zerolog.md

• What's zerolog?
• zerolog Usage
  • Installation:
  • Contextual Logger
  • Multi-level Logger

What's zerolog?

zerolog package 提供了一個專門用於 JSON 輸出的 logger, 獨特的鏈式 API 允許通過避免記憶體分配及反射來寫入 JSON(or CBOR) log

此方法由 uber 的 zap 開創, zerolog 通過更簡單的 interface 及更優秀的性能將此概念提升到更高的層次

zerolog Usage

Installation:

go get -u github.com/rs/zerolog/log

Contextual Logger

func TestContextualLogger(t *testing.T) {
 log := zerolog.New(os.Stdout)
 log.Info().Str("content", "Hello world").Int("count", 3).Msg("TestContextualLogger")


  // add context (file name / column / string)
 log = log.With().Caller().Str("foo", "bar").Logger()
 log.Info().Msg("Hello wrold")
}

output:

{"level":"info","content":"Hello world","count":3,"message":"TestContextualLogger"}
{"level":"info","caller":"log_example_test.go:29","message":"Hello wrold"}

與 zap 相同, 都定義了強型別 field, 不同點在於 zerolog 採用鏈式調用

Multi-level Logger

zerolog 提供了從 Trace 到 Panic 七個 level:

 zerolog.SetGlobalLevel(zerolog.WarnLevel)
 log.Trace().Msg("Trace")
 log.Debug().Msg("Debug")
 log.Info().Msg("Info")
 log.Warn().Msg("Warn")
 log.Error().Msg("Error")
 log.Log().Msg("no level")

output:

{"level":"warn","message":"Warn"}
{"level":"error","message":"Error"}
{"message":"no level"}

❗️NOTE

1. zerolog 不會刪除重複 field

   logger := zerolog.New(os.Stderr).With().Timestamp().Logger()
   logger.Info().
       Timestamp().
       Msg("dup")

   output:

   {"level":"info","time":1494567715,"time":1494567715,"message":"dup"}

2. 鍊式調用必須調用 Msg 或 Msgf, Send 才能輸出 log, Send 相當於調用 Msg("")

3. 一但調用 Msg, Event 將會被處理(放回 pool 或丟棄), 不允許二次調用