Log level for Exporter failures

[kenfinnigan]

Is your feature request related to a problem? Please describe.
Currently, a log warning is produced when any failure during span export occurs.

In looking at the JaegerGrpcSpanExporter in particular, I was curious how it's possible to know whether a failure to export is a transient failure vs a more serious problem, such as an endpoint that can not be connected to because the URI is wrong, even if it's a valid URI.

Describe the solution you'd like
In the situation of an endpoint that can't be connected to, maybe it's possible to track such a connection issue and log an error instead of a warning if that same error occurs a certain number of times, and then stop logging if the failure continues.

I appreciate it needs to handle transient failures and log those at a warning level, but for a persistent failure, something more than a log warning would be preferred.

[jkwatson]

@kenfinnigan do you have any ideas on how to actually implement this feature? Would you be willing to write the code for one of the exporters to support this?

[kenfinnigan]

I can find some time to take a crack at it