Ignore remote vertex instance if it appears in the local set.

src/Orleans.Runtime/Placement/Rebalancing/ActivationRebalancer.cs

@@ -17,6 +17,7 @@
 using Orleans.Runtime.Utilities;
 using System.Runtime.InteropServices;
 using System.Diagnostics.CodeAnalysis;
+using Microsoft.CodeAnalysis;
 
 namespace Orleans.Runtime.Placement.Rebalancing;
 
@@ -369,19 +370,25 @@ private static (MaxHeap<CandidateVertexHeapElement> Local, MaxHeap<CandidateVert
             sourceIndex[element.Id] = element;
         }
 
-        Dictionary<GrainId, CandidateVertexHeapElement> index = [];
+        Dictionary<GrainId, CandidateVertexHeapElement> heapIndex = [];
         List<CandidateVertexHeapElement> localVertexList = new(local.Count);
         foreach (var element in local)
         {
-            var vertex = CreateVertex(sourceIndex, index, element);
+            var vertex = CreateVertex(sourceIndex, heapIndex, element);
             vertex.Location = VertexLocation.Local;
             localVertexList.Add(vertex);
         }
 
         List<CandidateVertexHeapElement> remoteVertexList = new(remote.Length);
         foreach (var element in remote)
         {
-            var vertex = CreateVertex(sourceIndex, index, element);
+            var vertex = CreateVertex(sourceIndex, heapIndex, element);
+            if (vertex.Location is not VertexLocation.Unknown)
+            {
+                // This vertex is already part of the local set, so assume that the vertex is local and ignore the remote vertex.
+                continue;
+            }
+
             vertex.Location = VertexLocation.Remote;
             remoteVertexList.Add(vertex);
         }
@@ -439,7 +446,7 @@ private async Task FinalizeProtocol(ImmutableArray<GrainId> giving, ImmutableArr
         {
             await Task.WhenAll(migrationTasks);
         }
-        catch (Exception)
+        catch
         {
             // This should happen rarely, but at this point we cant really do much, as its out of our control.
             // Even if some fail, the algorithm will eventually run again, so activations will have more chances to migrate.
@@ -694,4 +701,4 @@ private enum Direction : byte
     /// <param name="Direction">The edge's direction</param>
     /// <param name="Weight">The number of estimated messages exchanged between <paramref name="SourceId"/> and <paramref name="TargetId"/>.</param>
     private readonly record struct VertexEdge(GrainId SourceId, GrainId TargetId, bool IsMigratable, SiloAddress PartnerSilo, Direction Direction, long Weight);
-}
+}