b62f9a04a0
This change adds a simple sequence diagram showing the flow of a volume attachment between the various services, using the libvirt driver as an example virt driver. Change-Id: I631ac9de3d48aa0ad849f6615d0ad2052cb63e80
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35 lines
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..
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Licensed under the Apache License, Version 2.0 (the "License"); you may
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not use this file except in compliance with the License. You may obtain
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a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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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, WITHOUT
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WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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License for the specific language governing permissions and limitations
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under the License.
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=================
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Attaching Volumes
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=================
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The following sequence diagram outlines the current flow when attaching a
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volume to an instance using the ``os-volume_attachments`` API. This diagram
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uses the ``libvirt`` driver as an example virt driver to additionally document
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the optional interactions with the ``os-brick`` library on the compute hosts
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during the request.
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.. note:: ``os-brick`` is not always used to connect volumes to the host, most
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notibly when connecting an instance natively to ceph ``rbd`` volumes
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The diagram also outlines the various locks taken on the compute during the
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attach volume flow. In this example these include locks against the
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``instance.uuid``, ``cinder_backend.uuid`` orchestrated for ``nova-compute`` by
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``os-brick`` and the generic ``connect_volume`` lock taken within os-brick
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itself. This final ``connect_volume`` lock also being held when detaching and
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disconnecting a volume from the host by ``os-brick``.
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.. seqdiag:: attach_volume.diag
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