如何在http goroutines之间共享mysql连接？

Question

我是围棋菜鸟，无法找到打开围棋一个MySQL连接，然后处理HTTP之间共享它的任何一个完整的例子。这是我的代码到目前为止，我将如何使用我在HomeHandler中的main（）中打开的数据库连接？

package main 

import (
    "database/sql" 
    "fmt" 
    _ "github.com/go-sql-driver/mysql" 
    "github.com/gorilla/mux" 
    "log" 
    "net/http" 
) 

func main() { 

    fmt.Println("starting up") 

    db, err := sql.Open("mysql", "root:@/mydb?charset=utf8") 
    if err != nil { 
    log.Fatalf("Error opening database: %v", err) 
    } 

    db.SetMaxIdleConns(100) 

    r := mux.NewRouter() 
    r.HandleFunc("/", HomeHandler) 

    http.Handle("/", r) 
    http.ListenAndServe(":8080", nil) 

} 

func HomeHandler(w http.ResponseWriter, r *http.Request) { 

    fmt.Fprintf(w, "home") 

} 

Answer 1

数据库/ sql包为您自动管理连接池。

sql.Open(..)返回一个句柄，其中表示连接池，而不是单个连接。如果池中的所有连接都忙碌，那么数据库/ sql包会自动打开一个新连接。

应用到你的代码，这意味着，你只需要共享的DB-手柄，并在HTTP处理程序使用它：

package main 

import (
    "database/sql" 
    "fmt" 
    "github.com/gorilla/mux" 
    _ "github.com/go-sql-driver/mysql" 
    "log" 
    "net/http" 
) 

var db *sql.DB // global variable to share it between main and the HTTP handler 

func main() { 
    fmt.Println("starting up") 

    var err error 
    db, err = sql.Open("mysql", "root@unix(/tmp/mysql.sock)/mydb") // this does not really open a new connection 
    if err != nil { 
     log.Fatalf("Error on initializing database connection: %s", err.Error()) 
    } 

    db.SetMaxIdleConns(100) 

    err = db.Ping() // This DOES open a connection if necessary. This makes sure the database is accessible 
    if err != nil { 
     log.Fatalf("Error on opening database connection: %s", err.Error()) 
    } 

    r := mux.NewRouter() 
    r.HandleFunc("/", HomeHandler) 

    http.Handle("/", r) 
    http.ListenAndServe(":8080", nil) 
} 

func HomeHandler(w http.ResponseWriter, r *http.Request) { 
    var msg string 
    err := db.QueryRow("SELECT msg FROM hello WHERE page=?", "home").Scan(&msg) 
    if err != nil { 
     fmt.Fprintf(w, "Database Error!") 
    } else { 
     fmt.Fprintf(w, msg) 
    } 
}