聊聊golang的zap的ReflectType

序

本文主要研究一下golang的zap的ReflectType

sweetenFields

zap@v1.16.0/sugar.go

func (s *SugaredLogger) sweetenFields(args []interface{}) []Field {
    if len(args) == 0 {
        return nil
    }

    // Allocate enough space for the worst case; if users pass only structured
    // fields, we shouldn't penalize them with extra allocations.
    fields := make([]Field, 0, len(args))
    var invalid invalidPairs

    for i := 0; i < len(args); {
        // This is a strongly-typed field. Consume it and move on.
        if f, ok := args[i].(Field); ok {
            fields = append(fields, f)
            i++
            continue
        }

        // Make sure this element isn't a dangling key.
        if i == len(args)-1 {
            s.base.DPanic(_oddNumberErrMsg, Any("ignored", args[i]))
            break
        }

        // Consume this value and the next, treating them as a key-value pair. If the
        // key isn't a string, add this pair to the slice of invalid pairs.
        key, val := args[i], args[i+1]
        if keyStr, ok := key.(string); !ok {
            // Subsequent errors are likely, so allocate once up front.
            if cap(invalid) == 0 {
                invalid = make(invalidPairs, 0, len(args)/2)
            }
            invalid = append(invalid, invalidPair{i, key, val})
        } else {
            fields = append(fields, Any(keyStr, val))
        }
        i += 2
    }

    // If we encountered any invalid key-value pairs, log an error.
    if len(invalid) > 0 {
        s.base.DPanic(_nonStringKeyErrMsg, Array("invalid", invalid))
    }
    return fields
}

sweetenFields方法执行的是fields = append(fields, Any(keyStr, val))

Any

zap@v1.16.0/field.go

func Any(key string, value interface{}) Field {
    switch val := value.(type) {
    case zapcore.ObjectMarshaler:
        return Object(key, val)
    case zapcore.ArrayMarshaler:
        return Array(key, val)
    case bool:
        return Bool(key, val)
    case *bool:
        return Boolp(key, val)
    case []bool:
        return Bools(key, val)
    case complex128:
        return Complex128(key, val)
    case *complex128:
        return Complex128p(key, val)
    case []complex128:
        return Complex128s(key, val)
    case complex64:
        return Complex64(key, val)
    case *complex64:
        return Complex64p(key, val)
    case []complex64:
        return Complex64s(key, val)
    case float64:
        return Float64(key, val)
    case *float64:
        return Float64p(key, val)
    case []float64:
        return Float64s(key, val)
    case float32:
        return Float32(key, val)
    case *float32:
        return Float32p(key, val)
    case []float32:
        return Float32s(key, val)
    case int:
        return Int(key, val)
    case *int:
        return Intp(key, val)
    case []int:
        return Ints(key, val)
    case int64:
        return Int64(key, val)
    case *int64:
        return Int64p(key, val)
    case []int64:
        return Int64s(key, val)
    case int32:
        return Int32(key, val)
    case *int32:
        return Int32p(key, val)
    case []int32:
        return Int32s(key, val)
    case int16:
        return Int16(key, val)
    case *int16:
        return Int16p(key, val)
    case []int16:
        return Int16s(key, val)
    case int8:
        return Int8(key, val)
    case *int8:
        return Int8p(key, val)
    case []int8:
        return Int8s(key, val)
    case string:
        return String(key, val)
    case *string:
        return Stringp(key, val)
    case []string:
        return Strings(key, val)
    case uint:
        return Uint(key, val)
    case *uint:
        return Uintp(key, val)
    case []uint:
        return Uints(key, val)
    case uint64:
        return Uint64(key, val)
    case *uint64:
        return Uint64p(key, val)
    case []uint64:
        return Uint64s(key, val)
    case uint32:
        return Uint32(key, val)
    case *uint32:
        return Uint32p(key, val)
    case []uint32:
        return Uint32s(key, val)
    case uint16:
        return Uint16(key, val)
    case *uint16:
        return Uint16p(key, val)
    case []uint16:
        return Uint16s(key, val)
    case uint8:
        return Uint8(key, val)
    case *uint8:
        return Uint8p(key, val)
    case []byte:
        return Binary(key, val)
    case uintptr:
        return Uintptr(key, val)
    case *uintptr:
        return Uintptrp(key, val)
    case []uintptr:
        return Uintptrs(key, val)
    case time.Time:
        return Time(key, val)
    case *time.Time:
        return Timep(key, val)
    case []time.Time:
        return Times(key, val)
    case time.Duration:
        return Duration(key, val)
    case *time.Duration:
        return Durationp(key, val)
    case []time.Duration:
        return Durations(key, val)
    case error:
        return NamedError(key, val)
    case []error:
        return Errors(key, val)
    case fmt.Stringer:
        return Stringer(key, val)
    default:
        return Reflect(key, val)
    }
}

Any方法会根据value的类型返回不同的Field，如果value没有实现zapcore.ObjectMarshaler、zapcore.ArrayMarshaler，也不是基础类型，则走的是默认的Reflect(key, val)

Reflect

zap@v1.16.0/field.go

func Reflect(key string, val interface{}) Field {
    return Field{Key: key, Type: zapcore.ReflectType, Interface: val}
}

Reflect创建的Field类型的Type为zapcore.ReflectType

AddTo

zap@v1.16.0/zapcore/field.go

func (f Field) AddTo(enc ObjectEncoder) {
    var err error

    switch f.Type {
    case ArrayMarshalerType:
        err = enc.AddArray(f.Key, f.Interface.(ArrayMarshaler))
    case ObjectMarshalerType:
        err = enc.AddObject(f.Key, f.Interface.(ObjectMarshaler))
    case BinaryType:
        enc.AddBinary(f.Key, f.Interface.([]byte))
    case BoolType:
        enc.AddBool(f.Key, f.Integer == 1)
    case ByteStringType:
        enc.AddByteString(f.Key, f.Interface.([]byte))
    case Complex128Type:
        enc.AddComplex128(f.Key, f.Interface.(complex128))
    case Complex64Type:
        enc.AddComplex64(f.Key, f.Interface.(complex64))
    case DurationType:
        enc.AddDuration(f.Key, time.Duration(f.Integer))
    case Float64Type:
        enc.AddFloat64(f.Key, math.Float64frombits(uint64(f.Integer)))
    case Float32Type:
        enc.AddFloat32(f.Key, math.Float32frombits(uint32(f.Integer)))
    case Int64Type:
        enc.AddInt64(f.Key, f.Integer)
    case Int32Type:
        enc.AddInt32(f.Key, int32(f.Integer))
    case Int16Type:
        enc.AddInt16(f.Key, int16(f.Integer))
    case Int8Type:
        enc.AddInt8(f.Key, int8(f.Integer))
    case StringType:
        enc.AddString(f.Key, f.String)
    case TimeType:
        if f.Interface != nil {
            enc.AddTime(f.Key, time.Unix(0, f.Integer).In(f.Interface.(*time.Location)))
        } else {
            // Fall back to UTC if location is nil.
            enc.AddTime(f.Key, time.Unix(0, f.Integer))
        }
    case TimeFullType:
        enc.AddTime(f.Key, f.Interface.(time.Time))
    case Uint64Type:
        enc.AddUint64(f.Key, uint64(f.Integer))
    case Uint32Type:
        enc.AddUint32(f.Key, uint32(f.Integer))
    case Uint16Type:
        enc.AddUint16(f.Key, uint16(f.Integer))
    case Uint8Type:
        enc.AddUint8(f.Key, uint8(f.Integer))
    case UintptrType:
        enc.AddUintptr(f.Key, uintptr(f.Integer))
    case ReflectType:
        err = enc.AddReflected(f.Key, f.Interface)
    case NamespaceType:
        enc.OpenNamespace(f.Key)
    case StringerType:
        err = encodeStringer(f.Key, f.Interface, enc)
    case ErrorType:
        encodeError(f.Key, f.Interface.(error), enc)
    case SkipType:
        break
    default:
        panic(fmt.Sprintf("unknown field type: %v", f))
    }

    if err != nil {
        enc.AddString(fmt.Sprintf("%sError", f.Key), err.Error())
    }
}

AddTo方法根据Field的类型做不同处理，如果是ReflectType类型，则执行的是enc.AddReflected(f.Key, f.Interface)

AddReflected

zap@v1.16.0/zapcore/json_encoder.go

func (enc *jsonEncoder) AddReflected(key string, obj interface{}) error {
    valueBytes, err := enc.encodeReflected(obj)
    if err != nil {
        return err
    }
    enc.addKey(key)
    _, err = enc.buf.Write(valueBytes)
    return err
}

func (enc *jsonEncoder) encodeReflected(obj interface{}) ([]byte, error) {
    if obj == nil {
        return nullLiteralBytes, nil
    }
    enc.resetReflectBuf()
    if err := enc.reflectEnc.Encode(obj); err != nil {
        return nil, err
    }
    enc.reflectBuf.TrimNewline()
    return enc.reflectBuf.Bytes(), nil
}

func (enc *jsonEncoder) resetReflectBuf() {
    if enc.reflectBuf == nil {
        enc.reflectBuf = bufferpool.Get()
        enc.reflectEnc = json.NewEncoder(enc.reflectBuf)

        // For consistency with our custom JSON encoder.
        enc.reflectEnc.SetEscapeHTML(false)
    } else {
        enc.reflectBuf.Reset()
    }
}

jsonEncoder的AddReflected方法用enc.encodeReflected(obj)来序列化value；encodeReflected方法执行的是enc.resetReflectBuf()及enc.reflectEnc.Encode(obj)；resetReflectBuf方法在reflectBuf为nil时创建reflectBuf及json.NewEncoder(enc.reflectBuf)，不为nil时执行reflectBuf.Reset()；enc.reflectEnc用的是golang内置的json encoder

json.Encode

/usr/local/go/src/encoding/json/stream.go

func NewEncoder(w io.Writer) *Encoder {
    return &Encoder{w: w, escapeHTML: true}
}

func (enc *Encoder) Encode(v interface{}) error {
    if enc.err != nil {
        return enc.err
    }
    e := newEncodeState()
    err := e.marshal(v, encOpts{escapeHTML: enc.escapeHTML})
    if err != nil {
        return err
    }

    // Terminate each value with a newline.
    // This makes the output look a little nicer
    // when debugging, and some kind of space
    // is required if the encoded value was a number,
    // so that the reader knows there aren't more
    // digits coming.
    e.WriteByte('\n')

    b := e.Bytes()
    if enc.indentPrefix != "" || enc.indentValue != "" {
        if enc.indentBuf == nil {
            enc.indentBuf = new(bytes.Buffer)
        }
        enc.indentBuf.Reset()
        err = Indent(enc.indentBuf, b, enc.indentPrefix, enc.indentValue)
        if err != nil {
            return err
        }
        b = enc.indentBuf.Bytes()
    }
    if _, err = enc.w.Write(b); err != nil {
        enc.err = err
    }
    encodeStatePool.Put(e)
    return err
}

Encode方法通过encodeState的marshal方法进行序列化，这里它读取了enc.escapeHTML选项

实例

type User struct {
    Name      string
    Email     string
    CreatedAt time.Time
}

type Users []*User

func reflectTypeDemo() {
    logger, err := zap.NewProduction()
    defer logger.Sync()
    if err != nil {
        panic(err)
    }
    var user = &User{
        Name:      "hello1",
        Email:     "[e-mail]",
        CreatedAt: time.Date(2020, 12, 19, 8, 0, 0, 0, time.UTC),
    }
    var users Users
    users = append(users, &User{
        Name:      "hello2",
        Email:     "[e-mail]",
        CreatedAt: time.Date(2020, 12, 19, 9, 0, 0, 0, time.UTC),
    }, &User{
        Name:      "hello3",
        Email:     "[e-mail]",
        CreatedAt: time.Date(2020, 12, 20, 10, 0, 0, 0, time.UTC),
    })
    logger.Sugar().Infow("hello", "user", user, "users", users)
}

输出

{"level":"info","ts":1608350874.177944,"caller":"zap/zap_demo.go:42","msg":"hello","user":{"Name":"hello1","Email":"[e-mail]","CreatedAt":"2020-12-19T08:00:00Z"},"users":[{"Name":"hello2","Email":"[e-mail]","CreatedAt":"2020-12-19T09:00:00Z"},{"Name":"hello3","Email":"[e-mail]","CreatedAt":"2020-12-20T10:00:00Z"}]}

小结

zap的sugar提供Infow方法，它通过sweetenFields方法来将key，value封装为Field；sweetenFields方法使用的是Any方法，它会根据value的类型返回不同的Field，如果value没有实现zapcore.ObjectMarshaler、zapcore.ArrayMarshaler，也不是基础类型，则走的是默认的Reflect(key, val)；AddTo方法根据Field的类型做不同处理，如果是ReflectType类型，则执行的是enc.AddReflected(f.Key, f.Interface)；jsonEncoder的AddReflected方法使用golang内置的json.Encoder来序列化。

doc

• zap