# SECO Range

SECO range is a cluster-based metadata store developed and maintained by Yahoo!

The Range project is hosted here:

https://github.com/ytoolshed/range

Learn more about range here:

https://github.com/ytoolshed/range/wiki/

## Prerequisites

To utilize range support in Salt, a range server is required. Setting up a range server is outside the scope of this document. Apache modules are included in the range distribution.

With a working range server, cluster files must be defined. These files are written in YAML and define hosts contained inside a cluster. Full documentation on writing YAML range files is here:

https://github.com/ytoolshed/range/wiki/%22yamlfile%22-module-file-spec

Additionally, the Python seco range libraries must be installed on the salt master. One can verify that they have been installed correctly via the following command:

    python -c 'import seco.range'

If no errors are returned, range is installed successfully on the salt master.

## Preparing Salt

Range support must be enabled on the salt master by setting the hostname and port of the range server inside the master configuration file:

    range_server: my.range.server.com:80

Following this, the master must be restarted for the change to have an effect.

## Targeting with Range

Once a cluster has been defined, it can be targeted with a salt command by using the `-R` or `--range` flags.

For example, given the following range YAML file being served from a range server:

    $ cat /etc/range/test.yaml
    CLUSTER: host1..100.test.com
    APPS:
      - frontend
      - backend
      - mysql

One might target host1 through host100 in the test.com domain with Salt as follows:

    salt --range %test:CLUSTER test.version

The following salt command would target three hosts: `frontend`, `backend`, and `mysql`:

    salt --range %test:APPS test.version