Workflow-friendly concurrency primitives

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

@@ -109,6 +109,14 @@ public static <E> WorkflowQueue<E> newWorkflowQueue(int capacity) {
     return new WorkflowQueueImpl<>(capacity);
   }
 
+  public static WorkflowLock newWorkflowLock() {
+    return new WorkflowLockImpl();
+  }
+
+  public static WorkflowSemaphore newWorkflowSemaphore(int permits) {
+    return new WorkflowSemaphoreImpl(permits);
+  }
+
   public static <E> CompletablePromise<E> newCompletablePromise() {
     return new CompletablePromiseImpl<>();
   }
@@ -479,13 +487,13 @@ public static <R> R executeActivity(
 
   public static void await(String reason, Supplier<Boolean> unblockCondition)
       throws DestroyWorkflowThreadError {
-    assertNotReadOnly("await");
+    assertNotReadOnly(reason);
     getWorkflowOutboundInterceptor().await(reason, unblockCondition);
   }
 
   public static boolean await(Duration timeout, String reason, Supplier<Boolean> unblockCondition)
       throws DestroyWorkflowThreadError {
-    assertNotReadOnly("await with timeout");
+    assertNotReadOnly(reason);
     return getWorkflowOutboundInterceptor().await(timeout, reason, unblockCondition);
   }
 

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

@@ -0,0 +1,82 @@
+/*
+ * Copyright (C) 2022 Temporal Technologies, Inc. All Rights Reserved.
+ *
+ * Copyright (C) 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 material except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License 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;
+
+import static io.temporal.internal.sync.WorkflowInternal.assertNotReadOnly;
+
+import com.google.common.base.Preconditions;
+import io.temporal.workflow.CancellationScope;
+import io.temporal.workflow.WorkflowLock;
+import java.time.Duration;
+
+class WorkflowLockImpl implements WorkflowLock {
+  private boolean locked = false;
+
+  @Override
+  public void lock() {
+    WorkflowInternal.await(
+        "WorkflowLock.lock",
+        () -> {
+          CancellationScope.throwCanceled();
+          return !locked;
+        });
+    locked = true;
+  }
+
+  @Override
+  public boolean tryLock() {
+    assertNotReadOnly("WorkflowLock.tryLock");
+    if (!locked) {
+      locked = true;
+      return true;
+    }
+    return false;
+  }
+
+  @Override
+  public boolean tryLock(Duration timeout) {
+    boolean unlocked =
+        WorkflowInternal.await(
+            timeout,
+            "WorkflowLock.tryLock",
+            () -> {
+              CancellationScope.throwCanceled();
+              return !locked;
+            });
+    if (unlocked) {
+      locked = true;
+      return true;
+    }
+    return false;
+  }
+
+  @Override
+  public void unlock() {
+    assertNotReadOnly("WorkflowLock.unlock");
+    Preconditions.checkState(locked, "WorkflowLock.unlock called when not locked");
+    locked = false;
+  }
+
+  @Override
+  public boolean isHeld() {
+    return locked;
+  }
+}

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

@@ -0,0 +1,107 @@
+/*
+ * Copyright (C) 2022 Temporal Technologies, Inc. All Rights Reserved.
+ *
+ * Copyright (C) 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 material except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License 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;
+
+import static io.temporal.internal.sync.WorkflowInternal.assertNotReadOnly;
+
+import com.google.common.base.Preconditions;
+import io.temporal.workflow.CancellationScope;
+import io.temporal.workflow.WorkflowSemaphore;
+import java.time.Duration;
+
+class WorkflowSemaphoreImpl implements WorkflowSemaphore {
+  private int currentPermits;
+
+  public WorkflowSemaphoreImpl(int permits) {
+    this.currentPermits = permits;
+  }
+
+  @Override
+  public void acquire() {
+    acquire(1);
+  }
+
+  @Override
+  public void acquire(int permits) {
+    Preconditions.checkArgument(
+        permits >= 0, "WorkflowSemaphore.acquire called with negative permits");
+    WorkflowInternal.await(
+        "WorkflowSemaphore.acquire",
+        () -> {
+          CancellationScope.throwCanceled();
+          return currentPermits >= permits;
+        });
+    currentPermits -= permits;
+  }
+
+  @Override
+  public boolean tryAcquire() {
+    return tryAcquire(1);
+  }
+
+  @Override
+  public boolean tryAcquire(Duration timeout) {
+    return tryAcquire(1, timeout);
+  }
+
+  @Override
+  public boolean tryAcquire(int permits) {
+    assertNotReadOnly("WorkflowSemaphore.tryAcquire");
+    Preconditions.checkArgument(
+        permits >= 0, "WorkflowSemaphore.tryAcquire called with negative permits");
+    if (currentPermits >= permits) {
+      currentPermits -= permits;
+      return true;
+    }
+    return false;
+  }
+
+  @Override
+  public boolean tryAcquire(int permits, Duration timeout) {
+    Preconditions.checkArgument(
+        permits >= 0, "WorkflowSemaphore.tryAcquire called with negative permits");
+    boolean acquired =
+        WorkflowInternal.await(
+            timeout,
+            "WorkflowSemaphore.tryAcquire",
+            () -> {
+              CancellationScope.throwCanceled();
+              return currentPermits >= permits;
+            });
+    if (acquired) {
+      currentPermits -= permits;
+    }
+    return acquired;
+  }
+
+  @Override
+  public void release() {
+    release(1);
+  }
+
+  @Override
+  public void release(int permits) {
+    assertNotReadOnly("WorkflowSemaphore.release");
+    Preconditions.checkArgument(
+        permits >= 0, "WorkflowSemaphore.release called with negative permits");
+    currentPermits += permits;
+  }
+}

temporal-sdk/src/main/java/io/temporal/workflow/Workflow.java

@@ -507,6 +507,27 @@ public static <E> Promise<E> newFailedPromise(Exception failure) {
     return WorkflowInternal.newFailedPromise(failure);
   }
 
+  /**
+   * Creates a {@link WorkflowLock} implementation that can be used from workflow code.
+   *
+   * @apiNote The lock returned is not reentrant. If a workflow thread tries to acquire a lock that
+   *     it already holds, the call will block indefinitely.
+   * @return new instance of {@link WorkflowLock}
+   */
+  public static WorkflowLock newWorkflowLock() {
+    return WorkflowInternal.newWorkflowLock();
+  }
+
+  /**
+   * Creates a {@link WorkflowSemaphore} implementation that can be used from workflow code.
+   *
+   * @param permits the given number of permits for the semaphore.
+   * @return new instance of {@link WorkflowSemaphore}
+   */
+  public static WorkflowSemaphore newWorkflowSemaphore(int permits) {
+    return WorkflowInternal.newWorkflowSemaphore(permits);
+  }
+
   /**
    * Registers an implementation object. The object must implement at least one interface annotated
    * with {@link WorkflowInterface}. All its methods annotated with @{@link SignalMethod}

temporal-sdk/src/main/java/io/temporal/workflow/WorkflowLock.java

@@ -0,0 +1,67 @@
+/*
+ * Copyright (C) 2022 Temporal Technologies, Inc. All Rights Reserved.
+ *
+ * Copyright (C) 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 material except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License 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 java.time.Duration;
+
+/**
+ * Workflow lock is an alternative to {@link java.util.concurrent.locks.Lock} that is deterministic
+ * and compatible with Temporal's concurrency model. API is designed to be used in a workflow code
+ * only. It is not allowed to be used in an activity code.
+ *
+ * <p>In Temporal concurrency model, only one thread in a workflow code can execute at a time.
+ */
+public interface WorkflowLock {
+  /**
+   * Acquires the lock.
+   *
+   * @throws io.temporal.failure.CanceledFailure if thread (or current {@link CancellationScope} was
+   *     canceled).
+   */
+  void lock();
+
+  /**
+   * Acquires the lock only if it is free at the time of invocation.
+   *
+   * @return true if the lock was acquired and false otherwise
+   */
+  boolean tryLock();
+
+  /**
+   * Acquires the lock if it is free within the given waiting time.
+   *
+   * @throws io.temporal.failure.CanceledFailure if thread (or current {@link CancellationScope} was
+   *     canceled).
+   * @return true if the lock was acquired and false if the waiting time elapsed before the lock was
+   *     acquired.
+   */
+  boolean tryLock(Duration timeout);
+
+  /** Releases the lock. */
+  void unlock();
+
+  /**
+   * Checks if a lock is held.
+   *
+   * @return true if the lock is held and false otherwise.
+   */
+  boolean isHeld();
+}