Configurable actor reminder storage patitions

src/Dapr.Actors/Runtime/ActorRuntime.cs

@@ -93,6 +93,12 @@ namespace Dapr.Actors.Runtime
                 writer.WriteBoolean("drainRebalancedActors", (this.options.DrainRebalancedActors));
             }
 
+            // default is null, don't write it if default
+            if (this.options.RemindersStoragePartitions != null)
+            {
+                writer.WriteNumber("remindersStoragePartitions", this.options.RemindersStoragePartitions.Value);
+            }
+
             writer.WriteEndObject();
             return writer.FlushAsync();
         }

src/Dapr.Actors/Runtime/ActorRuntimeOptions.cs

@@ -22,6 +22,7 @@ namespace Dapr.Actors.Runtime
         private bool drainRebalancedActors;
         private JsonSerializerOptions jsonSerializerOptions = JsonSerializerDefaults.Web;
         private string daprApiToken = null;
+        private int? remindersStoragePartitions = null;
 
         /// <summary>
         /// Gets the collection of <see cref="ActorRegistration" /> instances.
@@ -162,6 +163,27 @@ namespace Dapr.Actors.Runtime
             }
         }
 
+        /// <summary>
+        /// An int used to determine how many partitions to use for reminders storage.
+        /// </summary>
+        public int? RemindersStoragePartitions
+        {
+            get
+            {
+                return this.remindersStoragePartitions;
+            }
+
+            set
+            {
+                if (value < 0)
+                {
+                    throw new ArgumentOutOfRangeException(nameof(remindersStoragePartitions), remindersStoragePartitions, "must be positive");
+                }
+
+                this.remindersStoragePartitions = value;
+            }
+        }
+
         /// <summary>
         /// Gets or sets the HTTP endpoint URI used to communicate with the Dapr sidecar.
         /// </summary>

test/Dapr.Actors.Test/Runtime/ActorRuntimeOptionsTests.cs

@@ -113,5 +113,14 @@ namespace Dapr.Actors.Test.Runtime
 
             action.Should().Throw<ArgumentNullException>();
         }
+
+        [Fact]
+        public void SettingRemindersStoragePartitionsToLessThanZero_Fails()
+        {
+            var options = new ActorRuntimeOptions();
+            Action action = () => options.RemindersStoragePartitions = -1;
+
+            action.Should().Throw<ArgumentOutOfRangeException>();
+        }
     }
 }

test/Dapr.Actors.Test/Runtime/ActorRuntimeTests.cs

@@ -7,6 +7,7 @@ namespace Dapr.Actors.Test
 {
     using System;
     using System.Buffers;
+    using System.Collections.Generic;
     using System.Linq;
     using System.IO;
     using System.Text;
@@ -144,6 +145,51 @@ namespace Dapr.Actors.Test
 
             element = root.GetProperty("drainRebalancedActors");
             Assert.True(element.GetBoolean());
+
+            try {
+                element = root.GetProperty("remindersStoragePartitions");
+                Assert.False(true, "remindersStoragePartitions should not be serialized");
+            }
+            catch (Exception ex) {
+                Assert.IsType<KeyNotFoundException>(ex);
+            }
+
+        }
+
+                [Fact]
+        public async Task TestActorSettingsWithRemindersStoragePartitions()
+        {
+            var actorType = typeof(TestActor);
+
+            var options = new ActorRuntimeOptions();
+            options.Actors.RegisterActor<TestActor>();
+            options.RemindersStoragePartitions = 12;
+
+            var runtime = new ActorRuntime(options, loggerFactory, activatorFactory, proxyFactory);
+
+            Assert.Contains(actorType.Name, runtime.RegisteredActors.Select(a => a.Type.ActorTypeName), StringComparer.InvariantCulture);
+
+            ArrayBufferWriter<byte> writer = new ArrayBufferWriter<byte>();
+            await runtime.SerializeSettingsAndRegisteredTypes(writer);
+
+            // read back the serialized json
+            var array = writer.WrittenSpan.ToArray();
+            string s = Encoding.UTF8.GetString(array, 0, array.Length);
+
+            JsonDocument document = JsonDocument.Parse(s);
+            JsonElement root = document.RootElement;
+
+            // parse out the entities array 
+            JsonElement element = root.GetProperty("entities");
+            Assert.Equal(1, element.GetArrayLength());
+
+            JsonElement arrayElement = element[0];
+            string actor = arrayElement.GetString();
+            Assert.Equal("TestActor", actor);
+
+            element = root.GetProperty("remindersStoragePartitions");
+            Assert.Equal(12, element.GetInt64());
+
         }
 
         private sealed class TestActor : Actor, ITestActor