xiangfu0 commented on code in PR #16409:
URL: https://github.com/apache/pinot/pull/16409#discussion_r2424889583
##########
pinot-core/src/main/java/org/apache/pinot/core/executor/ThrottleOnCriticalHeapUsageExecutor.java:
##########
@@ -18,44 +18,491 @@
*/
package org.apache.pinot.spi.executor;
+import java.util.concurrent.BlockingQueue;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.LinkedBlockingQueue;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.function.BiConsumer;
+import java.util.function.LongSupplier;
import org.apache.pinot.spi.accounting.ThreadAccountant;
import org.apache.pinot.spi.exception.QueryErrorCode;
import org.apache.pinot.spi.query.QueryThreadContext;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
/**
- * An Executor that throttles task submission when the heap usage is critical.
+ * An Executor that queues tasks when the heap usage is critical instead of
rejecting them.
* Heap Usage level is obtained from {@link
ThreadAccountant#throttleQuerySubmission()}.
+ *
+ * Features:
+ * - Tasks are queued when heap usage is critical
+ * - Queued tasks are processed when heap usage drops below critical level
+ * - Configurable queue size and timeout (global default or per-task)
+ * - Background monitoring of heap usage to process queued tasks
*/
public class ThrottleOnCriticalHeapUsageExecutor extends
DecoratorExecutorService {
+ private static final Logger LOGGER =
LoggerFactory.getLogger(ThrottleOnCriticalHeapUsageExecutor.class);
+
+ // Default configuration values
+ // Defaults are kept near config in CommonConstants; no local defaults
needed here
+ private static final long LOG_THROTTLE_INTERVAL_MS = 30000; // Log queue
status every 30 seconds
+
+ private final BlockingQueue<QueuedTask<?>> _taskQueue;
+ private final int _maxQueueSize;
+ private final long _defaultQueueTimeoutMs;
+ private final ScheduledExecutorService _monitorExecutor;
+ private final AtomicBoolean _isShutdown = new AtomicBoolean(false);
+ private final AtomicInteger _queuedTaskCount = new AtomicInteger(0);
+ private final AtomicInteger _processedTaskCount = new AtomicInteger(0);
+ private final AtomicInteger _timedOutTaskCount = new AtomicInteger(0);
+ private final AtomicInteger _shutdownCanceledTaskCount = new
AtomicInteger(0);
+ private volatile long _lastQueueStatusLogTime = 0;
- public ThrottleOnCriticalHeapUsageExecutor(ExecutorService executorService) {
+ public ThrottleOnCriticalHeapUsageExecutor(ExecutorService executorService,
+ int maxQueueSize, long defaultQueueTimeoutMs, long monitorIntervalMs) {
super(executorService);
+ _maxQueueSize = maxQueueSize;
+ _defaultQueueTimeoutMs = defaultQueueTimeoutMs;
+ // Ensure a valid capacity for the backing queue even when queueing is
disabled (maxQueueSize == 0).
+ // We will not enqueue when maxQueueSize == 0, but a minimal non-zero
capacity avoids constructor exceptions.
+ _taskQueue = new LinkedBlockingQueue<>(Math.max(1, maxQueueSize));
+
+ // Create a single-threaded scheduler for monitoring heap usage
+ _monitorExecutor = Executors.newSingleThreadScheduledExecutor(r -> {
+ Thread t = new Thread(r, "throttle-heap-monitor");
+ t.setDaemon(true);
+ return t;
+ });
+
+ // Start the monitoring task
+ _monitorExecutor.scheduleWithFixedDelay(this::processQueuedTasks,
+ monitorIntervalMs, monitorIntervalMs, TimeUnit.MILLISECONDS);
+
+ LOGGER.info(
+ "ThrottleOnCriticalHeapUsageExecutor initialized with queue size: {},
default timeout: {}ms, "
+ + "monitor interval: {}ms (queueSize=0 => reject)", maxQueueSize,
defaultQueueTimeoutMs,
+ monitorIntervalMs);
}
- protected void checkTaskAllowed() {
- if (QueryThreadContext.get().getAccountant().throttleQuerySubmission()) {
- throw QueryErrorCode.SERVER_RESOURCE_LIMIT_EXCEEDED.asException("Tasks
throttled due to high heap usage.");
+ /**
+ * Check if a task should be queued due to critical heap usage
+ * @return true if the task should be queued, false if it can be executed
immediately
+ */
+ protected boolean shouldQueueTask() {
+ return QueryThreadContext.get().getAccountant().throttleQuerySubmission();
+ }
+
+ /**
+ * Process queued tasks when heap usage is below critical level
+ */
+ private void processQueuedTasks() {
+ if (_isShutdown.get()) {
+ return;
+ }
+
+ try {
+ int initialQueueSize = _taskQueue.size();
+ long currentTime = System.currentTimeMillis();
+
+ // Log queue size for monitoring if there are queued tasks (throttled to
prevent log flooding)
+ if (initialQueueSize > 0 && (currentTime - _lastQueueStatusLogTime) >
LOG_THROTTLE_INTERVAL_MS) {
+ LOGGER.info("Processing queued tasks. Current queue size: {}, Queued:
{}, Processed: {}, "
+ + "Timed out: {}, Shutdown canceled: {}",
+ initialQueueSize, _queuedTaskCount.get(),
_processedTaskCount.get(),
+ _timedOutTaskCount.get(), _shutdownCanceledTaskCount.get());
+ _lastQueueStatusLogTime = currentTime;
+ // Metrics are exported via ServerMetrics global gauges registered by
callers
+ }
+
+ // Process tasks while heap usage is not critical and queue is not empty
+ while (!shouldQueueTask() && !_taskQueue.isEmpty()) {
+ QueuedTask<?> queuedTask = _taskQueue.poll();
+ if (queuedTask != null) {
+ long queueTime = System.currentTimeMillis() -
queuedTask.getQueueTime();
+
+ if (queueTime > queuedTask.getTimeoutMs()) {
+ // Task has timed out in queue
+ queuedTask.timeout();
+ _timedOutTaskCount.incrementAndGet();
+ LOGGER.warn("Task timed out after {}ms in queue (timeout: {}ms)",
queueTime, queuedTask.getTimeoutMs());
+ } else {
+ // Submit the task for execution
+ try {
+ queuedTask.execute();
+ _processedTaskCount.incrementAndGet();
+ LOGGER.debug("Processed queued task after {}ms in queue",
queueTime);
+ } catch (Exception e) {
+ LOGGER.error("Error executing queued task", e);
+ queuedTask.fail(e);
+ }
+ }
+ }
+ }
+
+ // Log completion only for significant processing (5+ tasks) to avoid
log spam
+ int finalQueueSize = _taskQueue.size();
+ if (initialQueueSize > 0 && initialQueueSize != finalQueueSize) {
+ int processedThisCycle = initialQueueSize - finalQueueSize;
+ if (processedThisCycle >= 5) {
+ LOGGER.info("Completed processing cycle. Processed {} tasks,
remaining queue size: {}",
+ processedThisCycle, finalQueueSize);
+ } else {
+ LOGGER.debug("Completed processing cycle. Processed {} tasks,
remaining queue size: {}",
+ processedThisCycle, finalQueueSize);
+ }
+ }
+ } catch (Exception e) {
+ LOGGER.error("Error in processQueuedTasks", e);
}
}
@Override
protected <T> Callable<T> decorate(Callable<T> task) {
- checkTaskAllowed();
return () -> {
- checkTaskAllowed();
- return task.call();
+ if (shouldQueueTask()) {
+ if (_maxQueueSize == 0) {
+ throw QueryErrorCode.SERVER_RESOURCE_LIMIT_EXCEEDED.asException(
+ "Heap usage critical; rejecting task per configuration.");
+ }
+ // Queue the task if heap usage is critical
+ long timeoutMs = computePerTaskTimeoutMs(_defaultQueueTimeoutMs);
+ return queueCallableTask(task, timeoutMs);
+ } else {
+ // Execute immediately if heap usage is normal
+ return task.call();
+ }
};
}
@Override
protected Runnable decorate(Runnable task) {
- checkTaskAllowed();
return () -> {
- checkTaskAllowed();
- task.run();
+ if (shouldQueueTask()) {
+ if (_maxQueueSize == 0) {
+ throw QueryErrorCode.SERVER_RESOURCE_LIMIT_EXCEEDED.asException(
+ "Heap usage critical; rejecting task per configuration.");
+ }
+ // Queue the task if heap usage is critical
+ long timeoutMs = computePerTaskTimeoutMs(_defaultQueueTimeoutMs);
+ queueRunnableTask(task, timeoutMs);
+ } else {
+ // Execute immediately if heap usage is normal
+ task.run();
+ }
};
}
+
+ private long computePerTaskTimeoutMs(long configuredTimeoutMs) {
+ try {
+ if (QueryThreadContext.getIfAvailable() != null &&
QueryThreadContext.get().getExecutionContext() != null) {
+ long remaining =
QueryThreadContext.get().getExecutionContext().getPassiveDeadlineMs()
+ - System.currentTimeMillis();
+ if (remaining <= 0) {
+ return 0L;
+ }
+ // Do not wait in the queue longer than the query's remaining passive
deadline
+ return Math.min(configuredTimeoutMs, remaining);
+ }
+ } catch (Throwable t) {
+ // Be conservative and use configured timeout if context is not available
+ LOGGER.debug("Failed to compute per-task timeout from thread context;
using configured timeout.", t);
+ }
+ return configuredTimeoutMs;
+ }
+
+ /**
+ * Queue a callable task and wait for its execution
+ */
+ private <T> T queueCallableTask(Callable<T> task, long timeoutMs)
+ throws Exception {
+ QueuedCallableTask<T> queuedTask = new QueuedCallableTask<>(task,
timeoutMs);
+
+ if (!_taskQueue.offer(queuedTask)) {
+ // Queue is full
+ throw QueryErrorCode.SERVER_RESOURCE_LIMIT_EXCEEDED.asException(
+ "Task queue is full (size: " + _maxQueueSize + ") due to high heap
usage.");
+ }
+
+ _queuedTaskCount.incrementAndGet();
+ LOGGER.debug("Queued callable task, queue size: {}", _taskQueue.size());
+ // Metrics are exported via ServerMetrics global gauges registered by
callers
+
+ // Wait for the task to complete or timeout
+ return queuedTask.get(timeoutMs, TimeUnit.MILLISECONDS);
+ }
+
+ /**
+ * Queue a runnable task and wait for its execution
+ */
+ private void queueRunnableTask(Runnable task, long timeoutMs) {
+ QueuedRunnableTask queuedTask = new QueuedRunnableTask(task, timeoutMs);
+
+ if (!_taskQueue.offer(queuedTask)) {
+ // Queue is full
+ throw QueryErrorCode.SERVER_RESOURCE_LIMIT_EXCEEDED.asException(
+ "Task queue is full (size: " + _maxQueueSize + ") due to high heap
usage.");
+ }
+
+ _queuedTaskCount.incrementAndGet();
+ LOGGER.debug("Queued runnable task, queue size: {}", _taskQueue.size());
+ // Metrics are exported via ServerMetrics global gauges registered by
callers
+
+ try {
+ // Wait for the task to complete or timeout
+ queuedTask.get(timeoutMs, TimeUnit.MILLISECONDS);
+ } catch (Exception e) {
+ if (e.getCause() instanceof RuntimeException) {
+ throw (RuntimeException) e.getCause();
+ } else {
+ throw new RuntimeException("Error executing queued task", e);
+ }
+ }
+ }
+
+ @Override
+ public void shutdown() {
+ _isShutdown.set(true);
+ _monitorExecutor.shutdownNow();
+
+ // Allow the monitor thread to complete current processing
+ try {
+ if (!_monitorExecutor.awaitTermination(30, TimeUnit.SECONDS)) {
+ LOGGER.warn("Monitor executor did not terminate within the timeout
period.");
+ }
+ } catch (InterruptedException e) {
+ LOGGER.warn("Interrupted while waiting for monitor executor to
terminate.", e);
+ Thread.currentThread().interrupt();
+ }
+
+ // Cancel remaining tasks in the queue - fail them with shutdown exception
+ int remainingTasks = 0; // keep local counter for logging
+ while (!_taskQueue.isEmpty()) {
+ QueuedTask<?> task = _taskQueue.poll();
+ if (task != null) {
+ remainingTasks++;
+ task.fail(new IllegalStateException("Executor is shutting down"));
+ _shutdownCanceledTaskCount.incrementAndGet();
+ // Metrics are exported via ServerMetrics global gauges registered by
callers
+ }
+ }
+
+ super.shutdown();
+
+ LOGGER.info("ThrottleOnCriticalHeapUsageExecutor shutdown. Stats - Queued:
{}, Processed: {}, "
+ + "Timed out: {}, Shutdown canceled: {}, Remaining: {}",
+ _queuedTaskCount.get(), _processedTaskCount.get(),
_timedOutTaskCount.get(),
+ _shutdownCanceledTaskCount.get(), remainingTasks);
+ }
+
+ /**
+ * Get current queue size
+ */
+ public int getQueueSize() {
+ return _taskQueue.size();
+ }
+
+ /**
+ * Get total number of tasks queued
+ */
+ public int getQueuedTaskCount() {
+ return _queuedTaskCount.get();
+ }
+
+ /**
+ * Get total number of tasks processed from queue
+ */
+ public int getProcessedTaskCount() {
+ return _processedTaskCount.get();
+ }
+
+ /**
+ * Get total number of tasks that timed out in queue
+ */
+ public int getTimedOutTaskCount() {
+ return _timedOutTaskCount.get();
+ }
+
+ /**
+ * Get total number of tasks canceled during shutdown
+ */
+ public int getShutdownCanceledTaskCount() {
+ return _shutdownCanceledTaskCount.get();
+ }
+
+ /**
+ * Register gauges for this throttle executor using a provided registrar.
+ * The registrar should bind a gauge identified by its name (matching
ServerGauge enum names)
+ * to a {@link LongSupplier} that provides the metric value.
+ *
+ * This avoids introducing module dependencies from SPI to pinot-common's
metrics classes.
+ */
+ public static void
registerThrottleMetrics(ThrottleOnCriticalHeapUsageExecutor throttle,
+ BiConsumer<String, LongSupplier> gaugeRegistrar) {
+ gaugeRegistrar.accept("THROTTLE_EXECUTOR_QUEUE_SIZE", () -> (long)
throttle.getQueueSize());
+ gaugeRegistrar.accept("THROTTLE_EXECUTOR_QUEUED_TASKS_TOTAL", () -> (long)
throttle.getQueuedTaskCount());
+ gaugeRegistrar.accept("THROTTLE_EXECUTOR_PROCESSED_TASKS_TOTAL", () ->
(long) throttle.getProcessedTaskCount());
+ gaugeRegistrar.accept("THROTTLE_EXECUTOR_TIMED_OUT_TASKS_TOTAL", () ->
(long) throttle.getTimedOutTaskCount());
+ gaugeRegistrar.accept("THROTTLE_EXECUTOR_SHUTDOWN_CANCELED_TASKS_TOTAL",
+ () -> (long) throttle.getShutdownCanceledTaskCount());
+ }
+
+ /**
+ * Base class for queued tasks.
+ *
+ * <p>The {@code QueuedTask} class represents a task that can be queued for
execution when the system is under
+ * critical heap usage. It provides a common interface for handling task
execution, timeouts, and failures.</p>
+ *
+ * <p>Lifecycle:
+ * <ul>
+ * <li>Tasks are created and added to the queue when heap usage is
critical.</li>
+ * <li>When heap usage drops below the critical level, tasks are dequeued
and executed.</li>
+ * <li>If a task remains in the queue beyond a configured timeout, the
{@code timeout()} method is invoked.</li>
+ * <li>If an exception occurs during execution, the {@code fail(Exception
e)} method is invoked.</li>
+ * </ul>
+ * </p>
+ *
+ * <p>Thread-safety:
+ * <ul>
+ * <li>Instances of {@code QueuedTask} are not inherently thread-safe and
should be accessed in a thread-safe
+ * manner by the enclosing executor.</li>
+ * <li>The enclosing {@code ThrottleOnCriticalHeapUsageExecutor} ensures
proper synchronization when accessing
+ * and modifying the queue.</li>
+ * </ul>
+ * </p>
+ */
+ private abstract static class QueuedTask<T> {
+ private final long _queueTime;
+ private final long _timeoutMs;
+ private volatile T _result;
+ private volatile Exception _exception;
+ private volatile boolean _completed = false;
+ private final Object _lock = new Object();
Review Comment:
fail complete etc method calls are from different threads.
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