Please reconfigure rate-limits to at least 500-1000 hits per minute.
API calls rate limits could be configured using this manual.
Or by disabling ratelimits in the /etc/nova/api-paste.ini file.
...
[composite:openstack_compute_api_v2]
use = call:nova.api.auth:pipeline_factory
#noauth = faultwrap sizelimit noauth ratelimit osapi_compute_app_v2
#keystone = faultwrap sizelimit authtoken keystonecontext ratelimit osapi_compute
noauth = faultwrap sizelimit noauth osapi_compute_app_v2
keystone = faultwrap sizelimit authtoken keystonecontext osapi_compute_app_v2
keystone_nolimit = faultwrap sizelimit authtoken keystonecontext osapi_compute_ap
...
