363 lines
15 KiB
Python
363 lines
15 KiB
Python
import uuid
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from datetime import datetime, timedelta
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from contextlib import contextmanager
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from data.database import QueueItem, db, db_for_update, db_random_func
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from util.morecollections import AttrDict
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MINIMUM_EXTENSION = timedelta(seconds=20)
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DEFAULT_BATCH_SIZE = 1000
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class BuildMetricQueueReporter(object):
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""" Metric queue reporter for the build system. """
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def __init__(self, metric_queue):
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self._metric_queue = metric_queue
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def __call__(self, currently_processing, running_count, total_count):
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need_capacity_count = total_count - running_count
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self._metric_queue.put_deprecated('BuildCapacityShortage', need_capacity_count, unit='Count')
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self._metric_queue.build_capacity_shortage.Set(need_capacity_count)
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building_percent = 100 if currently_processing else 0
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self._metric_queue.percent_building.Set(building_percent)
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class WorkQueue(object):
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""" Work queue defines methods for interacting with a queue backed by the database. """
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def __init__(self, queue_name, transaction_factory,
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canonical_name_match_list=None, reporter=None, metric_queue=None,
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has_namespace=False):
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self._queue_name = queue_name
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self._reporter = reporter
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self._metric_queue = metric_queue
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self._transaction_factory = transaction_factory
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self._currently_processing = False
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self._has_namespaced_items = has_namespace
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if canonical_name_match_list is None:
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self._canonical_name_match_list = []
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else:
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self._canonical_name_match_list = canonical_name_match_list
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@staticmethod
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def _canonical_name(name_list):
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return '/'.join(name_list) + '/'
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@classmethod
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def _running_jobs(cls, now, name_match_query):
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return (cls
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._running_jobs_where(QueueItem.select(QueueItem.queue_name), now)
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.where(QueueItem.queue_name ** name_match_query))
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@classmethod
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def _available_jobs(cls, now, name_match_query):
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return (cls
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._available_jobs_where(QueueItem.select(), now)
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.where(QueueItem.queue_name ** name_match_query))
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@staticmethod
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def _running_jobs_where(query, now):
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return query.where(QueueItem.available == False, QueueItem.processing_expires > now)
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@staticmethod
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def _available_jobs_where(query, now):
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return query.where(QueueItem.available_after <= now,
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((QueueItem.available == True) | (QueueItem.processing_expires <= now)),
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QueueItem.retries_remaining > 0)
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@classmethod
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def _available_jobs_not_running(cls, now, name_match_query, running_query):
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return (cls
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._available_jobs(now, name_match_query)
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.where(~(QueueItem.queue_name << running_query)))
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def num_available_jobs_between(self, available_min_time, available_max_time, canonical_name_list):
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"""
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Returns the number of available queue items with a given prefix, between the two provided times.
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"""
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def strip_slash(name):
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return name.lstrip('/')
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canonical_name_list = map(strip_slash, canonical_name_list)
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available = self._available_jobs(available_max_time,
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'/'.join([self._queue_name] + canonical_name_list) + '%')
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return available.where(QueueItem.available_after >= available_min_time).count()
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def _name_match_query(self):
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return '%s%%' % self._canonical_name([self._queue_name] + self._canonical_name_match_list)
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@staticmethod
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def _item_by_id_for_update(queue_id):
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return db_for_update(QueueItem.select().where(QueueItem.id == queue_id)).get()
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def get_metrics(self):
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now = datetime.utcnow()
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name_match_query = self._name_match_query()
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running_query = self._running_jobs(now, name_match_query)
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running_count = running_query.distinct().count()
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available_query = self._available_jobs(now, name_match_query)
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available_count = available_query.select(QueueItem.queue_name).distinct().count()
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available_not_running_query = self._available_jobs_not_running(now, name_match_query,
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running_query)
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available_not_running_count = (available_not_running_query
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.select(QueueItem.queue_name)
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.distinct()
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.count())
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return (running_count, available_not_running_count, available_count)
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def update_metrics(self):
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if self._reporter is None and self._metric_queue is None:
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return
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(running_count, available_not_running_count, available_count) = self.get_metrics()
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if self._metric_queue:
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self._metric_queue.work_queue_running.Set(running_count, labelvalues=[self._queue_name])
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self._metric_queue.work_queue_available.Set(available_count, labelvalues=[self._queue_name])
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self._metric_queue.work_queue_available_not_running.Set(available_not_running_count,
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labelvalues=[self._queue_name])
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if self._reporter:
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self._reporter(self._currently_processing, running_count,
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running_count + available_not_running_count)
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def has_retries_remaining(self, item_id):
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""" Returns whether the queue item with the given id has any retries remaining. If the
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queue item does not exist, returns False. """
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with self._transaction_factory(db):
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try:
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return QueueItem.get(id=item_id).retries_remaining > 0
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except QueueItem.DoesNotExist:
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return False
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def delete_namespaced_items(self, namespace, subpath=None):
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""" Deletes all items in this queue that exist under the given namespace. """
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if not self._has_namespaced_items:
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return False
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subpath_query = '%s/' % subpath if subpath else ''
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queue_prefix = '%s/%s/%s%%' % (self._queue_name, namespace, subpath_query)
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return QueueItem.delete().where(QueueItem.queue_name ** queue_prefix).execute()
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def alive(self, canonical_name_list):
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"""
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Returns True if a job matching the canonical name list is currently processing
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or available.
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"""
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canonical_name = self._canonical_name([self._queue_name] + canonical_name_list)
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try:
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select_query = QueueItem.select().where(QueueItem.queue_name == canonical_name)
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now = datetime.utcnow()
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overall_query = (self._available_jobs_where(select_query.clone(), now) |
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self._running_jobs_where(select_query.clone(), now))
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overall_query.get()
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return True
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except QueueItem.DoesNotExist:
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return False
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def _queue_dict(self, canonical_name_list, message, available_after, retries_remaining):
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return dict(
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queue_name=self._canonical_name([self._queue_name] + canonical_name_list),
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body=message,
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retries_remaining=retries_remaining,
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available_after=datetime.utcnow() + timedelta(seconds=available_after or 0),
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)
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@contextmanager
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def batch_insert(self, batch_size=DEFAULT_BATCH_SIZE):
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items_to_insert = []
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def batch_put(canonical_name_list, message, available_after=0, retries_remaining=5):
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"""
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Put an item, if it shouldn't be processed for some number of seconds,
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specify that amount as available_after. Returns the ID of the queue item added.
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"""
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items_to_insert.append(self._queue_dict(canonical_name_list, message, available_after,
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retries_remaining))
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yield batch_put
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# Chunk the inserted items into batch_size chunks and insert_many
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remaining = list(items_to_insert)
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while remaining:
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QueueItem.insert_many(remaining[0:batch_size]).execute()
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remaining = remaining[batch_size:]
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def put(self, canonical_name_list, message, available_after=0, retries_remaining=5):
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"""
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Put an item, if it shouldn't be processed for some number of seconds,
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specify that amount as available_after. Returns the ID of the queue item added.
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"""
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item = QueueItem.create(**self._queue_dict(canonical_name_list, message, available_after,
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retries_remaining))
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return str(item.id)
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def _select_available_item(self, ordering_required, now):
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""" Selects an available queue item from the queue table and returns it, if any. If none,
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return None.
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"""
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name_match_query = self._name_match_query()
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try:
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if ordering_required:
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# The previous solution to this used a select for update in a
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# transaction to prevent multiple instances from processing the
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# same queue item. This suffered performance problems. This solution
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# instead has instances attempt to update the potential queue item to be
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# unavailable. However, since their update clause is restricted to items
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# that are available=False, only one instance's update will succeed, and
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# it will have a changed row count of 1. Instances that have 0 changed
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# rows know that another instance is already handling that item.
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running = self._running_jobs(now, name_match_query)
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avail = self._available_jobs_not_running(now, name_match_query, running)
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return avail.order_by(QueueItem.id).get()
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else:
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# If we don't require ordering, we grab a random item from any of the first 50 available.
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subquery = self._available_jobs(now, name_match_query).limit(50).alias('j1')
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return (QueueItem
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.select()
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.join(subquery, on=QueueItem.id == subquery.c.id)
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.order_by(db_random_func())
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.get())
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except QueueItem.DoesNotExist:
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# No available queue item was found.
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return None
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def _attempt_to_claim_item(self, db_item, now, processing_time):
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""" Attempts to claim the specified queue item for this instance. Returns True on success and
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False on failure.
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Note that the underlying QueueItem row in the database will be changed on success, but
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the db_item object given as a parameter will *not* have its fields updated.
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"""
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# Try to claim the item. We do so by updating the item's information only if its current
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# state ID matches that returned in the previous query. Since all updates to the QueueItem
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# must change the state ID, this is guarenteed to only succeed if the item has not yet been
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# claimed by another caller.
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#
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# Note that we use this method because InnoDB takes locks on *every* clause in the WHERE when
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# performing the update. Previously, we would check all these columns, resulting in a bunch
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# of lock contention. This change mitigates the problem significantly by only checking two
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# columns (id and state_id), both of which should be absolutely unique at all times.
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set_unavailable_query = (QueueItem
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.update(available=False,
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processing_expires=now + timedelta(seconds=processing_time),
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retries_remaining=QueueItem.retries_remaining - 1,
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state_id=str(uuid.uuid4()))
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.where(QueueItem.id == db_item.id,
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QueueItem.state_id == db_item.state_id))
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changed = set_unavailable_query.execute()
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return changed == 1
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def get(self, processing_time=300, ordering_required=False):
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"""
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Get an available item and mark it as unavailable for the default of five
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minutes. The result of this method must always be composed of simple
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python objects which are JSON serializable for network portability reasons.
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"""
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now = datetime.utcnow()
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# Select an available queue item.
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db_item = self._select_available_item(ordering_required, now)
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if db_item is None:
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self._currently_processing = False
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return None
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# Attempt to claim the item for this instance.
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was_claimed = self._attempt_to_claim_item(db_item, now, processing_time)
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if not was_claimed:
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self._currently_processing = False
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return None
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self._currently_processing = True
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# Return a view of the queue item rather than an active db object
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return AttrDict({
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'id': db_item.id,
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'body': db_item.body,
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'retries_remaining': db_item.retries_remaining - 1,
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})
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def cancel(self, item_id):
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""" Attempts to cancel the queue item with the given ID from the queue. Returns true on success
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and false if the queue item could not be canceled.
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"""
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count_removed = QueueItem.delete().where(QueueItem.id == item_id).execute()
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return count_removed > 0
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def complete(self, completed_item):
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self._currently_processing = not self.cancel(completed_item.id)
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def incomplete(self, incomplete_item, retry_after=300, restore_retry=False):
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with self._transaction_factory(db):
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retry_date = datetime.utcnow() + timedelta(seconds=retry_after)
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try:
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incomplete_item_obj = self._item_by_id_for_update(incomplete_item.id)
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incomplete_item_obj.available_after = retry_date
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incomplete_item_obj.available = True
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if restore_retry:
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incomplete_item_obj.retries_remaining += 1
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incomplete_item_obj.save()
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self._currently_processing = False
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return incomplete_item_obj.retries_remaining > 0
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except QueueItem.DoesNotExist:
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return False
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def extend_processing(self, item, seconds_from_now, minimum_extension=MINIMUM_EXTENSION,
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updated_data=None):
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with self._transaction_factory(db):
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try:
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queue_item = self._item_by_id_for_update(item.id)
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new_expiration = datetime.utcnow() + timedelta(seconds=seconds_from_now)
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has_change = False
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# Only actually write the new expiration to the db if it moves the expiration some minimum
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if new_expiration - queue_item.processing_expires > minimum_extension:
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queue_item.processing_expires = new_expiration
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has_change = True
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if updated_data is not None and queue_item.body != updated_data:
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queue_item.body = updated_data
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has_change = True
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if has_change:
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queue_item.save()
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return has_change
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except QueueItem.DoesNotExist:
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return False
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def delete_expired(expiration_threshold, deletion_threshold, batch_size):
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"""
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Deletes all queue items that are older than the provided expiration threshold in batches of the
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provided size. If there are less items than the deletion threshold, this method does nothing.
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Returns the number of items deleted.
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"""
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to_delete = list(QueueItem
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.select()
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.where(QueueItem.processing_expires <= expiration_threshold)
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.limit(batch_size))
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if len(to_delete) < deletion_threshold:
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return 0
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QueueItem.delete().where(QueueItem.id << to_delete).execute()
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return len(to_delete)
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