MongoDB文件句柄数限制

在实际使用mongodb时, 由于分表较多, 每个表又有若干索引. 当业务量起来时, 经常出现连接池socket连接断开的错误, 排查mongodb的日志, 发现基本都是"Too many open files"错误.

排查问题

1. 查看当前文件的数量限制

   [root@ip-172-16-1-149 rocky]# 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) 29303
   max locked memory       (kbytes, -l) 64
   max memory size         (kbytes, -m) unlimited
   open files                      (-n) 655350
   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) 655350
   virtual memory          (kbytes, -v) unlimited
   file locks                      (-x) unlimited
   

   重点看open files​的值, 此处是655350, 理论上是够用的.

2. 查找到mongodb的进程

   [root@ip-172-16-1-149 rocky]# ps -axu | grep mongod
   root      647090  2.9 11.3 3419876 860280 ?      Sl   05:56   2:02 /usr/bin/mongod -f /etc/mongod.conf
   

3. 查看mongodb进行的限制

   [root@ip-172-16-1-149 rocky]# cat /proc/647090/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             29303                29303                processes
   Max open files            1024                 65535                files
   Max locked memory         65536                65536                bytes
   Max address space         unlimited            unlimited            bytes
   Max file locks            unlimited            unlimited            locks
   Max pending signals       29303                29303                signals
   Max msgqueue size         819200               819200               bytes
   Max nice priority         0                    0
   Max realtime priority     0                    0
   Max realtime timeout      unlimited            unlimited            us
   

   可以看到mongodb进程open files​数量限制中, 被Soft Limit​限制为1024了

4. 临时方案修改

   [root@ip-172-16-1-149 rocky]# prlimit --pid 647090--nofile=65535:65535
   

   再次通过查看/proc/{pid}/limits​可以看到, open files​的限制都被修改为65535了. 但是这种方式只能针对这个mongodb进程临时生效, 当mongodb重启后又会恢复为之前的状态

5. 永久方案修改

   在实际操作时, 修改service信息没有生效, 暂时没有继续研究了, 后续可以参考以下文档进行测试

   too many open files 问题解决方法

   MongoDB Too many open files 异常的解决

   MongoDB报Too many open files解决方法

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