logg: A Go repository from bep

This is a fork of the exellent Apex Log library.

Main changes:

Trim unneeded dependencies.
Make Fields into a slice to preserve log order.
Split the old Interface in two and remove all but one Log method (see below).
This allows for lazy creation of messages in Log(fmt.Stringer) and ignoring fields added in LevelLoggers with levels below the Loggers.
The pointer passed to HandleLog is not safe to use outside of the current log chain, and needs to be cloned with Clone first if that's needed.
See Benchmarks for more info.

This is probably the very fastest structured log library when logging is disabled:

One can never have enough log libraries!

// Logger is the main interface for the logger.
type Logger interface {
	// WithLevel returns a new entry with `level` set.
	WithLevel(Level) *Entry
}

// LevelLogger is the logger at a given level.
type LevelLogger interface {
	// Log logs a message at the given level using the string from calling s.String().
	// Note that s.String() will not be called if the level is not enabled.
	Log(s fmt.Stringer)

	// Logf logs a message at the given level using the format and args from calling fmt.Sprintf().
	// Note that fmt.Sprintf() will not be called if the level is not enabled.
	Logf(format string, a ...any)

	// WithLevel returns a new entry with `level` set.
	WithLevel(Level) *Entry

	// WithFields returns a new entry with the`fields` in fields set.
	// This is a noop if LevelLogger's level is less than Logger's.
	WithFields(fields Fielder) *Entry

	// WithLevel returns a new entry with the field f set with value v
	// This is a noop if LevelLogger's level is less than Logger's.
	WithField(f string, v any) *Entry

	// WithDuration returns a new entry with the "duration" field set
	// to the given duration in milliseconds.
	// This is a noop if LevelLogger's level is less than Logger's.
	WithDuration(time.Duration) *Entry

	// WithError returns a new entry with the "error" set to `err`.
	// This is a noop if err is nil or  LevelLogger's level is less than Logger's.
	WithError(error) *Entry
}

Benchmarks

Benchmarks below are borrowed and adapted from Zap.

Logging at a disabled level without any structured context

name                                      time/op
DisabledWithoutFields/apex/log-10         33.9ns ± 0%
DisabledWithoutFields/bep/logg-10         0.28ns ± 0%
DisabledWithoutFields/sirupsen/logrus-10  6.54ns ± 0%
DisabledWithoutFields/rs/zerolog-10       0.31ns ± 0%

name                                      alloc/op
DisabledWithoutFields/apex/log-10           112B ± 0%
DisabledWithoutFields/bep/logg-10          0.00B
DisabledWithoutFields/sirupsen/logrus-10   16.0B ± 0%
DisabledWithoutFields/rs/zerolog-10        0.00B

name                                      allocs/op
DisabledWithoutFields/apex/log-10           1.00 ± 0%
DisabledWithoutFields/bep/logg-10           0.00
DisabledWithoutFields/sirupsen/logrus-10    1.00 ± 0%
DisabledWithoutFields/rs/zerolog-10         0.00

Logging at a disabled level with some accumulated context

name                                           time/op
DisabledAccumulatedContext/apex/log-10         0.29ns ± 0%
DisabledAccumulatedContext/bep/logg-10         0.27ns ± 0%
DisabledAccumulatedContext/sirupsen/logrus-10  6.61ns ± 0%
DisabledAccumulatedContext/rs/zerolog-10       0.32ns ± 0%

name                                           alloc/op
DisabledAccumulatedContext/apex/log-10          0.00B
DisabledAccumulatedContext/bep/logg-10          0.00B
DisabledAccumulatedContext/sirupsen/logrus-10   16.0B ± 0%
DisabledAccumulatedContext/rs/zerolog-10        0.00B

name                                           allocs/op
DisabledAccumulatedContext/apex/log-10           0.00
DisabledAccumulatedContext/bep/logg-10           0.00
DisabledAccumulatedContext/sirupsen/logrus-10    1.00 ± 0%
DisabledAccumulatedContext/rs/zerolog-10         0.00

Logging at a disabled level, adding context at each log site

name                                     time/op
DisabledAddingFields/apex/log-10          328ns ± 0%
DisabledAddingFields/bep/logg-10         0.38ns ± 0%
DisabledAddingFields/sirupsen/logrus-10   610ns ± 0%
DisabledAddingFields/rs/zerolog-10       10.5ns ± 0%

name                                     alloc/op
DisabledAddingFields/apex/log-10           886B ± 0%
DisabledAddingFields/bep/logg-10          0.00B
DisabledAddingFields/sirupsen/logrus-10  1.52kB ± 0%
DisabledAddingFields/rs/zerolog-10        24.0B ± 0%

name                                     allocs/op
DisabledAddingFields/apex/log-10           10.0 ± 0%
DisabledAddingFields/bep/logg-10           0.00
DisabledAddingFields/sirupsen/logrus-10    12.0 ± 0%
DisabledAddingFields/rs/zerolog-10         1.00 ± 0%

Logging without any structured context

name                                    time/op
WithoutFields/apex/log-10                964ns ± 0%
WithoutFields/bep/logg-10                100ns ± 0%
WithoutFields/go-kit/kit/log-10          232ns ± 0%
WithoutFields/inconshreveable/log15-10  2.13µs ± 0%
WithoutFields/sirupsen/logrus-10         866ns ± 0%
WithoutFields/stdlib.Println-10         7.08ns ± 0%
WithoutFields/stdlib.Printf-10          56.4ns ± 0%
WithoutFields/rs/zerolog-10             30.9ns ± 0%
WithoutFields/rs/zerolog.Formatting-10  1.33µs ± 0%
WithoutFields/rs/zerolog.Check-10       32.1ns ± 0%

name                                    alloc/op
WithoutFields/apex/log-10                 352B ± 0%
WithoutFields/bep/logg-10                56.0B ± 0%
WithoutFields/go-kit/kit/log-10           520B ± 0%
WithoutFields/inconshreveable/log15-10  1.43kB ± 0%
WithoutFields/sirupsen/logrus-10        1.14kB ± 0%
WithoutFields/stdlib.Println-10          16.0B ± 0%
WithoutFields/stdlib.Printf-10            136B ± 0%
WithoutFields/rs/zerolog-10              0.00B
WithoutFields/rs/zerolog.Formatting-10  1.92kB ± 0%
WithoutFields/rs/zerolog.Check-10        0.00B

name                                    allocs/op
WithoutFields/apex/log-10                 6.00 ± 0%
WithoutFields/bep/logg-10                 2.00 ± 0%
WithoutFields/go-kit/kit/log-10           9.00 ± 0%
WithoutFields/inconshreveable/log15-10    20.0 ± 0%
WithoutFields/sirupsen/logrus-10          23.0 ± 0%
WithoutFields/stdlib.Println-10           1.00 ± 0%
WithoutFields/stdlib.Printf-10            6.00 ± 0%
WithoutFields/rs/zerolog-10               0.00
WithoutFields/rs/zerolog.Formatting-10    58.0 ± 0%
WithoutFields/rs/zerolog.Check-10         0.00

Logging with some accumulated context

name                                         time/op
AccumulatedContext/apex/log-10               12.7µs ± 0%
AccumulatedContext/bep/logg-10               1.52µs ± 0%
AccumulatedContext/go-kit/kit/log-10         2.52µs ± 0%
AccumulatedContext/inconshreveable/log15-10  9.36µs ± 0%
AccumulatedContext/sirupsen/logrus-10        3.41µs ± 0%
AccumulatedContext/rs/zerolog-10             37.9ns ± 0%
AccumulatedContext/rs/zerolog.Check-10       34.0ns ± 0%
AccumulatedContext/rs/zerolog.Formatting-10  1.36µs ± 0%

name                                         alloc/op
AccumulatedContext/apex/log-10               3.30kB ± 0%
AccumulatedContext/bep/logg-10               1.16kB ± 0%
AccumulatedContext/go-kit/kit/log-10         3.67kB ± 0%
AccumulatedContext/inconshreveable/log15-10  3.31kB ± 0%
AccumulatedContext/sirupsen/logrus-10        4.73kB ± 0%
AccumulatedContext/rs/zerolog-10              0.00B
AccumulatedContext/rs/zerolog.Check-10        0.00B
AccumulatedContext/rs/zerolog.Formatting-10  1.92kB ± 0%

name                                         allocs/op
AccumulatedContext/apex/log-10                 53.0 ± 0%
AccumulatedContext/bep/logg-10                 25.0 ± 0%
AccumulatedContext/go-kit/kit/log-10           56.0 ± 0%
AccumulatedContext/inconshreveable/log15-10    70.0 ± 0%
AccumulatedContext/sirupsen/logrus-10          68.0 ± 0%
AccumulatedContext/rs/zerolog-10               0.00
AccumulatedContext/rs/zerolog.Check-10         0.00
AccumulatedContext/rs/zerolog.Formatting-10    58.0 ± 0%

Logging with additional context at each log site

name                                   time/op
AddingFields/apex/log-10               13.2µs ± 0%
AddingFields/bep/logg-10               1.79µs ± 0%
AddingFields/go-kit/kit/log-10         2.23µs ± 0%
AddingFields/inconshreveable/log15-10  14.3µs ± 0%
AddingFields/sirupsen/logrus-10        4.46µs ± 0%
AddingFields/rs/zerolog-10              398ns ± 0%
AddingFields/rs/zerolog.Check-10        389ns ± 0%

name                                   alloc/op
AddingFields/apex/log-10               4.19kB ± 0%
AddingFields/bep/logg-10               2.02kB ± 0%
AddingFields/go-kit/kit/log-10         3.31kB ± 0%
AddingFields/inconshreveable/log15-10  6.68kB ± 0%
AddingFields/sirupsen/logrus-10        6.27kB ± 0%
AddingFields/rs/zerolog-10              24.0B ± 0%
AddingFields/rs/zerolog.Check-10        24.0B ± 0%

name                                   allocs/op
AddingFields/apex/log-10                 63.0 ± 0%
AddingFields/bep/logg-10                 34.0 ± 0%
AddingFields/go-kit/kit/log-10           57.0 ± 0%
AddingFields/inconshreveable/log15-10    74.0 ± 0%
AddingFields/sirupsen/logrus-10          79.0 ± 0%
AddingFields/rs/zerolog-10               1.00 ± 0%
AddingFields/rs/zerolog.Check-10         1.00 ± 0%