SnapshotStore can reply with SnapshotNotFound if it is saving an EntitySnapshot

CHANGELOG.md

@@ -41,6 +41,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Snapshot synchronization could remove committed log entries that not be included in snapshots
   [#167](https://github.com/lerna-stack/akka-entity-replication/issues/167)
   [#PR168](https://github.com/lerna-stack/akka-entity-replication/pull/168)
+- SnapshotStore doesn't reply with SnapshotNotFound sometimes
+  [#182](https://github.com/lerna-stack/akka-entity-replication/issues/182),
+  [#PR183](https://github.com/lerna-stack/akka-entity-replication/pull/183)
 
 ## [v2.1.0] - 2022-03-24
 [v2.1.0]: https://github.com/lerna-stack/akka-entity-replication/compare/v2.0.0...v2.1.0

src/main/scala/lerna/akka/entityreplication/raft/snapshot/SnapshotStore.scala

@@ -96,8 +96,11 @@ private[entityreplication] class SnapshotStore(
               cmd.entityId,
             )
         case FetchSnapshot(_, replyTo) =>
-          prevSnapshot.foreach { s =>
-            replyTo ! SnapshotProtocol.SnapshotFound(s)
+          prevSnapshot match {
+            case Some(prevSnapshot) =>
+              replyTo ! SnapshotProtocol.SnapshotFound(prevSnapshot)
+            case None =>
+              replyTo ! SnapshotProtocol.SnapshotNotFound(entityId)
           }
       }
     case _: persistence.SaveSnapshotSuccess =>

src/test/scala/lerna/akka/entityreplication/raft/snapshot/ShardSnapshotStoreFailureSpec.scala

@@ -22,7 +22,6 @@ import lerna.akka.entityreplication.raft.{ ActorSpec, RaftSettings }
 import lerna.akka.entityreplication.testkit.KryoSerializable
 
 import scala.concurrent.Promise
-import scala.util.Using
 
 object ShardSnapshotStoreFailureSpec {
   final case object DummyState extends KryoSerializable
@@ -93,34 +92,41 @@ class ShardSnapshotStoreFailureSpec
   "ShardSnapshotStore (with time-consuming writes)" should {
 
     // Emulates a time-consuming write
-    class TimeConsumingWriteSnapshotPolicy extends SnapshotStorage.SnapshotPolicies.PolicyType with AutoCloseable {
+    // Note:
+    //   The promise (`processingResultPromise`) must be fulfilled.
+    //   The succeeding tests will fail unless the promise is fulfilled.
+    class TimeConsumingWriteSnapshotPolicy extends SnapshotStorage.SnapshotPolicies.PolicyType {
       val processingResultPromise = Promise[ProcessingResult]()
       override def tryProcess(persistenceId: String, processingUnit: SnapshotOperation): ProcessingResult = {
         processingUnit match {
           case _: WriteSnapshot => processingResultPromise.future.await
           case _                => ProcessingSuccess
         }
       }
-      override def close(): Unit = {
+      def trySuccess(): Unit = {
         processingResultPromise.trySuccess(ProcessingSuccess)
       }
     }
 
-    "reply with `SnapshotNotFound` to `FetchSnapshot` if it has no EntitySnapshot and is saving an EntitySnapshot" ignore {
-      // TODO Change SnapshotStore.savingSnapshot such that this test passes.
+    "reply with `SnapshotNotFound` to `FetchSnapshot` if it has no EntitySnapshot and is saving an EntitySnapshot" in {
       val entityId           = generateUniqueEntityId()
       val shardSnapshotStore = createShardSnapshotStore()
       val metadata           = EntitySnapshotMetadata(entityId, LogEntryIndex(1))
       val snapshot           = EntitySnapshot(metadata, EntityState(DummyState))
 
-      Using(new TimeConsumingWriteSnapshotPolicy()) { timeConsumingWriteSnapshotPolicy =>
+      val timeConsumingWriteSnapshotPolicy = new TimeConsumingWriteSnapshotPolicy()
+      try {
         // Prepare: SnapshotStore is saving the snapshot
         snapshotTestKit.withPolicy(timeConsumingWriteSnapshotPolicy)
         shardSnapshotStore ! SaveSnapshot(snapshot, replyTo = testActor)
 
         // Test:
         shardSnapshotStore ! FetchSnapshot(entityId, replyTo = testActor)
-        expectMsg(SnapshotNotFound)
+        expectMsg(SnapshotNotFound(entityId))
+      } finally {
+        // Cleanup:
+        // The succeeding tests will fail unless the promise is fulfilled.
+        timeConsumingWriteSnapshotPolicy.trySuccess()
       }
     }
 
@@ -134,7 +140,8 @@ class ShardSnapshotStoreFailureSpec
       shardSnapshotStore ! SaveSnapshot(firstSnapshot, replyTo = testActor)
       expectMsg(SaveSnapshotSuccess(firstSnapshotMetadata))
 
-      Using(new TimeConsumingWriteSnapshotPolicy()) { timeConsumingWriteSnapshotPolicy =>
+      val timeConsumingWriteSnapshotPolicy = new TimeConsumingWriteSnapshotPolicy()
+      try {
         // Prepare: SnapshotStore is saving the second snapshot
         snapshotTestKit.withPolicy(timeConsumingWriteSnapshotPolicy)
         val secondSnapshot =
@@ -144,6 +151,10 @@ class ShardSnapshotStoreFailureSpec
         // Test:
         shardSnapshotStore ! FetchSnapshot(entityId, replyTo = testActor)
         expectMsg(SnapshotFound(firstSnapshot))
+      } finally {
+        // Cleanup:
+        // The succeeding tests will fail unless the promise is fulfilled.
+        timeConsumingWriteSnapshotPolicy.trySuccess()
       }
     }
 
@@ -155,7 +166,8 @@ class ShardSnapshotStoreFailureSpec
       val metadata           = EntitySnapshotMetadata(entityId, LogEntryIndex(1))
       val snapshot           = EntitySnapshot(metadata, EntityState(DummyState))
 
-      Using(new TimeConsumingWriteSnapshotPolicy()) { timeConsumingWriteSnapshotPolicy =>
+      val timeConsumingWriteSnapshotPolicy = new TimeConsumingWriteSnapshotPolicy()
+      try {
         // Prepare: SnapshotStore is saving the snapshot
         snapshotTestKit.withPolicy(timeConsumingWriteSnapshotPolicy)
         shardSnapshotStore ! SaveSnapshot(snapshot, replyTo = testActor)
@@ -168,6 +180,10 @@ class ShardSnapshotStoreFailureSpec
             shardSnapshotStore ! SaveSnapshot(snapshot, replyTo = testActor)
           }
         expectNoMessage()
+      } finally {
+        // Cleanup:
+        // The succeeding tests will fail unless the promise is fulfilled.
+        timeConsumingWriteSnapshotPolicy.trySuccess()
       }
     }