2016-04-12T08:33:33.801+0800 I CONTROL  [initandlisten] ** WARNING: soft rlimits too low. rlimits set to 4096 processes, 64000 files. Number of processes should be at least 32000 : 0.5 times number of files.

0x00 limits

limits可以对cpu、文件数等进行限制，通过它可以针对某个用户或全部进行限制。limits分为soft limit和hard limit。soft limit可以超过，而不能超过hard limit (除非有root权限)。

ulimit -Sn 查看soft limit
ulimit -Hn 查看hard limit

0x01 MongoDB 建议设置

从这条warning来看，process建议设置至少为0.5倍的文件数(0.5x32000=16000)。

MongoDB ulimit建议设置：https://docs.mongodb.org/manual/reference/ulimit/#memory-size

0x02 ulimit 设置

修改配置文件 /etc/security/limits.conf

mongod soft fsize unlimited
mongod hard fsize unlimited
mongod soft cpu unlimited
mongod hard cpu unlimited
mongod soft as unlimited
mongod hard as unlimited
mongod soft nofile 64000
mongod hard nofile 64000
mongod soft nproc 64000
mongod hard nproc 64000

MongoDB推荐设置:

limit fsize unlimited unlimited  # (file size)
limit cpu unlimited unlimited    # (cpu time)
limit as unlimited unlimited     # (virtual memory size)
limit nofile 64000 64000         # (open files)
limit nproc 64000 64000          # (processes/threads)

重启MongoDB服务:

systemctl restart mongod

0x03 查看 MongoDB limits

ps -ef | grep mongod
mongod   14795     1  1 09:02 ?        00:00:02 /usr/bin/mongod -f /etc/mongod.conf

cat /proc/14795/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        0                    unlimited            bytes     
Max resident set          unlimited            unlimited            bytes     
Max processes             64000                64000                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       1883                 1883                 signals   
Max msgqueue size         819200               819200               bytes     
Max nice priority         0                    0                    
Max realtime priority     0                    0