Function PollForTasks

src/backend/task/pg_cron.c:790–976

* PollForTasks calls poll() for the sockets of all tasks. It checks for * read or write events based on the pollingStatus of the task. */

 * read or write events based on the pollingStatus of the task.
 */
static void
PollForTasks(List *taskList)
{
	TimestampTz currentTime = 0;
	TimestampTz nextEventTime = 0;
	int pollTimeout = 0;
	long waitSeconds = 0;
	int waitMicros = 0;
	CronTask **polledTasks = NULL;
	struct pollfd *pollFDs = NULL;
	int pollResult = 0;

	int taskIndex = 0;
	int taskCount = list_length(taskList);
	int activeTaskCount = 0;
	ListCell *taskCell = NULL;

	polledTasks = (CronTask **) palloc0(taskCount * sizeof(CronTask *));
	pollFDs = (struct pollfd *) palloc0(taskCount * sizeof(struct pollfd));

	currentTime = GetCurrentTimestamp();

	/*
	 * At the latest, wake up when the next minute starts.
	 */
	nextEventTime = TimestampMinuteEnd(currentTime);

	foreach(taskCell, taskList)
	{
		CronTask *task = (CronTask *) lfirst(taskCell);
		PostgresPollingStatusType pollingStatus = task->pollingStatus;
		struct pollfd *pollFileDescriptor = &pollFDs[activeTaskCount];

		if (activeTaskCount >= max_running_tasks)
		{
			/* already polling the maximum number of tasks */
			break;
		}

		if (task->state == CRON_TASK_ERROR || task->state == CRON_TASK_DONE ||
			CanStartTask(task))
		{
			/* there is work to be done, don't wait */
			pfree(polledTasks);
			pfree(pollFDs);
			return;
		}

		if (task->state == CRON_TASK_WAITING && task->pendingRunCount == 0)
		{
			/*
			 * Make sure we do not wait past the next run time of an interval
			 * job.
			 */
			if (task->secondsInterval > 0)
			{
				TimestampTz nextRunTime =
					TimestampTzPlusMilliseconds(task->lastStartTime,