b63d025135
In Train we will switch to use py37 for tests. There is a breaking change between Python 3.6 and 3.7 that is making it an error to raise a StopIteration exception from a function or generator(https://www.python.org/dev/peps/pep-0479/). So we need to fix it in code. Change-Id: I003be4193944bc4176768c488f2f71b58fcbd58d Closes-Bug: #1837856 Story: #2005924 Task: #34258
340 lines
14 KiB
Python
340 lines
14 KiB
Python
# Copyright (c) 2013 Red Hat, Inc.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
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# implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""Implements the MongoDB storage controller for claims.
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Field Mappings:
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In order to reduce the disk / memory space used,
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field names will be, most of the time, the first
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letter of their long name.
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"""
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import datetime
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from bson import objectid
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from oslo_log import log as logging
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from oslo_utils import timeutils
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from pymongo.collection import ReturnDocument
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from zaqar import storage
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from zaqar.storage import errors
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from zaqar.storage.mongodb import utils
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LOG = logging.getLogger(__name__)
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def _messages_iter(msg_iter):
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"""Used to iterate through messages."""
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try:
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msg = next(msg_iter)
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yield msg.pop('claim')
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yield msg
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# Smoke it!
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for msg in msg_iter:
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del msg['claim']
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yield msg
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except StopIteration:
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return
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class ClaimController(storage.Claim):
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"""Implements claim resource operations using MongoDB.
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No dedicated collection is being used
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for claims.
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Claims are created in the messages
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collection and live within messages, that is,
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in the c field.
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This implementation certainly uses more space
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on disk but reduces the number of queries to
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be executed and the time needed to retrieve
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claims and claimed messages.
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As for the memory usage, this implementation
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requires less memory since a single index is
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required. The index is a compound index between
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the claim id and it's expiration timestamp.
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"""
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@utils.raises_conn_error
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@utils.retries_on_autoreconnect
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def get(self, queue, claim_id, project=None):
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msg_ctrl = self.driver.message_controller
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# Base query, always check expire time
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now = timeutils.utcnow_ts()
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cid = utils.to_oid(claim_id)
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if cid is None:
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raise errors.ClaimDoesNotExist(claim_id, queue, project)
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try:
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# Lets get claim's data
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# from the first message
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# in the iterator
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msgs = _messages_iter(msg_ctrl._claimed(queue, cid, now,
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project=project))
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claim = next(msgs)
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update_time = claim['e'] - claim['t']
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age = now - update_time
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claim_meta = {
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'age': int(age),
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'ttl': claim['t'],
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'id': str(claim['id']),
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}
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except StopIteration:
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raise errors.ClaimDoesNotExist(cid, queue, project)
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return claim_meta, msgs
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# NOTE(kgriffs): If we get an autoreconnect or any other connection error,
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# the worst that can happen is you get an orphaned claim, but it will
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# expire eventually and free up those messages to be claimed again. We
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# might consider setting a "claim valid" flag similar to how posting
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# messages works, in order to avoid this situation if it turns out to
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# be a real problem for users.
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@utils.raises_conn_error
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@utils.retries_on_autoreconnect
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def create(self, queue, metadata, project=None,
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limit=storage.DEFAULT_MESSAGES_PER_CLAIM):
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"""Creates a claim.
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This implementation was done in a best-effort fashion.
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In order to create a claim we need to get a list
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of messages that can be claimed. Once we have that
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list we execute a query filtering by the ids returned
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by the previous query.
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Since there's a lot of space for race conditions here,
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we'll check if the number of updated records is equal to
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the max number of messages to claim. If the number of updated
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messages is lower than limit we'll try to claim the remaining
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number of messages.
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This 2 queries are required because there's no way, as for the
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time being, to execute an update on a limited number of records.
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"""
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msg_ctrl = self.driver.message_controller
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queue_ctrl = self.driver.queue_controller
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# Get the maxClaimCount, deadLetterQueue and DelayTTL
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# from current queue's meta
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queue_meta = queue_ctrl.get(queue, project=project)
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ttl = metadata['ttl']
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grace = metadata['grace']
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oid = objectid.ObjectId()
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now = timeutils.utcnow_ts()
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claim_expires = now + ttl
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claim_expires_dt = datetime.datetime.utcfromtimestamp(claim_expires)
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message_ttl = ttl + grace
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message_expiration = datetime.datetime.utcfromtimestamp(
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claim_expires + grace)
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meta = {
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'id': oid,
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't': ttl,
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'e': claim_expires,
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'c': 0 # NOTE(flwang): A placeholder which will be updated later
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}
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# NOTE(cdyangzhenyu): If the ``_default_message_delay`` is 0 means
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# queue is not delayed queue, So we don't filter for delay messages.
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include_delayed = False if queue_meta.get('_default_message_delay',
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0) else True
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# Get a list of active, not claimed nor expired
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# messages that could be claimed.
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msgs = msg_ctrl._active(queue, projection={'_id': 1, 'c': 1},
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project=project,
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limit=limit,
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include_delayed=include_delayed)
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messages = iter([])
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be_claimed = [(msg['_id'], msg['c'].get('c', 0)) for msg in msgs]
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ids = [_id for _id, _ in be_claimed]
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if len(ids) == 0:
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return None, messages
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# NOTE(kgriffs): Set the claim field for
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# the active message batch, while also
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# filtering out any messages that happened
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# to get claimed just now by one or more
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# parallel requests.
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#
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# Filtering by just 'c.e' works because
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# new messages have that field initialized
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# to the current time when the message is
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# posted. There is no need to check whether
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# 'c' exists or 'c.id' is None.
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collection = msg_ctrl._collection(queue, project)
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updated = collection.update_many({'_id': {'$in': ids},
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'c.e': {'$lte': now}},
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{'$set': {'c': meta}},
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upsert=False)
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# NOTE(flaper87): Dirty hack!
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# This sets the expiration time to
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# `expires` on messages that would
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# expire before claim.
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new_values = {'e': message_expiration, 't': message_ttl}
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collection.update_many({'p_q': utils.scope_queue_name(queue, project),
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'e': {'$lt': claim_expires_dt},
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'c.id': oid},
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{'$set': new_values},
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upsert=False)
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msg_count_moved_to_DLQ = 0
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if ('_max_claim_count' in queue_meta and
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'_dead_letter_queue' in queue_meta):
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LOG.debug(u"The list of messages being claimed: %(be_claimed)s",
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{"be_claimed": be_claimed})
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for _id, claimed_count in be_claimed:
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# NOTE(flwang): We have claimed the message above, but we will
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# update the claim count below. So that means, when the
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# claimed_count equals queue_meta['_max_claim_count'], the
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# message has met the threshold. And Zaqar will move it to the
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# DLQ.
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if claimed_count < queue_meta['_max_claim_count']:
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# 1. Save the new max claim count for message
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collection.update_one({'_id': _id,
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'c.id': oid},
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{'$set': {'c.c': claimed_count + 1}},
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upsert=False)
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LOG.debug(u"Message %(id)s has been claimed %(count)d "
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u"times.", {"id": str(_id),
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"count": claimed_count + 1})
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else:
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# 2. Check if the message's claim count has exceeded the
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# max claim count defined in the queue, if so, move the
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# message to the dead letter queue.
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# NOTE(flwang): We're moving message directly. That means,
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# the queue and dead letter queue must be created on the
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# same storage pool. It's a technical tradeoff, because if
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# we re-send the message to the dead letter queue by
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# message controller, then we will lost all the claim
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# information.
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dlq_name = queue_meta['_dead_letter_queue']
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new_msg = {'c.c': claimed_count,
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'p_q': utils.scope_queue_name(dlq_name,
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project)}
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dlq_ttl = queue_meta.get("_dead_letter_queue_messages_ttl")
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if dlq_ttl:
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new_msg['t'] = dlq_ttl
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kwargs = {"return_document": ReturnDocument.AFTER}
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msg = collection.find_one_and_update({'_id': _id,
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'c.id': oid},
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{'$set': new_msg},
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**kwargs)
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dlq_collection = msg_ctrl._collection(dlq_name, project)
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if not dlq_collection:
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LOG.warning(u"Failed to find the message collection "
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u"for queue %(dlq_name)s", {"dlq_name":
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dlq_name})
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return None, iter([])
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# NOTE(flwang): If dead letter queue and queue are in the
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# same partition, the message has been already
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# modified.
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if collection != dlq_collection:
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result = dlq_collection.insert_one(msg)
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if result.inserted_id:
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collection.delete_one({'_id': _id})
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LOG.debug(u"Message %(id)s has met the max claim count "
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u"%(count)d, now it has been moved to dead "
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u"letter queue %(dlq_name)s.",
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{"id": str(_id), "count": claimed_count,
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"dlq_name": dlq_name})
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msg_count_moved_to_DLQ += 1
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if updated.modified_count != 0:
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# NOTE(kgriffs): This extra step is necessary because
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# in between having gotten a list of active messages
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# and updating them, some of them may have been
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# claimed by a parallel request. Therefore, we need
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# to find out which messages were actually tagged
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# with the claim ID successfully.
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if msg_count_moved_to_DLQ < updated.modified_count:
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claim, messages = self.get(queue, oid, project=project)
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else:
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# NOTE(flwang): Though messages are claimed, but all of them
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# have met the max claim count and have been moved to DLQ.
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return None, iter([])
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return str(oid), messages
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@utils.raises_conn_error
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@utils.retries_on_autoreconnect
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def update(self, queue, claim_id, metadata, project=None):
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cid = utils.to_oid(claim_id)
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if cid is None:
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raise errors.ClaimDoesNotExist(claim_id, queue, project)
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now = timeutils.utcnow_ts()
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grace = metadata['grace']
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ttl = metadata['ttl']
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claim_expires = now + ttl
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claim_expires_dt = datetime.datetime.utcfromtimestamp(claim_expires)
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message_ttl = ttl + grace
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message_expires = datetime.datetime.utcfromtimestamp(
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claim_expires + grace)
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msg_ctrl = self.driver.message_controller
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claimed = msg_ctrl._claimed(queue, cid, expires=now,
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limit=1, project=project)
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try:
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next(claimed)
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except StopIteration:
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raise errors.ClaimDoesNotExist(claim_id, queue, project)
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meta = {
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'id': cid,
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't': ttl,
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'e': claim_expires,
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}
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# TODO(kgriffs): Create methods for these so we don't interact
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# with the messages collection directly (loose coupling)
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scope = utils.scope_queue_name(queue, project)
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collection = msg_ctrl._collection(queue, project)
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collection.update_many({'p_q': scope, 'c.id': cid},
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{'$set': {'c': meta}},
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upsert=False)
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# NOTE(flaper87): Dirty hack!
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# This sets the expiration time to
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# `expires` on messages that would
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# expire before claim.
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collection.update_many({'p_q': scope,
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'e': {'$lt': claim_expires_dt},
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'c.id': cid},
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{'$set': {'e': message_expires,
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't': message_ttl}},
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upsert=False)
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@utils.raises_conn_error
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@utils.retries_on_autoreconnect
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def delete(self, queue, claim_id, project=None):
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msg_ctrl = self.driver.message_controller
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msg_ctrl._unclaim(queue, claim_id, project=project)
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