Http request being sent twice for each client.post call

Hi

I am using http to call a web app(hosted on heroku) and I have noticed in the logs that I am seeing two requests per call that I issues from the core:

2014-09-07T09:00:07.624183+00:00 app[web.1]: Started GET “/record/create?device_id=53ff7206507553516xxxxxxx” for 81.nnn.nnn.250 at 2014-09-07 09:00:07 +0000
2014-09-07T09:00:07.624193+00:00 app[web.1]: Started GET “/record/create?device_id=53ff7206507553516xxxxxxx” for 81.nnn.nnn.250 at 2014-09-07 09:00:07 +0000

The app processes each request, so I am getting duplicate db records. The core also freezes intermittently (usually after only a few calls).

I have used curl to duplicate the request and, as expected, I see only one call in the logs (and i db record created)

I have tried two http libraries (HttpClient and rest_client) and I see the same pattern. At a loss to think what is causing this - any ideas?

Thank you

Kevin

Update - I have tried a different service and it works fine.