log

Documentation

Overview

Package log provides a structured, leveled logging abstraction.

It defines a Logger interface with Debug, Info, Warn, and Error methods. Two implementations are provided:

• StdLogger: writes to an io.Writer with configurable level filtering and text or JSON output format.
• nopLogger: a zero-allocation no-op logger for when logging is disabled.

Index

• type Format
• type Level
  • func (l Level) String() string
• type Logger
  • func Nop() Logger
• type StdLogger
  • func New(w io.Writer, level Level, format Format) *StdLogger
  • func (l *StdLogger) Debug(msg string, fields ...string)
  • func (l *StdLogger) Error(msg string, fields ...string)
  • func (l *StdLogger) Info(msg string, fields ...string)
  • func (l *StdLogger) Warn(msg string, fields ...string)
  • func (l *StdLogger) WithLevel(level Level) Logger

Types

type Format

type Format int

Format controls the output format of the logger.

const (
	// FormatText outputs human-readable text lines.
	FormatText Format = iota
	// FormatJSON outputs one JSON object per line.
	FormatJSON
)

type Level

type Level int

Level represents a log severity level.

const (
	// LevelDebug is the most verbose level.
	LevelDebug Level = iota
	// LevelInfo is for general operational messages.
	LevelInfo
	// LevelWarn is for warning conditions.
	LevelWarn
	// LevelError is for error conditions.
	LevelError
)

func (Level) String

func (l Level) String() string

String returns the human-readable name of a log level.

type Logger

type Logger interface {
	// Debug logs a message at DEBUG level.
	Debug(msg string, fields ...string)
	// Info logs a message at INFO level.
	Info(msg string, fields ...string)
	// Warn logs a message at WARN level.
	Warn(msg string, fields ...string)
	// Error logs a message at ERROR level.
	Error(msg string, fields ...string)
	// WithLevel returns a new Logger with the given minimum level.
	WithLevel(level Level) Logger
}

Logger is the interface for structured, leveled logging. Each method accepts a message and optional key-value pairs. Keys and values are provided as alternating string arguments.

func Nop

func Nop() Logger

Nop returns a Logger that discards all log output with zero allocation.

type StdLogger

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

StdLogger writes structured log entries to an io.Writer.

func New

func New(w io.Writer, level Level, format Format) *StdLogger

New creates a new StdLogger writing to w at the given minimum level and output format.

func (*StdLogger) Debug

func (l *StdLogger) Debug(msg string, fields ...string)

Debug logs at DEBUG level.

func (*StdLogger) Error

func (l *StdLogger) Error(msg string, fields ...string)

Error logs at ERROR level.

func (*StdLogger) Info

func (l *StdLogger) Info(msg string, fields ...string)

Info logs at INFO level.

func (*StdLogger) Warn

func (l *StdLogger) Warn(msg string, fields ...string)

Warn logs at WARN level.

func (*StdLogger) WithLevel

func (l *StdLogger) WithLevel(level Level) Logger

WithLevel returns a new StdLogger sharing the same writer but with a different minimum log level.