mysql连接应在golang中生存多长时间

Question

I am using mysql with golang and reading this doc. It says

Although it’s idiomatic to Close() the database when you’re finished with it, the sql.DB object is designed to be long-lived. Don’t Open() and Close() databases frequently.

I don't know how long should the connnection be. For now, I open the connection each http request if necessary. Is it too frequently?

Answer 1

There is no authoritative answer, as it depends on the driver you're using. If you're using either:

• The popular mySQL driver - https://github.com/go-sql-driver/mysql
• or the popular postgres driver- https://github.com/lib/pq

... then you shouldn't close your sql.DB at all. The sql.DB in those cases represents a connection pool, and using it in your handlers/requests/functions means you are just using a connection from that pool (if available).

e.g.

var db *sql.DB

func setup() error {
    var err error
    db, err = sql.Open(...)
    if err != nil {
        log.Fatal(err)
    }

    // Other setup-related activities
}

func main()
    err := setup()
    if err != nil {
        log.Fatal(err)
    }

    // No need to call `defer db.Close()` here
    http.ListenAndServe(...)
}

func SomeHandler(w http.ResponseWriter, r *http.Request) {
    u := User{}
    res, err := db.GetThings(&u)
    // No need to close this here - it's just a connection dynamically pulled
    // from our sql.DB connection pool in most cases
}