Support Workflow.getInfo from query method body

Author: Quinn-With-Two-Ns

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

@@ -2,6 +2,7 @@
 
 import io.temporal.internal.worker.WorkflowExecutorCache;
 import io.temporal.workflow.CancellationScope;
+import java.util.Optional;
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 
@@ -90,4 +91,17 @@ static DeterministicRunner newRunner(
   /** Creates a new instance of a workflow callback thread. */
   @Nonnull
   WorkflowThread newCallbackThread(Runnable runnable, @Nullable String name);
+
+  /**
+   * Retrieve data from runner locals. Returns 1. not found (an empty Optional) 2. found but null
+   * (an Optional of an empty Optional) 3. found and non-null (an Optional of an Optional of a
+   * value). The type nesting is because Java Optionals cannot understand "Some null" vs "None",
+   * which is exactly what we need here.
+   *
+   * @param key
+   * @return one of three cases
+   * @param <T>
+   */
+  @SuppressWarnings("unchecked")
+  <T> Optional<Optional<T>> getRunnerLocal(RunnerLocalInternal<T> key);
 }

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

@@ -586,7 +586,7 @@ private boolean areThreadsToBeExecuted() {
    * @param <T>
    */
   @SuppressWarnings("unchecked")
-  <T> Optional<Optional<T>> getRunnerLocal(RunnerLocalInternal<T> key) {
+  public <T> Optional<Optional<T>> getRunnerLocal(RunnerLocalInternal<T> key) {
     if (!runnerLocalMap.containsKey(key)) {
       return Optional.empty();
     }

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

@@ -23,11 +23,33 @@ class QueryDispatcher {
 
   private DynamicQueryHandler dynamicQueryHandler;
   private WorkflowInboundCallsInterceptor inboundCallsInterceptor;
+  private static final ThreadLocal<SyncWorkflowContext> queryHandlerWorkflowContext =
+      new ThreadLocal<>();
 
   public QueryDispatcher(DataConverter dataConverterWithWorkflowContext) {
     this.dataConverterWithWorkflowContext = dataConverterWithWorkflowContext;
   }
 
+  /**
+   * @return True if the current thread is executing a query handler.
+   */
+  public static boolean isQueryHandler() {
+    SyncWorkflowContext value = queryHandlerWorkflowContext.get();
+    return value != null;
+  }
+
+  /**
+   * @return The current workflow context if the current thread is executing a query handler.
+   * @throws IllegalStateException if not in a query handler.
+   */
+  public static SyncWorkflowContext getWorkflowContext() {
+    SyncWorkflowContext value = queryHandlerWorkflowContext.get();
+    if (value == null) {
+      throw new IllegalStateException("Not in a query handler");
+    }
+    return value;
+  }
+
   public void setInboundCallsInterceptor(WorkflowInboundCallsInterceptor inboundCallsInterceptor) {
     this.inboundCallsInterceptor = inboundCallsInterceptor;
   }
@@ -51,7 +73,11 @@ public WorkflowInboundCallsInterceptor.QueryOutput handleInterceptedQuery(
     return new WorkflowInboundCallsInterceptor.QueryOutput(result);
   }
 
-  public Optional<Payloads> handleQuery(String queryName, Header header, Optional<Payloads> input) {
+  public Optional<Payloads> handleQuery(
+      SyncWorkflowContext replayContext,
+      String queryName,
+      Header header,
+      Optional<Payloads> input) {
     WorkflowOutboundCallsInterceptor.RegisterQueryInput handler = queryCallbacks.get(queryName);
     Object[] args;
     if (queryName.startsWith(TEMPORAL_RESERVED_PREFIX)) {
@@ -69,11 +95,18 @@ public Optional<Payloads> handleQuery(String queryName, Header header, Optional<
           dataConverterWithWorkflowContext.fromPayloads(
               input, handler.getArgTypes(), handler.getGenericArgTypes());
     }
-    Object result =
-        inboundCallsInterceptor
-            .handleQuery(new WorkflowInboundCallsInterceptor.QueryInput(queryName, header, args))
-            .getResult();
-    return dataConverterWithWorkflowContext.toPayloads(result);
+    try {
+      replayContext.setReadOnly(true);
+      queryHandlerWorkflowContext.set(replayContext);
+      Object result =
+          inboundCallsInterceptor
+              .handleQuery(new WorkflowInboundCallsInterceptor.QueryInput(queryName, header, args))
+              .getResult();
+      return dataConverterWithWorkflowContext.toPayloads(result);
+    } finally {
+      replayContext.setReadOnly(false);
+      queryHandlerWorkflowContext.set(null);
+    }
   }
 
   public void registerQueryHandlers(WorkflowOutboundCallsInterceptor.RegisterQueryInput request) {

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

@@ -16,8 +16,15 @@ public RunnerLocalInternal(boolean useCaching) {
   }
 
   public T get(Supplier<? extends T> supplier) {
-    Optional<Optional<T>> result =
-        DeterministicRunnerImpl.currentThreadInternal().getRunner().getRunnerLocal(this);
+    Optional<Optional<T>> result;
+    // Query handlers are special in that they are executing in a different context
+    // than the main workflow execution threads. We need to fetch the runner local from the
+    // correct context based on whether we are in a query handler or not.
+    if (QueryDispatcher.isQueryHandler()) {
+      result = QueryDispatcher.getWorkflowContext().getRunner().getRunnerLocal(this);
+    } else {
+      result = DeterministicRunnerImpl.currentThreadInternal().getRunner().getRunnerLocal(this);
+    }
     T out = result.orElseGet(() -> Optional.ofNullable(supplier.get())).orElse(null);
     if (!result.isPresent() && useCaching) {
       // This is the first time we've tried fetching this, and caching is enabled. Store it.

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

@@ -349,7 +349,7 @@ public WorkflowInboundCallsInterceptor.QueryOutput handleInterceptedQuery(
   }
 
   public Optional<Payloads> handleQuery(String queryName, Header header, Optional<Payloads> input) {
-    return queryDispatcher.handleQuery(queryName, header, input);
+    return queryDispatcher.handleQuery(this, queryName, header, input);
   }
 
   public boolean isEveryHandlerFinished() {

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

@@ -843,6 +843,12 @@ static WorkflowOutboundCallsInterceptor getWorkflowOutboundInterceptor() {
   }
 
   static SyncWorkflowContext getRootWorkflowContext() {
+    // If we are in a query handler, we need to get the workflow context from the
+    // QueryDispatcher, otherwise we get it from the current thread's internal context.
+    // This is necessary because query handlers run in a different context than the main workflow threads.
+    if (QueryDispatcher.isQueryHandler()) {
+      return QueryDispatcher.getWorkflowContext();
+    }
     return DeterministicRunnerImpl.currentThreadInternal().getWorkflowContext();
   }
 

temporal-sdk/src/test/java/io/temporal/internal/sync/QueryDispatcherTest.java

@@ -49,7 +49,7 @@ public void testQuerySuccess() {
 
     // Invoke functionality under test, expect no exceptions for an existing query.
     Optional<Payloads> queryResult =
-        dispatcher.handleQuery("QueryB", Header.empty(), Optional.empty());
+        dispatcher.handleQuery(null, "QueryB", Header.empty(), Optional.empty());
     assertTrue(queryResult.isPresent());
   }
 
@@ -61,7 +61,7 @@ public void testQueryDispatcherException() {
         assertThrows(
             IllegalArgumentException.class,
             () -> {
-              dispatcher.handleQuery("QueryC", Header.empty(), null);
+              dispatcher.handleQuery(null, "QueryC", Header.empty(), null);
             });
     assertEquals("Unknown query type: QueryC, knownTypes=[QueryA, QueryB]", exception.getMessage());
   }