Workflow thread deadlock detector

temporal-sdk/src/main/java/io/temporal/internal/sync/DeterministicRunner.java

@@ -32,6 +32,8 @@
  */
 interface DeterministicRunner {
 
+  long DEFAULT_DEADLOCK_DETECTION_TIMEOUT = 1000;
+
   static DeterministicRunner newRunner(Runnable root) {
     return new DeterministicRunnerImpl(root);
   }
@@ -74,8 +76,9 @@ static DeterministicRunner newRunner(
    * completed or blocked.
    *
    * @throws Throwable if one of the threads didn't handle an exception.
+   * @param deadlockDetectionTimeout the maximum time a thread can run without calling yield.
    */
-  void runUntilAllBlocked();
+  void runUntilAllBlocked(long deadlockDetectionTimeout);
 
   /** IsDone returns true when all of threads are completed */
   boolean isDone();

temporal-sdk/src/main/java/io/temporal/internal/sync/DeterministicRunnerImpl.java

@@ -219,7 +219,7 @@ SyncWorkflowContext getWorkflowContext() {
   }
 
   @Override
-  public void runUntilAllBlocked() {
+  public void runUntilAllBlocked(long deadlockDetectionTimeout) {
     if (rootWorkflowThread == null) {
       // TODO: workflow instance specific thread name
       rootWorkflowThread =
@@ -276,7 +276,7 @@ public void runUntilAllBlocked() {
         Iterator<WorkflowThread> ci = threads.iterator();
         while (ci.hasNext()) {
           WorkflowThread c = ci.next();
-          progress = c.runUntilBlocked() || progress;
+          progress = c.runUntilBlocked(deadlockDetectionTimeout) || progress;
           if (exitRequested) {
             close();
             break outerLoop;

temporal-sdk/src/main/java/io/temporal/internal/sync/DeterministicRunnerWrapper.java

@@ -45,7 +45,9 @@ public Object invoke(Object proxy, Method method, Object[] args) throws Throwabl
                 result.completeExceptionally(throwable);
               }
             });
-    runner.runUntilAllBlocked();
+    // Used to execute activities under TestActivityEnvironment
+    // So it is expected that a workflow thread is blocked for a long time.
+    runner.runUntilAllBlocked(Long.MAX_VALUE);
     try {
       return result.get();
     } catch (ExecutionException e) {

temporal-sdk/src/main/java/io/temporal/internal/sync/PotentialDeadlockException.java

@@ -0,0 +1,29 @@
+/*
+ *  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.internal.sync;
+
+class PotentialDeadlockException extends RuntimeException {
+
+  PotentialDeadlockException(StackTraceElement[] stackTrace) {
+    super(
+        "Potential deadlock detected: workflow thread blocked for over a second", null, true, true);
+    setStackTrace(stackTrace);
+  }
+}

temporal-sdk/src/main/java/io/temporal/internal/sync/SyncWorkflow.java

@@ -19,6 +19,8 @@
 
 package io.temporal.internal.sync;
 
+import static io.temporal.internal.sync.DeterministicRunner.DEFAULT_DEADLOCK_DETECTION_TIMEOUT;
+
 import io.temporal.api.common.v1.Payloads;
 import io.temporal.api.common.v1.WorkflowType;
 import io.temporal.api.enums.v1.EventType;
@@ -134,7 +136,7 @@ public boolean eventLoop() {
     if (runner == null) {
       return false;
     }
-    runner.runUntilAllBlocked();
+    runner.runUntilAllBlocked(DEFAULT_DEADLOCK_DETECTION_TIMEOUT);
     return runner.isDone() || workflowProc.isDone(); // Do not wait for all other threads.
   }
 

temporal-sdk/src/main/java/io/temporal/internal/sync/WorkflowThread.java

@@ -82,7 +82,7 @@ static WorkflowThread newThread(Runnable runnable, boolean detached, String name
 
   SyncWorkflowContext getWorkflowContext();
 
-  boolean runUntilBlocked();
+  boolean runUntilBlocked(long deadlockDetectionTimeout);
 
   Throwable getUnhandledException();
 

temporal-sdk/src/main/java/io/temporal/internal/sync/WorkflowThreadContext.java

@@ -19,8 +19,11 @@
 
 package io.temporal.internal.sync;
 
+import static io.temporal.internal.sync.DeterministicRunner.DEFAULT_DEADLOCK_DETECTION_TIMEOUT;
+
 import com.google.common.base.Throwables;
 import io.temporal.workflow.Functions;
+import java.util.concurrent.TimeUnit;
 import java.util.concurrent.locks.Condition;
 import java.util.concurrent.locks.Lock;
 import java.util.function.Supplier;
@@ -43,6 +46,7 @@ class WorkflowThreadContext {
   private boolean remainedBlocked;
   private String yieldReason;
   private boolean destroyRequested;
+  private Thread currentThread;
 
   WorkflowThreadContext(Lock lock) {
     this.lock = lock;
@@ -194,15 +198,20 @@ public void setUnhandledException(Throwable unhandledException) {
     }
   }
 
+  public void setCurrentThread(Thread currentThread) {
+    this.currentThread = currentThread;
+  }
+
   public String getYieldReason() {
     return yieldReason;
   }
 
   /**
    * @return true if thread made some progress. Which is await was unblocked and some code after it
    *     was executed.
+   * @param deadlockDetectionTimeout
    */
-  public boolean runUntilBlocked() {
+  public boolean runUntilBlocked(long deadlockDetectionTimeout) {
     lock.lock();
     try {
       if (status == Status.DONE) {
@@ -218,7 +227,10 @@ public boolean runUntilBlocked() {
       remainedBlocked = true;
       yieldCondition.signal();
       while (status == Status.RUNNING || status == Status.CREATED) {
-        runCondition.await();
+        if (!runCondition.await(deadlockDetectionTimeout, TimeUnit.MILLISECONDS)) {
+          throw new PotentialDeadlockException(currentThread.getStackTrace());
+        }
+        ;
         if (evaluationFunction != null) {
           throw new IllegalStateException("Cannot runUntilBlocked while evaluating");
         }
@@ -259,7 +271,7 @@ public void destroy() {
         (r) -> {
           throw new DestroyWorkflowThreadError();
         });
-    runUntilBlocked();
+    runUntilBlocked(DEFAULT_DEADLOCK_DETECTION_TIMEOUT);
   }
 
   /** To be called only from a workflow thread. */

temporal-sdk/src/main/java/io/temporal/internal/sync/WorkflowThreadImpl.java

@@ -87,6 +87,7 @@ class RunnableWrapper implements Runnable {
     @Override
     public void run() {
       thread = Thread.currentThread();
+      threadContext.setCurrentThread(thread);
       originalName = thread.getName();
       thread.setName(name);
       DeterministicRunnerImpl.setCurrentThreadInternal(WorkflowThreadImpl.this);
@@ -99,7 +100,6 @@ public void run() {
       // Repopulate the context(s)
       ContextThreadLocal.setContextPropagators(this.contextPropagators);
       ContextThreadLocal.propagateContextToCurrentThread(this.propagatedContexts);
-
       try {
         // initialYield blocks thread until the first runUntilBlocked is called.
         // Otherwise r starts executing without control of the sync.
@@ -125,6 +125,7 @@ public void run() {
         threadContext.setStatus(Status.DONE);
         thread.setName(originalName);
         thread = null;
+        threadContext.setCurrentThread(null);
         MDC.clear();
       }
     }
@@ -308,13 +309,16 @@ public int getPriority() {
     return priority;
   }
 
-  /** @return true if coroutine made some progress. */
+  /**
+   * @return true if coroutine made some progress.
+   * @param deadlockDetectionTimeout maximum time the thread can run before calling yield.
+   */
   @Override
-  public boolean runUntilBlocked() {
+  public boolean runUntilBlocked(long deadlockDetectionTimeout) {
     if (taskFuture == null) {
       start();
     }
-    return context.runUntilBlocked();
+    return context.runUntilBlocked(deadlockDetectionTimeout);
   }
 
   @Override