Trove-Instance-Metadata
Contents
Introduction
This wiki page describes the design for adding user managed metadata to instances.
Blueprint
https://blueprints.launchpad.net/trove/+spec/trove-metadata
Goals
- Give trove users the ability to store key/value pairs that have significance to them but is not essential to trove's functionality
- Create a user accessible rest API to manage instance metadata
- Mimic the design/interface used by Nova for metadata
- Implement the model so that it acts like a dictionary to make hooking in metadata into the instance very easy and small
Description
Instance metadata is a feature that has been requested frequently by our users. They need a way to store critical information for their instances and have that be associated with the instance so that it is displayed whenever that instance is listed via the API. This also becomes very usable from a testing perspective when doing integration/ci. We can utilize the metadata to store things like what process created the instance, what the instance is being used for, etc... The design for this feature is modeled heavily on the Nova metadata API with a few tweaks in how it works internally.
With the likelihood of an Openstack official metadata service on the horizon I felt like we needed to keep the entry point of integration very small so that when that service becomes available there will be little code in the instance model to change to make that integration happen. To achieve this I made the model work using the dictionary interface and kept all the heavy lifting and fetching/saving operations are internal to the model and happen automatically when keys are modified.
API
The following section describes the API interface both what needs to be sent to the api and what the responses look like.
Create
API Call
API Path and Method
POST /instances/{id}/metadata
Body
{ "metadata": { "value": {"one": {"two": [3, 4, 5]}} } }
API Response
Response Codes
- Positive: 200
- Negative: 400
Response Body
{ "metadata": { "newKey": {"one": {"two": [3, 4, 5]}} } }
Update
Substitute a key and value in the database with a new key and value.
API Call
API Path and Method
PUT /instances/{id}/metadata/{key}
Body
{ "metadata": { "key": "newKey2", "value": {"one": {"two": [3, 4, 5]}} } }
API Response
Response Codes
- Positive: 200
- Negative: 404
Response Body
None
Replace
API Call
API Path and Method
PATCH /instances/{id}/metadata/{key}
Body
{ "metadata": { "value": {"one": {"two": [3, 4, 5], "key2": "the value of this key is a string"}} } }
API Response
Response Codes
- Positive: 200
- Negative: 404
Response Body
None
Delete
API Call
API Path and Method
DELETE /instances/{id}/metadata/{key}
Body
None
API Response
Response Codes
- Positive 200
- Negative 404
Response Body
None