quay/data/queue.py

import uuid

from datetime import datetime, timedelta
from contextlib import contextmanager

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


MINIMUM_EXTENSION = timedelta(seconds=20)
DEFAULT_BATCH_SIZE = 1000


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.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 (cls
            ._running_jobs_where(QueueItem.select(QueueItem.queue_name), now)
            .where(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 _running_jobs_where(query, now):
    return query.where(QueueItem.available == False, QueueItem.processing_expires > now)

  @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 num_alive_jobs(self, canonical_name_list):
    """
    Returns the number of alive queue items with a given prefix.
    """
    def strip_slash(name):
      return name.lstrip('/')
    canonical_name_list = map(strip_slash, canonical_name_list)
    canonical_name_query = '/'.join([self._queue_name] + canonical_name_list) + '%'

    return (QueueItem
            .select()
            .where(QueueItem.queue_name ** canonical_name_query)
            .where(QueueItem.retries_remaining > 0)
            .count())

  def num_available_jobs_between(self, available_min_time, available_max_time, canonical_name_list):
    """
    Returns the number of available queue items with a given prefix, between the two provided times.
    """
    def strip_slash(name):
      return name.lstrip('/')
    canonical_name_list = map(strip_slash, canonical_name_list)

    available = self._available_jobs(available_max_time,
                                     '/'.join([self._queue_name] + canonical_name_list) + '%')

    return available.where(QueueItem.available_after >= available_min_time).count()

  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:
      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])
      self._metric_queue.work_queue_available_not_running.Set(available_not_running_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)
    return QueueItem.delete().where(QueueItem.queue_name ** queue_prefix).execute()

  def alive(self, canonical_name_list):
    """
    Returns True if a job matching the canonical name list is currently processing
    or available.
    """
    canonical_name = self._canonical_name([self._queue_name] + canonical_name_list)
    try:
      select_query = QueueItem.select().where(QueueItem.queue_name == canonical_name)
      now = datetime.utcnow()

      overall_query = (self._available_jobs_where(select_query.clone(), now) |
                       self._running_jobs_where(select_query.clone(), now))
      overall_query.get()
      return True
    except QueueItem.DoesNotExist:
      return False

  def _queue_dict(self, canonical_name_list, message, available_after, retries_remaining):
    return dict(
      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),
    )

  @contextmanager
  def batch_insert(self, batch_size=DEFAULT_BATCH_SIZE):
    items_to_insert = []
    def batch_put(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.
      """
      items_to_insert.append(self._queue_dict(canonical_name_list, message, available_after,
                                              retries_remaining))

    yield batch_put

    # Chunk the inserted items into batch_size chunks and insert_many
    remaining = list(items_to_insert)
    while remaining:
      QueueItem.insert_many(remaining[0:batch_size]).execute()
      remaining = remaining[batch_size:]

  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(**self._queue_dict(canonical_name_list, message, available_after,
                                               retries_remaining))
    return str(item.id)

  def _select_available_item(self, ordering_required, now):
    """ Selects an available queue item from the queue table and returns it, if any. If none,
        return None.
    """
    name_match_query = self._name_match_query()

    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)
        return 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')
        return (QueueItem
                .select()
                .join(subquery, on=QueueItem.id == subquery.c.id)
                .order_by(db_random_func())
                .get())

    except QueueItem.DoesNotExist:
      # No available queue item was found.
      return None

  def _attempt_to_claim_item(self, db_item, now, processing_time):
    """ Attempts to claim the specified queue item for this instance. Returns True on success and
        False on failure.

        Note that the underlying QueueItem row in the database will be changed on success, but
        the db_item object given as a parameter will *not* have its fields updated.
    """

    # Try to claim the item. We do so by updating the item's information only if its current
    # state ID matches that returned in the previous query. Since all updates to the QueueItem
    # must change the state ID, this is guarenteed to only succeed if the item has not yet been
    # claimed by another caller.
    #
    # Note that we use this method because InnoDB takes locks on *every* clause in the WHERE when
    # performing the update. Previously, we would check all these columns, resulting in a bunch
    # of lock contention. This change mitigates the problem significantly by only checking two
    # columns (id and state_id), both of which should be absolutely unique at all times.
    set_unavailable_query = (QueueItem
                             .update(available=False,
                                     processing_expires=now + timedelta(seconds=processing_time),
                                     retries_remaining=QueueItem.retries_remaining - 1,
                                     state_id=str(uuid.uuid4()))
                             .where(QueueItem.id == db_item.id,
                                    QueueItem.state_id == db_item.state_id))

    changed = set_unavailable_query.execute()
    return changed == 1


  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()

    # Select an available queue item.
    db_item = self._select_available_item(ordering_required, now)
    if db_item is None:
      self._currently_processing = False
      return None

    # Attempt to claim the item for this instance.
    was_claimed = self._attempt_to_claim_item(db_item, now, processing_time)
    if not was_claimed:
      self._currently_processing = False
      return None

    self._currently_processing = True

    # Return a view of the queue item rather than an active db object
    return AttrDict({
      'id': db_item.id,
      'body': db_item.body,
      'retries_remaining': db_item.retries_remaining - 1,
    })

  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.
    """
    count_removed = QueueItem.delete().where(QueueItem.id == item_id).execute()
    return count_removed > 0

  def complete(self, completed_item):
    self._currently_processing = not self.cancel(completed_item.id)

  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 and queue_item.body != updated_data:
          queue_item.body = updated_data
          has_change = True

        if has_change:
          queue_item.save()

        return has_change
      except QueueItem.DoesNotExist:
        return False


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)