How to Share a MySQL Connection Among HTTP Goroutines in Go?

Sharing MySQL Connection among HTTP Goroutines in Go

In Go, managing database connections in concurrency can be a bit confusing. This article explores how to effectively share a MySQL connection among multiple HTTP goroutines.

Overview

When using the database/sql package in Go, calling sql.Open() doesn't establish an immediate database connection. Instead, it creates a connection pool, a collection of connections managed by the package. The package automatically handles the pooling, opening new connections when needed.

Sharing the Connection

To share the connection between main() and HTTP handlers, declare a global db variable:

var db *sql.DB

In main(), initialize the connection pool:

db, err := sql.Open("mysql", "root@unix(/tmp/mysql.sock)/mydb")
if err != nil {
    log.Fatalf("Error on initializing database connection: %s", err.Error())
}

db.SetMaxIdleConns(100)

err = db.Ping() // Opens a connection if necessary
if err != nil {
    log.Fatalf("Error on opening database connection: %s", err.Error())
}

HTTP handlers can then access the shared database connection:

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)
    }
}

Conclusion

By following these steps, you can effectively share a MySQL connection among multiple HTTP goroutines in Go, ensuring efficient database access without unnecessary overhead.

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