Prevent node.js process from dying on MySQL query error

Question

I have a node.js script that runs a MySQL query. When error is encountered with this query, the node.js process dies. It uses the mysql-node module. https://github.com/mysqljs/mysql

Here is my code;

  function runQuery() {
         return new Promise(function (resolve, reject) {
            try {
                var connection = test_mysql.create_MySQL_conn();

            var query_str =
                //MySQL query. blah blah
                ;

            var query_param = [];

            connection.query(query_str, query_param, function (err, rows, fields) {
                if (err) {
                    console.log(err);                        
                    return reject(err);
                }
                else {
                    resolve(rows);
                }
            });
        } 
        catch (err) {
            reject(err);
        }
    });
}

How do I modify it such that the script does not die when error is encountered with the mysql query?

Answer 1

The premise of your question is likely to be wrong. The script may not die even if you encounter error in the MySQL query. You can do a simple test.

You can run the code below.

function Delay(duration) {
    return new Promise((resolve) => {
        setTimeout(() => resolve(), duration);
    });
}

function test_func() {
    Promise.resolve()        
        .then(() => runQuery()  );
}

Promise.resolve()
    .then(() => Delay(3000))
    .then(() => test_func() )
    .then(() => Delay(3000))
    .then(() => test_func() );

If test_func() runs 2 times, it means the script did not die. Probably, you encountered a long error message and thought the script died when it actually did not.