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我们的服务器中使用了很多启动脚本为 shell 脚本，为了方便管理改为 systemctl 方式管理。
早上重启后正常，但是晚上流量高峰期间，大量用户无法链接服务器。
查看服务器进程日志出现大量报警日志。
后经过大佬排查。发现是因为 systemctl 启动的进程没有遵循 limits 资源限制，导致到达 systemctl 默认限定值后无法加载更多文件！

[root@kilig ~]# ulimit -a
core file size          (blocks, -c) unlimited
data seg size           (kbytes, -d) unlimited
scheduling priority             (-e) 0
file size               (blocks, -f) unlimited
pending signals                 (-i) 15082
max locked memory       (kbytes, -l) 64
max memory size         (kbytes, -m) unlimited
open files                      (-n) 102400
pipe size            (512 bytes, -p) 8
POSIX message queues     (bytes, -q) 819200
real-time priority              (-r) 0
stack size              (kbytes, -s) 8192
cpu time               (seconds, -t) unlimited
max user processes              (-u) 102400
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited

对比进程启动 limits

[root@kilig ~]# cat /proc/1024/limits 
Limit                     Soft Limit           Hard Limit           Units     
Max cpu time              unlimited            unlimited            seconds   
Max file size             unlimited            unlimited            bytes     
Max data size             unlimited            unlimited            bytes     
Max stack size            8388608              unlimited            bytes     
Max core file size        unlimited            unlimited            bytes     
Max resident set          unlimited            unlimited            bytes     
Max processes             1024               1024              processes 
Max open files            1024           1024               files     
Max locked memory       8048                   8048              bytes     
Max address space         unlimited            unlimited            bytes     
Max file locks            unlimited            unlimited            locks     
Max pending signals       1508                1508                signals   
Max msgqueue size         8192               8192              bytes     
Max nice priority         0                    0                    
Max realtime priority     0                    0                    
Max realtime timeout      unlimited            unlimited            us      

发现明显差异
解决办法加上 LimitNOFILE LimitNOFILE LimitNOFILE 指定参数即可

[Unit]
Description=kilig.systemctl

[Service]
LimitNOFILE=infinity
LimitNOFILE=102400
LimitNOFILE=102400
WorkingDirectory=xxxxxxx
ExecStart=xxxxxxxxxxxxxx
ExecStopPost=xxxxxxxxxxxxxxxxxxxxxx
Restart=always