使用
logrus 通过 formatter 来定义输出日志的格式,具体例子如下:
package main
import (
log "github.com/Sirupsen/logrus"
)
func main() {
formatter := &log.TextFormatter{
// 不需要彩色日志
DisableColors: true,
// 定义时间戳格式
TimestampFormat: "2006-01-02 15:04:05",
}
log.SetFormatter(formatter)
log.Printf("hello world")
}
打印的日志内容如下:
time="2019-11-07 17:41:20" level=info msg="hello world"
说明:
- time: 日志的打印时间
- level: 日志的等级
- msg: 日志内容
分析
本身 formatter 是接口类型,只要实现该结构我们就可以自定义日志输出格式:
// Any additional fields added with `WithField` or `WithFields` are also in
// `entry.Data`. Format is expected to return an array of bytes which are then
// logged to `logger.Out`.
type Formatter interface {
Format(*Entry) ([]byte, error)
}
logrus 提供了两种默认的日志输出格式, TextFormatter和JSONFormatter.上面的示例使用的就是TextFormatter.
TextFormatter
type TextFormatter struct {
// Set to true to bypass checking for a TTY before outputting colors.
ForceColors bool
//不使用彩色日志
DisableColors bool
// Override coloring based on CLICOLOR and CLICOLOR_FORCE. - https://bixense.com/clicolors/
EnvironmentOverrideColors bool
// 是否打印时间戳
DisableTimestamp bool
// Enable logging the full timestamp when a TTY is attached instead of just
// 是否按照时间戳格式打印,置为false则只打印从程序启动到打印日志的时间差(单位:秒)
FullTimestamp bool
// 时间戳格式
TimestampFormat string
// 设置 fields 不排序
DisableSorting bool
// 设置 fields 的排序规则
SortingFunc func([]string)
// Disables the truncation of the level text to 4 characters.
DisableLevelTruncation bool
// QuoteEmptyFields will wrap empty fields in quotes if true
QuoteEmptyFields bool
// 是否打印日志到终端
isTerminal bool
// fieldMap
// As an example:
// formatter := &TextFormatter{
// FieldMap: FieldMap{
// FieldKeyTime: "@timestamp",
// FieldKeyLevel: "@level",
// FieldKeyMsg: "@message"}}
FieldMap FieldMap
// 设置 func 和 file 这两个 field的输出格式
CallerPrettyfier func(*runtime.Frame) (function string, file string)
terminalInitOnce sync.Once
}
TextFormatter 实现 Formatter接口
// Format renders a single log entry
func (f *TextFormatter) Format(entry *Entry) ([]byte, error) {
data := make(Fields)
for k, v := range entry.Data {
data[k] = v
}
// prefixFieldClashes 删除默认的 4 个 field,防止冲突(msg, level, time, logrus_error)
prefixFieldClashes(data, f.FieldMap, entry.HasCaller())
keys := make([]string, 0, len(data))
for k := range data {
keys = append(keys, k)
}
// 拼接待打印日志的各个元素
var funcVal, fileVal string
// 拼接元素过程省略 ...
f.terminalInitOnce.Do(func() { f.init(entry) })
// 修改时间戳
timestampFormat := f.TimestampFormat
if timestampFormat == "" {
timestampFormat = defaultTimestampFormat
}
// 以下省略 ...
// 打印换行符
b.WriteByte('\n')
return b.Bytes(), nil
}
JSONFormatter
// JSONFormatter formats logs into parsable json
type JSONFormatter struct {
// TimestampFormat sets the format used for marshaling timestamps.
TimestampFormat string
// DisableTimestamp allows disabling automatic timestamps in output
DisableTimestamp bool
// DataKey allows users to put all the log entry parameters into a nested dictionary at a given key.
DataKey string
// FieldMap allows users to customize the names of keys for default fields.
// As an example:
// formatter := &JSONFormatter{
// FieldMap: FieldMap{
// FieldKeyTime: "@timestamp",
// FieldKeyLevel: "@level",
// FieldKeyMsg: "@message",
// FieldKeyFunc: "@caller",
// },
// }
FieldMap FieldMap
// CallerPrettyfier can be set by the user to modify the content
// of the function and file keys in the json data when ReportCaller is
// activated. If any of the returned value is the empty string the
// corresponding key will be removed from json fields.
CallerPrettyfier func(*runtime.Frame) (function string, file string)
// PrettyPrint will indent all json logs
PrettyPrint bool
}
JSONFormatter的实现方式与TextFormatter类同,这里就不再赘述。总之logrus的formatter实现比较简单,常用参数也在注释里进行了详细的说明。
自定义 Formatter
这里我们自定义一个 formatter,这个 formatter会在打印的日志前后分别加上前缀和后缀。
package main
import (
"bytes"
"fmt"
log "github.com/Sirupsen/logrus"
)
func main() {
// 初始化自定义 formatter
formatter := &MyFormatter{
Prefix: "prefix",
Suffix: "suffix",
}
log.SetFormatter(formatter)
log.Infoln("hello world")
}
// MyFormatter 自定义 formatter
type MyFormatter struct {
Prefix string
Suffix string
}
// Format implement the Formatter interface
func (mf *MyFormatter) Format(entry *log.Entry) ([]byte, error) {
var b *bytes.Buffer
if entry.Buffer != nil {
b = entry.Buffer
} else {
b = &bytes.Buffer{}
}
// entry.Message 就是需要打印的日志
b.WriteString(fmt.Sprintf("%s - %s - %s", mf.Prefix, entry.Message, mf.Suffix))
return b.Bytes(), nil
}
打印结果如下:
prefix - hello world - suffix