Devstack plugin sets service instance parameters for all drivers

[Goutham Pacha Ravi]

Description
===========

Manila's devstack plugin allows configuring any shared file system backend with the help of Devstack's local.conf options..

For example, the options required for setting up the LVM backend and driver are as follows:

MANILA_BACKEND1_CONFIG_GROUP_NAME="london"
MANILA_BACKEND2_CONFIG_GROUP_NAME="Paris"
MANILA_ENABLED_BACKENDS="london,paris"
MANILA_OPTGROUP_london_driver_handles_share_servers="False"
MANILA_OPTGROUP_paris_driver_handles_share_servers="False"
MANILA_SHARE_BACKEND1_NAME="LONDON"
MANILA_SHARE_BACKEND2_NAME="PARIS"

A more complete example is at [1]

After deployment, you can see that the manila.conf has some unnecessary config opts set for this driver:

 <relevant sections snip>

 [london]
 lvm_share_export_ips = 172.24.5.1,fd9d:85ed:75c3:1::1
 backend_availability_zone = manila-zone-0
 driver_handles_share_servers = False
 service_instance_user = manila <---- This option is not required
 service_image_name = manila-service-image-master <---- This option is not required
 path_to_private_key = /opt/stack/.ssh/id_rsa <---- This option is not required
 path_to_public_key = /opt/stack/.ssh/id_rsa.pub <---- This option is not required
 share_backend_name = LONDON
 share_driver = manila.share.drivers.lvm.LVMShareDriver

 [paris]
 lvm_share_export_ips = 172.24.5.1,fd9d:85ed:75c3:1::1
 backend_availability_zone = manila-zone-1
 driver_handles_share_servers = False
 service_instance_user = manila <---- This option is not required
 service_image_name = manila-service-image-master <---- This option is not required
 path_to_private_key = /opt/stack/.ssh/id_rsa <---- This option is not required
 path_to_public_key = /opt/stack/.ssh/id_rsa.pub <---- This option is not required
 share_backend_name = PARIS
 share_driver = manila.share.drivers.lvm.LVMShareDriver

Steps to reproduce
==================

* Setup manila with devstack specifying a custom backend, not generic driver (e.g. [1])
* After devstack completes, check manila.conf

Expected result
===============

I expect only options relevant to my custom backend to be set

Actual result
=============
The devstack plugin seems to be forcing some options to be set: https://opendev.org/openstack/manila/src/commit/9fbde73868a728b27c9e5b09e4792e5b04388003/devstack/plugin.sh#L94-L98

Environment
===========
1. Devstack with manila on master (Ussuri release)

2. Which storage backend did you use? LVM

3. Which networking type did you use? Neutron, devstack/defaults

Logs & Configs
==============

[1] https://docs.openstack.org/manila/latest/_downloads/42245fd942d8a3ac38aa3aebbc9c2ad1/lvm_local.conf

[Goutham Pacha Ravi (gouthamr)]

Additional comments http://eavesdrop.openstack.org/meetings/manila/2020/manila.2020-05-14-15.00.log.html#l-90

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/756405

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/manila 12.0.0.0rc1 release candidate.