Cluster and Fork mode difference in PM2
<p>I've searched a lot to figure out this question, but I didn't get clear explanation. Is there only one difference thing that clustered app can be scaled out and forked app cannot be?</p>

<p>PM2's public site explains Cluster mode can do <a href="http://pm2.keymetrics.io/docs/usage/cluster-mode/" rel="noreferrer">these feature</a> but no one says about pros of Fork mode (maybe, it can get <code>NODE_APP_INSTANCE</code> variable).</p>

<p>I feel like Cluster might be part of Fork because Fork seems like to be used in general. So, I guess Fork means just 'forked process' from the point of PM2 and Cluster means 'forked process that is able to be scaled out'. Then, why should I use Fork mode?</p>