Bug in log output in hardware.py "Not enough available memory to schedule instance" prints full memory instead of available memory

[Andreas Karis]

Description of problem:
Bug in log output in hardware.py "Not enough available memory to schedule instance" prints full memory instead of available memory

Version-Release number of selected component (if applicable):

Additional info:

When nova fails scheduling, it will print:
~~~
2017-11-29 10:50:16.904 325123 DEBUG nova.virt.hardware [req-b62c53d2-13db-4fac-a125-409b4f046418 8f883df20fce46dbef3ce634610c51be53b87e658359f05b7eba1062ce7e5d8b 5b54e36678a542d899f1ff62268fc25a - - -] Not enough available memory to schedule instance. Oversubscription is not possible with pinned instances. Required: 32768, actual: 65406 _numa_fit_instance_cell_with_pinning /usr/lib/python2.7/site-packages/nova/virt/hardware.py:845
2017-11-29 10:50:16.904 325123 DEBUG oslo_concurrency.lockutils [req-b62c53d2-13db-4fac-a125-409b4f046418 8f883df20fce46dbef3ce634610c51be53b87e658359f05b7eba1062ce7e5d8b 5b54e36678a542d899f1ff62268fc25a - - -] Lock "compute_resources" released by "nova.compute.resource_tracker.instance_claim" :: held 0.021s inner /usr/lib/python2.7/site-packages/oslo_concurrency/lockutils.py:282
2017-11-29 10:50:16.905 325123 DEBUG nova.compute.manager [req-b62c53d2-13db-4fac-a125-409b4f046418 8f883df20fce46dbef3ce634610c51be53b87e658359f05b7eba1062ce7e5d8b 5b54e36678a542d899f1ff62268fc25a - - -] [instance: 86cc16bd-5f51-402b-aa03-01ab0c3ffaf4] Insufficient compute resources: Requested instance NUMA topology cannot fit the given host NUMA topology. _build_and_run_instance /usr/lib/python2.7/site-packages/nova/compute/manager.py:1934
~~~

This of course looks very confusing (we need 32 GB, we have 64, so why is this failing?).

The problem here is the log output, which is flawed --- /usr/lib/python2.7/site-packages/nova/virt/hardware.py:
~~~
    840 if host_cell.avail_memory < instance_cell.memory:
    841 LOG.debug('Not enough available memory to schedule instance. '
    842 'Oversubscription is not possible with pinned instances. '
    843 'Required: %(required)s, actual: %(actual)s',
    844 {'required': instance_cell.memory,
    845 'actual': host_cell.memory})
    846 return
~~~

This should be:
~~~
    840 if host_cell.avail_memory < instance_cell.memory:
    841 LOG.debug('Not enough available memory to schedule instance. '
    842 'Oversubscription is not possible with pinned instances. '
    843 'Required: %(required)s, actual: %(actual)s',
    844 {'required': instance_cell.memory,
    845 'actual': host_cell.avail_memory})
    846 return
~~~

Or even better:
~~~
    840 if host_cell.avail_memory < instance_cell.memory:
    841 LOG.debug('Not enough available memory to schedule instance. '
    842 'Oversubscription is not possible with pinned instances. '
    843 'Required: %(required)s, actual: %(actual)s, total: %(total)s',
    844 {'required': instance_cell.memory,
    845 'actual': host_cell.avail_memory,
    846 'total': host_cell.memory})
    847 return
~~~

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/524038

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/524038
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=4fd51617fb408fa389baa1aed10db3a06cc1539b
Submitter: Zuul
Branch: master

commit 4fd51617fb408fa389baa1aed10db3a06cc1539b
Author: Andreas Karis <email address hidden>
Date: Wed Nov 29 20:55:17 2017 -0500

    Fixes 'Not enough available memory' log message

    Fixes a bug in log output about where 'Not enough available
    memory to schedule instance' printed full memory instead of
    available memory

    Change-Id: Id65e9f5eec9ba1f39bcba24539b11f2e27226941
    Closes-Bug: #1735321

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/pike
Review: https://review.openstack.org/536297

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/nova 17.0.0.0b3 development milestone.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/536297
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=863515187575b9630c02f7318b94bd2ef9a6f4a9
Submitter: Zuul
Branch: stable/pike

commit 863515187575b9630c02f7318b94bd2ef9a6f4a9
Author: Andreas Karis <email address hidden>
Date: Wed Nov 29 20:55:17 2017 -0500

    Fixes 'Not enough available memory' log message

    Fixes a bug in log output about where 'Not enough available
    memory to schedule instance' printed full memory instead of
    available memory

    Change-Id: Id65e9f5eec9ba1f39bcba24539b11f2e27226941
    Closes-Bug: #1735321
    (cherry picked from commit 4fd51617fb408fa389baa1aed10db3a06cc1539b)

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/nova 16.1.0 release.