logger

README

go-logger

This is a fork of the logger from gmkit.

A structured, leveled logger. Output is logfmt by default.

Usage

Minimal configuration

l := logger.New()

l.Info("some message", "anotherkey", "another value")

// Output would resemble:
// ts=2023-04-21T16:09:00.026753Z caller=github.com/jasonhancock/go-logger_test/example_test.go:43 src=go-logger.test level=info msg="some message" anotherkey="another value"

Customized config

l := logger.New(
	logger.WithDestination(os.Stdout),
	logger.WithName("myapp"),
	logger.WithLevel("info"),
	logger.WithFormat(logger.FormatLogFmt),
	logger.With("somekey", "someval"),
)

l.Info("some message", "anotherkey", "another value")

// Output would resemble:
// ts=2023-04-13T17:38:13.516398Z caller=github.com/jasonhancock/go-logger_test/example_test.go:11 somekey=someval src=myapp level=info msg="some message" anotherkey="another value"

JSON

l := logger.New(
	logger.WithFormat(logger.FormatJSON),
	logger.WithName("myapp"),
)

l.Info("some message", "anotherkey", "another value")

// Output would resemble:
// {"anotherkey":"another value","caller":"github.com/jasonhancock/go-logger_test/example_test.go:32","level":"info","msg":"some message","src":"myapp","ts":"2023-04-21T16:08:24.224597Z"}

Using the default logger

l := logger.Default()
l.Info("some message")

// Output would resemble:
// ts=2023-04-21T16:09:28.653472Z caller=github.com/jasonhancock/go-logger_test/example_test.go:51 src=default level=info msg="some message"

Documentation

Index

• Constants
• Variables
• func ParseLevel(s string) slog.Leveler
• type DynamicLeveler
  • func NewDynamicLeveler(initialLevel string) *DynamicLeveler
  • func (d *DynamicLeveler) Level() slog.Level
  • func (d *DynamicLeveler) SetLevel(level string)
• type L
  • func Default() *L
  • func New(opts ...Option) *L
  • func Silence() *L
  • func (l *L) Debug(msg any, keyvals ...any)
  • func (l *L) Err(msg any, keyvals ...any)
  • func (l *L) Fatal(msg any, keyvals ...any)
  • func (l *L) Info(msg any, keyvals ...any)
  • func (l *L) LogError(msg string, err error, keyvals ...any)
  • func (l *L) New(name string) *L
  • func (l *L) Warn(msg any, keyvals ...any)
  • func (l *L) With(keyvals ...any) *L
• type Option
  • func With(keyvals ...interface{}) Option
  • func WithAutoCallerPrefixTrim() Option
  • func WithCaller(showCaller bool) Option
  • func WithCallerPrefixTrim(str string) Option
  • func WithDestination(w io.Writer) Option
  • func WithFormat(format string) Option
  • func WithLevel(level string) Option
  • func WithLeveler(leveler slog.Leveler) Option
  • func WithName(name string) Option
  • func WithTimeLocation(loc *time.Location) Option
• type TimeFormatterFunc

Examples

• Default
• New (Customized)
• New (Json)
• New (Minimum)

Constants

const (
	FormatLogFmt = "logfmt"
	FormatJSON   = "json"
)

Constants defining various output formats.

const (
	LevelAll   = slog.Level(-10)
	LevelFatal = slog.Level(12)
)

Variables

var AvailableFormats = []string{
	FormatLogFmt,
	FormatJSON,
}

AvailableFormats lists the available format types.

Functions

func ParseLevel

func ParseLevel(s string) slog.Leveler

ParseLevel parses the string into a Level.

Types

type DynamicLeveler

type DynamicLeveler struct {
	// contains filtered or unexported fields
}

DynamicLeveler gives you the ability to adjust the log level of the application without having to restart it.

func NewDynamicLeveler

func NewDynamicLeveler(initialLevel string) *DynamicLeveler

NewDynamicLeveler initializes a DynamicLeveler and sets the initial log level to initialLevel.

func (*DynamicLeveler) Level

func (d *DynamicLeveler) Level() slog.Level

Level returns the latest log level.

func (*DynamicLeveler) SetLevel

func (d *DynamicLeveler) SetLevel(level string)

SetLevel changes the log level.

type L

type L struct {
	// contains filtered or unexported fields
}

L is the logger implementation

func Default

func Default() *L

Default returns a default logger implementation

Example

l := logger.Default()
l.Info("some message")

// Output would resemble:
// ts=2023-04-21T16:09:28.653472Z caller=github.com/jasonhancock/go-logger_test/example_test.go:51 src=default level=info msg="some message"

func New

func New(opts ...Option) *L

New initializes a new logger. If w is nil, logs will be sent to stdout.

Example (Customized)

l := logger.New(
	logger.WithDestination(os.Stdout),
	logger.WithName("myapp"),
	logger.WithLevel("info"),
	logger.WithFormat(logger.FormatLogFmt),
	logger.With("somekey", "someval"),
)

l.Info("some message", "anotherkey", "another value")

// Output would resemble:
// ts=2023-04-13T17:38:13.516398Z caller=github.com/jasonhancock/go-logger_test/example_test.go:11 somekey=someval src=myapp level=info msg="some message" anotherkey="another value"

Example (Json)

l := logger.New(
	logger.WithFormat(logger.FormatJSON),
	logger.WithName("myapp"),
)

l.Info("some message", "anotherkey", "another value")

// Output would resemble:
// {"anotherkey":"another value","caller":"github.com/jasonhancock/go-logger_test/example_test.go:32","level":"info","msg":"some message","src":"myapp","ts":"2023-04-21T16:08:24.224597Z"}

Example (Minimum)

l := logger.New()

l.Info("some message", "anotherkey", "another value")

// Output would resemble:
// ts=2023-04-21T16:09:00.026753Z caller=github.com/jasonhancock/go-logger_test/example_test.go:43 src=go-logger.test level=info msg="some message" anotherkey="another value"

func Silence

func Silence() *L

Silence returns a logger that writes everything to /dev/null. Useful for silencing log output from tests

func (*L) Debug

func (l *L) Debug(msg any, keyvals ...any)

Debug logs a message at the debug level

func (*L) Err

func (l *L) Err(msg any, keyvals ...any)

Err logs a message at the error level

func (*L) Fatal

func (l *L) Fatal(msg any, keyvals ...any)

Fatal logs a message at the fatal level and also exits the program by calling os.Exit

func (*L) Info

func (l *L) Info(msg any, keyvals ...any)

Info logs a message at the info level

func (*L) LogError

func (l *L) LogError(msg string, err error, keyvals ...any)

LogError logs an error. It automatically unwinds multi-errors (not recursively...yet).

func (*L) New

func (l *L) New(name string) *L

New returns a sub-logger with the name appended to the existing logger's source

func (*L) Warn

func (l *L) Warn(msg any, keyvals ...any)

Warn logs a message at the warning level

func (*L) With

func (l *L) With(keyvals ...any) *L

With returns a logger with the keyvals appended to the existing logger

type Option

type Option func(*options)

Option is used to customize the logger.

func With

func With(keyvals ...interface{}) Option

With adds key value pairs to the logger.

func WithAutoCallerPrefixTrim

func WithAutoCallerPrefixTrim() Option

WithAutoCallerPrefixTrim intelligently figures out the prefix to trim from the caller value of each log message.

func WithCaller

func WithCaller(showCaller bool) Option

WithCaller sets whether or not to include the source file and line number of where the message originated.

func WithCallerPrefixTrim

func WithCallerPrefixTrim(str string) Option

WithCallerPrefixTrim manually specifies a path to trim from the caller value of each log message.

func WithDestination

func WithDestination(w io.Writer) Option

WithDestination sets the target for where the output of the logger should be written.

func WithFormat

func WithFormat(format string) Option

WithFormat sets the format to log in.

func WithLevel

func WithLevel(level string) Option

WithLevel sets the logging level of the logger.

func WithLeveler

func WithLeveler(leveler slog.Leveler) Option

WithLeveler gives you the ability to provide a leveler for dyanmically adjusting the log level.

func WithName

func WithName(name string) Option

WithName specifies the name of the application. If not specified, the current processes name will be used.

func WithTimeLocation

func WithTimeLocation(loc *time.Location) Option

WithTimeLocation specifies the locale to log the time in.

type TimeFormatterFunc

type TimeFormatterFunc func(time.Time) string