93 lines
2 KiB
Go
93 lines
2 KiB
Go
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package log
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import (
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"encoding"
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"encoding/json"
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"fmt"
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"io"
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"reflect"
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)
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type jsonLogger struct {
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io.Writer
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}
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// NewJSONLogger returns a Logger that encodes keyvals to the Writer as a
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// single JSON object. Each log event produces no more than one call to
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// w.Write. The passed Writer must be safe for concurrent use by multiple
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// goroutines if the returned Logger will be used concurrently.
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func NewJSONLogger(w io.Writer) Logger {
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return &jsonLogger{w}
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}
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func (l *jsonLogger) Log(keyvals ...interface{}) error {
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n := (len(keyvals) + 1) / 2 // +1 to handle case when len is odd
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m := make(map[string]interface{}, n)
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for i := 0; i < len(keyvals); i += 2 {
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k := keyvals[i]
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var v interface{} = ErrMissingValue
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if i+1 < len(keyvals) {
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v = keyvals[i+1]
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}
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merge(m, k, v)
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}
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return json.NewEncoder(l.Writer).Encode(m)
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}
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func merge(dst map[string]interface{}, k, v interface{}) {
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var key string
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switch x := k.(type) {
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case string:
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key = x
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case fmt.Stringer:
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key = safeString(x)
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default:
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key = fmt.Sprint(x)
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}
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if x, ok := v.(error); ok {
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v = safeError(x)
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}
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// We want json.Marshaler and encoding.TextMarshaller to take priority over
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// err.Error() and v.String(). But json.Marshall (called later) does that by
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// default so we force a no-op if it's one of those 2 case.
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switch x := v.(type) {
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case json.Marshaler:
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case encoding.TextMarshaler:
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case error:
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v = safeError(x)
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case fmt.Stringer:
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v = safeString(x)
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}
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dst[key] = v
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}
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func safeString(str fmt.Stringer) (s string) {
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defer func() {
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if panicVal := recover(); panicVal != nil {
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if v := reflect.ValueOf(str); v.Kind() == reflect.Ptr && v.IsNil() {
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s = "NULL"
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} else {
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panic(panicVal)
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}
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}
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}()
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s = str.String()
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return
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}
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func safeError(err error) (s interface{}) {
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defer func() {
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if panicVal := recover(); panicVal != nil {
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if v := reflect.ValueOf(err); v.Kind() == reflect.Ptr && v.IsNil() {
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s = nil
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} else {
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panic(panicVal)
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}
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}
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}()
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s = err.Error()
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return
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}
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