Issue with suggestion?

When I enter a metric in the "Add Widget" window, I get no suggestions.
If I hit [Enter], I get: `Suggested Tags: No tags found`

In the logs, I see:

```
[2014-08-11 19:37:26] myapp.INFO: Populated SecurityContext with an anonymous Token [] []
[2014-08-11 19:37:26] myapp.INFO: > GET /api/datasource/opentsdb/suggest_metrics?query=proc [] []
[2014-08-11 19:37:26] myapp.INFO: < 200 [] []
```

On the commandline, I get:

```
$ curl http://localhost:9653/api/datasource/opentsdb/suggest_metrics?query=proc
{"query":"proc","suggestions":null}
```

If I query OpenTSDB directly, I get:

```
$ curl -i "http://localhost:4242/api/suggest?type=metrics&q=proc"
HTTP/1.1 200 OK
Content-Type: application/json; charset=UTF-8
Content-Length: 618

["proc.interrupts","proc.kernel.entropy_avail","proc.loadavg.15min","proc.loadavg.1min","proc.loadavg.5min","proc.loadavg.runnable","proc.loadavg.total_threads","proc.meminfo.active","proc.meminfo.anonhugepages","proc.meminfo.anonpages","proc.meminfo.bounce","proc.meminfo.buffers","proc.meminfo.cached","proc.meminfo.commitlimit","proc.meminfo.committed_as","proc.meminfo.directmap1g","proc.meminfo.directmap2m","proc.meminfo.directmap4k","proc.meminfo.dirty","proc.meminfo.hardwarecorrupted","proc.meminfo.hugepagesize","proc.meminfo.inactive","proc.meminfo.kernelstack","proc.meminfo.mapped","proc.meminfo.memfree"]
```

It might be a configuration issue, as I don't get any metric data either. Unlike the logs would suggest:

```
[2014-08-11 19:40:09] myapp.INFO: Populated SecurityContext with an anonymous Token [] []
[2014-08-11 19:40:09] myapp.INFO: > POST /api/datasource/opentsdb/search [] []
[2014-08-11 19:40:09] myapp.INFO: Retrieved metrics from OpenTSDB, total execution time: 0 seconds [] []
[2014-08-11 19:40:09] myapp.INFO: < 200 [] []
```

This is my sw_datasources.conf:
(the :4243 is nginx wrapping to add a header for Grafana, which does suggest timeseries)

```
$ cat conf/sw_datasource.json
{
"datasource": {
"OpenTSDB": {
"enabled": true,
"type": "ajax",
"url": [
"7334r.w05.comscore.mgmt:4243/"
],
"trim": "301",
"proxy": false
}
}
}
```

What is the best place to start looking?