fix: address PR review — skip retry sleep on shutdown, add tests

- Capture workerThread in startAndBlock() so close() can interrupt
  the thread even when startAndBlock() is called directly (not via
  start()), fixing the case where the 5s sleep blocks shutdown.
- Add isNormalShutdown guard before the retry sleep so any exception
  code (UNAVAILABLE, CANCELLED, etc.) exits promptly during shutdown.
- Add DurableTaskGrpcWorkerShutdownTest with 3 scenarios:
  - start() + close() terminates the worker thread promptly
  - startAndBlock() on a separate thread exits on close()
  - startAndBlock() exits on thread interrupt

Signed-off-by: Javier Aliaga <javier@diagrid.io>

Author: javier-aliaga

durabletask-client/src/main/java/io/dapr/durabletask/DurableTaskGrpcWorker.java

@@ -158,6 +158,7 @@ public void close() {
    * interrupt signal.</p>
    */
   public void startAndBlock() {
+    this.workerThread = Thread.currentThread();
     logger.log(Level.INFO, "Durable Task worker is connecting to sidecar at {0}.", this.getSidecarAddress());
 
     TaskOrchestrationExecutor taskOrchestrationExecutor = new TaskOrchestrationExecutor(
@@ -218,6 +219,10 @@ public void startAndBlock() {
               String.format("Unexpected failure connecting to %s", this.getSidecarAddress()), e);
         }
 
+        if (this.isNormalShutdown) {
+          break;
+        }
+
         // Retry after 5 seconds
         try {
           Thread.sleep(5000);

durabletask-client/src/test/java/io/dapr/durabletask/DurableTaskGrpcWorkerShutdownTest.java

@@ -0,0 +1,128 @@
+/*
+ * Copyright 2025 The Dapr Authors
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file 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.dapr.durabletask;
+
+import io.grpc.ManagedChannel;
+import io.grpc.ManagedChannelBuilder;
+import org.junit.jupiter.api.Test;
+
+import java.time.Duration;
+import java.time.Instant;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+/**
+ * Unit tests for DurableTaskGrpcWorker shutdown behavior.
+ */
+public class DurableTaskGrpcWorkerShutdownTest {
+
+  /**
+   * Verifies that calling close() on a worker that was started via start()
+   * causes the worker thread to terminate promptly (within a bounded time),
+   * rather than hanging in the retry loop.
+   */
+  @Test
+  void workerThreadTerminatesPromptlyOnClose() throws Exception {
+    // Use an arbitrary port where no sidecar is running — the worker will
+    // enter the retry loop (UNAVAILABLE → sleep 5s → retry).
+    DurableTaskGrpcWorker worker = new DurableTaskGrpcWorkerBuilder()
+        .port(19876)
+        .build();
+
+    worker.start();
+
+    // Give the worker thread time to enter the retry loop
+    Thread.sleep(500);
+
+    Instant before = Instant.now();
+    worker.close();
+
+    // Wait for the worker thread to finish — the join is bounded so the
+    // test doesn't hang if the fix regresses.
+    Thread workerThread = getWorkerThread(worker);
+    if (workerThread != null) {
+      workerThread.join(Duration.ofSeconds(3).toMillis());
+      assertFalse(workerThread.isAlive(),
+          "Worker thread should have terminated after close()");
+    }
+
+    Duration elapsed = Duration.between(before, Instant.now());
+    assertTrue(elapsed.toMillis() < 3000,
+        "close() should return promptly, but took " + elapsed.toMillis() + "ms");
+  }
+
+  /**
+   * Verifies that calling close() on a worker that was started via
+   * startAndBlock() on a separate thread terminates that thread promptly.
+   */
+  @Test
+  void startAndBlockExitsOnClose() throws Exception {
+    DurableTaskGrpcWorker worker = new DurableTaskGrpcWorkerBuilder()
+        .port(19877)
+        .build();
+
+    Thread blockingThread = new Thread(worker::startAndBlock);
+    blockingThread.start();
+
+    // Give the blocking thread time to enter the retry loop
+    Thread.sleep(500);
+
+    Instant before = Instant.now();
+    worker.close();
+
+    blockingThread.join(Duration.ofSeconds(3).toMillis());
+    assertFalse(blockingThread.isAlive(),
+        "startAndBlock() thread should have terminated after close()");
+
+    Duration elapsed = Duration.between(before, Instant.now());
+    assertTrue(elapsed.toMillis() < 3000,
+        "close() should terminate startAndBlock() promptly, but took " + elapsed.toMillis() + "ms");
+  }
+
+  /**
+   * Verifies that interrupting the thread running startAndBlock() causes it
+   * to exit and preserves the interrupt status.
+   */
+  @Test
+  void startAndBlockExitsOnInterrupt() throws Exception {
+    DurableTaskGrpcWorker worker = new DurableTaskGrpcWorkerBuilder()
+        .port(19878)
+        .build();
+
+    Thread blockingThread = new Thread(worker::startAndBlock);
+    blockingThread.start();
+
+    // Give the blocking thread time to enter the retry loop
+    Thread.sleep(500);
+
+    blockingThread.interrupt();
+    blockingThread.join(Duration.ofSeconds(3).toMillis());
+
+    assertFalse(blockingThread.isAlive(),
+        "startAndBlock() thread should have exited after interrupt");
+
+    worker.close();
+  }
+
+  private Thread getWorkerThread(DurableTaskGrpcWorker worker) {
+    try {
+      java.lang.reflect.Field f = DurableTaskGrpcWorker.class.getDeclaredField("workerThread");
+      f.setAccessible(true);
+      return (Thread) f.get(worker);
+    } catch (Exception e) {
+      return null;
+    }
+  }
+}