The Hidden Cost of Info Logging in Prod

I was reluctant to adopt Zap for a long time because... Log performance shouldn't matter.

If your app is bottlenecked by logging performance in production, you've got bigger problems.

What is of concern to me is the performance cost of ignored logs in production.

What happens when production code encounters a statement like log.Debug(err)? Production environments use log levels to ignore info and debug statements, but that log statement must still be evaluated.

So I grabbed a couple of popular Golang logging libraries (Zap, Logrus), set their log level to Warn and benchmarked Info logging.

Results:

    $ go test -bench=. -benchmem

    BenchmarkZapInfo-12                     41377027             28.3 ns/op             0 B/op          0 allocs/op
    BenchmarkZapSugarInfo-12                100000000            11.5 ns/op             0 B/op          0 allocs/op
    BenchmarkLogrusInfo-12                  249465934             4.81 ns/op            0 B/op          0 allocs/op

    BenchmarkZapInfoWithFields-12           11537806            104 ns/op             128 B/op          1 allocs/op
    BenchmarkZapSugarInfoWithFields-12      24488396             47.0 ns/op            16 B/op          1 allocs/op
    BenchmarkLogrusInfoWithFields-12         2154274            558 ns/op             512 B/op          5 allocs/op

    BenchmarkZapWarn-12                      1308540            919 ns/op             216 B/op          2 allocs/op
    BenchmarkZapSugarWarn-12                  999940           1210 ns/op             248 B/op          3 allocs/op
    BenchmarkLogrusWarn-12                    499970           2406 ns/op             480 B/op         15 allocs/op

    BenchmarkZapSugarWarnWithFields-12        857092           1439 ns/op             280 B/op          4 allocs/op
    BenchmarkZapWarnWithFields-12             857092           1393 ns/op             344 B/op          3 allocs/op
    BenchmarkLogrusWarnWithFields-12          333314           3492 ns/op            1009 B/op         21 allocs/op

    PASS
    ok      github.com/main 16.594s
        

See repository for analysis: https://github.com/kevburnsjr/log-info-bench