rTryPrunePeer) (Event, error) {
 		return noOp, nil
 	}
 	for _, peerID := range prunablePeers {
-		err := sc.removePeer(peerID)
-		if err != nil {
-			// Should never happen as prunablePeers() returns only existing peers in Ready state.
-			panic("scheduler data corruption")
-		}
+		sc.removePeer(peerID)
 	}
 
 	// If all blocks are processed we should finish.
@@ -656,7 +631,6 @@ func (sc *scheduler) handleTryPrunePeer(event rTryPrunePeer) (Event, error) {
 	}
 
 	return scPeersPruned{peers: prunablePeers}, nil
-
 }
 
 func (sc *scheduler) handleResetState(event bcResetState) (Event, error) {

blockchain/v2/scheduler_test.go

@@ -418,7 +418,6 @@ func TestScRemovePeer(t *testing.T) {
 					"P1": {height: 10, state: peerStateRemoved},
 					"P2": {height: 11, state: peerStateReady}},
 				allB: []int64{8, 9, 10, 11}},
-			wantErr: true,
 		},
 		{
 			name: "remove Ready peer with blocks requested",
@@ -492,9 +491,7 @@ func TestScRemovePeer(t *testing.T) {
 		tt := tt
 		t.Run(tt.name, func(t *testing.T) {
 			sc := newTestScheduler(tt.fields)
-			if err := sc.removePeer(tt.args.peerID); (err != nil) != tt.wantErr {
-				t.Errorf("removePeer() wantErr %v, error = %v", tt.wantErr, err)
-			}
+			sc.removePeer(tt.args.peerID)
 			wantSc := newTestScheduler(tt.wantFields)
 			assert.Equal(t, wantSc, sc, "wanted peers %v, got %v", wantSc.peers, sc.peers)
 		})
@@ -1416,13 +1413,13 @@ func TestScHandleBlockResponse(t *testing.T) {
 			name:      "empty scheduler",
 			fields:    scTestParams{},
 			args:      args{event: block6FromP1},
-			wantEvent: scPeerError{peerID: "P1", reason: fmt.Errorf("some error")},
+			wantEvent: noOpEvent{},
 		},
 		{
 			name:      "block from removed peer",
 			fields:    scTestParams{peers: map[string]*scPeer{"P1": {height: 8, state: peerStateRemoved}}},
 			args:      args{event: block6FromP1},
-			wantEvent: scPeerError{peerID: "P1", reason: fmt.Errorf("some error")},
+			wantEvent: noOpEvent{},
 		},
 		{
 			name: "block we haven't asked for",
@@ -1441,7 +1438,7 @@ func TestScHandleBlockResponse(t *testing.T) {
 				pendingTime: map[int64]time.Time{6: now},
 			},
 			args:      args{event: block6FromP1},
-			wantEvent: scPeerError{peerID: "P1", reason: fmt.Errorf("some error")},
+			wantEvent: noOpEvent{},
 		},
 		{
 			name: "block with bad timestamp",

p2p/switch.go

@@ -322,6 +322,10 @@ func (sw *Switch) Peers() IPeerSet {
 // If the peer is persistent, it will attempt to reconnect.
 // TODO: make record depending on reason.
 func (sw *Switch) StopPeerForError(peer Peer, reason interface{}) {
+	if !peer.IsRunning() {
+		return
+	}
+
 	sw.Logger.Error("Stopping peer for error", "peer", peer, "err", reason)
 	sw.stopAndRemovePeer(peer, reason)