kfaraz commented on code in PR #14293:
URL: https://github.com/apache/druid/pull/14293#discussion_r1195888479
##########
indexing-service/src/main/java/org/apache/druid/indexing/overlord/TaskQueue.java:
##########
@@ -156,314 +153,248 @@ public TaskQueue(
this.emitter = Preconditions.checkNotNull(emitter, "emitter");
}
- @VisibleForTesting
- void setActive(boolean active)
- {
- this.active = active;
- }
-
/**
* Starts this task queue. Allows {@link #add(Task)} to accept new tasks.
*/
@LifecycleStart
- public void start()
+ public synchronized void start()
{
- giant.lock();
-
- try {
- Preconditions.checkState(!active, "queue must be stopped");
- active = true;
- syncFromStorage();
- // Mark these tasks as failed as they could not reacuire the lock
- // Clean up needs to happen after tasks have been synced from storage
- Set<Task> tasksToFail = taskLockbox.syncFromStorage().getTasksToFail();
- for (Task task : tasksToFail) {
- shutdown(task.getId(),
- "Shutting down forcefully as task failed to reacquire lock
while becoming leader");
+ Preconditions.checkState(!active, "queue must be stopped");
+
+ // Mark queue as active only after first sync is complete
+ syncFromStorage();
+ active = true;
+
+ // Mark these tasks as failed as they could not reacquire locks
+ Set<Task> tasksToFail = taskLockbox.syncFromStorage().getTasksToFail();
+ for (Task task : tasksToFail) {
+ shutdown(
+ task.getId(),
+ "Shutting down forcefully as task failed to reacquire lock while
becoming leader"
+ );
+ }
+ requestManagement();
+ // Remove any unacquired locks from storage (shutdown only clears entries
for which a TaskLockPosse was acquired)
+ // This is called after requesting management as locks need to be cleared
after notifyStatus is processed
+ for (Task task : tasksToFail) {
+ for (TaskLock lock : taskStorage.getLocks(task.getId())) {
+ taskStorage.removeLock(task.getId(), lock);
}
- managerExec.submit(
- new Runnable()
- {
- @Override
- public void run()
- {
- while (true) {
- try {
- manage();
- break;
- }
- catch (InterruptedException e) {
- log.info("Interrupted, exiting!");
- break;
- }
- catch (Exception e) {
- final long restartDelay =
config.getRestartDelay().getMillis();
- log.makeAlert(e, "Failed to manage").addData("restartDelay",
restartDelay).emit();
- try {
- Thread.sleep(restartDelay);
- }
- catch (InterruptedException e2) {
- log.info("Interrupted, exiting!");
- break;
- }
- }
- }
+ }
+ log.info("Cleaned up [%d] tasks which failed to reacquire locks.",
tasksToFail.size());
+
+ // Submit task management job
+ managerExec.submit(
+ () -> {
+ log.info("Beginning task management in [%s].",
config.getStartDelay());
+ long startDelayMillis = config.getStartDelay().getMillis();
+ while (active) {
+ try {
+ Thread.sleep(startDelayMillis);
+ runTaskManagement();
+ }
+ catch (InterruptedException e) {
+ log.info("Interrupted, stopping task management.");
+ break;
+ }
+ catch (Exception e) {
+ startDelayMillis = config.getRestartDelay().getMillis();
+ log.makeAlert(e, "Failed to manage").addData("restartDelay",
startDelayMillis).emit();
}
}
- );
- ScheduledExecutors.scheduleAtFixedRate(
- storageSyncExec,
- config.getStorageSyncRate(),
- new Callable<ScheduledExecutors.Signal>()
- {
- @Override
- public ScheduledExecutors.Signal call()
- {
- try {
- syncFromStorage();
- }
- catch (Exception e) {
- if (active) {
- log.makeAlert(e, "Failed to sync with storage").emit();
- }
- }
- if (active) {
- return ScheduledExecutors.Signal.REPEAT;
- } else {
- return ScheduledExecutors.Signal.STOP;
- }
+ }
+ );
+
+ // Schedule storage sync job
+ ScheduledExecutors.scheduleAtFixedRate(
+ storageSyncExec,
+ config.getStorageSyncRate(),
+ () -> {
+ if (!active) {
+ log.info("Stopping storage sync as TaskQueue has been stopped");
+ return ScheduledExecutors.Signal.STOP;
+ }
+
+ try {
+ syncFromStorage();
+ }
+ catch (Exception e) {
+ if (active) {
+ log.makeAlert(e, "Failed to sync with storage").emit();
}
}
- );
- requestManagement();
- // Remove any unacquired locks from storage (shutdown only clears
entries for which a TaskLockPosse was acquired)
- // This is called after requesting management as locks need to be
cleared after notifyStatus is processed
- for (Task task : tasksToFail) {
- for (TaskLock lock : taskStorage.getLocks(task.getId())) {
- taskStorage.removeLock(task.getId(), lock);
+
+ return active ? ScheduledExecutors.Signal.REPEAT :
ScheduledExecutors.Signal.STOP;
}
- }
- }
- finally {
- giant.unlock();
- }
+ );
}
/**
* Shuts down the queue.
*/
@LifecycleStop
- public void stop()
+ public synchronized void stop()
{
- giant.lock();
-
- try {
- tasks.clear();
- taskFutures.clear();
- active = false;
- managerExec.shutdownNow();
- storageSyncExec.shutdownNow();
- requestManagement();
- }
- finally {
- giant.unlock();
- }
- }
-
- public boolean isActive()
- {
- return active;
+ active = false;
+ tasks.clear();
+ submittedTaskIds.clear();
+ recentlyCompletedTaskIds.clear();
+ managerExec.shutdownNow();
+ storageSyncExec.shutdownNow();
+ requestManagement();
}
/**
* Request management from the management thread. Non-blocking.
- *
- * Other callers (such as notifyStatus) should trigger activity on the
- * TaskQueue thread by requesting management here.
+ * <p>
+ * Callers (such as notifyStatus) can trigger task management by calling
+ * this method.
*/
- void requestManagement()
+ private void requestManagement()
{
- // use a BlockingQueue since the offer/poll/wait behaviour is simple
- // and very easy to reason about
-
- // the request has to be offer (non blocking), since someone might request
- // while already holding giant lock
-
- // do not care if the item fits into the queue:
- // if the queue is already full, request has been triggered anyway
- managementMayBeNecessary.offer(this);
+ synchronized (managementRequested) {
+ managementRequested.set(true);
+ managementRequested.notify();
+ }
}
/**
- * Await for an event to manage.
- *
- * This should only be called from the management thread to wait for
activity.
+ * Waits for a management request to be triggered by another thread.
*
- * @param nanos
- * @throws InterruptedException
+ * @throws InterruptedException if the thread is interrupted while waiting.
*/
- @SuppressFBWarnings(value = "RV_RETURN_VALUE_IGNORED", justification =
"using queue as notification mechanism, result has no value")
- void awaitManagementNanos(long nanos) throws InterruptedException
+ private void awaitManagementRequest() throws InterruptedException
{
// mitigate a busy loop, it can get pretty busy when there are a lot of
start/stops
try {
- Thread.sleep(MIN_WAIT_TIME_MS);
+ Thread.sleep(MIN_WAIT_TIME_MILLIS);
}
catch (InterruptedException e) {
throw new RuntimeException(e);
}
- // wait for an item, if an item arrives (or is already available),
complete immediately
- // (does not actually matter what the item is)
- managementMayBeNecessary.poll(nanos -
(TimeUnit.MILLISECONDS.toNanos(MIN_WAIT_TIME_MS)), TimeUnit.NANOSECONDS);
-
- // there may have been multiple requests, clear them all
- managementMayBeNecessary.clear();
+ // Wait for management to be requested
+ synchronized (managementRequested) {
+ while (!managementRequested.get()) {
+ managementRequested.wait(MANAGEMENT_WAIT_TIMEOUT_MILLIS -
MIN_WAIT_TIME_MILLIS);
+ }
+ managementRequested.compareAndSet(true, false);
+ }
}
/**
* Main task runner management loop. Meant to run forever, or, at least
until we're stopped.
*/
- private void manage() throws InterruptedException
+ private void runTaskManagement() throws InterruptedException
{
- log.info("Beginning management in %s.", config.getStartDelay());
- Thread.sleep(config.getStartDelay().getMillis());
-
// Ignore return value- we'll get the IDs and futures from getKnownTasks
later.
taskRunner.restore();
while (active) {
- manageInternal();
-
- // awaitNanos because management may become necessary without this
condition signalling,
- // due to e.g. tasks becoming ready when other folks mess with the
TaskLockbox.
- awaitManagementNanos(MANAGEMENT_WAIT_TIMEOUT_NANOS);
+ manageTasks();
+ awaitManagementRequest();
}
}
@VisibleForTesting
- void manageInternal()
+ void manageTasks()
{
- Set<String> knownTaskIds = new HashSet<>();
- Map<String, ListenableFuture<TaskStatus>> runnerTaskFutures = new
HashMap<>();
-
- giant.lock();
-
- try {
- manageInternalCritical(knownTaskIds, runnerTaskFutures);
- }
- finally {
- giant.unlock();
- }
-
- manageInternalPostCritical(knownTaskIds, runnerTaskFutures);
+ runReadyTasks();
+ killUnknownTasks();
}
/**
- * Management loop critical section tasks.
- *
- * @param knownTaskIds will be modified - filled with known task IDs
- * @param runnerTaskFutures will be modified - filled with futures related
to getting the running tasks
+ * Submits ready tasks to the TaskRunner.
+ * <p>
+ * This method should be called only by the management thread.
*/
- @GuardedBy("giant")
- private void manageInternalCritical(
- final Set<String> knownTaskIds,
- final Map<String, ListenableFuture<TaskStatus>> runnerTaskFutures
- )
+ private synchronized void runReadyTasks()
{
// Task futures available from the taskRunner
+ final Map<String, ListenableFuture<TaskStatus>> runnerTaskFutures = new
HashMap<>();
for (final TaskRunnerWorkItem workItem : taskRunner.getKnownTasks()) {
- if (!recentlyCompletedTasks.contains(workItem.getTaskId())) {
- // Don't do anything with tasks that have recently finished;
notifyStatus will handle it.
+ if (!recentlyCompletedTaskIds.contains(workItem.getTaskId())) {
+ // Don't do anything with recently completed tasks; notifyStatus will
handle it.
runnerTaskFutures.put(workItem.getTaskId(), workItem.getResult());
}
}
+
// Attain futures for all active tasks (assuming they are ready to run).
- // Copy tasks list, as notifyStatus may modify it.
- for (final Task task : ImmutableList.copyOf(tasks.values())) {
- if (recentlyCompletedTasks.contains(task.getId())) {
- // Don't do anything with tasks that have recently finished;
notifyStatus will handle it.
- continue;
+ for (final String taskId : Lists.newArrayList(activeTaskIdQueue)) {
+ final Task task = tasks.get(taskId);
+ if (task == null || recentlyCompletedTaskIds.contains(taskId)) {
+ // Don't do anything for unknown tasks or recently completed tasks
+ } else if (submittedTaskIds.contains(taskId)) {
+ // Re-trigger execution of pending task to avoid unnecessary delays
+ // see https://github.com/apache/druid/pull/6991
+ if (isTaskPending(task)) {
+ taskRunner.run(task);
+ }
+ } else if (runnerTaskFutures.containsKey(taskId)) {
+ attachCallbacks(task, runnerTaskFutures.get(taskId));
+ submittedTaskIds.add(taskId);
+ } else if (isTaskReady(task)) {
+ log.info("Asking taskRunner to run ready task [%s].", taskId);
+ attachCallbacks(task, taskRunner.run(task));
+ submittedTaskIds.add(taskId);
+ } else {
+ // Release all locks (possibly acquired by task.isReady()) if task is
not ready
+ taskLockbox.unlockAll(task);
}
+ }
+ }
- knownTaskIds.add(task.getId());
-
- if (!taskFutures.containsKey(task.getId())) {
- final ListenableFuture<TaskStatus> runnerTaskFuture;
- if (runnerTaskFutures.containsKey(task.getId())) {
- runnerTaskFuture = runnerTaskFutures.get(task.getId());
- } else {
- // Task should be running, so run it.
- final boolean taskIsReady;
- try {
- taskIsReady = task.isReady(taskActionClientFactory.create(task));
- }
- catch (Exception e) {
- log.warn(e, "Exception thrown during isReady for task: %s",
task.getId());
- final String errorMessage;
- if (e instanceof MaxAllowedLocksExceededException) {
- errorMessage = e.getMessage();
- } else {
- errorMessage = "Failed while waiting for the task to be ready to
run. "
- + "See overlord logs for more
details.";
- }
- notifyStatus(task, TaskStatus.failure(task.getId(), errorMessage),
errorMessage);
- continue;
- }
- if (taskIsReady) {
- log.info("Asking taskRunner to run: %s", task.getId());
- runnerTaskFuture = taskRunner.run(task);
- } else {
- // Task.isReady() can internally lock intervals or segments.
- // We should release them if the task is not ready.
- taskLockbox.unlockAll(task);
- continue;
- }
- }
- taskFutures.put(task.getId(), attachCallbacks(task, runnerTaskFuture));
- } else if (isTaskPending(task)) {
- // if the taskFutures contain this task and this task is pending, also
let the taskRunner
- // to run it to guarantee it will be assigned to run
- // see https://github.com/apache/druid/pull/6991
- taskRunner.run(task);
+ private boolean isTaskReady(Task task)
+ {
+ try {
+ return task.isReady(taskActionClientFactory.create(task));
+ }
+ catch (Exception e) {
+ log.warn(e, "Error while checking if task [%s] is ready to run.",
task.getId());
+ final String errorMessage;
+ if (e instanceof MaxAllowedLocksExceededException) {
+ errorMessage = e.getMessage();
+ } else {
+ errorMessage = "Failed while waiting for the task to be ready to run. "
+ + "See overlord logs for more details.";
}
+ notifyStatus(task, TaskStatus.failure(task.getId(), errorMessage),
errorMessage);
+ return false;
}
}
- @VisibleForTesting
- private void manageInternalPostCritical(
- final Set<String> knownTaskIds,
- final Map<String, ListenableFuture<TaskStatus>> runnerTaskFutures
- )
+ /**
+ * Kills tasks not present in the set of known tasks.
+ */
+ private void killUnknownTasks()
{
- // Kill tasks that shouldn't be running
- final Set<String> tasksToKill =
Sets.difference(runnerTaskFutures.keySet(), knownTaskIds);
- if (!tasksToKill.isEmpty()) {
- log.info("Asking taskRunner to clean up %,d tasks.", tasksToKill.size());
-
- // On large installations running several thousands of tasks,
- // concatenating the list of known task ids can be compupationally
expensive.
- final boolean logKnownTaskIds = log.isDebugEnabled();
- final String reason = logKnownTaskIds
- ? StringUtils.format("Task is not in knownTaskIds[%s]",
knownTaskIds)
- : "Task is not in knownTaskIds";
-
- for (final String taskId : tasksToKill) {
- try {
- taskRunner.shutdown(taskId, reason);
- }
- catch (Exception e) {
- log.warn(e, "TaskRunner failed to clean up task: %s", taskId);
- }
+ final Set<String> knownTaskIds = tasks.keySet();
Review Comment:
The changes in #12099 were a lot of help in cleaning up the `TaskQueue` in
this patch.
The major difference from #12099 is that I am now using a synchronization on
an `AtomicBoolean managementRequested` instead of a queue to track if
management needs to be done. This choice was made in favour of readability and
clarification of intent.
I think you had called out this possible approach here:
> I chose a BlockingQueue implementation because it is easy to reason about
the submission / poll / offer ordering. Other options would be Semaphore etc.
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