This sls will look and include a file named by the minion's grain 'host' value from a directory specified. If the file doesn't exists, it will try to create it while leaving it empty.

hosts.sls

#!py
import logging
import yaml
import sys
import os

PILLAR_HOST_DIR = "/srv/salt/hosts"

log = logging.getLogger(__name__)


def run():
    log.debug("Checking if there is a file for host {0}"
              .format(__grains__['host']))
    pillar_host_file = os.path.join(PILLAR_HOST_DIR,
                                    __grains__['host']) + '.sls'

    log.debug("Pillar host filename: {0}".format(pillar_host_file))
    try:
        if os.path.isfile(pillar_host_file):
            log.debug("File exists, trying to read {0}"
                      .format(pillar_host_file))
            stream = file(pillar_host_file)
            data = yaml.load(stream)

            return data
        else:
            log.debug("Pillar host file doesn't exists, creating it")
            open(pillar_host_file, 'a').close()

            return {}
    except IOError as e:
        log.error("Cannot open pillar host file {0}: {1}".format(
                  pillar_host_file, e))
        sys.exit(1)


# vim: syntax=python