Metrics aggregation pipeline

[bogdandrutu]

Here is the picture that describes the MetricsSDK design:

Some details:

• Every instrument has associated (based on the instrument type) an Accumulator.
• The Accumulator passes all the accumulated pairs <LabelSet, Accumulation> to the Processor.
• Accumulation is an immutable representation of an accumulated value by the Aggregator in case of a synchronous instrument, or created by the asynchronous accumulator in case of async instruments.

[bogdandrutu]

@jkwatson I will update the picture with detail in the processor once I get to work and clear that code. For the moment I am only focused on the aggregator/accumulation stuff.

[jkwatson]

awesome. sounds good. this helps my visual brain quite a bit. 👍