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No valid host was found

I am using OpenStack Mitaka and trying to create a stack through heat consisting only one VM. In my setup, I have 2 compute nodes with 4 physical cores each.

The flavor of the Vm is as follows -

Memory Size: 1024 MB
Disk Size: 10 GB
Number Of CPU: 8

The stack creation fails with error -

No valid host was found. There are not enough hosts available

The nova logs indicates a CoreFilter failure. The logs looks like this -

<182>Jul 31 06:07:27 node-63 nova-scheduler: 2017-07-31 06:07:27.139 12099 INFO nova.filters [req-ef103670-3aa6-4373-8918-a57dbc6703f4 43ae940aea77409eb40014fa24f663b2 22ece5e4daef4489934e3ce3ee282b41 - - -] Filter CoreFilter returned 0 hosts
<182>Jul 31 06:07:27 node-63 nova-scheduler: 2017-07-31 06:07:27.139 12099 INFO nova.filters [req-ef103670-3aa6-4373-8918-a57dbc6703f4 43ae940aea77409eb40014fa24f663b2 22ece5e4daef4489934e3ce3ee282b41 - - -] Filtering removed all hosts for the request with instance ID 'fd547faa-9390-42fc-8bbe-1d461c8c8ab2'. Filter results: ['RetryFilter: (start: 2, end: 2)', 'AvailabilityZoneFilter: (start: 2, end: 2)', 'RamFilter: (start: 2, end: 2)', 'CoreFilter: (start: 2, end: 0)']
<180>Jul 31 06:07:27 node-63 nova-conductor: 2017-07-31 06:07:27.144 13289 WARNING nova.scheduler.utils [req-ef103670-3aa6-4373-8918-a57dbc6703f4 43ae940aea77409eb40014fa24f663b2 22ece5e4daef4489934e3ce3ee282b41 - - -] Failed to compute_task_build_instances: No valid host was found. There are not enough hosts available.
Traceback (most recent call last):

  File "/usr/lib/python2.7/dist-packages/oslo_messaging/rpc/server.py", line 150, in inner
    return func(*args, **kwargs)

  File "/usr/lib/python2.7/dist-packages/nova/scheduler/manager.py", line 104, in select_destinations
    dests = self.driver.select_destinations(ctxt, spec_obj)

  File "/usr/lib/python2.7/dist-packages/nova/scheduler/filter_scheduler.py", line 74, in select_destinations
    raise exception.NoValidHost(reason=reason)

NoValidHost: No valid host was found. There are not enough hosts available.
<180>Jul 31 06:07:27 node-63 nova-conductor: 2017-07-31 06:07:27.144 13289 WARNING nova.scheduler.utils [req-ef103670-3aa6-4373-8918-a57dbc6703f4 43ae940aea77409eb40014fa24f663b2 22ece5e4daef4489934e3ce3ee282b41 - - -] [instance: fd547faa-9390-42fc-8bbe-1d461c8c8ab2] Setting instance to ERROR state.

But the cpu_allocation_ratio is set in nova.conf to 8.0. The nova.conf file have following lines -

scheduler_default_filters=RetryFilter,AvailabilityZoneFilter,RamFilter,CoreFilter,DiskFilter,ComputeFilter,ComputeCapabilitiesFilter,ImagePropertiesFilter,ServerGroupAntiAffinityFilter,ServerGroupAffinityFilter
cpu_allocation_ratio=8.0

But interesting thing is if I create say 16 VMs with core 2, it doesn't fail, even if the total physical core is 8. It only fails to create VM with 8 core, even if there are no VMs present in cloud.

No valid host was found

I am using OpenStack Mitaka and trying to create a stack through heat consisting only one VM. In my setup, I have 2 compute nodes with 4 physical cores each.

The flavor of the Vm is as follows -

Memory Size: 1024 MB
Disk Size: 10 GB
Number Of CPU: 8

The stack creation fails with error -

No valid host was found. There are not enough hosts available

The nova logs indicates a CoreFilter CoreFilter failure. The logs looks like this -

<182>Jul 31 06:07:27 node-63 nova-scheduler: 2017-07-31 06:07:27.139 12099 INFO nova.filters [req-ef103670-3aa6-4373-8918-a57dbc6703f4 43ae940aea77409eb40014fa24f663b2 22ece5e4daef4489934e3ce3ee282b41 - - -] Filter CoreFilter returned 0 hosts
<182>Jul 31 06:07:27 node-63 nova-scheduler: 2017-07-31 06:07:27.139 12099 INFO nova.filters [req-ef103670-3aa6-4373-8918-a57dbc6703f4 43ae940aea77409eb40014fa24f663b2 22ece5e4daef4489934e3ce3ee282b41 - - -] Filtering removed all hosts for the request with instance ID 'fd547faa-9390-42fc-8bbe-1d461c8c8ab2'. Filter results: ['RetryFilter: (start: 2, end: 2)', 'AvailabilityZoneFilter: (start: 2, end: 2)', 'RamFilter: (start: 2, end: 2)', 'CoreFilter: (start: 2, end: 0)']
<180>Jul 31 06:07:27 node-63 nova-conductor: 2017-07-31 06:07:27.144 13289 WARNING nova.scheduler.utils [req-ef103670-3aa6-4373-8918-a57dbc6703f4 43ae940aea77409eb40014fa24f663b2 22ece5e4daef4489934e3ce3ee282b41 - - -] Failed to compute_task_build_instances: No valid host was found. There are not enough hosts available.
Traceback (most recent call last):

  File "/usr/lib/python2.7/dist-packages/oslo_messaging/rpc/server.py", line 150, in inner
    return func(*args, **kwargs)

  File "/usr/lib/python2.7/dist-packages/nova/scheduler/manager.py", line 104, in select_destinations
    dests = self.driver.select_destinations(ctxt, spec_obj)

  File "/usr/lib/python2.7/dist-packages/nova/scheduler/filter_scheduler.py", line 74, in select_destinations
    raise exception.NoValidHost(reason=reason)

NoValidHost: No valid host was found. There are not enough hosts available.
<180>Jul 31 06:07:27 node-63 nova-conductor: 2017-07-31 06:07:27.144 13289 WARNING nova.scheduler.utils [req-ef103670-3aa6-4373-8918-a57dbc6703f4 43ae940aea77409eb40014fa24f663b2 22ece5e4daef4489934e3ce3ee282b41 - - -] [instance: fd547faa-9390-42fc-8bbe-1d461c8c8ab2] Setting instance to ERROR state.

But the cpu_allocation_ratio is set in nova.conf to 8.0. The nova.conf file have following lines -

scheduler_default_filters=RetryFilter,AvailabilityZoneFilter,RamFilter,CoreFilter,DiskFilter,ComputeFilter,ComputeCapabilitiesFilter,ImagePropertiesFilter,ServerGroupAntiAffinityFilter,ServerGroupAffinityFilter
cpu_allocation_ratio=8.0

But interesting thing is if I create say 16 VMs with core 2, it doesn't fail, even if the total physical core is 8. It only fails to create VM with 8 core, even if there are no VMs present in cloud.