From 67bdd195600cde0512bbbbaab853ef3b4d0fb9a4 Mon Sep 17 00:00:00 2001
From: Nils Enkelmann <nils.enkelmann@tngtech.com>
Date: Fri, 28 Mar 2025 13:48:06 +0100
Subject: [PATCH] Rework to ensure transactional consistency in
 PeerChangedResponse again

---
 hscontrol/db/node.go       | 19 +++++++++++++++++++
 hscontrol/mapper/mapper.go | 37 +++++++++++++++----------------------
 2 files changed, 34 insertions(+), 22 deletions(-)

diff --git a/hscontrol/db/node.go b/hscontrol/db/node.go
index f36f66b7..1b9d5408 100644
--- a/hscontrol/db/node.go
+++ b/hscontrol/db/node.go
@@ -77,6 +77,25 @@ func ListNodes(tx *gorm.DB) (types.Nodes, error) {
 	return nodes, nil
 }
 
+func (hsdb *HSDatabase) ListNodesSubset(nodeIDs types.NodeIDs) (types.Nodes, error) {
+	return Read(hsdb.DB, func(rx *gorm.DB) (types.Nodes, error) {
+		return ListNodesSubset(rx, nodeIDs)
+	})
+}
+
+func ListNodesSubset(tx *gorm.DB, nodeIDs types.NodeIDs) (types.Nodes, error) {
+	nodes := types.Nodes{}
+	if err := tx.
+		Preload("AuthKey").
+		Preload("AuthKey.User").
+		Preload("User").
+		Where(nodeIDs).Find(&nodes).Error; err != nil {
+		return nil, err
+	}
+
+	return nodes, nil
+}
+
 func (hsdb *HSDatabase) ListEphemeralNodes() (types.Nodes, error) {
 	return Read(hsdb.DB, func(rx *gorm.DB) (types.Nodes, error) {
 		nodes := types.Nodes{}
diff --git a/hscontrol/mapper/mapper.go b/hscontrol/mapper/mapper.go
index cc048712..80d6c721 100644
--- a/hscontrol/mapper/mapper.go
+++ b/hscontrol/mapper/mapper.go
@@ -3,9 +3,7 @@ package mapper
 import (
 	"encoding/binary"
 	"encoding/json"
-	"errors"
 	"fmt"
-	"gorm.io/gorm"
 	"io/fs"
 	"net/url"
 	"os"
@@ -263,28 +261,20 @@ func (m *Mapper) PeerChangedResponse(
 	var changedIDs []types.NodeID
 	for nodeID, nodeChanged := range changed {
 		if nodeChanged {
-			changedIDs = append(changedIDs, nodeID)
+			if nodeID != node.ID {
+				changedIDs = append(changedIDs, nodeID)
+			}
 		} else {
 			removedIDs = append(removedIDs, nodeID.NodeID())
 		}
 	}
 
-	changedNodes := make(types.Nodes, 0, len(changedIDs))
-	for _, changedID := range changedIDs {
-		if changedID != node.ID {
-			changedNode, err := m.GetNode(changedID)
-			if err != nil {
-				if errors.Is(err, gorm.ErrRecordNotFound) {
-					continue
-				} else {
-					return nil, err
-				}
-			}
-			changedNodes = append(changedNodes, changedNode)
-		}
+	changedNodes, err := m.ListNodesSubset(changedIDs)
+	if err != nil {
+		return nil, err
 	}
 
-	err := appendPeerChanges(
+	err = appendPeerChanges(
 		&resp,
 		false, // partial change
 		m.polMan,
@@ -501,15 +491,18 @@ func (m *Mapper) ListPeers(nodeID types.NodeID) (types.Nodes, error) {
 	return peers, nil
 }
 
-func (m *Mapper) GetNode(nodeID types.NodeID) (*types.Node, error) {
-	node, err := m.db.GetNodeByID(nodeID)
+func (m *Mapper) ListNodesSubset(nodeIDs []types.NodeID) (types.Nodes, error) {
+	nodes, err := m.db.ListNodesSubset(nodeIDs)
 	if err != nil {
 		return nil, err
 	}
-	online := m.notif.IsLikelyConnected(node.ID)
-	node.IsOnline = &online
 
-	return node, nil
+	for _, node := range nodes {
+		online := m.notif.IsLikelyConnected(node.ID)
+		node.IsOnline = &online
+	}
+
+	return nodes, nil
 }
 
 func nodeMapToList(nodes map[uint64]*types.Node) types.Nodes {