Clear cache of operations if no more left

Prioritize clearing memory over saving the small amount of operation we have to perform is the session stays open but there is no active operations

Author: Shane Myrick

graphql-kotlin-spring-server/src/main/kotlin/com/expediagroup/graphql/spring/execution/ApolloSubscriptionSessionState.kt

@@ -58,6 +58,10 @@ internal class ApolloSubscriptionSessionState {
             val operationsForSession = activeOperations[session.id]
             operationsForSession?.get(operationMessage.id)?.cancel()
             operationsForSession?.remove(operationMessage.id)
+
+            if (operationsForSession?.isEmpty() == true) {
+                activeOperations.remove(session.id)
+            }
         }
     }
 

graphql-kotlin-spring-server/src/test/kotlin/com/expediagroup/graphql/spring/execution/ApolloSubscriptionSessionStateTest.kt

@@ -25,6 +25,7 @@ import org.reactivestreams.Subscription
 import org.springframework.web.reactive.socket.WebSocketSession
 import reactor.core.publisher.Mono
 import kotlin.test.assertEquals
+import kotlin.test.assertNull
 
 class ApolloSubscriptionSessionStateTest {
 
@@ -131,7 +132,7 @@ class ApolloSubscriptionSessionStateTest {
     }
 
     @Test
-    fun `stopOperation cancels the subscription if operation id is valid`() {
+    fun `stopOperation clears entire operation cache if it is empty after removal`() {
         val state = ApolloSubscriptionSessionState()
         val mockSubscription: Subscription = mockk { every { cancel() } returns Unit }
         val mockSession: WebSocketSession = mockk { every { id } returns "123" }
@@ -144,11 +145,33 @@ class ApolloSubscriptionSessionStateTest {
 
         state.stopOperation(mockSession, inputOperation)
 
-        assertEquals(expected = 1, actual = state.activeOperations.size)
-        assertEquals(expected = 0, actual = state.activeOperations["123"]?.size)
+        assertEquals(expected = 0, actual = state.activeOperations.size)
+        assertNull(state.activeOperations["123"])
         verify(exactly = 1) { mockSubscription.cancel() }
     }
 
+    @Test
+    fun `stopOperation cancels the subscription if operation id is valid`() {
+        val state = ApolloSubscriptionSessionState()
+        val mockSession: WebSocketSession = mockk { every { id } returns "123" }
+        val mockSubscription1: Subscription = mockk { every { cancel() } returns Unit }
+        val mockSubscription2: Subscription = mockk { every { cancel() } returns Unit }
+        val inputOperation1: SubscriptionOperationMessage = mockk { every { id } returns "abc" }
+        val inputOperation2: SubscriptionOperationMessage = mockk { every { id } returns "def" }
+
+        state.saveOperation(mockSession, inputOperation1, mockSubscription1)
+        state.saveOperation(mockSession, inputOperation2, mockSubscription2)
+
+        assertEquals(expected = 1, actual = state.activeOperations.size)
+        assertEquals(expected = 2, actual = state.activeOperations["123"]?.size)
+
+        state.stopOperation(mockSession, inputOperation1)
+
+        assertEquals(expected = 1, actual = state.activeOperations.size)
+        assertEquals(expected = 1, actual = state.activeOperations["123"]?.size)
+        verify(exactly = 1) { mockSubscription1.cancel() }
+    }
+
     @Test
     fun `terminateSession cancels the keep alive subscription`() {
         val state = ApolloSubscriptionSessionState()