How to print time taken for SQL query to execute in loopback console?

Question

I'm printing SQL queries executed in my application using below code

var chalk = require('chalk');

module.exports = (app) => {
  var connector = app.datasources.mysqlDs.connector;
  connector.observe('after execute', function(ctx, next) {
    console.log(chalk.green(ctx.req.sql));
    next();
  });
}

The above code prints sql query in console like this,

SELECT `users`.* FROM `users` WHERE `users`.`id` = 1 LIMIT 1

I'm interested to print time take to execute the sql query.

Ruby on rails applications prints sql query along with timing, similar to this given below

 User Load (0.2ms)  SELECT `users`.* FROM `users` WHERE `users`.`id` = 1 LIMIT 1

Is there any way to achieve this in loopback 3?

Answer 1

I am afraid LoopBack does not provide timing information out of the box. You can use before execute and after execute hooks to gather timing data yourself.

module.exports = (app) => {
  var connector = app.datasources.mysqlDs.connector;
  connector.observe('before execute', function(ctx, next) {
    // store the start time in the context
    ctx.__started = process.hrtime();
    next();
  });

  connector.observe('after execute', function(ctx, next) {
    // compute the time difference as [seconds, nanoseconds]
    const delta = process.hrtime(ctx.__started);
    // convert the two-part value into number of milliseconds elapsed
    // and round it to a single decimal place
    const durationInMs = 10 * Math.round((delta[0]*1000 + delta[1]/1e6)/10);
    console.log('(%s ms) %s', durationInMs, chalk.green(ctx.req.sql));
    next();
  });
}