java.io.IOException: Too many open files

Tomado de: http://www.cyberciti.biz/faq/linux-increase-the-maximum-number-of-open-files/

How do I increase the maximum number of open files under CentOS Linux? How do I open more file descriptors under Linux?

The ulimit command provides control over the resources available to the shell and/or to processes started by it, on systems that allow such control. The maximum number of open file descriptors displayed with following command (login as the root user).

Command To List Number Of Open File Descriptors

Use the following command command to display maximum number of open file descriptors:
cat /proc/sys/fs/file-max
Output:

75000

75000 files normal user can have open in single login session. To see the hard and soft values, issue the command as follows:

# ulimit -Hn
# ulimit -Sn

To see the hard and soft values for httpd or oracle user, issue the command as follows:

# su - username

In this example, su to oracle user, enter:

# su - oracle
$ ulimit -Hn
$ ulimit -Sn




Cambiar valor:

You can change ulimit settings by issuing a command in the following form:


Solo para la sesión:
ulimit -Hn 10240
ulimit -Sn 10240


Permanente mente:
vi /etc/security/limits.conf
add:
root    soft    nofile  4096
root    hard    nofile  10240

*    soft    nofile  4096
*    hard    nofile  10240

Recommended Settings

Every deployment may have unique requirements and settings; however, the following thresholds and settings are particularly important for mongod and mongos deployments:

• -f (file size): unlimited
• -t (cpu time): unlimited
• -v (virtual memory): unlimited [1]
• -n (open files): 64000
• -m (memory size): unlimited [1]
• -u (processes/threads): 32000

Always remember to restart your mongod and mongos instances after changing the ulimit settings to make sure that the settings change takes effect.

You can change ulimit settings by issuing a command in the following form:

ulimit -n <value>

For many distributions of Linux you can change values by substituting the -n option for any possible value in the output ofulimit -a. See your operating system documentation for the precise procedure for changing system limits on running systems.

Note

After changing the ulimit settings, you must restart the process to take advantage of the modified settings. You can use the /proc file system to see the current limitations on a running process.

Depending on your system’s configuration, and default settings, any change to system limits made using ulimitmay revert following system a system restart. Check your distribution and operating system documentation for more information.

/proc File System

Note

This section applies only to Linux operating systems.

The /proc file-system stores the per-process limits in the file system object located at /proc/<pid>/limits, where<pid> is the process’s PID or process identifier. You can use the following bash function to return the content of the limitsobject for a process or processes with a given name:

return-limits(){

     for process in $@; do
          process_pids=`ps -C $process -o pid --no-headers | cut -d " " -f 2`

          if [ -z $@ ]; then
             echo "[no $process running]"
          else
             for pid in $process_pids; do
                   echo "[$process #$pid -- limits]"
                   cat /proc/$pid/limits
             done
          fi

     done

}

You can copy and paste this function into a current shell session or load it as part of a script. Call the function with one the following invocations:

return-limits mongod
return-limits mongos
return-limits mongod mongos

The output of the first command may resemble the following:

[mongod #6809 -- 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            8720000              unlimited            bytes
Max core file size        0                    unlimited            bytes
Max resident set          unlimited            unlimited            bytes
Max processes             192276               192276               processes
Max open files            1024                 4096                 files
Max locked memory         40960000             40960000             bytes
Max address space         unlimited            unlimited            bytes
Max file locks            unlimited            unlimited            locks
Max pending signals       192276               192276               signals
Max msgqueue size         819200               819200               bytes
Max nice priority         30                   30
Max realtime priority     65                   65
Max realtime timeout      unlimited            unlimited            us

Recommended Settings

Every deployment may have unique requirements and settings; however, the following thresholds and settings are particularly important for mongod and mongos deployments:

• -f (file size): unlimited
• -t (cpu time): unlimited
• -v (virtual memory): unlimited [1]
• -n (open files): 64000
• -m (memory size): unlimited [1]
• -u (processes/threads): 32000

Always remember to restart your mongod and mongos instances after changing the ulimit settings to make sure that the settings change takes effect.

[1]	(1, 2) If you limit virtual or resident memory size on a system running MongoDB the operating system will refuse to honor additional allocation requests.