Specify host during share creation as scheduler-hint

[kiran pawar]

Description
===========
Manila allows to create shares agnostic to user/admin. However in certain use cases, user/admin wants to create share on specific host since other hosts might be overloaded. User can create new share-type and then create shares using that type to get allocation on new host. But it has limitation since, we need to add new type every-time for new host and we can not delete it unless all shares of that type are deleted.
Thus we need a simple way to create share on specific host, since its first share it will in-turn create SVM. As manila does not provide a way to create SVM, this is another use case as well.

Approach
========
Recently added affinity/anti-affinity filters take scheduler-hints for share creation. We can extend those scheduler-hints to create share on specific backed.
e.g. manila create 1 nfs --scheduler-hints "only_host=host@backend#pool"

This hint will not be stored as metadata and only used for creating share. May be we can restrict to admin only.

[kiran pawar (kpdev)]

PR raised https://review.opendev.org/c/openstack/manila/+/813293

[kiran pawar (kpdev)]

Tempest tests PR https://review.opendev.org/c/openstack/manila-tempest-plugin/+/816168

[Vida Haririan (vhariria)]

Additional comments in: https://meetings.opendev.org/irclogs/%23openstack-meeting-alt/%23openstack-meeting-alt.2021-11-04.log.html#t2021-11-04T15:01:06

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/openstack/manila/+/813293
Committed: https://opendev.org/openstack/manila/commit/746fb7e2df142ba490dc5457ac6a0f47c1d5cc8e
Submitter: "Zuul (22348)"
Branch: master

commit 746fb7e2df142ba490dc5457ac6a0f47c1d5cc8e
Author: Kiran Pawar <email address hidden>
Date: Sun Oct 10 08:06:23 2021 +0000

    OnlyHostFilter allows user to specify host during share create.

    e.g. manila create NFS 1 --name Share1 --share-network net1 \
    --scheduler_hint="only_host=host1@generic1#GENERIC1"

    Since there is no way to create share server in manila, we can use a
    workaround of creating first share on specific host
    (e.g. host@backend#pool). This will then create the share server
    automatically on that host and admin can use idle host when other
    hosts are overloaded.

    New microversion 2.67 introduced.

    DocImpact

    Closes-Bug: #1946462
    Change-Id: I603434cac246e2c0946672d3f0fe469ed5423fa4

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/manila 14.0.0.0rc1 release candidate.