Minor Optimizations

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

@@ -37,6 +37,7 @@ public final class DurableTaskGrpcWorker implements AutoCloseable {
     private final ExecutorService workerPool;
 
     private final TaskHubSidecarServiceBlockingStub sidecarClient;
+    private final boolean isExecutorServiceManaged;
     private volatile boolean isNormalShutdown = false;
 
     DurableTaskGrpcWorker(DurableTaskGrpcWorkerBuilder builder) {
@@ -67,6 +68,7 @@ public final class DurableTaskGrpcWorker implements AutoCloseable {
         this.dataConverter = builder.dataConverter != null ? builder.dataConverter : new JacksonDataConverter();
         this.maximumTimerInterval = builder.maximumTimerInterval != null ? builder.maximumTimerInterval : DEFAULT_MAXIMUM_TIMER_INTERVAL;
         this.workerPool = builder.executorService != null ? builder.executorService : Executors.newCachedThreadPool();
+        this.isExecutorServiceManaged = builder.executorService == null;
     }
 
     /**
@@ -81,10 +83,10 @@ public void start() {
     }
 
     /**
-     * Closes the internally managed gRPC channel, if one exists.
+     * Closes the internally managed gRPC channel and executor service, if one exists.
      * <p>
-     * This method is a no-op if this client object was created using a builder with a gRPC channel object explicitly
-     * configured.
+     * Only the internally managed GRPC Channel and Executor services are closed. If any of them are supplied,
+     * it is the responsibility of the supplier to take care of them.
      */
     public void close() {
         this.isNormalShutdown = true;
@@ -116,7 +118,7 @@ public void startAndBlock() {
                 logger);
 
         // TODO: How do we interrupt manually?
-        while (!this.workerPool.isShutdown()) {
+        while (true) {
             try {
                 GetWorkItemsRequest getWorkItemsRequest = GetWorkItemsRequest.newBuilder().build();
                 Iterator<WorkItem> workItemStream = this.sidecarClient.getWorkItems(getWorkItemsRequest);
@@ -236,17 +238,19 @@ private void closeSideCarChannel() {
     }
 
     private void shutDownWorkerPool() {
-        if (!this.isNormalShutdown) {
-            logger.log(Level.WARNING, "ExecutorService shutdown initiated unexpectedly. No new tasks will be accepted");
-        }
+        if (this.isExecutorServiceManaged) {
+            if (!this.isNormalShutdown) {
+                logger.log(Level.WARNING, "ExecutorService shutdown initiated unexpectedly. No new tasks will be accepted");
+            }
 
-        this.workerPool.shutdown();
-        try {
-            if (!this.workerPool.awaitTermination(60, TimeUnit.SECONDS)) {
-                this.workerPool.shutdownNow();
+            this.workerPool.shutdown();
+            try {
+                if (!this.workerPool.awaitTermination(60, TimeUnit.SECONDS)) {
+                    this.workerPool.shutdownNow();
+                }
+            } catch (InterruptedException ex) {
+                Thread.currentThread().interrupt();
             }
-        } catch (InterruptedException ex) {
-            Thread.currentThread().interrupt();
         }
     }