live migration does not accept 'None' as host

[goek-han]

The help message says that if no destination host is provided, the scheduler will choose a host. However, I get an error:

❯ osc --version
osc 0.13.5

❯ osce compute server live-migrate -h                                                                                                                                                                 
Live-Migrate Server (os-migrateLive Action) (microversion = 2.68)

Usage: osc compute server live-migrate268 [OPTIONS] --block-migration <BLOCK_MIGRATION> --host <HOST> <ID>

Options:
  -h, --help     Print help (see more with '--help')
  -V, --version  Print version

Path parameters:
  <ID>  id parameter for /v2.1/servers/{id}/action API

Body parameters:
      --block-migration <BLOCK_MIGRATION>
          Migrates local disks by using block migration. Set to `auto` which means nova will detect whether source and destination hosts on shared storage. if they are on shared storage, the live-migration won’t be block migration. Otherwise the block migration will be executed. Set to `True`, means the request will fail when the source or destination host uses shared storage. Set to `False` means the request will fail when the source and destination hosts are not on the shared storage [possible values: true, false]
      --host <HOST>
          The host to which to migrate the server. If this parameter is `None`, the scheduler chooses a host
..

❯ osc compute server live-migrate ee0da048-2e08-459e-91aa-90a1c78456fa                                                                                                                               
error: the following required arguments were not provided:
  --block-migration <BLOCK_MIGRATION>
  --host <HOST>

Usage: osc compute server live-migrate268 --block-migration <BLOCK_MIGRATION> --host <HOST> --os-project-name <OS_PROJECT_NAME> --os-region-name <OS_REGION_NAME> <ID>

For more information, try '--help'.


❯ osce compute server live-migrate --block-migration false ee0da048-2e08-459e-91aa-90a1c78456fa                                                                                                       
error: the following required arguments were not provided:
  --host <HOST>

Usage: osc compute server live-migrate268 --block-migration <BLOCK_MIGRATION> --host <HOST> --os-project-name <OS_PROJECT_NAME> --os-region-name <OS_REGION_NAME> <ID>

For more information, try '--help'.

Maybe the following is the reason?

• In the sdk the host is optional:

  openstack/openstack_sdk/src/api/compute/v2/server/os_migrate_live_268.rs

  Line 57 in 28247a8

  pub(crate) host: Option<Cow<'a, str>>,

• But in the cli not, I think:

  openstack/openstack_cli/src/compute/v2/server/os_migrate_live_268.rs

  Line 94 in 28247a8

  host: String,

However I am not sure why this is.

In a similar vein, shouldn't the block-migration be set to auto?

[gtema]

Let me give a short explanation on why "help on param says one thing, but it works not that way". All such descriptions are being retrieved from the api spec of the service. In some rare cases they are adapted, but mostly it is 1-to-1. On the CLI side, however, there is a handling of the parameters based on their type, and not the description. So it is absolutely possible those are not in sync. Main purpose is to re-expose whatever the service says without us investing additional work in copy-pasting.
This does not answer the question of the why optional in sdk is not optional in cli - this is handled in the codegenerator and I will have a look at it tomorrow.
wrt default values - there is no easy possibility how to do this since, as I said, the code is generated based on the openapi spec. CLI serves as an api wrapper without adding own logic. There are "manually" created commands that either combine few API calls or do some other convenience work, but otherwise spirit of the cli is to wrap the api in an automatic way.

[gtema]

https://opendev.org/openstack/nova/src/branch/master/nova/api/openstack/compute/schemas/migrate_server.py#L65 defines, that since 2.25 nova expects block-migration and host parameter to be set in the request. From that pov the cli is correct. The Option around the param in the SDK is to allow it being explicit None. So when you invoke sdk programatically you need a way to set None. From the cli this is only possible by having a mandatory parameter. The bug here is that it does not allow you to set it to an explicit None (i.e. as a string "none" or so). I would need to think how to address it.

To answer your initial question: nova expects the parameter (host) to be always set while it allows also a None value. It is not trivial to differentiate on the CLI side between unset Null and set Null, therefore this confusion. Parameter descriptions in the sdk/cli are being always fetched directly from the service apis and there is no logic that would try to align what is said there with what the schema describes.