profiler.js

var profiler = require('profiler');

profiler.monitor('redis', redisClient);
// What is redisCLient ? Is it the return of require('redis') ?

profiler.monitor('mongodb', mongodb_client);

profiler.monitor('rethinkdb', rethinkdb_client);

profiler.on('query', function(parameters){
  console.log(parameters);
  /**
   * 
   * Get something like
   * 
   * {
   *    db : 'redis',
   *    timespan : 35,   // time took to do the query
   *    at : 234234423   // UTC time when the query has been finished
   *    arguments : {
   *         {} {}       // Mixed object that can describe in details the query (parameters...)
   *    }
   * }
   * 
   *******/
});

// What is redisCLient ? Is it the return of require('redis') ?
no, instance of redis client

   require('redis').createClient(port, host, callback)