Can't get exports to work ???

[Timothy Potter]

I have defined a simple export in metainfo.xml:

<exportGroups>
  <exportGroup>
    <name>Servers</name>
    <exports>
      <export>
        <name>host_port</name>
        <value>http://${THIS_HOST}:${site.global.listen_port}/</value>
      </export>
    </exports>
  </exportGroup>
</exportGroups>

<components>
  <component>
    <name>SOLR</name>
    <category>SLAVE</category>
    <compExports>Servers-host_port</compExports>
    <commandScript>
      <script>scripts/solr_node.py</script>
      <scriptType>PYTHON</scriptType>
    </commandScript>
  </component>
</components>

The app deploys fine and my SOLR component is running ... but when I
go to the exports endpoint, I don't see my host_port???

{"exports":{"servers":{"description":"Servers","updated":1432052275319,"updatedTime":"Tue
May 19 10:17:55 MDT
2015","entries":{},"empty":true},"container_log_dirs":{"description":"container_log_dirs","updated":1432052275319,"updatedTime":"Tue
May 19 10:17:55 MDT
2015","entries":{},"empty":true},"container_work_dirs":{"description":"container_work_dirs","updated":1432052275319,"updatedTime":"Tue
May 19 10:17:55 MDT 2015","entries":{},"empty":true}}}

Any ideas what I'm doing wrong here?