Important System configuration

Ideally, Snow Owl should run alone on a server and use all of the resources available to it. In order to do so, you need to configure your operating system to allow the user running Snow Owl to access more resources than allowed by default.

The following settings must be considered before going to production:

• Disable swapping

• Increase file descriptors

• Ensure sufficient virtual memory

• Ensure sufficient threads

• Tweaking for performance

Configuring system settings

Where to configure systems settings depends on which package you have used to install Snow Owl, and which operating system you are using.

When using the .zip or .tar.gz packages, system settings can be configured:

• temporarily with ulimit, or

• permanently in /etc/security/limits.conf.

When using the RPM or Debian packages, most system settings are set in the system configuration file. However, systems which use systemd require that system limits are specified in a systemd configuration file.

ulimit

On Linux systems, ulimit can be used to change resource limits on a temporary basis. Limits usually need to be set as root before switching to the user that will run Snow Owl. For example, to set the number of open file handles (ulimit -n) to 65,536, you can do the following:

sudo su # Become `root`
ulimit -n 65536 # Change the max number of open files
su snowowl # Become the `snowowl` user in order to start Snow Owl

The new limit is only applied during the current session.

You can consult all currently applied limits with ulimit -a.

/etc/security/limits.conf

On Linux systems, persistent limits can be set for a particular user by editing the /etc/security/limits.conf file. To set the maximum number of open files for the snowowl user to 65,536, add the following line to the limits.conf file:

snowowl  -  nofile  65536

This change will only take effect the next time the snowowl user opens a new session.

Ubuntu and limits.conf

Ubuntu ignores the limits.conf file for processes started by init.d. To enable the limits.conf file, edit /etc/pam.d/su and uncomment the following line:

# session    required   pam_limits.so

Sysconfig file

When using the RPM or Debian packages, system settings and environment variables can be specified in the system configuration file, which is located in:

Package	Location
RPM	/etc/sysconfig/snowowl
Debian	/etc/default/snowowl

However, for systems which uses systemd, system limits need to be specified via systemd.

Systemd configuration

When using the RPM or Debian packages on systems that use systemd, system limits must be specified via systemd.

The systemd service file (/usr/lib/systemd/system/snowowl.service) contains the limits that are applied by default.

To override them, add a file called /etc/systemd/system/snowowl.service.d/override.conf (alternatively, you may run sudo systemctl edit snowowl which opens the file automatically inside your default editor). Set any changes in this file, such as:

[Service]
LimitMEMLOCK=infinity

Once finished, run the following command to reload units:

sudo systemctl daemon-reload