diff options
| -rw-r--r-- | design/56345-structured-logging.md | 114 |
1 files changed, 75 insertions, 39 deletions
diff --git a/design/56345-structured-logging.md b/design/56345-structured-logging.md index 98c8322..9a0bde1 100644 --- a/design/56345-structured-logging.md +++ b/design/56345-structured-logging.md @@ -134,7 +134,7 @@ func main() { slog.SetDefault(slog.New(slog.NewTextHandler(os.Stderr))) slog.Info("hello", "name", "Al") slog.Error("oops", net.ErrClosed, "status", 500) - slog.LogAttrs(slog.ErrorLevel, "oops", + slog.LogAttrs(slog.LevelError, "oops", slog.Int("status", 500), slog.Any("err", net.ErrClosed)) } ``` @@ -554,7 +554,7 @@ It can be set and retrieved with the `SetDefault` and func SetDefault(l *Logger) SetDefault makes l the default Logger. After this call, output from the log package's default Logger (as with log.Print, etc.) will be logged at - InfoLevel using l's Handler. + LevelInfo using l's Handler. func Default() *Logger Default returns the default Logger. @@ -600,16 +600,16 @@ func (l *Logger) LogAttrs(level Level, msg string, attrs ...Attr) LogAttrs is a more efficient version of Logger.Log that accepts only Attrs. func (l *Logger) Debug(msg string, args ...any) - Debug logs at DebugLevel. + Debug logs at LevelDebug. func (l *Logger) Info(msg string, args ...any) - Info logs at InfoLevel. + Info logs at LevelInfo. func (l *Logger) Warn(msg string, args ...any) - Warn logs at WarnLevel. + Warn logs at LevelWarn. func (l *Logger) Error(msg string, err error, args ...any) - Error logs at ErrorLevel. If err is non-nil, Error appends Any("err", + Error logs at LevelError. If err is non-nil, Error appends Any("err", err) to the list of attributes. ``` @@ -831,10 +831,10 @@ represented as slog Levels by using the appropriate integers. ``` const ( - DebugLevel Level = -4 - InfoLevel Level = 0 - WarnLevel Level = 4 - ErrorLevel Level = 8 + LevelDebug Level = -4 + LevelInfo Level = 0 + LevelWarn Level = 4 + LevelError Level = 8 ) ``` @@ -861,7 +861,7 @@ type LevelVar struct { } A LevelVar is a Level variable, to allow a Handler level to change dynamically. It implements Leveler as well as a Set method, and it is safe - for use by multiple goroutines. The zero LevelVar corresponds to InfoLevel. + for use by multiple goroutines. The zero LevelVar corresponds to LevelInfo. func (v *LevelVar) Level() Level Level returns v's level. @@ -890,23 +890,37 @@ type HandlerOptions struct { // Level reports the minimum record level that will be logged. // The handler discards records with lower levels. - // If Level is nil, the handler assumes InfoLevel. + // If Level is nil, the handler assumes LevelInfo. // The handler calls Level.Level for each record processed; // to adjust the minimum level dynamically, use a LevelVar. Level Leveler - // ReplaceAttr is called to rewrite each attribute before it is logged. + // ReplaceAttr is called to rewrite each non-group attribute before it is logged. + // The attribute's value has been resolved (see [Value.Resolve]). // If ReplaceAttr returns an Attr with Key == "", the attribute is discarded. // // The built-in attributes with keys "time", "level", "source", and "msg" - // are passed to this function first, except that time and level are omitted + // are passed to this function, except that time and level are omitted // if zero, and source is omitted if AddSourceLine is false. // + // The first argument is a list of currently open groups that contain the + // Attr. It must not be retained or modified. ReplaceAttr is never called + // for Group attributes, only their contents. For example, the attribute + // list + // + // Int("a", 1), Group("g", Int("b", 2)), Int("c", 3) + // + // results in consecutive calls to ReplaceAttr with the following arguments: + // + // nil, Int("a", 1) + // []string{"g"}, Int("b", 2) + // nil, Int("c", 3) + // // ReplaceAttr can be used to change the default keys of the built-in // attributes, convert types (for example, to replace a `time.Time` with the // integer seconds since the Unix epoch), sanitize personal information, or // remove attributes from the output. - ReplaceAttr func(a Attr) Attr + ReplaceAttr func(groups []string, a Attr) Attr } ``` @@ -983,6 +997,9 @@ const ( // SourceKey is the key used by the built-in handlers for the source file // and line of the log call. The associated value is a string. SourceKey = "source" + // ErrorKey is the key used for errors by Logger.Error. + // The associated value is an [error]. + ErrorKey = "err" ) Keys for "built-in" attributes. @@ -1011,7 +1028,7 @@ func NewContext(ctx context.Context, l *Logger) context.Context func SetDefault(l *Logger) SetDefault makes l the default Logger. After this call, output from the log package's default Logger (as with log.Print, etc.) will be logged at - InfoLevel using l's Handler. + LevelInfo using l's Handler. func Warn(msg string, args ...any) Warn calls Logger.Warn on the default logger. @@ -1122,23 +1139,37 @@ type HandlerOptions struct { // Level reports the minimum record level that will be logged. // The handler discards records with lower levels. - // If Level is nil, the handler assumes InfoLevel. + // If Level is nil, the handler assumes LevelInfo. // The handler calls Level.Level for each record processed; // to adjust the minimum level dynamically, use a LevelVar. Level Leveler - // ReplaceAttr is called to rewrite each attribute before it is logged. + // ReplaceAttr is called to rewrite each non-group attribute before it is logged. + // The attribute's value has been resolved (see [Value.Resolve]). // If ReplaceAttr returns an Attr with Key == "", the attribute is discarded. // // The built-in attributes with keys "time", "level", "source", and "msg" - // are passed to this function first, except that time and level are omitted + // are passed to this function, except that time and level are omitted // if zero, and source is omitted if AddSourceLine is false. // + // The first argument is a list of currently open groups that contain the + // Attr. It must not be retained or modified. ReplaceAttr is never called + // for Group attributes, only their contents. For example, the attribute + // list + // + // Int("a", 1), Group("g", Int("b", 2)), Int("c", 3) + // + // results in consecutive calls to ReplaceAttr with the following arguments: + // + // nil, Int("a", 1) + // []string{"g"}, Int("b", 2) + // nil, Int("c", 3) + // // ReplaceAttr can be used to change the default keys of the built-in // attributes, convert types (for example, to replace a `time.Time` with the // integer seconds since the Unix epoch), sanitize personal information, or // remove attributes from the output. - ReplaceAttr func(a Attr) Attr + ReplaceAttr func(groups []string, a Attr) Attr } HandlerOptions are options for a TextHandler or JSONHandler. A zero HandlerOptions consists entirely of default values. @@ -1218,10 +1249,10 @@ type Level int the more important or severe the event. const ( - DebugLevel Level = -4 - InfoLevel Level = 0 - WarnLevel Level = 4 - ErrorLevel Level = 8 + LevelDebug Level = -4 + LevelInfo Level = 0 + LevelWarn Level = 4 + LevelError Level = 8 ) Second, we wanted to make it easy to use levels to specify logger verbosity. Since a larger level means a more severe event, a logger that accepts events @@ -1251,15 +1282,15 @@ func (l Level) String() string name in uppercase is returned. If the level is between named values, then an integer is appended to the uppercased name. Examples: - WarnLevel.String() => "WARN" - (WarnLevel-2).String() => "WARN-2" + LevelWarn.String() => "WARN" + (LevelInfo+2).String() => "INFO+2" type LevelVar struct { // Has unexported fields. } A LevelVar is a Level variable, to allow a Handler level to change dynamically. It implements Leveler as well as a Set method, and it is safe - for use by multiple goroutines. The zero LevelVar corresponds to InfoLevel. + for use by multiple goroutines. The zero LevelVar corresponds to LevelInfo. func (v *LevelVar) Level() Level Level returns v's level. @@ -1310,29 +1341,29 @@ func FromContext(ctx context.Context) *Logger Logger if there is none. func New(h Handler) *Logger - New creates a new Logger with the given Handler. + New creates a new Logger with the given non-nil Handler and a nil context. func With(args ...any) *Logger With calls Logger.With on the default logger. func (l *Logger) Context() context.Context - Context returns l's context. + Context returns l's context, which may be nil. func (l *Logger) Debug(msg string, args ...any) - Debug logs at DebugLevel. + Debug logs at LevelDebug. func (l *Logger) Enabled(level Level) bool Enabled reports whether l emits log records at the given level. func (l *Logger) Error(msg string, err error, args ...any) - Error logs at ErrorLevel. If err is non-nil, Error appends Any("err", + Error logs at LevelError. If err is non-nil, Error appends Any(ErrorKey, err) to the list of attributes. func (l *Logger) Handler() Handler Handler returns l's Handler. func (l *Logger) Info(msg string, args ...any) - Info logs at InfoLevel. + Info logs at LevelInfo. func (l *Logger) Log(level Level, msg string, args ...any) Log emits a log record with the current time and the given level and @@ -1355,27 +1386,31 @@ func (l *Logger) LogAttrsDepth(calldepth int, level Level, msg string, attrs ... func (l *Logger) LogDepth(calldepth int, level Level, msg string, args ...any) LogDepth is like Logger.Log, but accepts a call depth to adjust the file - and line number in the log record. 0 refers to the caller of LogDepth; - 1 refers to the caller's caller; and so on. + and line number in the log record. 1 refers to the caller of LogDepth; + 2 refers to the caller's caller; and so on. func (l *Logger) Warn(msg string, args ...any) - Warn logs at WarnLevel. + Warn logs at LevelWarn. func (l *Logger) With(args ...any) *Logger With returns a new Logger that includes the given arguments, converted to Attrs as in Logger.Log. The Attrs will be added to each output from the - Logger. + Logger. The new Logger shares the old Logger's context. The new Logger's handler is the result of calling WithAttrs on the receiver's handler. func (l *Logger) WithContext(ctx context.Context) *Logger WithContext returns a new Logger with the same handler as the receiver and - the given context. + the given context. It uses the same handler as the original. func (l *Logger) WithGroup(name string) *Logger WithGroup returns a new Logger that starts a group. The keys of all - attributes added to the Logger will be qualified by the given name. + attributes added to the Logger will be qualified by the given name. The new + Logger shares the old Logger's context. + + The new Logger's handler is the result of calling WithGroup on the + receiver's handler. type Record struct { // The time at which the output method (Log, Info, etc.) was called. @@ -1485,6 +1520,8 @@ type Value struct { func AnyValue(v any) Value AnyValue returns a Value for the supplied value. + If the supplied value is of type Value, it is returned unmodified. + Given a value of one of Go's predeclared string, bool, or (non-complex) numeric types, AnyValue returns a Value of kind String, Bool, Uint64, Int64, or Float64. The width of the original numeric type is not preserved. @@ -1570,5 +1607,4 @@ func (v Value) Time() time.Time func (v Value) Uint64() uint64 Uint64 returns v's value as a uint64. It panics if v is not an unsigned integer. - ``` |