title: What is a "worker" in Odoo?
body: <p>What is the purpose of workers? Are these workers for multi-threading or something else? When the <code>Odoo</code> instance start I see at least 6 workers on command line that informed:</p>
  
  <pre><code>2016-03-10 13:55:09,602 15504 INFO ? openerp.service.server: Worker WorkerHTTP (15504) alive
  2016-03-10 13:55:09,606 15503 INFO ? openerp.service.server: Worker WorkerHTTP (15503) alive
  2016-03-10 13:55:09,625 15507 INFO ? openerp.service.server: Worker WorkerCron (15507) alive
  2016-03-10 13:55:09,628 15506 INFO ? openerp.service.server: Worker WorkerCron (15506) alive
  2016-03-10 13:55:09,629 15508 INFO ? openerp.service.server: Worker WorkerCron (15508) alive
  2016-03-10 13:55:09,629 15509 INFO ? openerp.service.server: Worker WorkerCron (15509) alive
  </code></pre>
  
  <p>And what is the difference between <code>WorkerHTTP</code> and <code>WorkerCron</code>? Honestly I don't know what they do.</p>