How to check if the db connection is success or not in node js and mysql

user_7992336 0
Viewed 14990

I'm using mysql connection pool to create connection. The code looks like the following.

var pool = mysql.createPool(connectionProps);

by accessing pool, I'll get the an Object, even if the connection is not Successful. I checked it with starting and stopping mysql.

What I want is that, I need to check connection is successful or not as follows.

if(pool){ // mysql is started && connected successfully.
   console.log('Connection Success');
   doSomething();
}else{
   console.log('Cant connect to db, Check ur db connection');
}

I want something like this. So how can we do this with the mysql pool Object. Can someone please help me?

Thanks n Regards

connection-pool node-mysql node.js mysql javascript
2 Answers

Commonly you would do something like select something arbitrary from the db, and catch an error if that failed. Example from the docs.

const pool = mysql.createPool(connectionProps);
pool.query('SELECT 1 + 1 AS solution', (error, results, fields) => {
  if (error) throw error;
  console.log('The solution is: ', results[0].solution);
});
user_66227810 
var pool = mysql.createPool(config.db);
exports.connection = {
query: function () {
    var queryArgs = Array.prototype.slice.call(arguments),
        events = [],
        eventNameIndex = {};

    pool.getConnection(function (err, conn) {
        if (err) {
            if (eventNameIndex.error) {
                eventNameIndex.error();
            }
        }
        if (conn) { 
            var q = conn.query.apply(conn, queryArgs);
            q.on('end', function () {
                conn.release();
            });

            events.forEach(function (args) {
                q.on.apply(q, args);
            });
        }
    });

    return {
        on: function (eventName, callback) {
            events.push(Array.prototype.slice.call(arguments));
            eventNameIndex[eventName] = callback;
            return this;
        }
    };
}
};

And require to use it like:

db.connection.query("SELECT * FROM `table` WHERE `id` = ? ", row_id)
      .on('result', function (row) {
        setData(row);
      })
      .on('error', function (err) {
        callback({error: true, err: err});
      });
user_55549810
Related