* Add periodic callhome functionality
Periodically (every 24hrs by default), fetch callhome information and
upload it to SUBNET.
New config keys under the `callhome` subsystem:
enable - Set to `on` for enabling callhome. Default `off`
frequency - Interval between callhome cycles. Default `24h`
* Improvements based on review comments
- Update `enableCallhome` safely
- Rename pctx to ctx
- Block during execution of callhome
- Store parsed proxy URL in global subnet config
- Store callhome URL(s) in constants
- Use existing global transport
- Pass auth token to subnetPostReq
- Use `config.EnableOn` instead of `"on"`
* Use atomic package instead of lock
* Use uber atomic package
* Use `Cancel` instead of `cancel`
Co-authored-by: Harshavardhana <harsha@minio.io>
Co-authored-by: Harshavardhana <harsha@minio.io>
Co-authored-by: Aditya Manthramurthy <donatello@users.noreply.github.com>
The earlier approach of using a license token for
communicating with SUBNET is being replaced
with a simpler mechanism of API keys. Unlike the
license which is a JWT token, these API keys will
be simple UUID tokens and don't have any embedded
information in them. SUBNET would generate the
API key on cluster registration, and then it would
be saved in this config, to be used for subsequent
communication with SUBNET.
