Add support for callbacks for success/failure

[alexanderdean]

Using an inner class? This is functionality which exists in the Python Tracker - @fblundun can explain more...

[fblundun]

https://github.com/snowplow/snowplow-python-tracker/blob/master/snowplow_tracker/emitters.py#L169-174

The idea is that when you create an emitter you can provide on_success and on_failure callback functions.

Whenever the buffer tries to flush:

• If all the events get sent successfully, the on_success function gets called with one argument: the number of events sent
• If not all the events get sent successfully, the on_failure function gets called with two arguments: the number of events sent successfully and a list of payloads corresponding to unsent requests. Each payload in the list is a Python dictionary object like {"e": "pv", "tna": "my_tracker", ...}. The idea being that failed requests don't need to get lost forever - you can do something with them in the on_failure function.

Does that make sense?

[jonalmeida]

Makes sense, thanks!

[alexanderdean]

Nice collaboration guys