fix java UT about multi-threading (#8014)

java/test/src/main/java/io/ray/api/test/MultiThreadingTest.java

@@ -136,10 +136,13 @@ public class MultiThreadingTest extends BaseTest {
     Assert.assertEquals(actorId, actorIdTester.getId());
   }
 
-  static boolean testMissingWrapRunnable() throws InterruptedException {
+  /**
+   * Call this method each time to avoid hitting the cache in {@link RayObject#get()}.
+   */
+  static Runnable[] generateRunnables() {
     final RayObject<Integer> fooObject = Ray.put(1);
     final RayActor<Echo> fooActor = Ray.createActor(Echo::new);
-    final Runnable[] runnables = new Runnable[]{
+    return new Runnable[]{
         () -> Ray.put(1),
         () -> Ray.get(fooObject.getId(), fooObject.getType()),
         fooObject::get,
@@ -149,58 +152,72 @@ public class MultiThreadingTest extends BaseTest {
         () -> Ray.createActor(Echo::new),
         () -> fooActor.call(Echo::echo, 1),
     };
+  }
 
-    // It's OK to run them in main thread.
-    for (Runnable runnable : runnables) {
-      runnable.run();
-    }
-
-    Exception[] exception = new Exception[1];
-
-    Thread thread = new Thread(Ray.wrapRunnable(() -> {
-      try {
-        // It would be OK to run them in another thread if wrapped the runnable.
-        for (Runnable runnable : runnables) {
-          runnable.run();
-        }
-      } catch (Exception ex) {
-        exception[0] = ex;
+  static boolean testMissingWrapRunnable() throws InterruptedException {
+    {
+      Runnable[] runnables = generateRunnables();
+      // It's OK to run them in main thread.
+      for (Runnable runnable : runnables) {
+        runnable.run();
       }
-    }));
-    thread.start();
-    thread.join();
-    if (exception[0] != null) {
-      throw new RuntimeException("Exception occurred in thread.", exception[0]);
     }
 
-    thread = new Thread(() -> {
-      try {
-        // It wouldn't be OK to run them in another thread if not wrapped the runnable.
-        for (Runnable runnable : runnables) {
-          Assert.expectThrows(RayException.class, runnable::run);
+    Throwable[] throwable = new Throwable[1];
+
+    {
+      Runnable[] runnables = generateRunnables();
+      Thread thread = new Thread(Ray.wrapRunnable(() -> {
+        try {
+          // It would be OK to run them in another thread if wrapped the runnable.
+          for (Runnable runnable : runnables) {
+            runnable.run();
+          }
+        } catch (Throwable ex) {
+          throwable[0] = ex;
         }
-      } catch (Exception ex) {
-        exception[0] = ex;
+      }));
+      thread.start();
+      thread.join();
+      if (throwable[0] != null) {
+        throw new RuntimeException("Exception occurred in thread.", throwable[0]);
       }
-    });
-    thread.start();
-    thread.join();
-    if (exception[0] != null) {
-      throw new RuntimeException("Exception occurred in thread.", exception[0]);
     }
 
-    Runnable[] wrappedRunnables = new Runnable[runnables.length];
-    for (int i = 0; i < runnables.length; i++) {
-      wrappedRunnables[i] = Ray.wrapRunnable(runnables[i]);
-    }
-    // It would be OK to run the wrapped runnables in the current thread.
-    for (Runnable runnable : wrappedRunnables) {
-      runnable.run();
+    {
+      Runnable[] runnables = generateRunnables();
+      Thread thread = new Thread(() -> {
+        try {
+          // It wouldn't be OK to run them in another thread if not wrapped the runnable.
+          for (Runnable runnable : runnables) {
+            Assert.expectThrows(RayException.class, runnable::run);
+          }
+        } catch (Throwable ex) {
+          throwable[0] = ex;
+        }
+      });
+      thread.start();
+      thread.join();
+      if (throwable[0] != null) {
+        throw new RuntimeException("Exception occurred in thread.", throwable[0]);
+      }
     }
 
-    // It would be OK to invoke Ray APIs after executing a wrapped runnable in the current thread.
-    wrappedRunnables[0].run();
-    runnables[0].run();
+    {
+      Runnable[] runnables = generateRunnables();
+      Runnable[] wrappedRunnables = new Runnable[runnables.length];
+      for (int i = 0; i < runnables.length; i++) {
+        wrappedRunnables[i] = Ray.wrapRunnable(runnables[i]);
+      }
+      // It would be OK to run the wrapped runnables in the current thread.
+      for (Runnable runnable : wrappedRunnables) {
+        runnable.run();
+      }
+
+      // It would be OK to invoke Ray APIs after executing a wrapped runnable in the current thread.
+      wrappedRunnables[0].run();
+      runnables[0].run();
+    }
 
     // Return true here to make the Ray.call returns an RayObject.
     return true;
@@ -219,19 +236,19 @@ public class MultiThreadingTest extends BaseTest {
   @Test
   public void testGetAndSetAsyncContext() throws InterruptedException {
     Object asyncContext = Ray.getAsyncContext();
-    Exception[] exception = new Exception[1];
+    Throwable[] throwable = new Throwable[1];
     Thread thread = new Thread(() -> {
       try {
         Ray.setAsyncContext(asyncContext);
         Ray.put(1);
-      } catch (Exception ex) {
-        exception[0] = ex;
+      } catch (Throwable ex) {
+        throwable[0] = ex;
       }
     });
     thread.start();
     thread.join();
-    if (exception[0] != null) {
-      throw new RuntimeException("Exception occurred in thread.", exception[0]);
+    if (throwable[0] != null) {
+      throw new RuntimeException("Exception occurred in thread.", throwable[0]);
     }
   }