83 lines
2.4 KiB
Go
83 lines
2.4 KiB
Go
package logging
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import (
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"context"
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"io"
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"log"
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)
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// Classification the log entry's classification name
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type Classification string
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// Set of standard classifications that can be used by clients and middleware
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const (
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Warn Classification = "WARN"
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Debug Classification = "DEBUG"
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)
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// Logger is an interface for logging entries at certain classifications.
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type Logger interface {
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// Logf is expected to support the standard fmt package "verbs".
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Logf(classification Classification, format string, v ...interface{})
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}
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// LoggerFunc is a wrapper around a function to satisfy the Logger interface.
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type LoggerFunc func(classification Classification, format string, v ...interface{})
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// Logf delegates the logging request to the wrapped function.
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func (f LoggerFunc) Logf(classification Classification, format string, v ...interface{}) {
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f(classification, format, v...)
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}
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// ContextLogger is an optional interface a Logger implementation may expose that provides
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// the ability to create context aware log entries.
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type ContextLogger interface {
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WithContext(context.Context) Logger
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}
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// WithContext will pass the provided context to logger if it implements the ContextLogger interface and return the resulting
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// logger. Otherwise the logger will be returned as is. As a special case if a nil logger is provided, a Nop logger will
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// be returned to the caller.
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func WithContext(ctx context.Context, logger Logger) Logger {
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if logger == nil {
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return Nop{}
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}
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cl, ok := logger.(ContextLogger)
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if !ok {
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return logger
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}
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return cl.WithContext(ctx)
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}
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// Nop is a Logger implementation that simply does not perform any logging.
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type Nop struct{}
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// Logf simply returns without performing any action
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func (n Nop) Logf(Classification, string, ...interface{}) {
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return
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}
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// StandardLogger is a Logger implementation that wraps the standard library logger, and delegates logging to it's
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// Printf method.
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type StandardLogger struct {
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Logger *log.Logger
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}
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// Logf logs the given classification and message to the underlying logger.
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func (s StandardLogger) Logf(classification Classification, format string, v ...interface{}) {
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if len(classification) != 0 {
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format = string(classification) + " " + format
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}
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s.Logger.Printf(format, v...)
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}
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// NewStandardLogger returns a new StandardLogger
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func NewStandardLogger(writer io.Writer) *StandardLogger {
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return &StandardLogger{
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Logger: log.New(writer, "SDK ", log.LstdFlags),
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}
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}
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