mxm commented on code in PR #15312:
URL: https://github.com/apache/iceberg/pull/15312#discussion_r2841704066
##########
core/src/main/java/org/apache/iceberg/util/ThreadPools.java:
##########
@@ -149,8 +166,98 @@ public static ExecutorService newWorkerPool(String
namePrefix, int poolSize) {
* that should be automatically cleaned up on JVM shutdown.
*/
public static ExecutorService newExitingWorkerPool(String namePrefix, int
poolSize) {
- return MoreExecutors.getExitingExecutorService(
- (ThreadPoolExecutor) newFixedThreadPool(namePrefix, poolSize));
+ ExecutorService service =
+ Executors.unconfigurableExecutorService(newFixedThreadPool(namePrefix,
poolSize));
+ THREAD_POOLS_TO_SHUTDOWN.add(service);
+ return service;
+ }
+
+ /**
+ * Force manual shutdown of the thread pools created via the {@link
#newExitingWorkerPool(String,
+ * int)}.
+ *
+ * <p>This method allows: (1) to stop thread pools manually, to avoid leaks
in hot-reload
+ * environments; (2) opt-out of the standard shutdown mechanism to manage
graceful service stops
+ * (and commit the last pending files, if the client application needs to
react to shutdown hooks
+ * on its own).
+ *
+ * <p>Please only call this method at the end of the intended usage of the
library, and NEVER
+ * before, as this method will stop thread pools required for normal library
workflows.
+ */
+ public static void shutdownThreadPools() {
+ removeShutdownHook();
+ long startTime = System.nanoTime();
+ ExecutorService item;
+ Queue<ExecutorService> pendingShutdown = new ArrayDeque<>();
+ while ((item = THREAD_POOLS_TO_SHUTDOWN.poll()) != null) {
+ item.shutdown();
+ pendingShutdown.add(item);
+ }
+ while ((item = pendingShutdown.poll()) != null) {
+ long timeElapsed = System.nanoTime() - startTime;
+ long remainingTime = SHUTDOWN_TIMEOUT.toNanos() - timeElapsed;
+ if (remainingTime > 0) {
+ try {
+ if (!item.awaitTermination(remainingTime, TimeUnit.NANOSECONDS)) {
+ item.shutdownNow();
+ }
+ } catch (InterruptedException ignored) {
+ // We're shutting down anyway, so just ignore.
+ }
+ } else {
+ item.shutdownNow();
+ }
+ }
+ }
+
+ /**
+ * Initialize a shutdown hook to stop the thread pools created via the {@link
+ * #newExitingWorkerPool(String, int)}.
+ */
+ @SuppressWarnings("ShutdownHook")
+ private static void initShutdownHook() {
+ if (shutdownHook == null) {
+ shutdownHook =
+ Executors.defaultThreadFactory()
+ .newThread(
+ new Runnable() {
+ @Override
+ public void run() {
+ shutdownHook = null;
+ shutdownThreadPools();
+ }
+ });
+
+ try {
+ shutdownHook.setName("DelayedShutdownHook-iceberg");
+ } catch (SecurityException e) {
+ LOG.warn("Cannot set thread name for the shutdown hook", e);
+ }
+
+ try {
+ Runtime.getRuntime().addShutdownHook(shutdownHook);
+ } catch (SecurityException e) {
+ LOG.warn("Cannot install a shutdown hook for thread pools clean up",
e);
+ }
+ }
+ }
+
+ /**
+ * Stop the shutdown hook for the thread pools created via the {@link
+ * #newExitingWorkerPool(String, int)}.
+ *
+ * <p>Thread pools can still be stopped manually via the {@link
#shutdownThreadPools()} method.
+ */
+ @SuppressWarnings("ShutdownHook")
+ public static void removeShutdownHook() {
+ if (shutdownHook != null) {
+ try {
+ Runtime.getRuntime().removeShutdownHook(shutdownHook);
+ } catch (SecurityException e) {
+ LOG.warn("Cannot remove the shutdown hook for thread pools clean up",
e);
+ }
+ shutdownHook = null;
Review Comment:
This is not safe when called concurrently and can produce
`NullPointerException` when removing the shutdown hook if two threads execute
this at the same time.
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