slog: add an slog backed implementation of Logger

Author: ellemouton

attrs.go

@@ -0,0 +1,36 @@
+package btclog
+
+import (
+	"context"
+	"encoding/hex"
+	"log/slog"
+)
+
+// Hex is a convenience function for a hex-encoded log attributes.
+func Hex(key string, value []byte) slog.Attr {
+	h := hex.EncodeToString(value)
+
+	return slog.String(key, h)
+}
+
+type attrsKey struct{}
+
+// WithCtx returns a copy of the context with which the logging attributes are
+// associated.
+//
+// Usage:
+//
+//	ctx := log.WithCtx(ctx, "height", 1234)
+//	...
+//	log.Info(ctx, "Height processed") // Will contain attribute: height=1234
+func WithCtx(ctx context.Context, attrs ...any) context.Context {
+	return context.WithValue(ctx, attrsKey{}, mergeAttrs(ctx, attrs))
+}
+
+// mergeAttrs returns the attributes from the context merged with the provided attributes.
+func mergeAttrs(ctx context.Context, attrs []any) []any {
+	resp, _ := ctx.Value(attrsKey{}).([]any) // We know the type.
+	resp = append(resp, attrs...)
+
+	return resp
+}

slog.go

@@ -0,0 +1,220 @@
+package btclog
+
+import (
+	"context"
+	"fmt"
+	"log/slog"
+)
+
+// Handler wraps the slog.Handler interface with a few more methods that we
+// need in order to satisfy the Logger interface.
+type Handler interface {
+	slog.Handler
+
+	// Level returns the current logging level of the Handler.
+	Level() Level
+
+	// SetLevel changes the logging level of the Handler to the passed
+	// level.
+	SetLevel(level Level)
+}
+
+// sLogger is an implementation of Logger backed by a structured sLogger.
+type sLogger struct {
+	Handler
+	logger *slog.Logger
+}
+
+// NewSLogger constructs a new structured logger from the given Handler.
+func NewSLogger(handler Handler) Logger {
+	return &sLogger{
+		Handler: handler,
+		logger:  slog.New(handler),
+	}
+}
+
+// Tracef formats message according to format specifier, prepends the prefix as
+// necessary, and writes to log with LevelTrace.
+//
+// This is part of the Logger interface implementation.
+func (l *sLogger) Tracef(format string, params ...any) {
+	l.toSlogf(LevelTrace, format, params...)
+}
+
+// Debugf formats message according to format specifier, prepends the prefix as
+// necessary, and writes to log with LevelDebug.
+//
+// This is part of the Logger interface implementation.
+func (l *sLogger) Debugf(format string, params ...any) {
+	l.toSlogf(LevelDebug, format, params...)
+}
+
+// Infof formats message according to format specifier, prepends the prefix as
+// necessary, and writes to log with LevelInfo.
+//
+// This is part of the Logger interface implementation.
+func (l *sLogger) Infof(format string, params ...any) {
+	l.toSlogf(LevelInfo, format, params...)
+}
+
+// Warnf formats message according to format specifier, prepends the prefix as
+// necessary, and writes to log with LevelWarn.
+//
+// This is part of the Logger interface implementation.
+func (l *sLogger) Warnf(format string, params ...any) {
+	l.toSlogf(LevelWarn, format, params...)
+}
+
+// Errorf formats message according to format specifier, prepends the prefix as
+// necessary, and writes to log with LevelError.
+//
+// This is part of the Logger interface implementation.
+func (l *sLogger) Errorf(format string, params ...any) {
+	l.toSlogf(LevelError, format, params...)
+}
+
+// Criticalf formats message according to format specifier, prepends the prefix as
+// necessary, and writes to log with LevelCritical.
+//
+// This is part of the Logger interface implementation.
+func (l *sLogger) Criticalf(format string, params ...any) {
+	l.toSlogf(LevelCritical, format, params...)
+}
+
+// Trace formats message using the default formats for its operands, prepends
+// the prefix as necessary, and writes to log with LevelTrace.
+//
+// This is part of the Logger interface implementation.
+func (l *sLogger) Trace(v ...any) {
+	l.toSlog(LevelTrace, v...)
+}
+
+// Debug formats message using the default formats for its operands, prepends
+// the prefix as necessary, and writes to log with LevelDebug.
+//
+// This is part of the Logger interface implementation.
+func (l *sLogger) Debug(v ...any) {
+	l.toSlog(LevelDebug, v...)
+}
+
+// Info formats message using the default formats for its operands, prepends
+// the prefix as necessary, and writes to log with LevelInfo.
+//
+// This is part of the Logger interface implementation.
+func (l *sLogger) Info(v ...any) {
+	l.toSlog(LevelInfo, v...)
+}
+
+// Warn formats message using the default formats for its operands, prepends
+// the prefix as necessary, and writes to log with LevelWarn.
+//
+// This is part of the Logger interface implementation.
+func (l *sLogger) Warn(v ...any) {
+	l.toSlog(LevelWarn, v...)
+}
+
+// Error formats message using the default formats for its operands, prepends
+// the prefix as necessary, and writes to log with LevelError.
+//
+// This is part of the Logger interface implementation.
+func (l *sLogger) Error(v ...any) {
+	l.toSlog(LevelError, v...)
+}
+
+// Critical formats message using the default formats for its operands, prepends
+// the prefix as necessary, and writes to log with LevelCritical.
+//
+// This is part of the Logger interface implementation.
+func (l *sLogger) Critical(v ...any) {
+	l.toSlog(LevelCritical, v...)
+}
+
+// TraceS writes a structured log with the given message and key-value pair
+// attributes with LevelTrace to the log.
+//
+// This is part of the Logger interface implementation.
+func (l *sLogger) TraceS(ctx context.Context, msg string, attrs ...any) {
+	l.toSlogS(ctx, LevelTrace, msg, attrs...)
+}
+
+// DebugS writes a structured log with the given message and key-value pair
+// attributes with LevelDebug to the log.
+//
+// This is part of the Logger interface implementation.
+func (l *sLogger) DebugS(ctx context.Context, msg string, attrs ...any) {
+	l.toSlogS(ctx, LevelDebug, msg, attrs...)
+}
+
+// InfoS writes a structured log with the given message and key-value pair
+// attributes with LevelInfo to the log.
+//
+// This is part of the Logger interface implementation.
+func (l *sLogger) InfoS(ctx context.Context, msg string, attrs ...any) {
+	l.toSlogS(ctx, LevelInfo, msg, attrs...)
+}
+
+// WarnS writes a structured log with the given message and key-value pair
+// attributes with LevelWarn to the log.
+//
+// This is part of the Logger interface implementation.
+func (l *sLogger) WarnS(ctx context.Context, msg string, err error,
+	attrs ...any) {
+
+	if err != nil {
+		attrs = append([]any{slog.String("err", err.Error())}, attrs...)
+	}
+
+	l.toSlogS(ctx, LevelWarn, msg, attrs...)
+}
+
+// ErrorS writes a structured log with the given message and key-value pair
+// attributes with LevelError to the log.
+//
+// This is part of the Logger interface implementation.
+func (l *sLogger) ErrorS(ctx context.Context, msg string, err error,
+	attrs ...any) {
+
+	if err != nil {
+		attrs = append([]any{slog.String("err", err.Error())}, attrs...)
+	}
+
+	l.toSlogS(ctx, LevelError, msg, attrs...)
+}
+
+// CriticalS writes a structured log with the given message and key-value pair
+// attributes with LevelCritical to the log.
+//
+// This is part of the Logger interface implementation.
+func (l *sLogger) CriticalS(ctx context.Context, msg string, err error,
+	attrs ...any) {
+	if err != nil {
+		attrs = append([]any{slog.String("err", err.Error())}, attrs...)
+	}
+
+	l.toSlogS(ctx, LevelCritical, msg, attrs...)
+}
+
+// toSlogf is a helper method that converts an unstructured log call that
+// contains a format string and parameters for the string into the appropriate
+// form expected by the structured logger.
+func (l *sLogger) toSlogf(level Level, format string, params ...any) {
+	l.logger.Log(context.Background(), slog.Level(level),
+		fmt.Sprintf(format, params...))
+}
+
+// toSlog is a helper method that converts an unstructured log call that
+// contains a number of parameters into the appropriate form expected by the
+// structured logger.
+func (l *sLogger) toSlog(level Level, v ...any) {
+	l.logger.Log(context.Background(), slog.Level(level), fmt.Sprint(v...))
+}
+
+// toSlogS is a helper method that can be used by all the structured log calls
+// to access the underlying logger.
+func (l *sLogger) toSlogS(ctx context.Context, level Level, msg string,
+	attrs ...any) {
+
+	l.logger.Log(ctx, slog.Level(level), msg, mergeAttrs(ctx, attrs)...)
+}
+
+var _ Logger = (*sLogger)(nil)