Emit online/offline events

[xmidt-org]

Emit online/offline events

[johnabass]

A few questions:

1. Currently, talaria drops outbound messages when upstream servers (e.g. caduceus) are unable to keep up. What happens when talaria drops a connect or disconnect event?
2. Under heavy load, talaria cannot preserve ordering of events due to barging. That means that a disconnect event can be sent before a connect event. What happens in that situation?
3. What happens when a device emits a malformed convey header or no such header at all?

[schmidtw]

• At a minimum, all drops need to be accounted for in metrics.
• All events are treated equally, if the event drops, it drops the exact same way as any other event.
• The ordering of events is never assured and all consuming services must take that into account. Talaria may send events out of order.

If missing or malformed, that's a great question. I think we should add metadata that describes the state of the device (like trust). I propose adding /compliance with the enumeration:

• full - all needed information has been provided
• missing-convey - missing the convey header
• invalid-convey - invalid convey header
• convey-missing-fields - a convey header that does not meet our requirements

[schmidtw]

Clarification: The payload shall be JSON, regardless of the encoding of the WRP.

[schmidtw]

This has been completed.