fix(log): make global logger thread-safe with atomic.Pointer

pkg/log/levels.go

@@ -14,13 +14,13 @@ const (
 
 // DebugEnabled reports whether debug-level messages are currently logged.
 func DebugEnabled() bool {
-	return sugar.Desugar().Core().Enabled(zapcore.DebugLevel)
+	return sugar.Load().Desugar().Core().Enabled(zapcore.DebugLevel)
 }
 
 // LevelString returns the lowest enabled log level as a lowercase string
 // (e.g. "debug", "info", "warn", "error", "fatal").
 func LevelString() string {
-	core := sugar.Desugar().Core()
+	core := sugar.Load().Desugar().Core()
 	for _, l := range []zapcore.Level{
 		zapcore.DebugLevel,
 		zapcore.InfoLevel,

pkg/log/logger.go

@@ -2,18 +2,17 @@ package log
 
 import (
 	"os"
+	"sync/atomic"
 
 	"go.uber.org/zap"
 	"go.uber.org/zap/zapcore"
 	"golang.org/x/term"
 )
 
-// sugar is the package-level sugared logger. All package functions delegate to it.
-var sugar *zap.SugaredLogger
+var sugar atomic.Pointer[zap.SugaredLogger]
 
 func init() {
-	// Default: silent until Init() is called.
-	sugar = zap.NewNop().Sugar()
+	sugar.Store(zap.NewNop().Sugar())
 }
 
 // Config holds logger configuration parsed from CLI flags.
@@ -35,7 +34,7 @@ func Init(cfg Config) {
 		zap.AddStacktrace(zapcore.FatalLevel),
 	}
 	logger := zap.New(core, opts...)
-	sugar = logger.Sugar()
+	sugar.Store(logger.Sugar())
 }
 
 func resolveLevel(cfg Config) zapcore.Level {
@@ -86,30 +85,29 @@ func plainEncoderConfig() zapcore.EncoderConfig {
 
 // Underlying returns the raw *zap.Logger for advanced use cases.
 func Underlying() *zap.Logger {
-	return sugar.Desugar()
+	return sugar.Load().Desugar()
 }
 
 // Sync flushes any buffered log entries. Call before process exit.
 func Sync() error {
-	return sugar.Desugar().Sync()
+	return sugar.Load().Desugar().Sync()
 }
 
 // --- Package-level logging functions ---
 
-func Debugf(format string, args ...any) { sugar.Debugf(format, args...) }
-func Infof(format string, args ...any)  { sugar.Infof(format, args...) }
-func Warnf(format string, args ...any)  { sugar.Warnf(format, args...) }
-func Errorf(format string, args ...any) { sugar.Errorf(format, args...) }
-func Fatalf(format string, args ...any) { sugar.Fatalf(format, args...) }
-
-func Debug(args ...any) { sugar.Debug(args...) }
-func Info(args ...any)  { sugar.Info(args...) }
-func Warn(args ...any)  { sugar.Warn(args...) }
-func Error(args ...any) { sugar.Error(args...) }
-func Fatal(args ...any) { sugar.Fatal(args...) }
-
-// Structured logging.
-func Debugw(msg string, keysAndValues ...any) { sugar.Debugw(msg, keysAndValues...) }
-func Infow(msg string, keysAndValues ...any)  { sugar.Infow(msg, keysAndValues...) }
-func Warnw(msg string, keysAndValues ...any)  { sugar.Warnw(msg, keysAndValues...) }
-func Errorw(msg string, keysAndValues ...any) { sugar.Errorw(msg, keysAndValues...) }
+func Debugf(format string, args ...any) { sugar.Load().Debugf(format, args...) }
+func Infof(format string, args ...any)  { sugar.Load().Infof(format, args...) }
+func Warnf(format string, args ...any)  { sugar.Load().Warnf(format, args...) }
+func Errorf(format string, args ...any) { sugar.Load().Errorf(format, args...) }
+func Fatalf(format string, args ...any) { sugar.Load().Fatalf(format, args...) }
+
+func Debug(args ...any) { sugar.Load().Debug(args...) }
+func Info(args ...any)  { sugar.Load().Info(args...) }
+func Warn(args ...any)  { sugar.Load().Warn(args...) }
+func Error(args ...any) { sugar.Load().Error(args...) }
+func Fatal(args ...any) { sugar.Load().Fatal(args...) }
+
+func Debugw(msg string, keysAndValues ...any) { sugar.Load().Debugw(msg, keysAndValues...) }
+func Infow(msg string, keysAndValues ...any)  { sugar.Load().Infow(msg, keysAndValues...) }
+func Warnw(msg string, keysAndValues ...any)  { sugar.Load().Warnw(msg, keysAndValues...) }
+func Errorw(msg string, keysAndValues ...any) { sugar.Load().Errorw(msg, keysAndValues...) }

pkg/log/testing.go

@@ -13,20 +13,20 @@ import (
 // Log output is captured by t.Log() and only shown on test failure.
 func InitTest(t testing.TB) {
 	t.Helper()
-	prev := sugar
+	prev := sugar.Load()
 	logger := zaptest.NewLogger(t)
-	sugar = logger.Sugar()
-	t.Cleanup(func() { sugar = prev })
+	sugar.Store(logger.Sugar())
+	t.Cleanup(func() { sugar.Store(prev) })
 }
 
 // InitTestObserved replaces the package-level logger with an observable
 // logger at the given level. The returned ObservedLogs can be used to
 // assert that specific log messages were emitted.
 func InitTestObserved(t testing.TB, level zapcore.Level) *observer.ObservedLogs {
 	t.Helper()
-	prev := sugar
+	prev := sugar.Load()
 	core, logs := observer.New(level)
-	sugar = zap.New(core).Sugar()
-	t.Cleanup(func() { sugar = prev })
+	sugar.Store(zap.New(core).Sugar())
+	t.Cleanup(func() { sugar.Store(prev) })
 	return logs
 }

pkg/log/writer.go

@@ -16,7 +16,7 @@ func Writer(level int) io.WriteCloser {
 	return &levelWriter{
 		sink:  w,
 		level: zapLevel,
-		core:  sugar.Desugar().Core(),
+		core:  sugar.Load().Desugar().Core(),
 	}
 }