Fix race condition in side effect function. (#212)

* Added SideEffectRaceConditionTest

* Fixed race condition in DynamicTransitionAction

src/main/java/io/temporal/internal/statemachines/DynamicTransitionAction.java

@@ -27,7 +27,6 @@ class DynamicTransitionAction<State, Data> implements TransitionAction<State, Da
 
   final DynamicCallback<State, Data> callback;
   State[] expectedStates;
-  State state;
 
   DynamicTransitionAction(State[] expectedStates, DynamicCallback<State, Data> callback) {
     this.expectedStates = expectedStates;
@@ -36,7 +35,7 @@ class DynamicTransitionAction<State, Data> implements TransitionAction<State, Da
 
   @Override
   public State apply(Data data) {
-    state = callback.apply(data);
+    State state = callback.apply(data);
     for (State s : expectedStates) {
       if (s.equals(state)) {
         return state;
@@ -53,11 +52,6 @@ public List<State> getAllowedStates() {
 
   @Override
   public String toString() {
-    return "DynamicTransitionAction{"
-        + ", state="
-        + state
-        + "expectedStates="
-        + Arrays.toString(expectedStates)
-        + '}';
+    return "DynamicTransitionAction{" + "expectedStates=" + Arrays.toString(expectedStates) + '}';
   }
 }

src/test/java/io/temporal/workflow/SideEffectRaceConditionTest.java

@@ -0,0 +1,94 @@
+/*
+ *  Copyright (C) 2020 Temporal Technologies, Inc. All Rights Reserved.
+ *
+ *  Copyright 2012-2016 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ *  Modifications copyright (C) 2017 Uber Technologies, Inc.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License"). You may not
+ *  use this file except in compliance with the License. A copy of the License is
+ *  located at
+ *
+ *  http://aws.amazon.com/apache2.0
+ *
+ *  or in the "license" file accompanying this file. This file is distributed on
+ *  an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
+ *  express or implied. See the License for the specific language governing
+ *  permissions and limitations under the License.
+ */
+
+package io.temporal.workflow;
+
+import io.temporal.client.WorkflowClient;
+import io.temporal.client.WorkflowOptions;
+import io.temporal.testing.TestEnvironmentOptions;
+import io.temporal.testing.TestWorkflowEnvironment;
+import io.temporal.worker.Worker;
+import java.time.Duration;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Random;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ExecutionException;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+public class SideEffectRaceConditionTest {
+
+  private static final String TASK_QUEUE = "test-workflow";
+
+  private TestWorkflowEnvironment testEnvironment;
+  private Worker worker;
+
+  @Before
+  public void setUp() {
+    TestEnvironmentOptions options = TestEnvironmentOptions.newBuilder().build();
+    testEnvironment = TestWorkflowEnvironment.newInstance(options);
+    worker = testEnvironment.newWorker(TASK_QUEUE);
+  }
+
+  @After
+  public void tearDown() {
+    testEnvironment.close();
+  }
+
+  @WorkflowInterface
+  public interface TestWorkflow {
+    @WorkflowMethod
+    void execute();
+  }
+
+  public static class TestSideEffectBenchWorkflowImpl implements TestWorkflow {
+
+    @Override
+    public void execute() {
+      for (int i = 0; i < 100; i++) {
+        Workflow.sideEffect(long.class, () -> new Random().nextLong());
+        Workflow.sleep(Duration.ofMillis(100));
+        Workflow.sideEffect(long.class, () -> new Random().nextLong());
+      }
+    }
+  }
+
+  @Test
+  public void testSideEffectBench() throws ExecutionException, InterruptedException {
+    worker.registerWorkflowImplementationTypes(TestSideEffectBenchWorkflowImpl.class);
+    testEnvironment.start();
+    List<CompletableFuture<Void>> results = new ArrayList<>();
+    int count = 100;
+    for (int i = 0; i < count; i++) {
+      TestWorkflow workflowStub =
+          testEnvironment
+              .getWorkflowClient()
+              .newWorkflowStub(
+                  TestWorkflow.class,
+                  WorkflowOptions.newBuilder().setTaskQueue(TASK_QUEUE).build());
+      CompletableFuture<Void> result = WorkflowClient.execute(workflowStub::execute);
+      results.add(result);
+    }
+    for (int i = 0; i < count; i++) {
+      results.get(i).get();
+    }
+  }
+}