package level import "github.com/go-kit/log" // Error returns a logger that includes a Key/ErrorValue pair. func Error(logger log.Logger) log.Logger { return log.WithPrefix(logger, Key(), ErrorValue()) } // Warn returns a logger that includes a Key/WarnValue pair. func Warn(logger log.Logger) log.Logger { return log.WithPrefix(logger, Key(), WarnValue()) } // Info returns a logger that includes a Key/InfoValue pair. func Info(logger log.Logger) log.Logger { return log.WithPrefix(logger, Key(), InfoValue()) } // Debug returns a logger that includes a Key/DebugValue pair. func Debug(logger log.Logger) log.Logger { return log.WithPrefix(logger, Key(), DebugValue()) } // NewFilter wraps next and implements level filtering. See the commentary on // the Option functions for a detailed description of how to configure levels. // If no options are provided, all leveled log events created with Debug, // Info, Warn or Error helper methods are squelched and non-leveled log // events are passed to next unmodified. func NewFilter(next log.Logger, options ...Option) log.Logger { l := &logger{ next: next, } for _, option := range options { option(l) } return l } type logger struct { next log.Logger allowed level squelchNoLevel bool errNotAllowed error errNoLevel error } func (l *logger) Log(keyvals ...interface{}) error { var hasLevel, levelAllowed bool for i := 1; i < len(keyvals); i += 2 { if v, ok := keyvals[i].(*levelValue); ok { hasLevel = true levelAllowed = l.allowed&v.level != 0 break } } if !hasLevel && l.squelchNoLevel { return l.errNoLevel } if hasLevel && !levelAllowed { return l.errNotAllowed } return l.next.Log(keyvals...) } // Option sets a parameter for the leveled logger. type Option func(*logger) // AllowAll is an alias for AllowDebug. func AllowAll() Option { return AllowDebug() } // AllowDebug allows error, warn, info and debug level log events to pass. func AllowDebug() Option { return allowed(levelError | levelWarn | levelInfo | levelDebug) } // AllowInfo allows error, warn and info level log events to pass. func AllowInfo() Option { return allowed(levelError | levelWarn | levelInfo) } // AllowWarn allows error and warn level log events to pass. func AllowWarn() Option { return allowed(levelError | levelWarn) } // AllowError allows only error level log events to pass. func AllowError() Option { return allowed(levelError) } // AllowNone allows no leveled log events to pass. func AllowNone() Option { return allowed(0) } func allowed(allowed level) Option { return func(l *logger) { l.allowed = allowed } } // ErrNotAllowed sets the error to return from Log when it squelches a log // event disallowed by the configured Allow[Level] option. By default, // ErrNotAllowed is nil; in this case the log event is squelched with no // error. func ErrNotAllowed(err error) Option { return func(l *logger) { l.errNotAllowed = err } } // SquelchNoLevel instructs Log to squelch log events with no level, so that // they don't proceed through to the wrapped logger. If SquelchNoLevel is set // to true and a log event is squelched in this way, the error value // configured with ErrNoLevel is returned to the caller. func SquelchNoLevel(squelch bool) Option { return func(l *logger) { l.squelchNoLevel = squelch } } // ErrNoLevel sets the error to return from Log when it squelches a log event // with no level. By default, ErrNoLevel is nil; in this case the log event is // squelched with no error. func ErrNoLevel(err error) Option { return func(l *logger) { l.errNoLevel = err } } // NewInjector wraps next and returns a logger that adds a Key/level pair to // the beginning of log events that don't already contain a level. In effect, // this gives a default level to logs without a level. func NewInjector(next log.Logger, level Value) log.Logger { return &injector{ next: next, level: level, } } type injector struct { next log.Logger level interface{} } func (l *injector) Log(keyvals ...interface{}) error { for i := 1; i < len(keyvals); i += 2 { if _, ok := keyvals[i].(*levelValue); ok { return l.next.Log(keyvals...) } } kvs := make([]interface{}, len(keyvals)+2) kvs[0], kvs[1] = key, l.level copy(kvs[2:], keyvals) return l.next.Log(kvs...) } // Value is the interface that each of the canonical level values implement. // It contains unexported methods that prevent types from other packages from // implementing it and guaranteeing that NewFilter can distinguish the levels // defined in this package from all other values. type Value interface { String() string levelVal() } // Key returns the unique key added to log events by the loggers in this // package. func Key() interface{} { return key } // ErrorValue returns the unique value added to log events by Error. func ErrorValue() Value { return errorValue } // WarnValue returns the unique value added to log events by Warn. func WarnValue() Value { return warnValue } // InfoValue returns the unique value added to log events by Info. func InfoValue() Value { return infoValue } // DebugValue returns the unique value added to log events by Debug. func DebugValue() Value { return debugValue } var ( // key is of type interface{} so that it allocates once during package // initialization and avoids allocating every time the value is added to a // []interface{} later. key interface{} = "level" errorValue = &levelValue{level: levelError, name: "error"} warnValue = &levelValue{level: levelWarn, name: "warn"} infoValue = &levelValue{level: levelInfo, name: "info"} debugValue = &levelValue{level: levelDebug, name: "debug"} ) type level byte const ( levelDebug level = 1 << iota levelInfo levelWarn levelError ) type levelValue struct { name string level } func (v *levelValue) String() string { return v.name } func (v *levelValue) levelVal() {}