Updating SiloMetadata caching

src/Orleans.Runtime/MembershipService/SiloMetadata/SiloMetadaCache.cs

@@ -5,24 +5,32 @@
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Options;
+using Orleans.Configuration;
 
 #nullable enable
 namespace Orleans.Runtime.MembershipService.SiloMetadata;
 
 internal class SiloMetadataCache(
     ISiloMetadataClient siloMetadataClient,
     MembershipTableManager membershipTableManager,
+    IOptions<ClusterMembershipOptions> clusterMembershipOptions,
     ILogger<SiloMetadataCache> logger)
     : ISiloMetadataCache, ILifecycleParticipant<ISiloLifecycle>, IDisposable
 {
     private readonly ConcurrentDictionary<SiloAddress, SiloMetadata> _metadata = new();
+    private readonly Dictionary<SiloAddress, DateTime> _negativeCache = new();
     private readonly CancellationTokenSource _cts = new();
+    private TimeSpan negativeCachePeriod;
 
     void ILifecycleParticipant<ISiloLifecycle>.Participate(ISiloLifecycle lifecycle)
     {
         Task? task = null;
         Task OnStart(CancellationToken _)
         {
+            // This gives time for the cluster to be voted Dead and for membership updates to propagate that out
+            negativeCachePeriod = clusterMembershipOptions.Value.ProbeTimeout * clusterMembershipOptions.Value.NumMissedProbesLimit 
+                                  + (2 * clusterMembershipOptions.Value.TableRefreshTimeout);
             task = Task.Run(() => this.ProcessMembershipUpdates(_cts.Token));
             return Task.CompletedTask;
         }
@@ -51,26 +59,39 @@ private async Task ProcessMembershipUpdates(CancellationToken ct)
             await foreach (var update in membershipTableManager.MembershipTableUpdates.WithCancellation(ct))
             {
                 // Add entries for members that aren't already in the cache
-                foreach (var membershipEntry in update.Entries.Where(e => e.Value.Status is SiloStatus.Active or SiloStatus.Joining))
+                var now = DateTime.UtcNow;
+                var recentlyActiveSilos = update.Entries
+                    .Where(e => e.Value.Status is SiloStatus.Active or SiloStatus.Joining)
+                    .Where(e => !e.Value.HasMissedIAmAlives(clusterMembershipOptions.Value, now));
+                foreach (var membershipEntry in recentlyActiveSilos)
                 {
                     if (!_metadata.ContainsKey(membershipEntry.Key))
                     {
+                        if (_negativeCache.TryGetValue(membershipEntry.Key, out var expiration) && expiration > now)
+                        {
+                            continue;
+                        }
                         try
                         {
                             var metadata = await siloMetadataClient.GetSiloMetadata(membershipEntry.Key).WaitAsync(ct);
                             _metadata.TryAdd(membershipEntry.Key, metadata);
+                            _negativeCache.Remove(membershipEntry.Key, out _);
                         }
                         catch(Exception exception)
                         {
+                            _negativeCache.TryAdd(membershipEntry.Key, now + negativeCachePeriod);
                             logger.LogError(exception, "Error fetching metadata for silo {Silo}", membershipEntry.Key);
                         }
                     }
                 }
 
                 // Remove entries for members that are now dead
-                foreach (var membershipEntry in update.Entries.Where(e => e.Value.Status == SiloStatus.Dead))
+                var deadSilos = update.Entries
+                    .Where(e => e.Value.Status == SiloStatus.Dead);
+                foreach (var membershipEntry in deadSilos)
                 {
                     _metadata.TryRemove(membershipEntry.Key, out _);
+                    _negativeCache.Remove(membershipEntry.Key, out _);
                 }
 
                 // Remove entries for members that are no longer in the table
@@ -79,6 +100,7 @@ private async Task ProcessMembershipUpdates(CancellationToken ct)
                     if (!update.Entries.ContainsKey(silo))
                     {
                         _metadata.TryRemove(silo, out _);
+                        _negativeCache.Remove(silo, out _);
                     }
                 }
             }
@@ -102,4 +124,5 @@ private async Task ProcessMembershipUpdates(CancellationToken ct)
     public void SetMetadata(SiloAddress siloAddress, SiloMetadata metadata) => _metadata.TryAdd(siloAddress, metadata);
 
     public void Dispose() => _cts.Cancel();
-}
+}
+