<b>'Connection refused' under load and it's NOT your app</b>

<b>'Connection refused' under load and it's NOT your app</b>

Box is fine, app is fine, but new connections randomly drop during a traffic spike. Check dmesg for <code>nf_conntrack: table full</code>. The kernel's connection-tracking table maxed out and started dropping packets silently.

— <code>sysctl net.netfilter.nf_conntrack_max=131072</code>
— or drop conntrack entirely for stateless web traffic if you don't need it

Default max on a small box is tiny. This is the invisible ceiling that makes people 'upgrade their VPS' when they didn't need to. Try it tonight.