• The logic of the test is relatively simple, that is, Node accesses the database to query data. The execution time of the SQL statement is about 2 seconds. I used JMeter to conduct multi-thread testing (5 threads), and the results were as expected (according to Node non-blocking Features), 5 threads should return results in 2 seconds at the same time, but the result is like this:

• 

• 

• According to the results, Node is executed serially, which is inconsistent with the expected result. Can anyone explain it

• Code:

app.get('/', function (req, res) {
    var now = +(new Date())
    connection.query('select count(*) from ACTIVITY group by name', function (err, result, fields) {
        var curr = +(new Date())
        var tmp = '耗时:' + (curr - now)
        console.log(tmp)
        res.send(tmp)
    })
})

• Note: It is not a database processing problem, because I use two different machines to execute the same SQL statement, and the time is 2 seconds

The following is a supplement

• According to @Biancheng, the reason is that multiple SQL statements use the same connection. Now the code has been modified and the database connection pool is used. The execution result is as follows:

• code show as below:

app.get('/', function (req, res) {
    var now = +(new Date())
    pool.getConnection(function (err, conn) {
        console.log('--连接池连接成功!' + +(new Date()))
        conn.query('select count(*) from ACTIVITY group by name', function (err, result, fields) {
            var curr = +(new Date())
            var tmp = '耗时:' + (curr - now)
            console.log(tmp)
            res.send(tmp)
        })
    })
})

• This result is more consistent with expectations. Five threads query at the same time, and all returns are returned in 4 seconds. As the pressure increases, the query time will naturally become longer. After testing, when the number of threads is changed to 2 , the return time is 2s, which is consistent with expectations!