Candlepin has recently introduced rate-limitation for host-guest associations. It returns HTTP error code 429 when the guests (including virt-who) are sending request too often. The clients should increase checking-in interval when they get this error code.

Unfortunately current version of virt-who in RHEL-7 can't handle this kind of reply and it fails with following error:

> 2015-11-18 15:11:29,132 [INFO]  @subscriptionmanager.py:124 - Sending update
> in hosts-to-guests mapping: {inferno.mitre.org:
> [42203c35-09bc-cf00-6d2a-c60b55231418, 42205d69-c1f5-cda7-d93d-131dbabf7a67,
> 42202abf-3785-791d-b000-12cabc19f92b, 42205f24-2... blah blah
> 2015-11-18 15:11:30,038 [ERROR]  @virtwho.py:123 - Error in communication
> with subscription manager:
> Traceback (most recent call last):
>   File "/usr/share/virt-who/virtwho.py", line 105, in send
>     self._sendGuestAssociation(report)
>   File "/usr/share/virt-who/virtwho.py", line 134, in _sendGuestAssociation
>     result = manager.hypervisorCheckIn(report.config, report.association,
>     report.config.type)
>   File
>   "/usr/share/virt-who/manager/subscriptionmanager/subscriptionmanager.py",
>   line 134, in hypervisorCheckIn
>     return self.connection.hypervisorCheckIn(config.owner, config.env,
>     mapping)
>   File "/usr/lib64/python2.6/site-packages/rhsm/connection.py", line 815, in
>   hypervisorCheckIn
>     return self.conn.request_post(url, host_guest_mapping)
>   File "/usr/lib64/python2.6/site-packages/rhsm/connection.py", line 605, in
>   request_post
>     return self._request("POST", method, params)
>   File "/usr/lib64/python2.6/site-packages/rhsm/connection.py", line 530, in
>   _request
>     self.validateResponse(result, request_type, handler)
>   File "/usr/lib64/python2.6/site-packages/rhsm/connection.py", line 589, in
>   validateResponse
>     raise NetworkException(response['status'])
> NetworkException: Network error code: 429

Support for this error code has been added in virt-who upstream and needs to be backported to RHEL-7. This affects lots of customers.