mongodb3.4启动警告 WARNING: soft rlimits too low

启动警告如下：

# mongo
MongoDB shell version: 3.4.14
connecting to: test
Server has startup warnings: 
2020-05-09T12:34:19.688-0700 I CONTROL  [initandlisten] 
2020-05-09T12:34:19.688-0700 I CONTROL  [initandlisten] ** WARNING: soft rlimits too low. rlimits set to 1024 processes, 64000 files. Number of processes should be at least 32000 : 0.5 times number of files.
> 

mongodb当前限制：1024 processes, 64000 files

mongodb建议要求：processes = 0.5*files=32000（至少）

所以需要将 processes  从1024 改为 32000 或更大.

1.查看当前mongodb进程信息

ps -ef | grep mongod

mongod   24283     1  0 12:35 ?        00:00:04 /usr/bin/mongod -f /etc/mongod.conf  
root     24240 22049  0 12:45 pts/2    00:00:00 grep mongod  

2.查看限制：Max processes，Max open files 

cat /proc/24283/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            10485760             unlimited            bytes       
Max core file size        0                    unlimited            bytes       
Max resident set          unlimited            unlimited            bytes       
Max processes             1024                 32000                processes   
Max open files            64000                64000                files       
Max locked memory         65536                65536                bytes       
Max address space         unlimited            unlimited            bytes       
Max file locks            unlimited            unlimited            locks       
Max pending signals       14833                14833                signals     
Max msgqueue size         819200               819200               bytes       
Max nice priority         0                    0                      
Max realtime priority     0                    0                      
Max realtime timeout      unlimited            unlimited            us     

3.修改 Max processes 或者 files ，有几种方法

(1).方法一

修改配置文件 /etc/security/limits.d/90-nproc.conf 

vi /etc/security/limits.d/90-nproc.conf

*          soft    nproc     1024  
改为:  
*          soft    nproc     32000  

重启 mongodb 服务

service mongodb restart

(2).方法二

修改配置文件 /etc/security/limits.conf，添加配置信息

vi /etc/security/limits.conf

mongod soft nofile 64000  
mongod hard nofile 64000  
mongod soft nproc 32000  
mongod hard nproc 32000  

重启 mongod 服务

service mongod restart

也可以查看 limits.conf 更多配置信息和使用方法

man limits.conf

4.查看系统限制

ulimit -a

core file size          (blocks, -c) 0  
data seg size           (kbytes, -d) unlimited  
scheduling priority             (-e) 0  
file size               (blocks, -f) unlimited  
pending signals                 (-i) 14833  
max locked memory       (kbytes, -l) 64  
max memory size         (kbytes, -m) unlimited  
open files                      (-n) 1024  
pipe size            (512 bytes, -p) 8  
POSIX message queues     (bytes, -q) 819200  
real-time priority              (-r) 0  
stack size              (kbytes, -s) 10240  
cpu time               (seconds, -t) unlimited  
max user processes              (-u) 14833  
virtual memory          (kbytes, -v) unlimited  
file locks                      (-x) unlimited  

5.mongodb推荐设置

-f (file size): unlimited  
-t (cpu time): unlimited  
-v (virtual memory): unlimited  
-n (open files): 64000  
-m (memory size): unlimited  
-u (processes/threads): 64000  

直接在当前shell中设置：ulimit -n <value>

ulimit -f unlimited  
ulimit -t unlimited  
ulimit -v unlimited  
ulimit -n 64000  
ulimit -m unlimited  
ulimit -u 64000

若要系统启动时在所有生效，将上面的 ulimit 添加到 /etc/profile