Make default worker channel buffer length configurable and optionally non blocking

[bgcint]

Is your feature request related to a problem? Please describe.
Under load or when recording a number of metrics, the worker channel buffer can fill up and block the calling code.
This line in particular, for record commands here

Describe the solution you'd like
It would be useful to make the channel buffer length configurable so that users can accommodate
varying load on an application.
It would also be interesting to make the operation optionally non blocking in cases where high load is a constant but metric collection could be a lossy operation.