Added thread factory so we can set thread-name on (for example) pub-sub worker threads (#536)

Author: j256

gax/src/main/java/com/google/api/gax/core/InstantiatingExecutorProvider.java

@@ -33,6 +33,7 @@
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.ScheduledThreadPoolExecutor;
 import java.util.concurrent.ThreadFactory;
+import java.util.concurrent.atomic.AtomicInteger;
 
 /**
  * InstantiatingChannelProvider is an ExecutorProvider which constructs a new
@@ -42,22 +43,26 @@
 public abstract class InstantiatingExecutorProvider implements ExecutorProvider {
   // The number of threads to use with the default executor.
   private static final int DEFAULT_EXECUTOR_THREADS = 4;
+  // Thread factory to use to create our worker threads
+  private static final ThreadFactory DEFAULT_THREAD_FACTORY =
+      new ThreadFactory() {
+        private final AtomicInteger threadCount = new AtomicInteger();
+
+        @Override
+        public Thread newThread(Runnable runnable) {
+          Thread thread = new Thread(runnable);
+          thread.setName("Gax-" + threadCount.incrementAndGet());
+          thread.setDaemon(true);
+          return thread;
+        }
+      };
 
   // Package-private constructor prevents others from subclassing.
   InstantiatingExecutorProvider() {}
 
   @Override
   public ScheduledExecutorService getExecutor() {
-    return new ScheduledThreadPoolExecutor(
-        getExecutorThreadCount(),
-        new ThreadFactory() {
-          @Override
-          public Thread newThread(Runnable r) {
-            Thread t = new Thread(r);
-            t.setDaemon(true);
-            return t;
-          }
-        });
+    return new ScheduledThreadPoolExecutor(getExecutorThreadCount(), getThreadFactory());
   }
 
   @Override
@@ -68,13 +73,17 @@ public boolean shouldAutoClose() {
   /** The number of threads used by the executor created by this ExecutorProvider. */
   public abstract int getExecutorThreadCount();
 
+  /** Return a thread-factory to create gax processing threads so we can name them appropriately */
+  public abstract ThreadFactory getThreadFactory();
+
   public Builder toBuilder() {
     return new AutoValue_InstantiatingExecutorProvider.Builder(this);
   }
 
   public static Builder newBuilder() {
     return new AutoValue_InstantiatingExecutorProvider.Builder()
-        .setExecutorThreadCount(DEFAULT_EXECUTOR_THREADS);
+        .setExecutorThreadCount(DEFAULT_EXECUTOR_THREADS)
+        .setThreadFactory(DEFAULT_THREAD_FACTORY);
   }
 
   @AutoValue.Builder
@@ -83,6 +92,10 @@ public abstract static class Builder {
 
     public abstract int getExecutorThreadCount();
 
+    public abstract Builder setThreadFactory(ThreadFactory value);
+
+    public abstract ThreadFactory getThreadFactory();
+
     public abstract InstantiatingExecutorProvider build();
   }
 }