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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.
=================
Attaching Volumes
=================
The following sequence diagram outlines the current flow when attaching a
volume to an instance using the ``os-volume_attachments`` API. This diagram
uses the ``libvirt`` driver as an example virt driver to additionally document
the optional interactions with the ``os-brick`` library on the compute hosts
during the request.
.. note:: ``os-brick`` is not always used to connect volumes to the host, most
notibly when connecting an instance natively to ceph ``rbd`` volumes
The diagram also outlines the various locks taken on the compute during the
attach volume flow. In this example these include locks against the
``instance.uuid``, ``cinder_backend.uuid`` orchestrated for ``nova-compute`` by
``os-brick`` and the generic ``connect_volume`` lock taken within os-brick
itself. This final ``connect_volume`` lock also being held when detaching and
disconnecting a volume from the host by ``os-brick``.
.. seqdiag:: attach_volume.diag
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