1 // Copyright 2022 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
10 loginternal "log/internal"
17 var defaultLogger atomic.Value
20 defaultLogger.Store(New(newDefaultHandler(loginternal.DefaultOutput)))
23 // Default returns the default Logger.
24 func Default() *Logger { return defaultLogger.Load().(*Logger) }
26 // SetDefault makes l the default Logger.
27 // After this call, output from the log package's default Logger
28 // (as with [log.Print], etc.) will be logged at LevelInfo using l's Handler.
29 func SetDefault(l *Logger) {
30 defaultLogger.Store(l)
31 // If the default's handler is a defaultHandler, then don't use a handleWriter,
32 // or we'll deadlock as they both try to acquire the log default mutex.
33 // The defaultHandler will use whatever the log default writer is currently
34 // set to, which is correct.
35 // This can occur with SetDefault(Default()).
36 // See TestSetDefault.
37 if _, ok := l.Handler().(*defaultHandler); !ok {
38 capturePC := log.Flags()&(log.Lshortfile|log.Llongfile) != 0
39 log.SetOutput(&handlerWriter{l.Handler(), LevelInfo, capturePC})
40 log.SetFlags(0) // we want just the log message, no time or location
44 // handlerWriter is an io.Writer that calls a Handler.
45 // It is used to link the default log.Logger to the default slog.Logger.
46 type handlerWriter struct {
52 func (w *handlerWriter) Write(buf []byte) (int, error) {
53 if !w.h.Enabled(context.Background(), w.level) {
57 if !internal.IgnorePC && w.capturePC {
58 // skip [runtime.Callers, w.Write, Logger.Output, log.Print]
60 runtime.Callers(4, pcs[:])
64 // Remove final newline.
65 origLen := len(buf) // Report that the entire buf was written.
66 if len(buf) > 0 && buf[len(buf)-1] == '\n' {
67 buf = buf[:len(buf)-1]
69 r := NewRecord(time.Now(), w.level, string(buf), pc)
70 return origLen, w.h.Handle(context.Background(), r)
73 // A Logger records structured information about each call to its
74 // Log, Debug, Info, Warn, and Error methods.
75 // For each call, it creates a Record and passes it to a Handler.
77 // To create a new Logger, call [New] or a Logger method
78 // that begins "With".
80 handler Handler // for structured logging
83 func (l *Logger) clone() *Logger {
88 // Handler returns l's Handler.
89 func (l *Logger) Handler() Handler { return l.handler }
91 // With returns a new Logger that includes the given arguments, converted to
92 // Attrs as in [Logger.Log].
93 // The Attrs will be added to each output from the Logger.
94 // The new Logger shares the old Logger's context.
95 // The new Logger's handler is the result of calling WithAttrs on the receiver's
97 func (l *Logger) With(args ...any) *Logger {
103 attr, args = argsToAttr(args)
104 attrs = append(attrs, attr)
107 c.handler = l.handler.WithAttrs(attrs)
111 // WithGroup returns a new Logger that starts a group. The keys of all
112 // attributes added to the Logger will be qualified by the given name.
113 // (How that qualification happens depends on the [Handler.WithGroup]
114 // method of the Logger's Handler.)
115 // The new Logger shares the old Logger's context.
117 // The new Logger's handler is the result of calling WithGroup on the receiver's
119 func (l *Logger) WithGroup(name string) *Logger {
121 c.handler = l.handler.WithGroup(name)
126 // New creates a new Logger with the given non-nil Handler and a nil context.
127 func New(h Handler) *Logger {
131 return &Logger{handler: h}
134 // With calls Logger.With on the default logger.
135 func With(args ...any) *Logger {
136 return Default().With(args...)
139 // Enabled reports whether l emits log records at the given context and level.
140 func (l *Logger) Enabled(ctx context.Context, level Level) bool {
142 ctx = context.Background()
144 return l.Handler().Enabled(ctx, level)
147 // NewLogLogger returns a new log.Logger such that each call to its Output method
148 // dispatches a Record to the specified handler. The logger acts as a bridge from
149 // the older log API to newer structured logging handlers.
150 func NewLogLogger(h Handler, level Level) *log.Logger {
151 return log.New(&handlerWriter{h, level, true}, "", 0)
154 // Log emits a log record with the current time and the given level and message.
155 // The Record's Attrs consist of the Logger's attributes followed by
156 // the Attrs specified by args.
158 // The attribute arguments are processed as follows:
159 // - If an argument is an Attr, it is used as is.
160 // - If an argument is a string and this is not the last argument,
161 // the following argument is treated as the value and the two are combined
163 // - Otherwise, the argument is treated as a value with key "!BADKEY".
164 func (l *Logger) Log(ctx context.Context, level Level, msg string, args ...any) {
165 l.log(ctx, level, msg, args...)
168 // LogAttrs is a more efficient version of [Logger.Log] that accepts only Attrs.
169 func (l *Logger) LogAttrs(ctx context.Context, level Level, msg string, attrs ...Attr) {
170 l.logAttrs(ctx, level, msg, attrs...)
173 // Debug logs at LevelDebug.
174 func (l *Logger) Debug(msg string, args ...any) {
175 l.log(nil, LevelDebug, msg, args...)
178 // DebugCtx logs at LevelDebug with the given context.
179 func (l *Logger) DebugCtx(ctx context.Context, msg string, args ...any) {
180 l.log(ctx, LevelDebug, msg, args...)
183 // Info logs at LevelInfo.
184 func (l *Logger) Info(msg string, args ...any) {
185 l.log(nil, LevelInfo, msg, args...)
188 // InfoCtx logs at LevelInfo with the given context.
189 func (l *Logger) InfoCtx(ctx context.Context, msg string, args ...any) {
190 l.log(ctx, LevelInfo, msg, args...)
193 // Warn logs at LevelWarn.
194 func (l *Logger) Warn(msg string, args ...any) {
195 l.log(nil, LevelWarn, msg, args...)
198 // WarnCtx logs at LevelWarn with the given context.
199 func (l *Logger) WarnCtx(ctx context.Context, msg string, args ...any) {
200 l.log(ctx, LevelWarn, msg, args...)
203 // Error logs at LevelError.
204 func (l *Logger) Error(msg string, args ...any) {
205 l.log(nil, LevelError, msg, args...)
208 // ErrorCtx logs at LevelError with the given context.
209 func (l *Logger) ErrorCtx(ctx context.Context, msg string, args ...any) {
210 l.log(ctx, LevelError, msg, args...)
213 // log is the low-level logging method for methods that take ...any.
214 // It must always be called directly by an exported logging method
215 // or function, because it uses a fixed call depth to obtain the pc.
216 func (l *Logger) log(ctx context.Context, level Level, msg string, args ...any) {
217 if !l.Enabled(ctx, level) {
221 if !internal.IgnorePC {
223 // skip [runtime.Callers, this function, this function's caller]
224 runtime.Callers(3, pcs[:])
227 r := NewRecord(time.Now(), level, msg, pc)
230 ctx = context.Background()
232 _ = l.Handler().Handle(ctx, r)
235 // logAttrs is like [Logger.log], but for methods that take ...Attr.
236 func (l *Logger) logAttrs(ctx context.Context, level Level, msg string, attrs ...Attr) {
237 if !l.Enabled(ctx, level) {
241 if !internal.IgnorePC {
243 // skip [runtime.Callers, this function, this function's caller]
244 runtime.Callers(3, pcs[:])
247 r := NewRecord(time.Now(), level, msg, pc)
250 ctx = context.Background()
252 _ = l.Handler().Handle(ctx, r)
255 // Debug calls Logger.Debug on the default logger.
256 func Debug(msg string, args ...any) {
257 Default().log(nil, LevelDebug, msg, args...)
260 // DebugCtx calls Logger.DebugCtx on the default logger.
261 func DebugCtx(ctx context.Context, msg string, args ...any) {
262 Default().log(ctx, LevelDebug, msg, args...)
265 // Info calls Logger.Info on the default logger.
266 func Info(msg string, args ...any) {
267 Default().log(nil, LevelInfo, msg, args...)
270 // InfoCtx calls Logger.InfoCtx on the default logger.
271 func InfoCtx(ctx context.Context, msg string, args ...any) {
272 Default().log(ctx, LevelInfo, msg, args...)
275 // Warn calls Logger.Warn on the default logger.
276 func Warn(msg string, args ...any) {
277 Default().log(nil, LevelWarn, msg, args...)
280 // WarnCtx calls Logger.WarnCtx on the default logger.
281 func WarnCtx(ctx context.Context, msg string, args ...any) {
282 Default().log(ctx, LevelWarn, msg, args...)
285 // Error calls Logger.Error on the default logger.
286 func Error(msg string, args ...any) {
287 Default().log(nil, LevelError, msg, args...)
290 // ErrorCtx calls Logger.ErrorCtx on the default logger.
291 func ErrorCtx(ctx context.Context, msg string, args ...any) {
292 Default().log(ctx, LevelError, msg, args...)
295 // Log calls Logger.Log on the default logger.
296 func Log(ctx context.Context, level Level, msg string, args ...any) {
297 Default().log(ctx, level, msg, args...)
300 // LogAttrs calls Logger.LogAttrs on the default logger.
301 func LogAttrs(ctx context.Context, level Level, msg string, attrs ...Attr) {
302 Default().logAttrs(ctx, level, msg, attrs...)