Files
zaqar/marconi/queues/storage/mongodb/messages.py
Flavio Percoco 9b6350afa5 Change Marconi's codebase structure
This patch re-structures Marconi's codebase in a way that it'll be
possible to add other services such as marconi-proxy and
marconi-notification as standalone services within Marconi.

Implements blueprint change-marconi-structure

Change-Id: Id6061f04ec6e6959143fb0f5905bb8799fd86edd
2013-09-17 14:49:24 +02:00

691 lines
24 KiB
Python

# Copyright (c) 2013 Red Hat, Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
# implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Implements MongoDB the storage controller for messages.
Field Mappings:
In order to reduce the disk / memory space used,
field names will be, most of the time, the first
letter of their long name.
"""
import time
import pymongo.errors
import pymongo.read_preferences
from marconi.common import config
import marconi.openstack.common.log as logging
from marconi.openstack.common import timeutils
from marconi.queues import storage
from marconi.queues.storage import exceptions
from marconi.queues.storage.mongodb import options
from marconi.queues.storage.mongodb import utils
LOG = logging.getLogger(__name__)
CFG = config.namespace('limits:storage').from_options(
default_message_paging=10,
)
# For hinting
ID_INDEX_FIELDS = [('_id', 1)]
# NOTE(kgriffs): This index is for listing messages, usually
# filtering out claimed ones.
ACTIVE_INDEX_FIELDS = [
('p', 1), # Project will to be unique, so put first
('q', 1), # May not be unique, since user names it
('k', 1), # Used for sorting and paging, must come before range queries
('c.e', 1), # Used for filtering out claimed messages
]
# For counting
COUNTING_INDEX_FIELDS = [
('p', 1), # Project will to be unique, so put first
('q', 1), # May not be unique, since user names it
('c.e', 1), # Used for filtering out claimed messages
]
# Index used for claims
CLAIMED_INDEX_FIELDS = [
('p', 1),
('q', 1),
('c.id', 1),
('k', 1),
('c.e', 1),
]
# Index used for _next_marker() and also to ensure uniqueness.
MARKER_INDEX_FIELDS = [
('p', 1),
('q', 1),
('k', -1)
]
class MessageController(storage.MessageBase):
"""Implements message resource operations using MongoDB.
Messages:
Name Field
-----------------
queue_name -> q
expires -> e
ttl -> t
uuid -> u
claim -> c
marker -> k
"""
def __init__(self, *args, **kwargs):
super(MessageController, self).__init__(*args, **kwargs)
# Cache for convenience and performance (avoids extra lookups and
# recreating the range for every request.)
self._queue_controller = self.driver.queue_controller
self._db = self.driver.db
self._retry_range = range(options.CFG.max_attempts)
# Make sure indexes exist before,
# doing anything.
self._col = self._db['messages']
self._ensure_indexes()
#-----------------------------------------------------------------------
# Helpers
#-----------------------------------------------------------------------
def _ensure_indexes(self):
"""Ensures that all indexes are created."""
self._col.ensure_index(ACTIVE_INDEX_FIELDS,
name='active',
background=True)
self._col.ensure_index(CLAIMED_INDEX_FIELDS,
name='claimed',
background=True)
self._col.ensure_index(COUNTING_INDEX_FIELDS,
name='counting',
background=True)
# NOTE(kgriffs): This index must be unique so that
# inserting a message with the same marker to the
# same queue will fail; this is used to detect a
# race condition which can cause an observer client
# to miss a message when there is more than one
# producer posting messages to the same queue, in
# parallel.
self._col.ensure_index(MARKER_INDEX_FIELDS,
name='queue_marker',
unique=True,
background=True)
def _next_marker(self, queue_name, project=None):
"""Retrieves the next message marker for a given queue.
This helper is used to generate monotonic pagination
markers that are saved as part of the message
document. Simply taking the max of the current message
markers works, since Marconi always leaves the most recent
message in the queue (new queues always return 1).
Note 1: Markers are scoped per-queue and so are *not*
globally unique or globally ordered.
Note 2: If two or more requests to this method are made
in parallel, this method will return the same
marker. This is done intentionally so that the caller
can detect a parallel message post, allowing it to
mitigate race conditions between producer and
observer clients.
:param queue_name: Determines the scope for the marker
:param project: Queue's project
:returns: next message marker as an integer
"""
document = self._col.find_one({'p': project, 'q': queue_name},
sort=[('k', -1)],
fields={'k': 1, '_id': 0})
return 1 if document is None else (document['k'] + 1)
def _backoff_sleep(self, attempt):
"""Sleep between retries using a jitter algorithm.
Mitigates thrashing between multiple parallel requests, and
creates backpressure on clients to slow down the rate
at which they submit requests.
:param attempt: current attempt number, zero-based
"""
seconds = utils.calculate_backoff(attempt, options.CFG.max_attempts,
options.CFG.max_retry_sleep,
options.CFG.max_retry_jitter)
time.sleep(seconds)
def _remove_expired(self, queue_name, project):
"""Removes all expired messages except for the most recent
in each queue.
This method is used in lieu of mongo's TTL index since we
must always leave at least one message in the queue for
calculating the next marker.
:param queue_name: name for the queue from which to remove
expired messages
:param project: Project queue_name belong's too
"""
# Get the message with the highest marker, and leave
# it in the queue
head = self._col.find_one({'p': project, 'q': queue_name},
sort=[('k', -1)], fields={'k': 1})
if head is None:
# Assume queue was just deleted via a parallel request
LOG.debug(_(u'Queue %s is empty or missing.') % queue_name)
return
query = {
'p': project,
'q': queue_name,
'k': {'$ne': head['k']},
'e': {'$lte': timeutils.utcnow_ts()},
}
self._col.remove(query, w=0)
def _purge_queue(self, queue_name, project=None):
"""Removes all messages from the queue.
Warning: Only use this when deleting the queue; otherwise
you can cause a side-effect of reseting the marker counter
which can cause clients to miss tons of messages.
If the queue does not exist, this method fails silently.
:param queue_name: name of the queue to purge
:param project: ID of the project to which the queue belongs
"""
self._col.remove({'p': project, 'q': queue_name}, w=0)
def _list(self, queue_name, project=None, marker=None,
echo=False, client_uuid=None, fields=None,
include_claimed=False, sort=1, limit=None):
"""Message document listing helper.
:param queue_name: Name of the queue to list
:param project: (Default None) Project `queue_name` belongs to. If
not specified, queries the "global" namespace/project.
:param marker: (Default None) Message marker from which to start
iterating. If not specified, starts with the first message
available in the queue.
:param echo: (Default False) Whether to return messages that match
client_uuid
:param client_uuid: (Default None) UUID for the client that
originated this request
:param fields: (Default None) Fields to include in emmitted
documents
:param include_claimed: (Default False) Whether to include
claimed messages, not just active ones
:param sort: (Default 1) Sort order for the listing. Pass 1 for
ascending (oldest message first), or -1 for descending (newest
message first).
:param limit: (Default None) The maximum number of messages
to list. The results may include fewer messages than the
requested `limit` if not enough are available. If limit is
not specified
:returns: Generator yielding up to `limit` messages.
"""
if sort not in (1, -1):
raise ValueError(u'sort must be either 1 (ascending) '
u'or -1 (descending)')
now = timeutils.utcnow_ts()
query = {
# Messages must belong to this
# queue and project
'p': project,
'q': queue_name,
# The messages cannot be expired
'e': {'$gt': now},
}
if not echo:
query['u'] = {'$ne': client_uuid}
if marker is not None:
query['k'] = {'$gt': marker}
if not include_claimed:
# Only include messages that are not part of
# any claim, or are part of an expired claim.
query['c.e'] = {'$lte': now}
# Construct the request
cursor = self._col.find(query, fields=fields,
sort=[('k', sort)], limit=limit)
# NOTE(flaper87): Suggest the index to use for this query
return cursor.hint(ACTIVE_INDEX_FIELDS)
#-----------------------------------------------------------------------
# Interface
#-----------------------------------------------------------------------
def count(self, queue_name, project=None, include_claimed=False):
"""Return total number of messages in a queue.
This method is designed to very quickly count the number
of messages in a given queue. Expired messages are not
counted, of course. If the queue does not exist, the
count will always be 0.
Note: Some expired messages may be included in the count if
they haven't been GC'd yet. This is done for performance.
"""
query = {
# Messages must belong to this queue
'p': project,
'q': queue_name,
# The messages can not be expired
'e': {'$gt': timeutils.utcnow_ts()},
}
if not include_claimed:
# Exclude messages that are claimed
query['c.e'] = {'$lte': timeutils.utcnow_ts()}
return self._col.find(query).hint(COUNTING_INDEX_FIELDS).count()
def first(self, queue_name, project=None, sort=1):
"""Get first message in the queue (including claimed).
:param queue_name: Name of the queue to list
:param sort: (Default 1) Sort order for the listing. Pass 1 for
ascending (oldest message first), or -1 for descending (newest
message first).
:returns: First message in the queue, or None if the queue is
empty
"""
cursor = self._list(queue_name, project=project,
include_claimed=True, sort=sort,
limit=1)
try:
message = next(cursor)
except StopIteration:
raise exceptions.QueueIsEmpty(queue_name, project)
return message
def active(self, queue_name, marker=None, echo=False,
client_uuid=None, fields=None, project=None,
limit=None):
return self._list(queue_name, project=project, marker=marker,
echo=echo, client_uuid=client_uuid,
fields=fields, include_claimed=False,
limit=limit)
def claimed(self, queue_name, claim_id,
expires=None, limit=None, project=None):
if claim_id is None:
claim_id = {'$ne': None}
query = {
'p': project,
'q': queue_name,
'c.id': claim_id,
'c.e': {'$gt': expires or timeutils.utcnow_ts()},
}
# NOTE(kgriffs): Claimed messages bust be queried from
# the primary to avoid a race condition caused by the
# multi-phased "create claim" algorithm.
preference = pymongo.read_preferences.ReadPreference.PRIMARY
msgs = self._col.find(query, sort=[('k', 1)],
read_preference=preference)
if limit is not None:
msgs = msgs.limit(limit)
now = timeutils.utcnow_ts()
def denormalizer(msg):
doc = _basic_message(msg, now)
doc['claim'] = msg['c']
return doc
return utils.HookedCursor(msgs, denormalizer)
def unclaim(self, queue_name, claim_id, project=None):
cid = utils.to_oid(claim_id)
# NOTE(cpp-cabrera): early abort - avoid a DB query if we're handling
# an invalid ID
if cid is None:
return
# NOTE(cpp-cabrera): unclaim by setting the claim ID to None
# and the claim expiration time to now
now = timeutils.utcnow_ts()
self._col.update({'p': project, 'q': queue_name, 'c.id': cid},
{'$set': {'c': {'id': None, 'e': now}}},
upsert=False, multi=True)
def remove_expired(self):
"""Removes all expired messages except for the most recent
in each queue.
This method is used in lieu of mongo's TTL index since we
must always leave at least one message in the queue for
calculating the next marker.
Warning: This method is expensive, since it must perform
separate queries for each queue, due to the requirement that
it must leave at least one message in each queue, and it
is impractical to send a huge list of _id's to filter out
in a single call. That being said, this is somewhat mitigated
by the fact that remove() is run on each queue seperately,
thereby reducing the duration that any given lock is held.
"""
# TODO(kgriffs): Optimize first by batching the .removes, second
# by setting a 'last inserted ID' in the queue collection for
# each message inserted (TBD, may cause problematic side-effect),
# and third, by changing the marker algorithm such that it no
# longer depends on retaining the last message in the queue!
for name, project in self._queue_controller._get_np():
self._remove_expired(name, project)
def list(self, queue_name, project=None, marker=None, limit=None,
echo=False, client_uuid=None, include_claimed=False):
if limit is None:
limit = CFG.default_message_paging
if marker is not None:
try:
marker = int(marker)
except ValueError:
yield iter([])
messages = self._list(queue_name, project=project, marker=marker,
client_uuid=client_uuid, echo=echo,
include_claimed=include_claimed, limit=limit)
marker_id = {}
now = timeutils.utcnow_ts()
def denormalizer(msg):
marker_id['next'] = msg['k']
return _basic_message(msg, now)
yield utils.HookedCursor(messages, denormalizer)
yield str(marker_id['next'])
@utils.raises_conn_error
def get(self, queue_name, message_id, project=None):
"""Gets a single message by ID.
:raises: exceptions.MessageDoesNotExist
"""
mid = utils.to_oid(message_id)
if mid is None:
raise exceptions.MessageDoesNotExist(message_id, queue_name,
project)
now = timeutils.utcnow_ts()
query = {
'_id': mid,
'p': project,
'q': queue_name,
'e': {'$gt': now}
}
message = list(self._col.find(query).limit(1).hint(ID_INDEX_FIELDS))
if not message:
raise exceptions.MessageDoesNotExist(message_id, queue_name,
project)
return _basic_message(message[0], now)
@utils.raises_conn_error
def bulk_get(self, queue_name, message_ids, project=None):
message_ids = [mid for mid in map(utils.to_oid, message_ids) if mid]
if not message_ids:
return iter([])
now = timeutils.utcnow_ts()
# Base query, always check expire time
query = {
'_id': {'$in': message_ids},
'p': project,
'q': queue_name,
'e': {'$gt': now},
}
# NOTE(flaper87): Should this query
# be sorted?
messages = self._col.find(query).hint(ID_INDEX_FIELDS)
def denormalizer(msg):
return _basic_message(msg, now)
return utils.HookedCursor(messages, denormalizer)
@utils.raises_conn_error
def post(self, queue_name, messages, client_uuid, project=None):
now = timeutils.utcnow_ts()
if not self._queue_controller.exists(queue_name, project):
raise exceptions.QueueDoesNotExist(queue_name, project)
# Set the next basis marker for the first attempt.
next_marker = self._next_marker(queue_name, project)
prepared_messages = [
{
't': message['ttl'],
'q': queue_name,
'p': project,
'e': now + message['ttl'],
'u': client_uuid,
'c': {'id': None, 'e': now},
'b': message['body'] if 'body' in message else {},
'k': next_marker + index,
}
for index, message in enumerate(messages)
]
# Results are aggregated across all attempts
# NOTE(kgriffs): Using lazy instantiation...
aggregated_results = None
# Use a retry range for sanity, although we expect
# to rarely, if ever, reach the maximum number of
# retries.
for attempt in self._retry_range:
try:
ids = self._col.insert(prepared_messages)
# NOTE(kgriffs): Only use aggregated results if we must,
# which saves some cycles on the happy path.
if aggregated_results:
aggregated_results.extend(ids)
ids = aggregated_results
# Log a message if we retried, for debugging perf issues
if attempt != 0:
message = _(u'%(attempts)d attempt(s) required to post '
u'%(num_messages)d messages to queue '
u'%(queue_name)s and project %(project)s')
message %= dict(queue_name=queue_name, attempts=attempt+1,
num_messages=len(ids), project=project)
LOG.debug(message)
return map(str, ids)
except pymongo.errors.DuplicateKeyError as ex:
# Try again with the remaining messages
# NOTE(kgriffs): This can be used in conjunction with the
# log line, above, that is emitted after all messages have
# been posted, to guage how long it is taking for messages
# to be posted to a given queue, or overall.
#
# TODO(kgriffs): Add transaction ID to help match up loglines
if attempt == 0:
message = _(u'First attempt failed while '
u'adding messages to queue %s '
u'for current request') % queue_name
LOG.debug(message)
# TODO(kgriffs): Record stats of how often retries happen,
# and how many attempts, on average, are required to insert
# messages.
# NOTE(kgriffs): Slice prepared_messages. We have to interpret
# the error message to get the duplicate key, which gives
# us the marker that had a dupe, allowing us to extrapolate
# how many messages were consumed, since markers are monotonic
# counters.
duplicate_marker = utils.dup_marker_from_error(str(ex))
failed_index = duplicate_marker - next_marker
# Put the successful one's IDs into aggregated_results.
succeeded_messages = prepared_messages[:failed_index]
succeeded_ids = [msg['_id'] for msg in succeeded_messages]
# Results are aggregated across all attempts
if aggregated_results is None:
aggregated_results = succeeded_ids
else:
aggregated_results.extend(succeeded_ids)
# Retry the remaining messages with a new sequence
# of markers.
prepared_messages = prepared_messages[failed_index:]
next_marker = self._next_marker(queue_name, project)
for index, message in enumerate(prepared_messages):
message['k'] = next_marker + index
# Chill out for a moment to mitigate thrashing/thundering
self._backoff_sleep(attempt)
except Exception as ex:
# TODO(kgriffs): Query the DB to get the last marker that
# made it, and extrapolate from there to figure out what
# needs to be retried.
LOG.exception(ex)
raise
message = _(u'Hit maximum number of attempts (%(max)s) for queue '
u'%(id)s in project %(project)s')
message %= dict(max=options.CFG.max_attempts, id=queue_name,
project=project)
LOG.warning(message)
succeeded_ids = map(str, aggregated_results)
raise exceptions.MessageConflict(queue_name, project, succeeded_ids)
@utils.raises_conn_error
def delete(self, queue_name, message_id, project=None, claim=None):
# NOTE(cpp-cabrera): return early - this is an invalid message
# id so we won't be able to find it any way
mid = utils.to_oid(message_id)
if mid is None:
return
query = {
'_id': mid,
'p': project,
'q': queue_name,
}
# NOTE(cpp-cabrera): return early - the user gaves us an
# invalid claim id and that renders the rest of this
# request moot
cid = utils.to_oid(claim)
if cid is None:
return
now = timeutils.utcnow_ts()
query['e'] = {'$gt': now}
message = self._col.find_one(query)
if message is None:
return
is_claimed = (message['c']['id'] is not None and
message['c']['e'] > now)
if claim is None:
if is_claimed:
raise exceptions.MessageIsClaimed(message_id)
else:
if message['c']['id'] != cid:
raise exceptions.MessageIsClaimedBy(message_id, claim)
self._col.remove(query['_id'], w=0)
@utils.raises_conn_error
def bulk_delete(self, queue_name, message_ids, project=None):
message_ids = [mid for mid in map(utils.to_oid, message_ids) if mid]
query = {
'_id': {'$in': message_ids},
'p': project,
'q': queue_name,
}
self._col.remove(query, w=0)
def _basic_message(msg, now):
oid = msg['_id']
age = utils.oid_ts(oid) - now
return {
'id': str(oid),
'age': int(age),
'ttl': msg['t'],
'body': msg['b'],
}