Download Riak 2.0

Open Files Limit

Riak can consume a large number of open file handles during normal operation. The Bitcask backend in particular may accumulate a high number of data files before it has a chance to run a merge process. You can count the number of data files in the Bitcask directory with following command:

ls data/bitcask/*/* | wc -l

Please note that the creation of numerous data files is normal. Each time Riak is started, Bitcask creates a new data file per partition; once in a while, Bitcask will merge a collection of data files into a single file to avoid accumulating file handles. It’s possible to artificially inflate the number of file handles Bitcask uses by repeatedly writing data and restarting Riak. The shell command below illustrates this issue:

for i in {1..100}
  do
    riak stop
    riak start
    sleep 3
    curl http://localhost:8098/riak/test -X POST -d "x" \
      -H "Content-Type: text/plain"
    ls data/bitcask/*/* | wc -l
done

Changing the limit

Most operating systems can change the open-files limit using the ulimit -n command. Example:

ulimit -n 65536

However, this only changes the limit for the current shell session. Changing the limit on a system-wide, permanent basis varies more between systems.

Linux

On most Linux distributions, the total limit for open files is controlled by sysctl.

sysctl fs.file-max
fs.file-max = 50384

As seen above, it is generally set high enough for Riak. If you have other things running on the system, you might want to consult the sysctl manpage for how to change that setting. However, what most needs to be changed is the per-user open files limit. This requires editing /etc/security/limits.conf, for which you'll need superuser access. If you installed Riak from a binary package, add lines for the riak user like so, substituting your desired hard and soft limits:

riak soft nofile 4096
riak hard nofile 65536

On Ubuntu, if you’re always relying on the init scripts to start Riak, you can create the file /etc/default/riak and specify a manual limit like so:

ulimit -n 65536

This file is automatically sourced from the init script, and the Riak process started by it will properly inherit this setting. As init scripts are always run as the root user, there’s no need to specifically set limits in /etc/security/limits.conf if you’re solely relying on init scripts.

On CentOS/RedHat systems, make sure to set a proper limit for the user you’re usually logging in with to do any kind of work on the machine, including managing Riak. On CentOS, sudo properly inherits the values from the executing user.

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

Enable PAM-Based Limits for Debian & Ubuntu

It can be helpful to enable PAM user limits so that non-root users, such as the riak user, may specify a higher value for maximum open files. For example, follow these steps to enable PAM user limits and set the soft and hard values for all users of the system to allow for up to 65536 open files.

Edit /etc/pam.d/common-session and append the following line:

session    required   pam_limits.so

If /etc/pam.d/common-session-noninteractive exists, append the same line as above.

Save and close the file.

Edit /etc/security/limits.conf and append the following lines to the file:

*               soft     nofile          65536
*               hard     nofile          65536
  1. Save and close the file.

  2. (optional) If you will be accessing the Riak nodes via secure shell (ssh), you should also edit /etc/ssh/sshd_config and uncomment the following line:

    #UseLogin no
    

    and set its value to yes as shown here:

    UseLogin yes
    
  3. Restart the machine so that the limits to take effect and verify that the new limits are set with the following command:

    ulimit -a
    

Enable PAM-Based Limits for CentOS and Red Hat

  1. Edit /etc/security/limits.conf and append the following lines to the file:

    • soft nofile 65536
    • hard nofile 65536 “
  2. Save and close the file.

  3. Restart the machine so that the limits to take effect and verify that the new limits are set with the following command:

    ulimit -a
    
Note
In the above examples, the open files limit is raised for all users of the system. If you prefer, the limit can be specified for the riak user only by substituting the two asterisks (*) in the examples with riak.

Solaris

In Solaris 8, there is a default limit of 1024 file descriptors per process. In Solaris 9, the default limit was raised to 65536. To increase the per-process limit on Solaris, add the following line to /etc/system:

set rlim_fd_max=65536

Reference: http://blogs.oracle.com/elving/entry/too_many_open_files

Mac OS X

To check the current limits on your Mac OS X system, run:

launchctl limit maxfiles

The last two columns are the soft and hard limits, respectively.

Adjusting Open File Limits in Yosemite

To adjust open files limits on a system-wide basis in Mac OS X Yosemite, you must create two configuration files. The first is a property list (aka plist) file in /Library/LaunchDaemons/limit.maxfiles.plist that contains the following XML configuration:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
  <plist version="1.0">
    <dict>
      <key>Label</key>
        <string>limit.maxfiles</string>
      <key>ProgramArguments</key>
        <array>
          <string>launchctl</string>
          <string>limit</string>
          <string>maxfiles</string>
          <string>65536</string>
          <string>65536</string>
        </array>
      <key>RunAtLoad</key>
        <true/>
      <key>ServiceIPC</key>
        <false/>
    </dict>
  </plist>

This will set the open files limit to 65536. The second plist configuration file should be stored in /Library/LaunchDaemons/limit.maxproc.plist with the following contents:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple/DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
  <plist version="1.0">
    <dict>
      <key>Label</key>
        <string>limit.maxproc</string>
      <key>ProgramArguments</key>
        <array>
          <string>launchctl</string>
          <string>limit</string>
          <string>maxproc</string>
          <string>2048</string>
          <string>2048</string>
        </array>
      <key>RunAtLoad</key>
        <true />
      <key>ServiceIPC</key>
        <false />
    </dict>
  </plist>

Both plist files must be owned by root:wheel and have permissions -rw-r--r--. This permissions should be in place by default, but you can ensure that they are in place by running sudo chmod 644 <filename>. While the steps explained above will cause system-wide open file limits to be correctly set upon restart, you can apply them manually by running launchctl limit.

In addition to setting these limits at the system level, we recommend setting the at the session level as well by appending the following lines to your bashrc, bashprofile, or analogous file:

ulimit -n 65536
ulimit -u 2048

Like the plist files, your bashrc or similar file should have -rw-r--r-- permissions. At this point, you can restart your computer and enter ulimit -n into your terminal. If your system is configured correctly, you should see that maxfiles has been set to 65536.

Adjusting Open File Limits in Older Versions of OS X

To adjust the maximum open file limits in OS X 10.7 (Lion) up to but not including OS X Yosemite, edit /etc/launchd.conf and increase the limits for both values as appropriate.

For example, to set the soft limit to 16384 files, and the hard limit to 32768 files, perform the following steps:

  1. Verify current limits:

    launchctl limit
    

    The response output should look something like this:

    cpu         unlimited      unlimited
    filesize    unlimited      unlimited
    data        unlimited      unlimited
    stack       8388608        67104768
    core        0              unlimited
    rss         unlimited      unlimited
    memlock     unlimited      unlimited
    maxproc     709            1064
    maxfiles    10240          10240
    
  2. Edit (or create) /etc/launchd.conf and increase the limits. Add lines that look like the following (using values appropriate to your environment):

    limit maxfiles 16384 32768
    
  3. Save the file, and restart the system for the new limits to take effect. After restarting, verify the new limits with the launchctl limit command:

    launchctl limit
    

    The response output should look something like this:

    cpu         unlimited      unlimited
    filesize    unlimited      unlimited
    data        unlimited      unlimited
    stack       8388608        67104768
    core        0              unlimited
    rss         unlimited      unlimited
    memlock     unlimited      unlimited
    maxproc     709            1064
    maxfiles    16384          32768