How to disable a log.Logger

Question

I have some heavily instrumented code that makes use of the log package. Now it's come time to turn off the logging, and I can't determine how to turn off the standard logger.

Have I missed something? Should I be checking a flag before making log calls, or commenting them out in production?

Answer 1

No reason to create your own type for a common io.Writer when one exists in the io/ioutil package.

import (     "log"     "io/ioutil" )  func init() {     log.SetOutput(ioutil.Discard) } 

Answer 2

For completely disabling logs, it's actually better to call log.SetFlags(0)^Joril and set the output to a no-op io.Writer (i.e., log.SetOutput(ioutil.Discard))

But even after this, the operations will idle around 500-600 ns/op¹

This can still be cut short (to around 100 ns/op) by using a custom Logger implementation, and implementing all the functions to be no-op -- as demonstrated here (only overriding Println for bervity).

The alternative to all these is to use a custom logging framework with levels and set it to complete OFF.

Note though, one of the commonly used library for logging (logrus) has performance implications -- the same can be found in the benchmarks where it perform with 3K+ ns/op, regardless.

Biased opinion: from the benchmarks, the library go-logging performs in par with the custom Logger implementation when setting the Level to -1, regardless of the backend and formatting

(the benchmark source can be found here)

the output of the benchmark is as follows:

testing: warning: no tests to run PASS BenchmarkGoLogging-4                                             1000000          2068 ns/op BenchmarkGoLoggingNullBackend-4                                  5000000           308 ns/op BenchmarkGoLoggingNullBackendWithFancyFormatter-4                3000000           435 ns/op BenchmarkGoLoggingOffLevel-4                                    20000000           109 ns/op BenchmarkGoLoggingNullBackendAndOffLevel-4                      20000000           108 ns/op BenchmarkGoLoggingNullBackendWithFancyFormatterAndOffLevel-4    20000000           109 ns/op BenchmarkLog15-4                                                  200000          7359 ns/op BenchmarkLog15WithDiscardHandler-4                               2000000           922 ns/op BenchmarkLog15WithDiscardHandlerAndOffLevel-4                    2000000           926 ns/op BenchmarkLog15WithNopLogger-4                                   20000000           108 ns/op BenchmarkLog15WithNopLoggerDiscardHandlerA-4                    20000000           112 ns/op BenchmarkLog15WithNopLoggerAndDiscardHandlerAndOffLevel-4       20000000           112 ns/op BenchmarkLog-4                                                   1000000          1217 ns/op BenchmarkLogIoDiscardWriter-4                                    2000000           724 ns/op BenchmarkLogIoDiscardWriterWithoutFlags-4                        3000000           543 ns/op BenchmarkLogCustomNullWriter-4                                   2000000           731 ns/op BenchmarkLogCustomNullWriterWithoutFlags-4                       3000000           549 ns/op BenchmarkNopLogger-4                                            20000000           113 ns/op BenchmarkNopLoggerWithoutFlags-4                                20000000           112 ns/op BenchmarkLogrus-4                                                 300000          3832 ns/op BenchmarkLogrusWithDiscardWriter-4                                500000          3032 ns/op BenchmarkLogrusWithNullFormatter-4                                500000          3814 ns/op BenchmarkLogrusWithPanicLevel-4                                   500000          3872 ns/op BenchmarkLogrusWithDiscardWriterAndPanicLevel-4                   500000          3085 ns/op BenchmarkLogrusWithDiscardWriterAndNullFormatterAndPanicLevel-4   500000          3064 ns/op ok      log-benchmarks  51.378s go test -bench .  62.17s user 3.90s system 126% cpu 52.065 total 

^{#1: YMMV, tested on i7-4500U CPU @ 1.80GHz}