Adapt to file injection deprecation in nova

Trove currently uses –personality to inject files while booting an instance via Nova api. Unfortunately, this parameter is deprecated from Queens release, nova microversion 2.57. As bp Deprecate file injection [1] mentioned, the code to support it would remain, but having a microversion boundary would give Nova the ability to eventually remove the code in the future. In this spec, we try to adapt to file injection deprecation and implement another way to inject files into instance.

Launchpad Blueprint: https://blueprints.launchpad.net/trove/+spec/adapt-to-file-injection-deprecation-in-nova

Problem Description

Nova deprecates file injection by popping out –personality parameter in request schema of microversion 2.57, then no value of –personality would be passed to Nova api service. It’s the current way using this parameter to inject files in Trove. We’re facing the risk that it would break Trove completely.

Proposed Change

Using –user-data is one of the alternatives to inject files while booting an instance.

Here is what we are going to do:

  • Reorganize function trove.instance.models.BaseInstance#get_injected_files to get the files contents, injected path, owner and permission, then build an InjectedFile object. In case of injecting multiple files into instance, we should build and return an InjectedFile object list.

  • Change trove.taskmanager.models.FreshInstanceTasks#_prepare_userdata. Build cloud-config scripts based on InjectedFile object list. If there is a <datastore_manager>.cloudinit script, e.g, mysql.cloudinit, we should detect the format of the script, and then convert it alongside with cloud-config scripts [2] into a mime multi part file [3] in case that we have to pass more than one type of data to cloud-init. So here should be two main helpers, one for organizing cloud-config scripts which looks like below:

    #cloud-config
    write_files:
    -   encoding: b64
        content: CiMgVGhpcyBmaWxlIGNvbnRyb2xzIHRoZSBzdGF0ZSBvZiBTRUxpbnV4...
        owner: trove:trove
        path: /etc/trove/trove.conf
    

    the other one for generating mime messages if there is any *.cloudinit scripts.

    Note

    Noted that currently we’re going to support ONLY two formats for *.cloudinit file, cloud-config and user-data script [4]. It may be difficult for us to organize one user-data scripts based on one mime multi-part file or gzip compressed content, and other formats may not be used a lot. As for formats reference, please see [5] .

  • Use –user-data to pass the parameter we build above while booting an instance, then we can inject files into instance’s specified location, with proper owner and permission. One thing to clarify here is that according to configuration item:

    cfg.BoolOpt('use_nova_server_config_drive', default=True,
                help='Use config drive for file injection when booting '
                'instance.'),
    

    we enable –config-drive when calling novaclient to create a server by default.

  • Remove unused and deprecated codes.

Configuration

None

Database

None

Public API

None

Public API Security

None

Python API

None

CLI (python-troveclient)

None

Internal API

None

Guest Agent

None

Alternatives

None

Dashboard Impact (UX)

None

Implementation

Assignee(s)

Primary assignee:
Fan Zhang <zh.f@outlook.com>

Milestones

Target Milestone for completion:
Rocky-R2

Work Items

  • Add new InjectedFile object.
  • Add new helper functions.
  • Modify current code, including deprecating files parameter and changing to user-data.
  • Modify related code which uses –personality parameter to boot an instance.

Upgrade Implications

None

Dependencies

None

Testing

  • Current functional tests should cover the creating instance scenario.
  • Would need some new unit tests.

Documentation Impact

Docs needed for new configuration item usage.

Appendix

None.