《用Gin框架構建分散式應用》學習第5天，p77-p87總結，總計11頁。
一、技術總結
1.Go知識點
(1)context
2.on-premises software
p80, A container is like a separate OS, but not virtualized; it only contains the dependencies needed for that one application, which makes the container portable and deployable on-premises or on the cloud。
premises的意思是“the land and buildings owned by someone, especially by a company or organization(歸屬於某人(尤指公司、組織)的土地或建築物)”。簡單來說 on-premises software 指的是執行在本地的服務(軟體)。
wiki 對這個名稱的定義很好，這裡直接引用“On-premises software (abbreviated to on-prem, and often written as "on-premise") is installed and runs on computers on the premises of the person or organization using the software, rather than at a remote facility such as a server farm or cloud”。
3.openssl rand命令
openssl rand -base64 12 | docker secret create mongodb_password
-
rand 命令語法：
openssl rand [-help] [-out file] [-base64] [-hex] [-engine id] [-rand files] [-writerand file] [-provider name] [-provider-path path] [-propquery propq] num[K|M|G|T]
12對應 num引數。rand詳細用法參考https://docs.openssl.org/3.4/man1/openssl-rand/。對於一個命令，我們需要掌握其有哪些引數及每個引數的含義。
4.檢視docker latest tag對應的版本號
(1)未下載映象
開啟latest tag對應的頁面，如：https://hub.docker.com/layers/library/mongo/latest/images/sha256-e6e25844ac0e7bc174ab712bdd11bfca4128bf64d28f85d0c6835c979e4a5ff9，搜尋 VERSION，然後找到版本號。
(2)已下載映象
使用 docker inspect 命令進行檢視。
# docker inspect d32 | grep -i version
"DockerVersion": "",
"GOSU_VERSION=1.17",
"JSYAML_VERSION=3.13.1",
"MONGO_VERSION=8.0.1",
"org.opencontainers.image.version": "24.04"
5.mongo-go-driver示例
書上程式碼使用的mongo-go-driver v1.4.5，現在已經更新到了v2.0.0，導致有些程式碼無法執行，建議使用最新版。這裡還得再吐槽下 Go 生態圈的文件寫得太糟糕了。示例：
client, _ := mongo.Connect(options.Client().ApplyURI("mongodb://localhost:27017"))
ctx, cancel = context.WithTimeout(context.Background(), 2*time.Second)
defer cancel()
_ = client.Ping(ctx, readpref.Primary())
個人認為，上面的程式碼 err 就不應該忽略掉。而應該是：
package main
import (
"context"
"github.com/gin-gonic/gin"
"github.com/rs/xid"
"go.mongodb.org/mongo-driver/v2/mongo"
"go.mongodb.org/mongo-driver/v2/mongo/options"
"go.mongodb.org/mongo-driver/v2/mongo/readpref"
"log"
"net/http"
"strings"
"time"
)
type Recipe struct {
ID string `json:"id"`
Name string `json:"name"`
Tags []string `json:"tags"`
Ingredients []string `json:"ingredients"`
Instructions []string `json:"instructions"`
PublishAt time.Time `json:"publishAt"`
}
var recipes []Recipe
func init() {
// 方式1：使用記憶體進行初始化
// recipes = make([]Recipe, 0)
// file, err := os.Open("recipes.json")
// if err != nil {
// log.Fatal(err)
// return
// }
// defer file.Close()
//
// // 反序列化：將json轉為slice
// decoder := json.NewDecoder(file)
// err = decoder.Decode(&recipes)
// if err != nil {
// log.Fatal(err)
// return
// }
// 方式2：使用 MongoDB 儲存資料
ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
defer cancel()
// 建立連線,這裡的 err 針對的是 URI 錯誤
client, err := mongo.Connect(options.Client().ApplyURI("mongodb1://admin:admin@localhost:27017"))
if err != nil {
log.Fatal("MongoDB connect error: ", err)
}
// 判斷連線是否成功
if err := client.Ping(ctx, readpref.Primary()); err != nil {
log.Fatal("MongoDB Ping error: ", err)
}
log.Println("Connected to MongoDB successfully.")
}
// swagger:route POST /recipes createRecipe
//
// # Create a new recipe
//
// Responses:
//
// 200: recipeResponse
//
// NewRecipeHandler 新增recipe,是按照單個新增，所以這裡名稱這裡用的是單數
func NewRecipeHandler(c *gin.Context) {
var recipe Recipe
if err := c.ShouldBindJSON(&recipe); err != nil {
c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
return
}
recipe.ID = xid.New().String()
recipe.PublishAt = time.Now()
recipes = append(recipes, recipe)
c.JSON(http.StatusOK, recipe)
}
// swagger:route GET /recipes listRecipes
// Returns list of recipes
// ---
// produces:
// - application/json
// responses:
// '200':
// description: Successful operation
// ListRecipesHandler 差下recipes，因為是查詢所有，所以名稱這裡用的是複數
func ListRecipesHandler(c *gin.Context) {
c.JSON(http.StatusOK, recipes)
}
// UpdateRecipeHandler 更新 recipe，因為是單個，所以使用的是單數。
// id 從 path 獲取，其它引數從 body 獲取。
func UpdateRecipeHandler(c *gin.Context) {
id := c.Param("id")
// 資料解碼
var recipe Recipe
if err := c.ShouldBindJSON(&recipe); err != nil {
c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
return
}
// 判斷 id 是否存在
index := -1
for i := 0; i < len(recipes); i++ {
if recipes[i].ID == id {
index = i
}
}
// 如果 id 不存在
if index == -1 {
c.JSON(http.StatusNotFound, gin.H{"error": "recipe not found"})
return
}
// 如果 id 存在則進行更新
recipes[index] = recipe
c.JSON(http.StatusOK, recipe)
}
// DeleteRecipeHandler 刪除 recipe: 1.刪除之前判斷是否存在，存在就刪除，不存在就提示不存在。
func DeleteRecipeHandler(c *gin.Context) {
id := c.Param("id")
index := -1
for i := 0; i < len(recipes); i++ {
if recipes[i].ID == id {
index = i
}
}
if index == -1 {
c.JSON(http.StatusNotFound, gin.H{"message": "recipe not found"})
return
}
recipes = append(recipes[:index], recipes[index+1:]...)
c.JSON(http.StatusOK, gin.H{
"message": "recipe deleted",
})
}
// SearchRecipesHandler 查詢 recipes
func SearchRecipesHandler(c *gin.Context) {
tag := c.Query("tag")
listOfRecipes := make([]Recipe, 0)
for i := 0; i < len(recipes); i++ {
found := false
for _, t := range recipes[i].Tags {
if strings.EqualFold(t, tag) {
found = true
}
if found {
listOfRecipes = append(listOfRecipes, recipes[i])
}
}
}
c.JSON(http.StatusOK, listOfRecipes)
}
func main() {
router := gin.Default()
router.POST("/recipes", NewRecipeHandler)
router.GET("/recipes", ListRecipesHandler)
router.PUT("/recipes/:id", UpdateRecipeHandler)
router.DELETE("/recipes/:id", DeleteRecipeHandler)
router.GET("/recipes/search", SearchRecipesHandler)
err := router.Run()
if err != nil {
return
}
}
二、英語總結
1.ephemeral
p79, I opted to go with Docker duce to its popularity and simplicity in runing ephermeral environment.
(1)ephemeral: ephemera + -al。
(2)ephemera: epi-("on") + hemera("day"), lasting one day , short-lived"。
三、其它
從目前的閱讀體驗來看，作者預設讀者充分掌握Golang，絲毫不會展開介紹。
四、參考資料
1. 程式設計
(1) Mohamed Labouardy，《Building Distributed Applications in Gin》：https://book.douban.com/subject/35610349
2. 英語
(1) Etymology Dictionary：https://www.etymonline.com
(2) Cambridge Dictionary：https://dictionary.cambridge.org
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