隨筆: Golang 錯誤處理

值得參考的文章:

recover

gin中如果使用goroutine這類async邏輯，必須補充recover的邏輯，才可捕捉錯誤避免崩潰。非async邏輯可直接用r.Use(gin.Recovery())捕捉

panic發生在非async邏輯中: 如果使用r.Use(gin.Recovery())，發生panic會捕捉到此錯誤，並回傳500給呼叫端

package main

import (
	"github.com/gin-gonic/gin"
)

func main() {
	r := gin.New()
	r.Use(gin.Logger())
	r.Use(gin.Recovery())

	r.GET("/ping", func(c *gin.Context) {
		func() {
			panic("panic")
		}()

		c.JSON(200, gin.H{
			"message": "pong",
		})
	})

	r.Run()
}

panice發生在async邏輯中: 雖使用r.Use(gin.Recovery())，但panic發生在goroutine中，則panic不會捕捉，並且程序會崩潰，必須在goroutine補充recover的邏輯，才可捕捉錯誤避免崩潰

package main

import (
	"fmt"
	"sync"

	"github.com/gin-gonic/gin"
)

type WaitGroupWithError struct {
	sync.WaitGroup
	Error error
}

func (w *WaitGroupWithError) Wait() error {
	w.WaitGroup.Wait()
	return w.Error
}

func main() {
	r := gin.New()
	r.Use(gin.Logger())
	r.Use(gin.Recovery())

	r.GET("/ping", func(c *gin.Context) {
		var wg WaitGroupWithError
		wg.Add(1)
		go func() {
			defer func() {
				// 需要在此透過recover捕捉
				if err := recover(); err != nil {
					wg.Error = fmt.Errorf("get panic: %v", err)
				}
				wg.Done()
			}()
			panic("panic")
		}()
		if err := wg.Wait(); err != nil {
			fmt.Printf("get err: %+v", err)
			c.JSON(500, gin.H{
				"message": "internal error",
			})
			return
		}

		c.JSON(200, gin.H{
			"message": "pong",
		})
	})

	r.Run()
}

參考:
- https://segmentfault.com/a/1190000022886063