title: How cursor.observe works and how to avoid multiple instances running?
body: <h1>Observe</h1>
  
  <p>I was trying to figure it out how <strong><em>cursor</em>.observe</strong> runs inside meteor, but found nothing about it.
  <a href="http://docs.meteor.com/#observe" rel="nofollow noreferrer">Docs</a> says</p>
  
  <blockquote>
    <p>Establishes a <em>live query</em> that notifies callbacks on any change to the query result.</p>
  </blockquote>
  
  <p>I would like to understand better what <em>live query</em> means. </p>
  
  <ul>
  <li>Where will be my observer function executed? By Meteor or by mongo?</li>
  </ul>
  
  <h1>Multiple runs</h1>
  
  <p>When we have more than just a user subscribing an <em>observer</em>, one instance runs for each client, leading us to a performance and race condition issue.</p>
  
  <ul>
  <li>How can I implement my <code>observe</code> to it be like a <code>singleton</code>? Just one instance running for all.</li>
  </ul>
  
  <p><strong><em>Edit:</strong> There was a third question here, but now it is a separated question: <a href="https://stackoverflow.com/q/13297796/599991">How to avoid race conditions on cursor.observe?</a></em></p>