如何解决mongodb中打开大量files的问题

如何解决mongodb中打开大量files的问题，针对这个问题，这篇文章详细介绍了相对应的分析和解答，希望可以帮助更多想解决这个问题的小伙伴找到更简单易行的方法。

问题描述：

  mac osx 环境   通过tcp测试工具，创建3000个连接，就报 too many open files 具体错误：`2016-05-11T00:59:29.772+0800 E STORAGE  [thread1] WiredTiger (23) [1462899569:771906][60793:0x70000020a000], log-server: /data/db/journal: opendir: Too many open files in system2016-05-11T00:59:29.772+0800 E STORAGE  [thread1] WiredTiger (23) [1462899569:772155][60793:0x70000020a000], log-server: dirlist journal prefix WiredTigerPreplog: Too many open files in system2016-05-11T00:59:29.772+0800 E STORAGE  [thread1] WiredTiger (23) [1462899569:772199][60793:0x70000020a000], log-server: log pre-alloc server error: Too many open files in system2016-05-11T00:59:29.772+0800 E STORAGE  [thread1] WiredTiger (23) [1462899569:772239][60793:0x70000020a000], log-server: log server error: Too many open files in system2016-05-11T00:59:33.022+0800 W FTDC     [ftdc] Uncaught exception in 'FileNotOpen: Failed to open interim file /data/db/diagnostic.data/metrics.interim.temp' in full-time diagnostic data capture subsystem. Shutting down the full-time diagnostic data capture subsystem.2016-05-11T00:59:33.566+0800 E STORAGE  [thread2] WiredTiger (23) [1462899573:566795][60793:0x700000393000], file:WiredTiger.wt, WT_SESSION.checkpoint: WiredTiger.turtle: fopen: Too many open files in system2016-05-11T00:59:33.568+0800 E STORAGE  [thread2] WiredTiger (23) [1462899573:568812][60793:0x700000393000], checkpoint-server: checkpoint server error: Too many open files in system2016-05-11T00:59:33.568+0800 E STORAGE  [thread2] WiredTiger (-31804) [1462899573:568879][60793:0x700000393000], checkpoint-server: the process must exit and restart: WT_PANIC: WiredTiger library panic2016-05-11T00:59:33.568+0800 I -        [thread2] Fatal Assertion 285582016-05-11T00:59:33.568+0800 I -        [thread2]

可以先查看一下允许多少个打开文件

Yaoxings-MacBook-Pro:db yaoxing$ ulimit -acore file size          (blocks, -c) 0data seg size           (kbytes, -d) unlimitedfile size               (blocks, -f) unlimitedmax locked memory       (kbytes, -l) unlimitedmax memory size         (kbytes, -m) unlimitedopen files                      (-n) 256pipe size            (512 bytes, -p) 1stack size              (kbytes, -s) 8192cpu time               (seconds, -t) unlimitedmax user processes              (-u) 709virtual memory          (kbytes, -v) unlimited

实际上一进入mongoshell就会提示你这一点

2016-05-11T17:45:17.536+0800 I CONTROL [initandlisten] ** WARNING: soft rlimits too low. Number of files is 256, should be at least 1000

WiredTiger的工作原理跟MMAPv1不太一样，一个集合一个文件，一个索引一个文件。所以你一共有多少集合，至少就会有集合数量x2个打开文件（以1集合文件+1索引文件计算）被占用。再考虑到网络连接数量，要保证足够大的open files值。open files可以通过以下命令修改：

ulimit -n 1024

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