Introduce tripleo-ceph-ganesha spec
Change-Id: I81c4219d30bcb7a65e20717cee62595d7a4e0064
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Giulio Fidente
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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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TripleO Ceph Ganesha Integration for Manila
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===========================================
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https://blueprints.launchpad.net/tripleo/+spec/tripleo-ceph-ganesha
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Starting in the Octopus release, Ceph has its own day1 tool called cephadm and
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its own day2 tool called orchestrator which will replace ceph-ansible.
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During the Wallaby cycle TripleO will no longer use ceph-ansible for Ceph
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deployment and instead use cephadm [2]_ as described in [1]_. Ganesha deserves
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special attention because for its deployment we will use special functionalities
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in cephadm [2]_ meant to deploy the Ganesha service standalone when the Ceph
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cluster is external.
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Problem Description
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===================
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In TripleO we support deployment of Ganesha both when the Ceph cluster is itself
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managed by TripleO and when the Ceph cluster is itself not managed by TripleO.
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When the Ceph cluster is *not* managed by Tripleo, the Ganesha service must be
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deployed standalone; that is, without any additional core Ceph daemon and it
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should instead be configured to use the external Ceph MON and MDS daemons.
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Proposed Change
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===============
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Overview
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--------
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An ansible task will trigger cephadm [2]_ with special arguments for it to stand
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up a standalone Ganesha container and to it we will provide:
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- the Ceph cluster config file, generated using tripleo-ceph-client [3]_ role
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- the Ceph cluster keyring to interact with MDS
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- the Ganesha config file with pointers to the Ceph config/keyring to use
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The container will then be controlled by pacemaker, as it is today and reusing
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the same code which today manages the ceph-nfs systemd service created by
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ceph-ansible.
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Alternatives
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------------
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Forking and reusing the existing ceph-ansible role for ceph-nfs has been
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discussed but ultimately discarded as that would have moved ownership of the
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Ganesha deployment tasks in TripleO, while our goal remaing to keep ownership
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where subject expertise is, in the Ceph deployment tool.
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Security Impact
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---------------
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None, the same code which TripleO would already use for the generation of the
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Ceph cluster config and keyrings will be consumed.
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Upgrade Impact
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--------------
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Some upgrade tasks which stop and remove the pre-existing ceph-nfs container
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and systemd unit will be added to clean up the system from the ceph-ansible
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managed resources.
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Other End User Impact
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---------------------
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None, the existing input parameters will be reused to drive the newer deployment
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tool.
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Performance Impact
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------------------
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No changes.
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Other Deployer Impact
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---------------------
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No impact on users.
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Developer Impact
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----------------
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The Ganesha config file will be generated using a specific tripleo-ceph task
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while previously, with ceph-ansible, this was created by ceph-ansible itself.
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Implementation
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==============
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The existing implementation which depends on ceph-ansible will remain
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in-tree for at least 1 deprecation cycle. By reusing the existing Heat
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input parameters we should be able to transparently make the Ganesha
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deployment happen with ceph-ansible or the new role just by switching
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the environment file used at deployment time.
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Deployment Flow
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---------------
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The deployment and configuration described in this spec will
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happen before `openstack overcloud deploy`, as described in
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[1]_. This is consistent with how ceph-ansible used to run during
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step2 to configure these services. However, parts of the Manila
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configuration which use Ganesha will still happen when `openstack
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overcloud deploy` is run. This is because some of the configuration
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for Ganesha and Manila needs to happen during step 5. Thus, files like
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`environments/manila-cephfsganesha-config.yaml` will be updated to
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trigger the new required actions.
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Assignee(s)
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-----------
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- fmount
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- fultonj
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- gfidente
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Work Items
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----------
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- Create a set of tasks to deploy on overcloud nodes the Ganesha config file
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- Create a set of tasks to trigger cephadm with special arguments
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Dependencies
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============
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- The tripleo-ceph spec [1]_
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Testing
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=======
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Testing is currently impossible as we only have one network while for Ganesha
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we require at least two, one which connects it to the Ceph public network and
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another where the NFS proxy service is exposed to tenants.
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This is a design decision, one of the values added by the use of an NFS proxy
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for CephFS is to implement network isolation in between the tenant guests and
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the actual Ceph cluster.
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Such a limitation does not come from the migration to cephadm [2]_ but it has
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always existed; the code which enforces the use of two isolated networks is in
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fact in TripleO, not in the Ceph tool itself. We might revisit this in the
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future but it is not a goal of this spec to change this.
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Documentation Impact
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====================
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No changes should be necessary to the TripleO documentation.
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References
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==========
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.. [1] `tripleo-ceph <https://specs.openstack.org/openstack/tripleo-specs/specs/wallaby/tripleo-ceph.html>`_
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.. [2] `cephadm <https://github.com/ceph/ceph/tree/master/src/cephadm>`_
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.. [3] `tripleo-ceph-client <https://specs.openstack.org/openstack/tripleo-specs/specs/wallaby/tripleo-ceph-client.html>`_
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