Merge "Implement Cinder integration with zun"
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specs/cinder-integration.rst
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specs/cinder-integration.rst
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This work is licensed under a Creative Commons Attribution 3.0 Unported
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License.
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http://creativecommons.org/licenses/by/3.0/legalcode
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============================
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Container Cinder Integration
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============================
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Related Launchpad Blueprint:
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https://blueprints.launchpad.net/zun/+spec/cinder-zun-integration
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Zun needs to manage containers as well as their associated IaaS resources,
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such as IP addresses, security groups, ports, volumes, etc.
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Zun containers should be able to use volumes which has multiple storage
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vendors or plugins support.
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As zun is project belongs to OpenStack ecosystem and zun has integration
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with Cinder which is block storage service.
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Fuxi is new OpenStack project which aims to integrate Cinder to docker
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volumes. With Fuxi, Cinder can be used as the unified persistence storage
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provider for virtual machine, baremetal and Docker container.
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The implementation of Cinder is enabled using fuxi driver from zun. We need
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to implement Cinder driver in Zun which manages volumes, let Fuxi control the
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mount/unmount volume from Docker container.
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Problem description
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===================
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To store some large amount data in container is not possible. In case of
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of containers, all the storage resides in host storage which is not good
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solution. If host goes down, storage wont be accessible.
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We need to somehow use cloud storage, which is reliable and we can attach
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it to container so that people use containers for workloads also.
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Proposed change
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===============
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There are two approaches docker provides to add volume to Container.
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1. Using Docker run
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docker run -d --volume-driver= Fuxi -v my-named-volume --name web_app
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2. Create volume first & then add it to Container
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docker volume create --driver fuxi
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--name test_vol
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-o size=1
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-o fstype=ext4
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-o multiattach=true
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docker run -d -v my-named-volume
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--name web_app
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I think, we can support both
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1. To Implement first approach, we need following changes
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* Introduce fields in Container API - volume-driver, vol-name, vol-size.
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* We pass call to Volume Driver to create volume.
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* Volume driver connects to Cinder & handles volume creation.
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* Once volume is created in Cinder, then we finally go add volume-driver
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as Fuxi & add volume name which created in cinder.
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* Fuxi should be installed in Docker host and configured with Cinder engine.
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2. To Implement Second approach, we need following changes
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* Introduce Volume API in Zun which has fields volume-driver, volume-name,
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volume-size etc.
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* Volume API will connect to volume driver which will sit under
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/zun/volume/driver.py.
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* Volume Driver connects to Cinder and handles volume creation in Cinder.
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* Once the volume is created in Cinder, it communicates to Docker Volume API
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to attach the created volume in Docker.
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* Docker Volume API use --driver=Fuxi which goes talks to Cinder and attach
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created Volume in Docker.
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* Prerequisite here is, Fuxi should be installed on docker host & configured
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with Cinder. If not, it returns the 500 response.
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* Also we need to introduce new Volume table which contains field vol-driver,
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vol-name, vol-size fields.
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* We need to add storage section in conf file, where we can specify some
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default attributes like storage engine Cinder, Cinder endpoint etc.
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* We also need to configure Cinder endpoint in Fuxi conf file.
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* We can use same implementation for Flocker also as it supports Cinder.
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* I think if we can create seperate CinderDriver which calls from Volume
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volume driver. This approach enables way to implement multiple storages
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supports in the future and we can plug-in multiple storage implementation.
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The diagram below offers an overview of the system architecture. The Zun
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service may communicate with Fuxi and fuxi talks to Cinder for volumes.
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::
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+---------+
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| CLI |
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+----+----+
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|
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+----+----+
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|+-+ REST +----- Zun ----+|
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|+-- --+|
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|+------------+----------+|
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|+--------------------+ Volume Driver+-------------+|
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|| | | |
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|| | | |
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|| | | |
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|| +-----------+ +---------------+ |
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|| | Cinder | | Docker Volume | |
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|| +-----------+ +---------------+ |
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|| | | |
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|| +---------+ +-----------+ |
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|| | Fuxi | | Flocker | |
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|| +----+----+ +-----------+ |
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|+------------+ +---------------+ +----------------+|
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| |
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+---------------------------------------------------+
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Design Principles
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-----------------
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1. Similar user experience between VMs and containers. In particular, the ways
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to configure volumes of a container should be similar as the VM equivalent.
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2. Full-featured container APIs.
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Alternatives
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------------
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1. We can use rexray for storage support, its again third party tool which
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increases the dependancy.
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Data model impact
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-----------------
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Add volume-driver, vol-name, size field in the Volume Table.
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Need to add volume_id to Container Table.
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REST API impact
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---------------
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We need to add below APIs
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1. Create a volume - POST /v1/volumes
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2. List volumes - GET /v1/volumes
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3. Inspect volume - GET /v1/volumes/<uuid>
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4. Delect Volume - DELETE /v1/volumes/<uuid>
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Security impact
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---------------
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None
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Notifications impact
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--------------------
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None
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Other end user impact
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---------------------
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None
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Performance Impact
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------------------
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None
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Other deployer impact
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---------------------
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Deployers need to deploy a Fuxi and Cinder.
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Developer impact
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----------------
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None
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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:
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Digambar
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Other contributors:
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Work Items
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----------
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1. We need to introduce new Volume API.
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2. Implement volume driver in zun.
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3. Implement Cinder calls under the volume driver.
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4. Implement Docker volume support in Zun.
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5. Add volume section in zun.conf.
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6. Add volume-driver support in CLI.
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7. Implement unit/integration test.
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Dependencies
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============
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Add a dependency to Cinder.
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Testing
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=======
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Each patch will have unit tests, and Tempest functional tests covered.
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Documentation Impact
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====================
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A set of documentation for this new feature will be required.
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