Go Mgo 应用的连接池管理与 TCP 超时处理策略

package main

import (
    "context"
    "fmt"
    "log"
    "net/http"
    "time"

    "github.com/gin-gonic/gin"
    "gopkg.in/mgo.v2"
    "gopkg.in/mgo.v2/bson"
)

// 定义一个全局的Mgo主会话
var globalMgoSession *mgo.Session

// User 定义用户结构体
type User struct {
    ID    bson.ObjectId `bson:"_id,omitempty" json:"id"`
    Name  string        `bson:"name" json:"name"`
    Email string        `bson:"email" json:"email"`
}

func init() {
    // 初始化Mgo连接
    var err error
    dialInfo := &mgo.DialInfo{
        Addrs:    []string{"localhost:27017"}, // MongoDB地址
        Database: "testdb",                   // 数据库名称
        Username: "user",                     // 用户名 (如果需要)
        Password: "password",                 // 密码 (如果需要)
        Timeout:  10 * time.Second,           // 连接超时
    }

    globalMgoSession, err = mgo.DialWithInfo(dialInfo)
    if err != nil {
        log.Fatalf("Failed to connect to MongoDB: %v", err)
    }

    // 设置全局会话的连接池模式
    globalMgoSession.SetMode(mgo.Monotonic, true)

    // 设置操作超时和套接字超时
    // 这些超时会影响通过 Copy() 创建的所有会话副本
    globalMgoSession.SetSyncTimeout(30 * time.Second) // 单个操作的超时时间
    globalMgoSession.SetSocketTimeout(60 * time.Second) // 底层TCP套接字的读写超时

    log.Println("MongoDB connection initialized successfully.")
}

// GetUserHandler 处理获取用户请求
func GetUserHandler(c *gin.Context) {
    // 每次请求都复制一个会话副本
    sessionCopy := globalMgoSession.Copy()
    defer sessionCopy.Close() // 确保会话副本在使用后关闭并返回连接池

    userID := c.Param("id")
    if !bson.IsObjectIdHex(userID) {
        c.JSON(http.StatusBadRequest, gin.H{"error": "Invalid user ID"})
        return
    }

    collection := sessionCopy.DB("testdb").C("users")
    var user User
    err := collection.Find(bson.M{"_id": bson.ObjectIdHex(userID)}).One(&user)

    if err != nil {
        if err == mgo.ErrNotFound {
            c.JSON(http.StatusNotFound, gin.H{"error": "User not found"})
            return
        }
        // 捕获并处理可能的超时错误
        if mgo.Is = err { // 这是一个占位符，Mgo的超时错误通常是通用的网络错误
            log.Printf("MongoDB operation timeout or network error: %v", err)
            // 尝试刷新会话或返回错误
            // sessionCopy.Refresh() // 尝试刷新会话
            c.JSON(http.StatusServiceUnavailable, gin.H{"error": "Database temporarily unavailable, please retry"})
            return
        }
        log.Printf("Error fetching user: %v", err)
        c.JSON(http.StatusInternalServerError, gin.H{"error": "Internal server error"})
        return
    }

    c.JSON(http.StatusOK, user)
}

// CreateUserHandler 处理创建用户请求
func CreateUserHandler(c *gin.Context) {
    sessionCopy := globalMgoSession.Copy()
    defer sessionCopy.Close()

    var newUser User
    if err := c.BindJSON(&newUser); err != nil {
        c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
        return
    }

    newUser.ID = bson.NewObjectId()
    collection := sessionCopy.DB("testdb").C("users")
    err := collection.Insert(&newUser)
    if err != nil {
        log.Printf("Error creating user: %v", err)
        c.JSON(http.StatusInternalServerError, gin.H{"error": "Failed to create user"})
        return
    }

    c.JSON(http.StatusCreated, newUser)
}

func main() {
    defer globalMgoSession.Close() // 应用程序退出时关闭主会话

    router := gin.Default()

    router.GET("/users/:id", GetUserHandler)
    router.POST("/users", CreateUserHandler)

    log.Fatal(router.Run(":8080"))
}