We change the main exporter to be stored and fetched using atomics rather
than aquiring a mutex for a mild (but significant in the disabled case) speedup.
Also has the benefit of not holding a global lock over all telemetry operations.
benchstat of logging benchmatks before and after:
name old time/op new time/op delta
Baseline-8 329ns ± 2% 327ns ± 2% ~ (p=0.181 n=19+17)
LoggingNoExporter-8 3.08µs ± 3% 2.42µs ± 2% -21.42% (p=0.000 n=20+19)
Logging-8 13.7µs ± 2% 13.2µs ± 1% -3.49% (p=0.000 n=19+19)
LoggingStdlib-8 5.39µs ± 3% 5.41µs ± 2% ~ (p=0.177 n=19+20)
This is a replacement for https://go-review.googlesource.com/c/tools/+/212244
but built on the single exporter principle rather than the exporter list.
Change-Id: Icc99319c4357e0bcb63386c64372a733e8a76796
Reviewed-on: https://go-review.googlesource.com/c/tools/+/221218
Run-TryBot: Emmanuel Odeke <emm.odeke@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>