path: root/log/format.go

package log

import (
    "bytes"
    "encoding/json"
    "fmt"
    "reflect"
    "strconv"
    "strings"
    "sync"
    "time"
)

const (
    timeFormat     = "2006-01-02T15:04:05-0700"
    termTimeFormat = "01-02|15:04:05"
    floatFormat    = 'f'
    termMsgJust    = 40
)

type Format interface {
    Format(r *Record) []byte
}

// FormatFunc returns a new Format object which uses
// the given function to perform record formatting.
func FormatFunc(f func(*Record) []byte) Format {
    return formatFunc(f)
}

type formatFunc func(*Record) []byte

func (f formatFunc) Format(r *Record) []byte {
    return f(r)
}

// TerminalFormat formats log records optimized for human readability on
// a terminal with color-coded level output and terser human friendly timestamp.
// This format should only be used for interactive programs or while developing.
//
//     [TIME] [LEVEL] MESAGE key=value key=value ...
//
// Example:
//
//     [May 16 20:58:45] [DBUG] remove route ns=haproxy addr=127.0.0.1:50002
//
func TerminalFormat() Format {
    return FormatFunc(func(r *Record) []byte {
        var color = 0
        switch r.Lvl {
        case LvlCrit:
            color = 35
        case LvlError:
            color = 31
        case LvlWarn:
            color = 33
        case LvlInfo:
            color = 32
        case LvlDebug:
            color = 36
        case LvlTrace:
            color = 34
        }

        b := &bytes.Buffer{}
        lvl := strings.ToUpper(r.Lvl.String())
        if color > 0 {
            fmt.Fprintf(b, "\x1b[%dm%s\x1b[0m[%s] %s ", color, lvl, r.Time.Format(termTimeFormat), r.Msg)
        } else {
            fmt.Fprintf(b, "[%s] [%s] %s ", lvl, r.Time.Format(termTimeFormat), r.Msg)
        }

        // try to justify the log output for short messages
        if len(r.Ctx) > 0 && len(r.Msg) < termMsgJust {
            b.Write(bytes.Repeat([]byte{' '}, termMsgJust-len(r.Msg)))
        }

        // print the keys logfmt style
        logfmt(b, r.Ctx, color)
        return b.Bytes()
    })
}

// LogfmtFormat prints records in logfmt format, an easy machine-parseable but human-readable
// format for key/value pairs.
//
// For more details see: http://godoc.org/github.com/kr/logfmt
//
func LogfmtFormat() Format {
    return FormatFunc(func(r *Record) []byte {
        common := []interface{}{r.KeyNames.Time, r.Time, r.KeyNames.Lvl, r.Lvl, r.KeyNames.Msg, r.Msg}
        buf := &bytes.Buffer{}
        logfmt(buf, append(common, r.Ctx...), 0)
        return buf.Bytes()
    })
}

func logfmt(buf *bytes.Buffer, ctx []interface{}, color int) {
    for i := 0; i < len(ctx); i += 2 {
        if i != 0 {
            buf.WriteByte(' ')
        }

        k, ok := ctx[i].(string)
        v := formatLogfmtValue(ctx[i+1])
        if !ok {
            k, v = errorKey, formatLogfmtValue(k)
        }

        // XXX: we should probably check that all of your key bytes aren't invalid
        if color > 0 {
            fmt.Fprintf(buf, "\x1b[%dm%s\x1b[0m=%s", color, k, v)
        } else {
            buf.WriteString(k)
            buf.WriteByte('=')
            buf.WriteString(v)
        }
    }

    buf.WriteByte('\n')
}

// JsonFormat formats log records as JSON objects separated by newlines.
// It is the equivalent of JsonFormatEx(false, true).
func JsonFormat() Format {
    return JsonFormatEx(false, true)
}

// JsonFormatEx formats log records as JSON objects. If pretty is true,
// records will be pretty-printed. If lineSeparated is true, records
// will be logged with a new line between each record.
func JsonFormatEx(pretty, lineSeparated bool) Format {
    jsonMarshal := json.Marshal
    if pretty {
        jsonMarshal = func(v interface{}) ([]byte, error) {
            return json.MarshalIndent(v, "", "    ")
        }
    }

    return FormatFunc(func(r *Record) []byte {
        props := make(map[string]interface{})

        props[r.KeyNames.Time] = r.Time
        props[r.KeyNames.Lvl] = r.Lvl.String()
        props[r.KeyNames.Msg] = r.Msg

        for i := 0; i < len(r.Ctx); i += 2 {
            k, ok := r.Ctx[i].(string)
            if !ok {
                props[errorKey] = fmt.Sprintf("%+v is not a string key", r.Ctx[i])
            }
            props[k] = formatJsonValue(r.Ctx[i+1])
        }

        b, err := jsonMarshal(props)
        if err != nil {
            b, _ = jsonMarshal(map[string]string{
                errorKey: err.Error(),
            })
            return b
        }

        if lineSeparated {
            b = append(b, '\n')
        }

        return b
    })
}

func formatShared(value interface{}) (result interface{}) {
    defer func() {
        if err := recover(); err != nil {
            if v := reflect.ValueOf(value); v.Kind() == reflect.Ptr && v.IsNil() {
                result = "nil"
            } else {
                panic(err)
            }
        }
    }()

    switch v := value.(type) {
    case time.Time:
        return v.Format(timeFormat)

    case error:
        return v.Error()

    case fmt.Stringer:
        return v.String()

    default:
        return v
    }
}

func formatJsonValue(value interface{}) interface{} {
    value = formatShared(value)
    switch value.(type) {
    case int, int8, int16, int32, int64, float32, float64, uint, uint8, uint16, uint32, uint64, string:
        return value
    default:
        return fmt.Sprintf("%+v", value)
    }
}

// formatValue formats a value for serialization
func formatLogfmtValue(value interface{}) string {
    if value == nil {
        return "nil"
    }

    if t, ok := value.(time.Time); ok {
        // Performance optimization: No need for escaping since the provided
        // timeFormat doesn't have any escape characters, and escaping is
        // expensive.
        return t.Format(timeFormat)
    }
    value = formatShared(value)
    switch v := value.(type) {
    case bool:
        return strconv.FormatBool(v)
    case float32:
        return strconv.FormatFloat(float64(v), floatFormat, 3, 64)
    case float64:
        return strconv.FormatFloat(v, floatFormat, 3, 64)
    case int, int8, int16, int32, int64, uint, uint8, uint16, uint32, uint64:
        return fmt.Sprintf("%d", value)
    case string:
        return escapeString(v)
    default:
        return escapeString(fmt.Sprintf("%+v", value))
    }
}

var stringBufPool = sync.Pool{
    New: func() interface{} { return new(bytes.Buffer) },
}

func escapeString(s string) string {
    needsQuotes := false
    needsEscape := false
    for _, r := range s {
        if r <= ' ' || r == '=' || r == '"' {
            needsQuotes = true
        }
        if r == '\\' || r == '"' || r == '\n' || r == '\r' || r == '\t' {
            needsEscape = true
        }
    }
    if needsEscape == false && needsQuotes == false {
        return s
    }
    e := stringBufPool.Get().(*bytes.Buffer)
    e.WriteByte('"')
    for _, r := range s {
        switch r {
        case '\\', '"':
            e.WriteByte('\\')
            e.WriteByte(byte(r))
        case '\n':
            e.WriteString("\\n")
        case '\r':
            e.WriteString("\\r")
        case '\t':
            e.WriteString("\\t")
        default:
            e.WriteRune(r)
        }
    }
    e.WriteByte('"')
    var ret string
    if needsQuotes {
        ret = e.String()
    } else {
        ret = string(e.Bytes()[1 : e.Len()-1])
    }
    e.Reset()
    stringBufPool.Put(e)
    return ret
}