Brooklyn entity to generate '/etc/hosts' files

etc-hosts-polcy-example.yaml

brooklyn.catalog:
  version: "0.1.1-SNAPSHOT"
  description: |
    Entity that generates an '/etc/hosts' file containing the addresses
    of a group of entities that have the 'generate.hostsFile' config key set.
  publish:
    license_code: APACHE-2.0
    license_url: http://www.apache.org/licenses/LICENSE-2.0.txt

  items:
    - id: etc-hosts-generator
      name: "etc-hosts-generator"
      itemType: template
      item:
        type: org.apache.brooklyn.entity.group.DynamicGroup
        id: hosts-group
        name: "hosts-group"
        brooklyn.parameters:
          - name: domain.name
            label: "Domain Name"
            description: |
              The domain name suffix to use for generated hostnames
            default: "brooklyn.local"
        brooklyn.config:
          dynamicgroup.entityfilter:
            $brooklyn:object:
              type: org.apache.brooklyn.core.entity.EntityPredicates
              factoryMethod.name: "configEqualTo"
              factoryMethod.args:
                - "generate.hostsFile"
                - true
        brooklyn.enrichers:
          - type: org.apache.brooklyn.enricher.stock.MapAggregator
            brooklyn.config:
              uniqueTag: host-address-aggregator
              enricher.keySensor: $brooklyn:sensor("entity.id")
              enricher.valueSensor: $brooklyn:sensor("host.address")
              enricher.targetSensor: $brooklyn:sensor("host.map")
              enricher.aggregating.fromMembers: true
          - type: org.apache.brooklyn.enricher.stock.Joiner
            brooklyn.config:
              uniqueTag: host-address-joiner
              enricher.sourceSensor: $brooklyn:sensor("host.map")
              enricher.targetSensor: $brooklyn:sensor("host.addresses")
              enricher.joiner.quote: false
              enricher.joiner.separator: " "
              enricher.joiner.keyValueSeparator: "="
              enricher.joiner.joinMapEntries: true
        brooklyn.policies:
          - type: org.apache.brooklyn.entity.group.SshCommandMembershipTrackingPolicy
            brooklyn.config:
              sensorsToTrack:
                - $brooklyn:sensor("host.address")
              shell.env:
                HOST_ADDRESSES:
                  $brooklyn:entity("hosts-group").attributeWhenReady("host.addresses")
                DOMAIN_NAME:
                  $brooklyn:entity("hosts-group").config("domain.name")
              execution.target: ALL_MEMBERS
              update.command: |
                sudo sed -i.bk '/# BEGIN_BROOKLYN_HOSTS/,/# END_BROOKLYN_HOSTS/d' /etc/hosts
                ( echo "# BEGIN_BROOKLYN_HOSTS"
                  for host in ${HOST_ADDRESSES} ; do
                    name=$(echo ${host} | cut -d= -f1)
                    address=$(echo ${host} | cut -d= -f2)
                    echo "${address} ${name} ${name}.${DOMAIN_NAME}"
                  done
                  echo "# END_BROOKLYN_HOSTS" ) | sudo tee -a /etc/hosts