Good practice for checking database existence on startup

I understand that this library does a few things other than manage the mysql, it can be used as a query builder on it’s own.

I am however surprised that there is no option for knex to check if a connection actually has been made if using it with a mysql database.

I’m using the following:

const instance = knex({
  client: 'mysql',
  connection: {
    database: 'my_db',
    host: '127.0.0.1',
    port: '3306',
    user: 'my_user',
    password: 'pass'
  },
  pool: {
    min: 3,
    max: 7
  },
  migrations: {
    tableName: 'mig'
  },
    acquireConnectionTimeout: 5000
  });

The only way I can check this is to do a quick “check” query, which feels very dirty:

instance.raw('select 1+1 as result').catch(err => {
  console.log(err);
  process.exit(1);
});

It crashes and displays why (which is what I want).

I’m wondering if yous recommend a specific way of doing this, the quick query was actually taken from my search over on StackOverflow.

[hdon]

Because I found this issue when doing a Google search for techniques to test database connections, I’m going to leave this here.

const Promise = require('bluebird');
const knex = require('knex');
const fs = require('fs');
const _ = require('lodash');
module.exports = _.transform(require('./database.json'), (o,v,k) => {o[k]=knex(v)});
if (require.main === module) {
  Promise.map(
    Object.keys(module.exports)
  , dbName => module.exports[dbName].raw(`select 'I have ${dbName}' as status`)
    .then(result => {
      console.log(result[0][0].status);
      module.exports[dbName].destroy();
      return null;
    })
    .catch(err => {
      console.error(dbName, err);
      return {status: 'I do NOT have '+dbName}
    })
  ).then(ignore => console.log('database connection test complete'))
}

[elhigu]

That looks unnecessary complicated way to do few queries.