GrpcUtilPatchThreadFactories.java

public class GrpcUtilPatchThreadFactories {

	public static void patch() {

		Resource<ExecutorService> SHARED_CHANNEL_EXECUTOR = new Resource<ExecutorService>() {
			private static final String NAME = "grpc-default-executor";

			@Override
			public ExecutorService create() {
				return Executors.newCachedThreadPool(getThreadFactory(NAME + "-%d", true));
			}

			@Override
			public void close(ExecutorService instance) {
				instance.shutdown();
			}

			@Override
			public String toString() {
				return NAME;
			}
		};

		Resource<ScheduledExecutorService> TIMER_SERVICE = new Resource<ScheduledExecutorService>() {
			@Override
			public ScheduledExecutorService create() {
				// We don't use newSingleThreadScheduledExecutor because it doesn't return a
				// ScheduledThreadPoolExecutor.
				ScheduledExecutorService service = Executors.newScheduledThreadPool(1,
						getThreadFactory("grpc-timer-%d", true));

				// If there are long timeouts that are cancelled, they will not actually be
				// removed from
				// the executors queue. This forces immediate removal upon cancellation to avoid
				// a
				// memory leak. Reflection is used because we cannot use methods added in Java
				// 1.7. If
				// the method does not exist, we give up. Note that the method is not present in
				// 1.6, but
				// _is_ present in the android standard library.
				try {
					Method method = service.getClass().getMethod("setRemoveOnCancelPolicy", boolean.class);
					method.invoke(service, true);
				} catch (NoSuchMethodException e) {
					// no op
				} catch (RuntimeException e) {
					throw e;
				} catch (Exception e) {
					throw new RuntimeException(e);
				}

				return service;
			}

			@Override
			public void close(ScheduledExecutorService instance) {
				instance.shutdown();
			}
		};

		try {
			Field f = GrpcUtil.class.getDeclaredField("SHARED_CHANNEL_EXECUTOR");
			f.setAccessible(true);

			Field modifiersField = Field.class.getDeclaredField("modifiers");
			modifiersField.setAccessible(true);
			modifiersField.setInt(f, f.getModifiers() & ~Modifier.FINAL);

			f.set(null, SHARED_CHANNEL_EXECUTOR);
		} catch (NoSuchFieldException | SecurityException | IllegalArgumentException | IllegalAccessException e) {
			throw Throwables.propagate(e);
		}

		try {
			Field f = GrpcUtil.class.getDeclaredField("TIMER_SERVICE");
			f.setAccessible(true);

			Field modifiersField = Field.class.getDeclaredField("modifiers");
			modifiersField.setAccessible(true);
			modifiersField.setInt(f, f.getModifiers() & ~Modifier.FINAL);

			f.set(null, TIMER_SERVICE);
		} catch (NoSuchFieldException | SecurityException | IllegalArgumentException | IllegalAccessException e) {
			throw Throwables.propagate(e);
		}
	}

	private static ThreadFactory getThreadFactory(String nameFormat, boolean daemon) {
		return new ThreadFactoryBuilder().setThreadFactory(Executors.defaultThreadFactory()).setDaemon(daemon)
				.setNameFormat(nameFormat).build();
	}

}