Error: mod_fcgid: can't apply process slot for makes my server

mod_fcgid: can't apply process slot for varwwwcgi-bincgi_wrappercgi_wrapper, referer: [Thu Jan 07 10:02

Website hosted in Plesk server is not accessible under heavy load: mod_fcgid: can't apply process slot for varwwwcgi-bincgi_wrappercgi_wrapper · Symptoms

mod_fcgid_ can''t apply process slot  mod_fcgid: can't apply process slot for varwww

mod_fcgid_ can''t apply process slot for mod_fcgid: can't apply process slot for usrlibcgi-binprojectqgis_