Any ideas why an AWS instance would seemingly random close off port 80? It's running RHEL 7.
iptables?
Check this out - production site running with 213 days uptime and today bam - pingable but can't get to the index. Someone else checked the iptables and they were good but nmap not showing 80 open.
Annnnnnnnnd... It's back up. Ok...
check your logs, maybe its your apache crashing?
It runs nginx - I had checked the error and access log nothing really jumped out. Tried to restart the service but it wouldn't let me because something was already binding to 80... After fuser on 80 I could restart but still 80 was closed. Its bazaar. 200+ days uptime, no changes randomly shuts off 80.... Now its back up. (skeptical eyes)
check what was using it... maybe you have 2 services bound to port 80...
port 80 will be closed when there's no services listening at it. check if you have anything in cron, you can also set up trace... and let it run to find out whats up.
though im sure nginx is either being stopped at one point and other service pops in or something is erring out.
AWS live-migrating your VM to a new host? (I am guessing you are running a single host here?)