Linux PIDs have a maximum of 65535 processes (threads) running at once. Processes may fail to start if the processes limit is reached.
I must ask: How many hosts and services are you checking? How often are those checks going out? Every minute? How's the CPU and network usage on the Nagios XI machine (run top)?
You could greatly lessen the load on the system by increasing the delay between checks. It might even be a good idea for checks like disk usage and SSL cert expiration to have a much longer delay between checks -- say 1 hour to 1 day.
If you didn't get an 8% raise over the course of the pandemic, you took a pay cut.
Discussion of wages is protected speech under the National Labor Relations Act, and no employer can tell you you can't disclose your pay with your fellow employees.
Since you're using Mod Gearman, the warning isn't about a problem that can happen on your system; Mod Gearman splits the load between multiple servers, but the warning only applies if all checks went out from the same server.
Warnings are just warnings after all. Your system configuration is fine - it doesn't seem like it'll come anywhere near the process limit.
If you didn't get an 8% raise over the course of the pandemic, you took a pay cut.
Discussion of wages is protected speech under the National Labor Relations Act, and no employer can tell you you can't disclose your pay with your fellow employees.
The calculation is invalid because nagios doesn't run all the checks at the same time and that message should be ignored (this was told to me by the dev that wrote that RLIMIT_NPROC check into Core when I asked him about it).
There isn't currently a way to remove it from your system without increasing your nproc limits to be higher that the value listed, for example, you can add these to your /etc/security/limits.conf: