Scheduler: Adds per-aggregate filters

Scheduler: Adds per-aggregate filters

https://blueprints.launchpad.net/nova/+spec/per-aggregate-disk-allocation-ratio https://blueprints.launchpad.net/nova/+spec/per-aggregate-max-instances-per-host https://blueprints.launchpad.net/nova/+spec/per-aggregate-max-io-ops-per-host

The aim of this bp is to add the ability to the filters DiskFilter, NumInstancesFilter and IoOpsFilter to set our options by aggregates.

Problem description

Operator wants to define different filtering options (disk_allocation_ratio, max_instances_per_host, max_io_ops_per_host) for a subset of compute hosts.

Proposed change

Create new filters that extend DiskFilter, NumInstancesFilter and IoOpsAggregateFilter to provide the ability to read the metadata from aggregates. If no valid values found fall back to the global default configurations set in nova.conf.

Alternatives

None

Data model impact

None

REST API impact

None

Security impact

None

Notifications impact

None

Other end user impact

None

Performance Impact

Not related with this bp but a performance impact has been reported to the bug 1300775 about using aggregate with the scheduler on large cluster.

Other deployer impact

The operator needs to update the scheduler’s nova.conf to activate filters, also he has to set metadata of the aggregates with the configurations options disk_allocation_ratio, max_instances_per_host, max_io_ops_per_host.

$ # This one provides for hosts in the aggregate 'agr1' the possibility to
$ # host 60 instances.
$ nova aggregate-set-metadata agr1 set metadata max_instances_per_host=60

$ # This one provides for hosts in the aggregate 'agr2' the possibility to
$ # oversubscribe disk allocation and configures the scheduler to ignore
$ # hosts that have currently more than 3 heavy operations.
$ nova aggregate-set-metadata agr2 set\
$   metadata max_io_ops_per_host=3
$   disk_allocation_ratio=3

The operator also needs to reload the scheduler service to activate this new filter.

Developer impact

None

Implementation

Assignee(s)

Primary assignee:

sahid-ferdjaoui

Other contributors:

<None>

Work Items

  • New filter AggregateNumInstancesFilter

  • New filter AggregateDiskFilter

  • New filter AggregateIoOpsFilter

Dependencies

Testing

We need to add unit tests in test_host_filters.py also we probably need to think about adding functional tests in tempest.

Documentation Impact

We need to refer these new filters in the documentation, also ‘doc/source/devref/filter_scheduler.rst’ needs to be updated.

References

These blueprints was accepted for icehouse but because of a work started to add helper that provides utility methods to get metadata from aggregates and so remove duplicate code between filters (bug 1301340). The blueprints was deferred.

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nova-specs