Add getParent() API to TaskOrchestrationContext for parent instance support

CHANGELOG.md

@@ -1,4 +1,5 @@
 ## Unreleased
+* Add `getParent()` API to `TaskOrchestrationContext` for discovering parent orchestration info ([#284](https://github.com/microsoft/durabletask-java/pull/284))
 
 ## v1.9.0
 * Fix entity locking deserialization and add Jackson support for EntityInstanceId/EntityMetadata ([#281](https://github.com/microsoft/durabletask-java/pull/281))

client/src/main/java/com/microsoft/durabletask/ParentOrchestrationInstance.java

@@ -0,0 +1,65 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+package com.microsoft.durabletask;
+
+import java.util.Objects;
+import javax.annotation.Nullable;
+
+/**
+ * Represents the parent orchestration of a sub-orchestration.
+ * This is available via {@link TaskOrchestrationContext#getParent()} when the
+ * current orchestration was started as a sub-orchestration.
+ */
+public final class ParentOrchestrationInstance {
+    private final String name;
+    private final String instanceId;
+
+    /**
+     * Creates a new ParentOrchestrationInstance.
+     *
+     * @param name       the name of the parent orchestration
+     * @param instanceId the instance ID of the parent orchestration
+     */
+    public ParentOrchestrationInstance(String name, String instanceId) {
+        this.name = name;
+        this.instanceId = instanceId;
+    }
+
+    /**
+     * Gets the name of the parent orchestration.
+     *
+     * @return the parent orchestration name
+     */
+    @Nullable
+    public String getName() {
+        return this.name;
+    }
+
+    /**
+     * Gets the instance ID of the parent orchestration.
+     *
+     * @return the parent orchestration instance ID
+     */
+    @Nullable
+    public String getInstanceId() {
+        return this.instanceId;
+    }
+
+    @Override
+    public String toString() {
+        return String.format("ParentOrchestrationInstance{name='%s', instanceId='%s'}", name, instanceId);
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (!(o instanceof ParentOrchestrationInstance)) return false;
+        ParentOrchestrationInstance that = (ParentOrchestrationInstance) o;
+        return Objects.equals(name, that.name) && Objects.equals(instanceId, that.instanceId);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(name, instanceId);
+    }
+}

client/src/main/java/com/microsoft/durabletask/TaskOrchestrationContext.java

@@ -794,6 +794,17 @@ default Task<AutoCloseable> lockEntities(@Nonnull EntityInstanceId... entityIds)
      */
     void clearCustomStatus();
 
+    /**
+     * Gets the parent orchestration instance, or {@code null} if this orchestration
+     * was not started as a sub-orchestration.
+     *
+     * @return the parent orchestration instance, or {@code null}
+     */
+    @Nullable
+    default ParentOrchestrationInstance getParent() {
+        return null;
+    }
+
     /**
      * Makes a durable HTTP request using the specified {@link DurableHttpRequest} and returns a {@link Task}
      * that completes when the HTTP call completes.

client/src/main/java/com/microsoft/durabletask/TaskOrchestrationExecutor.java

@@ -146,6 +146,7 @@ private class ContextImplTask implements TaskOrchestrationContext {
         private boolean preserveUnprocessedEvents;
         private Object customStatus;
         private TraceContext parentTraceContext;
+        private ParentOrchestrationInstance parentInstance;
 
         // Entity integration state (Phase 4)
         private String executionId;
@@ -207,6 +208,12 @@ public String getInstanceId() {
             return this.instanceId;
         }
 
+        @Override
+        @Nullable
+        public ParentOrchestrationInstance getParent() {
+            return this.parentInstance;
+        }
+
         private void setInstanceId(String instanceId) {
             // TODO: Throw if instance ID is not null
             this.instanceId = instanceId;
@@ -1705,6 +1712,14 @@ private void processEvent(HistoryEvent e) {
                         } else {
                             this.parentTraceContext = null;
                         }
+                        if (startedEvent.hasParentInstance()) {
+                            ParentInstanceInfo parentInfo = startedEvent.getParentInstance();
+                            this.parentInstance = new ParentOrchestrationInstance(
+                                parentInfo.getName().getValue(),
+                                parentInfo.getOrchestrationInstance().getInstanceId());
+                        } else {
+                            this.parentInstance = null;
+                        }
                         TaskOrchestrationFactory factory = TaskOrchestrationExecutor.this.orchestrationFactories.get(name);
                         if (factory == null) {
                             // Try getting the default orchestrator