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syslog_formatter.go
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syslog_formatter.go
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package journalhook
import (
"bytes"
"fmt"
"io"
"runtime"
"sort"
"github.com/sirupsen/logrus"
)
const FieldKeyPrefix = "prefix"
// SyslogFormatter formats logs into text.
type SyslogFormatter struct {
// Force quoting of all values
ForceQuote bool
// DisableQuote disables quoting for all values.
// DisableQuote will have a lower priority than ForceQuote.
// If both of them are set to true, quote will be forced on all values.
DisableQuote bool
// QuoteEmptyFields will wrap empty fields in quotes if true
QuoteEmptyFields bool
// The keys sorting function, when uninitialized it uses sort.Strings.
SortingFunc func([]string)
// CallerPrettyfier can be set by the user to modify the content
// of the function and file keys in the data when ReportCaller is
// activated. If any of the returned value is the empty string the
// corresponding key will be removed from fields.
CallerPrettyfier func(*runtime.Frame) (function string, file string)
}
// Format renders a single log entry.
func (f *SyslogFormatter) Format(entry *logrus.Entry) ([]byte, error) {
var prefix string
data := make(logrus.Fields)
keys := make([]string, 0, len(data))
for k, v := range entry.Data {
if k == logrus.FieldKeyTime || k == logrus.FieldKeyLevel {
continue // skip this field
}
if k == FieldKeyPrefix {
prefix = toString(v)
continue
}
data[k] = v
keys = append(keys, k)
}
fixedKeys := make([]string, 0, 4+len(data))
if entry.Message != "" {
fixedKeys = append(fixedKeys, logrus.FieldKeyMsg)
}
var funcVal, fileVal string
if entry.HasCaller() {
if f.CallerPrettyfier != nil {
funcVal, fileVal = f.CallerPrettyfier(entry.Caller)
} else {
funcVal = entry.Caller.Function
fileVal = fmt.Sprintf("%s:%d", entry.Caller.File, entry.Caller.Line)
}
if funcVal != "" {
fixedKeys = append(fixedKeys, logrus.FieldKeyFunc)
}
if fileVal != "" {
fixedKeys = append(fixedKeys, logrus.FieldKeyFile)
}
}
// Sort
if f.SortingFunc == nil {
sort.Strings(keys)
fixedKeys = append(fixedKeys, keys...)
} else {
fixedKeys = append(fixedKeys, keys...)
f.SortingFunc(fixedKeys)
}
b := &bytes.Buffer{}
if prefix != "" {
fmt.Fprintf(b, "[%s]", prefix)
}
for _, key := range fixedKeys {
var value interface{}
switch {
case key == logrus.FieldKeyFunc && entry.HasCaller():
value = funcVal
case key == logrus.FieldKeyFile && entry.HasCaller():
value = fileVal
default:
value = data[key]
}
if value != nil {
f.appendKeyValue(b, key, value)
}
}
if entry.Message != "" {
f.appendKeyValue(b, "msg", entry.Message)
}
b.WriteByte('\n')
return b.Bytes(), nil
}
func (f *SyslogFormatter) appendKeyValue(b *bytes.Buffer, key string, value interface{}) {
if b.Len() > 0 {
b.WriteByte(' ')
}
b.WriteString(key)
b.WriteByte('=')
f.appendValue(b, value)
}
func (f *SyslogFormatter) appendValue(b io.StringWriter, value interface{}) {
if s := toString(value); f.needsQuoting(s) {
b.WriteString(fmt.Sprintf("%q", s))
} else {
b.WriteString(s)
}
}
func (f *SyslogFormatter) needsQuoting(text string) bool {
if f.ForceQuote {
return true
}
if f.QuoteEmptyFields && len(text) == 0 {
return true
}
if f.DisableQuote {
return false
}
return hasSpecialCharacter(text)
}
func hasSpecialCharacter(text string) bool {
for _, ch := range text {
if !((ch >= 'a' && ch <= 'z') ||
(ch >= 'A' && ch <= 'Z') ||
(ch >= '0' && ch <= '9') ||
ch == '-' || ch == '.' || ch == '_' || ch == '/' || ch == '@' || ch == '^' || ch == '+') {
return true
}
}
return false
}
func toString(v interface{}) string {
switch v.(type) {
case string:
s, _ := v.(string)
return s
case *string:
if s, _ := v.(*string); s != nil {
return *s
}
return ""
default:
return fmt.Sprint(v)
}
}