I am running an Apache Server with this config:
64GB RAM, 4x480GB SSD, Dual 12 cores @ 2.1 GHz
keepalivetimeout: 5 loglevel: warn maxclients: 2000 serverlimit: 2000 maxkeepaliverequests: 100 maxrequestsperchild: 10000 maxspareservers: 20 minspareservers: 5 startservers: 5
The server keeps crashing intermittently, yet server load will be low (less than 3).
I found out that each time the server crashes, there will be no workers available.
If I enable "under attack" on Cloudflare, workers get freed up.
This has been happening for several months, and I have been managing it like that. However, it is affecting users badly.
I also do not think that this is a DDoS, yet cannot explain what is going on and how to solve it.