'Updates an Event Hub.
hub_name:
Name of event hub.
hub:
Optional. Event hub properties. Instance of EventHub class.
hub.message_retention_in_days:
Number of days to retain the events for this Event Hub.'

def update_event_hub(self, hub_name, hub=None):

    _validate_not_none('hub_name', hub_name)
    request = HTTPRequest()
    request.method = 'PUT'
    request.host = self._get_host()
    request.path = (('/' + _str(hub_name)) + '?api-version=2014-01')
    request.body = _get_request_body(_convert_event_hub_to_xml(hub))
    (request.path, request.query) = self._httpclient._update_request_uri_query(request)
    request.headers.append(('If-Match', '*'))
    request.headers = self._update_service_bus_header(request)
    response = self._perform_request(request)
    return _convert_response_to_event_hub(response)
