bfd29252f5
This patch modifies the way message markers are generated and used, such that Marconi can guarantee FIFO for a single message producer posting to a single queue (FIFO for multiple producers is not guaranteed.) At the same time, these changes guarantee that observer clients will recieve messages once-and-only once by removing race conditions inherent in timestamp-based markers. Along the way, some technical debt was also addressed, particulary regarding style, as well as some minor optimizations. A new service, marconi-mongo-gc, was also added, and is required when using the MongoDB storage driver for Marconi. This service was necessary due to the special requirement that at least the most recent message always remain in each queue, which is an a-priori assumption upon which the FIFO/pagination algorithm is based, and arises from the particular constraints imposed by MongoDB's semantics. Note: While implementing this blueprint, many calculated tradeoffs were made in an attempt to balance performance, risk, readability, and maintainability. The goal was to create a resonable baseline implementation that can be iterated upon pending comprehensive system and performance testing. Due to the many subtleties of solving the FIFO/once-and-only-once problem for the MongoDB driver, future contributors should excercise extreme caution when modifying the algorithm introduced in this patch. Changes include: * Align text in comments * Add counter to queue, messages * Markers are now converted over to using monotonic counter * Handle DuplicateKeyError * Return resources in body as a response to a message POST * Added mongo driver claims tests * Return 503 when no messages were enqueued due to marker conflict * Added backoff sleep between retries * Added marconi-mongo-gc service. This is a new required servi Implements: blueprint message-pagination Change-Id: Ifa0bb9e1bc393545adc4c804d14c6eb2df01848c
290 lines
8.5 KiB
Python
290 lines
8.5 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 the DriverBase abstract class for Marconi storage drivers."""
|
|
|
|
import abc
|
|
|
|
|
|
class DriverBase:
|
|
__metaclass__ = abc.ABCMeta
|
|
|
|
def gc(self):
|
|
"""Runs a garbage collection operation.
|
|
|
|
Called periodically by mongo-gc to trigger removal
|
|
of expired resources from the storage provider.
|
|
|
|
If GC is supported by a given driver, the driver
|
|
MUST override this method.
|
|
"""
|
|
raise NotImplementedError
|
|
|
|
@property
|
|
def gc_interval(self):
|
|
"""Returns the GC interval, in seconds.
|
|
|
|
Used by mongo-gc to determine how often to
|
|
call driver.gc().
|
|
|
|
If GC is supported by a given driver, the driver
|
|
MUST override this method.
|
|
"""
|
|
raise NotImplementedError
|
|
|
|
@abc.abstractproperty
|
|
def queue_controller(self):
|
|
"""Returns storage's queues controller."""
|
|
raise NotImplementedError
|
|
|
|
@abc.abstractproperty
|
|
def message_controller(self):
|
|
"""Returns storage's messages controller."""
|
|
raise NotImplementedError
|
|
|
|
@abc.abstractproperty
|
|
def claim_controller(self):
|
|
"""Returns storage's claims controller."""
|
|
raise NotImplementedError
|
|
|
|
|
|
class ControllerBase(object):
|
|
"""Top-level class for controllers.
|
|
|
|
:param driver: Instance of the driver
|
|
instantiating this controller.
|
|
"""
|
|
|
|
def __init__(self, driver):
|
|
self.driver = driver
|
|
|
|
|
|
class QueueBase(ControllerBase):
|
|
"""This class is responsible for managing queues.
|
|
|
|
Queue operations include CRUD, monitoring, etc.
|
|
|
|
Storage driver implementations of this class should
|
|
be capable of handling high workloads and huge
|
|
numbers of queues.
|
|
"""
|
|
|
|
__metaclass__ = abc.ABCMeta
|
|
|
|
@abc.abstractmethod
|
|
def list(self, project=None, marker=None,
|
|
limit=10, detailed=False):
|
|
"""Base method for listing queues.
|
|
|
|
:param project: Project id
|
|
:param marker: The last queue name
|
|
:param limit: (Default 10) Max number
|
|
:param detailed: Whether metadata is included
|
|
|
|
:returns: An iterator giving a sequence of queues
|
|
and the marker of the next page.
|
|
"""
|
|
raise NotImplementedError
|
|
|
|
@abc.abstractmethod
|
|
def get(self, name, project=None):
|
|
"""Base method for queue retrieval.
|
|
|
|
:param name: The queue name
|
|
:param project: Project id
|
|
|
|
:returns: Dictionary containing queue metadata
|
|
:raises: DoesNotExist
|
|
"""
|
|
raise NotImplementedError
|
|
|
|
@abc.abstractmethod
|
|
def upsert(self, name, metadata, project=None):
|
|
"""This method handles both create and update operations.
|
|
|
|
:param name: The queue name
|
|
:param metadata: Arbitrary metadata
|
|
:param project: Project id
|
|
:returns: True if a queue was created and False
|
|
if it was updated.
|
|
"""
|
|
msg = _("Metadata should be an instance of dict")
|
|
assert isinstance(metadata, dict), msg
|
|
|
|
@abc.abstractmethod
|
|
def delete(self, name, project=None):
|
|
"""Base method for deleting a queue.
|
|
|
|
:param name: The queue name
|
|
:param project: Project id
|
|
"""
|
|
raise NotImplementedError
|
|
|
|
@abc.abstractmethod
|
|
def stats(self, name, project=None):
|
|
"""Base method for queue stats.
|
|
|
|
:param name: The queue name
|
|
:param project: Project id
|
|
:returns: Dictionary with the
|
|
queue stats
|
|
"""
|
|
raise NotImplementedError
|
|
|
|
@abc.abstractmethod
|
|
def actions(self, name, project=None, marker=None, limit=10):
|
|
"""Base method for queue actions.
|
|
|
|
:param name: Queue name
|
|
:param project: Project id
|
|
:param marker: Tail identifier
|
|
:param limit: (Default 10) Max number
|
|
of messages to retrieve.
|
|
"""
|
|
raise NotImplementedError
|
|
|
|
|
|
class MessageBase(ControllerBase):
|
|
"""This class is responsible for managing message CRUD."""
|
|
|
|
__metaclass__ = abc.ABCMeta
|
|
|
|
@abc.abstractmethod
|
|
def list(self, queue, project=None, marker=None,
|
|
limit=10, echo=False, client_uuid=None):
|
|
"""Base method for listing messages.
|
|
|
|
:param queue: Name of the queue to get the
|
|
message from.
|
|
:param project: Project id
|
|
:param marker: Tail identifier
|
|
:param limit: (Default 10) specifies up to 100
|
|
messages to return.
|
|
:param echo: (Default False) Boolean expressing whether
|
|
or not this client should receive its own messages.
|
|
:param client_uuid: Client's unique identifier. This param
|
|
is required when echo=False.
|
|
|
|
:returns: An iterator giving a sequence of messages and
|
|
the marker of the next page.
|
|
"""
|
|
raise NotImplementedError
|
|
|
|
def get(self, queue, message_id, project=None):
|
|
"""Base method for getting a message.
|
|
|
|
:param queue: Name of the queue to get the
|
|
message from.
|
|
:param project: Project id
|
|
:param message_id: Message ID
|
|
|
|
:returns: Dictionary containing message data
|
|
:raises: DoesNotExist
|
|
"""
|
|
raise NotImplementedError
|
|
|
|
@abc.abstractmethod
|
|
def post(self, queue, messages, client_uuid, project=None):
|
|
"""Base method for posting one or more messages.
|
|
|
|
Implementations of this method should guarantee
|
|
and preserve the order, in the returned list, of
|
|
incoming messages.
|
|
|
|
:param queue: Name of the queue to post message to.
|
|
:param messages: Messages to post to queue, an iterable
|
|
yielding 1 or more elements. An empty iterable
|
|
results in undefined behavior.
|
|
:param client_uuid: Client's unique identifier.
|
|
:param project: Project id
|
|
|
|
:returns: List of message ids
|
|
"""
|
|
raise NotImplementedError
|
|
|
|
@abc.abstractmethod
|
|
def delete(self, queue, message_id, project=None, claim=None):
|
|
"""Base method for deleting a single message.
|
|
|
|
:param queue: Name of the queue to post
|
|
message to.
|
|
:param message_id: Message to be deleted
|
|
:param project: Project id
|
|
:param claim: Claim this message
|
|
belongs to. When specified, claim must
|
|
be valid and message_id must belong to
|
|
it.
|
|
"""
|
|
raise NotImplementedError
|
|
|
|
|
|
class ClaimBase(ControllerBase):
|
|
|
|
__metaclass__ = abc.ABCMeta
|
|
|
|
@abc.abstractmethod
|
|
def get(self, queue, claim_id, project=None):
|
|
"""Base method for getting a claim.
|
|
|
|
:param queue: Name of the queue this
|
|
claim belongs to.
|
|
:param claim_id: The claim id
|
|
:param project: Project id
|
|
|
|
:returns: (Claim's metadata, claimed messages)
|
|
:raises: DoesNotExist
|
|
"""
|
|
raise NotImplementedError
|
|
|
|
@abc.abstractmethod
|
|
def create(self, queue, metadata, project=None, limit=10):
|
|
"""Base method for creating a claim.
|
|
|
|
:param queue: Name of the queue this
|
|
claim belongs to.
|
|
:param metadata: Claim's parameters
|
|
to be stored.
|
|
:param project: Project id
|
|
:param limit: (Default 10) Max number
|
|
of messages to claim.
|
|
|
|
:returns: (Claim ID, claimed messages)
|
|
"""
|
|
raise NotImplementedError
|
|
|
|
@abc.abstractmethod
|
|
def update(self, queue, claim_id, metadata, project=None):
|
|
"""Base method for updating a claim.
|
|
|
|
:param queue: Name of the queue this
|
|
claim belongs to.
|
|
:param claim_id: Claim to be updated
|
|
:param metadata: Claim's parameters
|
|
to be updated.
|
|
:param project: Project id
|
|
"""
|
|
raise NotImplementedError
|
|
|
|
@abc.abstractmethod
|
|
def delete(self, queue, claim_id, project=None):
|
|
"""Base method for deleting a claim.
|
|
|
|
:param queue: Name of the queue this
|
|
claim belongs to.
|
|
:param claim_id: Claim to be deleted
|
|
:param project: Project id
|
|
"""
|
|
raise NotImplementedError
|