quay/data/queue.py

from datetime import datetime, timedelta

from data.database import QueueItem, db, db_for_update, db_random_func
from util.morecollections import AttrDict


MINIMUM_EXTENSION = timedelta(seconds=20)


class NoopWith:
  def __enter__(self):
    pass

  def __exit__(self, type, value, traceback):
    pass


class BuildMetricQueueReporter(object):
  """ Metric queue reporter for the build system. """
  def __init__(self, metric_queue):
    self._metric_queue = metric_queue

  def __call__(self, currently_processing, running_count, total_count):
    need_capacity_count = total_count - running_count
    self._metric_queue.put_deprecated('BuildCapacityShortage', need_capacity_count, unit='Count')
    self._metric_queue.build_capacity_shortage.Set(need_capacity_count)

    building_percent = 100 if currently_processing else 0
    self._metric_queue.put_deprecated('PercentBuilding', building_percent, unit='Percent')
    self._metric_queue.percent_building.Set(building_percent)


class WorkQueue(object):
  """ Work queue defines methods for interacting with a queue backed by the database. """
  def __init__(self, queue_name, transaction_factory,
               canonical_name_match_list=None, reporter=None, metric_queue=None,
               has_namespace=False):
    self._queue_name = queue_name
    self._reporter = reporter
    self._metric_queue = metric_queue
    self._transaction_factory = transaction_factory
    self._currently_processing = False
    self._has_namespaced_items = has_namespace

    if canonical_name_match_list is None:
      self._canonical_name_match_list = []
    else:
      self._canonical_name_match_list = canonical_name_match_list

  @staticmethod
  def _canonical_name(name_list):
    return '/'.join(name_list) + '/'

  @classmethod
  def _running_jobs(cls, now, name_match_query):
    return (QueueItem
            .select(QueueItem.queue_name)
            .where(QueueItem.available == False,
                   QueueItem.processing_expires > now,
                   QueueItem.queue_name ** name_match_query))

  @classmethod
  def _available_jobs(cls, now, name_match_query):
    return (cls
            ._available_jobs_where(QueueItem.select(), now)
            .where(QueueItem.queue_name ** name_match_query))

  @staticmethod
  def _available_jobs_where(query, now):
    return query.where(QueueItem.available_after <= now,
                       ((QueueItem.available == True) | (QueueItem.processing_expires <= now)),
                       QueueItem.retries_remaining > 0)

  @classmethod
  def _available_jobs_not_running(cls, now, name_match_query, running_query):
    return (cls
            ._available_jobs(now, name_match_query)
            .where(~(QueueItem.queue_name << running_query)))

  def _name_match_query(self):
    return '%s%%' % self._canonical_name([self._queue_name] + self._canonical_name_match_list)

  @staticmethod
  def _item_by_id_for_update(queue_id):
    return db_for_update(QueueItem.select().where(QueueItem.id == queue_id)).get()

  def get_metrics(self):
    now = datetime.utcnow()
    name_match_query = self._name_match_query()

    running_query = self._running_jobs(now, name_match_query)
    running_count = running_query.distinct().count()

    available_query = self._available_jobs(now, name_match_query)
    available_count = available_query.select(QueueItem.queue_name).distinct().count()

    available_not_running_query = self._available_jobs_not_running(now, name_match_query,
                                                                   running_query)
    available_not_running_count = (available_not_running_query
                                   .select(QueueItem.queue_name)
                                   .distinct()
                                   .count())

    return (running_count, available_not_running_count, available_count)

  def update_metrics(self):
    if self._reporter is None and self._metric_queue is None:
      return

    (running_count, available_not_running_count, available_count) = self.get_metrics()

    if self._metric_queue:
      dim = {'queue': self._queue_name}
      self._metric_queue.put_deprecated('Running', running_count, dimensions=dim)
      self._metric_queue.put_deprecated('AvailableNotRunning', available_not_running_count,
                                        dimensions=dim)
      self._metric_queue.put_deprecated('Available', available_count, dimensions=dim)

      self._metric_queue.work_queue_running.set(running_count, labelvalues=[self._queue_name])
      self._metric_queue.work_queue_available.set(available_count, labelvalues=[self._queue_name])

    if self._reporter:
      self._reporter(self._currently_processing, running_count,
                     running_count + available_not_running_count)

  def has_retries_remaining(self, item_id):
    """ Returns whether the queue item with the given id has any retries remaining. If the
        queue item does not exist, returns False. """
    with self._transaction_factory(db):
      try:
        return QueueItem.get(id=item_id).retries_remaining > 0
      except QueueItem.DoesNotExist:
        return False

  def delete_namespaced_items(self, namespace, subpath=None):
    """ Deletes all items in this queue that exist under the given namespace. """
    if not self._has_namespaced_items:
      return False

    subpath_query = '%s/' % subpath if subpath else ''
    queue_prefix = '%s/%s/%s%%' % (self._queue_name, namespace, subpath_query)
    QueueItem.delete().where(QueueItem.queue_name ** queue_prefix).execute()

  def put(self, canonical_name_list, message, available_after=0, retries_remaining=5):
    """
    Put an item, if it shouldn't be processed for some number of seconds,
    specify that amount as available_after. Returns the ID of the queue item added.
    """
    item = QueueItem.create(
      queue_name=self._canonical_name([self._queue_name] + canonical_name_list),
      body=message,
      retries_remaining=retries_remaining,
      available_after=datetime.utcnow() + timedelta(seconds=available_after or 0),
    )

    if self._metric_queue:
      self._metric_queue.put_deprecated('Added', 1, dimensions={'queue': self._queue_name})

    return str(item.id)

  def get(self, processing_time=300, ordering_required=False):
    """
    Get an available item and mark it as unavailable for the default of five
    minutes. The result of this method must always be composed of simple
    python objects which are JSON serializable for network portability reasons.
    """
    now = datetime.utcnow()
    name_match_query = self._name_match_query()
    item = None

    try:
      if ordering_required:
        # The previous solution to this used a select for update in a
        # transaction to prevent multiple instances from processing the
        # same queue item. This suffered performance problems. This solution
        # instead has instances attempt to update the potential queue item to be
        # unavailable. However, since their update clause is restricted to items
        # that are available=False, only one instance's update will succeed, and
        # it will have a changed row count of 1. Instances that have 0 changed
        # rows know that another instance is already handling that item.
        running = self._running_jobs(now, name_match_query)
        avail = self._available_jobs_not_running(now, name_match_query, running)
        db_item = avail.order_by(QueueItem.id).get()
      else:
        # If we don't require ordering, we grab a random item from any of the first 50 available.
        subquery = self._available_jobs(now, name_match_query).limit(50).alias('j1')
        db_item = (QueueItem
                   .select()
                   .join(subquery, on=QueueItem.id == subquery.c.id)
                   .order_by(db_random_func())
                   .get())

      set_unavailable_query = (QueueItem
                               .update(available=False,
                                       processing_expires=now + timedelta(seconds=processing_time),
                                       retries_remaining=QueueItem.retries_remaining-1)
                               .where(QueueItem.id == db_item.id))
      changed_query = (self._available_jobs_where(set_unavailable_query, now)
                       .where(QueueItem.processing_expires == db_item.processing_expires))
      changed = changed_query.execute()
      if changed == 1:
        item = AttrDict({
          'id': db_item.id,
          'body': db_item.body,
          'retries_remaining': db_item.retries_remaining - 1,
        })
        self._currently_processing = True
    except QueueItem.DoesNotExist:
      self._currently_processing = False

    # Return a view of the queue item rather than an active db object
    return item

  def cancel(self, item_id):
    """ Attempts to cancel the queue item with the given ID from the queue. Returns true on success
        and false if the queue item could not be canceled. A queue item can only be canceled if
        if is available and has retries remaining.
    """

    with self._transaction_factory(db):
      # Load the build queue item for update.
      try:
        queue_item = db_for_update(QueueItem.select()
                                   .where(QueueItem.id == item_id)).get()
      except QueueItem.DoesNotExist:
        return False

      # Check the queue item.
      if not queue_item.available or queue_item.retries_remaining == 0:
        return False

      # Delete the queue item.
      queue_item.delete_instance(recursive=True)
      return True

  def complete(self, completed_item):
    with self._transaction_factory(db):
      try:
        completed_item_obj = self._item_by_id_for_update(completed_item.id)
      except QueueItem.DoesNotExist:
        self._currently_processing = False
        return

      completed_item_obj.delete_instance(recursive=True)
      self._currently_processing = False

  def incomplete(self, incomplete_item, retry_after=300, restore_retry=False):
    with self._transaction_factory(db):
      retry_date = datetime.utcnow() + timedelta(seconds=retry_after)

      try:
        incomplete_item_obj = self._item_by_id_for_update(incomplete_item.id)
        incomplete_item_obj.available_after = retry_date
        incomplete_item_obj.available = True

        if restore_retry:
          incomplete_item_obj.retries_remaining += 1

        incomplete_item_obj.save()
        self._currently_processing = False
        return incomplete_item_obj.retries_remaining > 0
      except QueueItem.DoesNotExist:
        return False

  def extend_processing(self, item, seconds_from_now, minimum_extension=MINIMUM_EXTENSION,
                        updated_data=None):
    with self._transaction_factory(db):
      try:
        queue_item = self._item_by_id_for_update(item.id)
        new_expiration = datetime.utcnow() + timedelta(seconds=seconds_from_now)
        has_change = False

        # Only actually write the new expiration to the db if it moves the expiration some minimum
        if new_expiration - queue_item.processing_expires > minimum_extension:
          queue_item.processing_expires = new_expiration
          has_change = True

        if updated_data is not None:
          queue_item.body = updated_data
          has_change = True

        if has_change:
          queue_item.save()

      except QueueItem.DoesNotExist:
        return


def delete_expired(expiration_threshold, deletion_threshold, batch_size):
  """
  Deletes all queue items that are older than the provided expiration threshold in batches of the
  provided size. If there are less items than the deletion threshold, this method does nothing.

  Returns the number of items deleted.
  """
  to_delete = list(QueueItem
                   .select()
                   .where(QueueItem.processing_expires <= expiration_threshold)
                   .limit(batch_size))

  if len(to_delete) < deletion_threshold:
    return 0

  QueueItem.delete().where(QueueItem.id << to_delete).execute()
  return len(to_delete)