92aa310652
This patch also ignore "queues" setences. Change-Id: If05d8238a1c92b336faab037b656ca5d5bbd3d49
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ReStructuredText
94 lines
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ReStructuredText
.. This template should be in ReSTructured text. The filename in the
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git repository should match the launchpad URL, for example a URL of
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https://blueprints.launchpad.net/zaqar/+spec/awesome-thing should be
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named awesome-thing.rst.
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Please do not delete any of the sections in this template. If you
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have nothing to say for a whole section, just write: None
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For help with syntax, see http://sphinx-doc.org/rest.html To test
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out your formatting, see http://www.tele3.cz/jbar/rest/rest.html
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============================
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Make FIFO guarantee optional
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============================
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FIFO has been one of Zaqar's most wanted guarantees. Besides
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reliability, durability and other latency requirements, users have
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always requested FIFO to be there. This feature, however, has proven
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to be an issue for some scenarios that don't necesarily require it,
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hence this proposal.
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https://blueprints.launchpad.net/zaqar/+spec/make-fifo-optional
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Problem description
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===================
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FIFO, despite being a great guarantee to have, brings in some scale
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and performance issues that Zaqar is not willing to accept as the
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default behavior. This spec proposes making FIFO optional and letting
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drivers capable of supporting such scenario to do so.
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Proposed change
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===============
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The proposed change, as stated in previous sections, is to make FIFO
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optional. It is possible to do so through `flavors`.
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Not all store drivers are capable of supporting FIFO but those who
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are, will have FIFO listed in their supported capabilities and such
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capabilities will be exposed through the `flavors` ones. However, it's
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not as straightforward as it seems. See the `Work Items`_ section for
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a list of required changes that will make this possible.
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Drawbacks
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---------
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As a side effect of this change, we'll have to relax the delivery
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guarantee for pub-sub. The reason being that walking through the queue
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won't prevent consumers to skip messages.
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Alternatives
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------------
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- Keep it as is
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- Remove FIFO completely
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Implementation
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==============
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Assignee(s)
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-----------
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Primary assignee: flaper87
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Milestones
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----------
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Target Milestone for completion: K-1
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Work Items
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----------
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* Allow driver to expose what features they support
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Each driver supporst a set of features and this set needs to be accessible
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from the upper layers
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* Standardize the *supported* capabilities
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Make a list of supported capabilities
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* Add a way to pass capabilities down to the driver
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We can do this when the driver is initialized since we know what the
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capabilities are at that time.
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* Support both, FIFO and non-FIFO, post methods.
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Dependencies
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============
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* https://review.openstack.org/#/c/126531/
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.. note::
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This work is licensed under a Creative Commons Attribution 3.0
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Unported License.
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http://creativecommons.org/licenses/by/3.0/legalcode
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