Scheduling a Cluster using Metrics¶

Goal: Schedule the cluster based on cloud metrics.

Introduction¶

Note

Refer to the Introduction and Metrics and Metrics Providers for useful information about metrics.

The Krake scheduler can use metrics to compute the score of a Krake Cloud resource. Each Cloud is associated with a list of metrics and their respective weights for this Cloud. This list is defined by the user who added the Cloud resource into Krake. A higher weight means that the metric has a higher influence in the score: a metric with a low value, but a high weight may has more impact on the score than a metric with a medium value but low weight. The Cloud metrics and the computed score are then used in the Cluster scheduling process.

Note

Note that file paths mentioned in this tutorial are relative to the root of the Krake repository.

Preparation¶

Add the static_provider metrics provider using the bootstrap script (from the root of the Krake repository):

cd <path_to_krake_root>
krake_bootstrap_db support/static_metrics.yaml

Check that the GlobalMetricsProvider and GlobalMetrics objects have been successfully added:

rok core globalmetricsprovider list
+-----------------+-----------+--------+---------------------+---------------------+---------+---------+
|      name       | namespace | labels |       created       |      modified       | deleted | mp_type |
+=================+===========+========+=====================+=====================+=========+=========+
| static_provider | None      | None   | 2000-01-01 08:00:00 | 2000-01-01 08:00:00 | None    | static  |
+-----------------+-----------+--------+---------------------+---------------------+---------+---------+
rok core globalmetric list
+----------------------+-----------+--------+---------------------+---------------------+---------+-----------------+-----+-----+
|         name         | namespace | labels |       created       |      modified       | deleted |    provider     | min | max |
+======================+===========+========+=====================+=====================+=========+=================+=====+=====+
| electricity_cost_1   | None      | None   | 2000-01-01 08:00:00 | 2000-01-01 08:00:00 | None    | static_provider | 0   | 1   |
| green_energy_ratio_1 | None      | None   | 2000-01-01 08:00:00 | 2000-01-01 08:00:00 | None    | static_provider | 0   | 1   |
+----------------------+-----------+--------+---------------------+---------------------+---------+-----------------+-----+-----+

Please go through the Preparation as well as through the Register an existing infrastructure provider to Krake and register an infrastructure provider. Validate the infrastructure provider registration as follows:

rok infra provider list
+-------------+--------------+--------+---------------------+---------------------+---------+------+-----------------------+
|    name     |  namespace   | labels |       created       |      modified       | deleted | type |          url          |
+=============+==============+========+=====================+=====================+=========+======+=======================+
| im-provider | system:admin | None   | 2000-01-01 08:00:00 | 2000-01-01 08:00:00 | None    | im   | http://localhost:8800 |
+-------------+--------------+--------+---------------------+---------------------+---------+------+-----------------------+

Register os-cloud-1 and os-cloud-2 Clouds, and associate the electricity_cost_1 and green_energy_ratio_1 metrics to them using different weights to get different ranking scores:

Note

Refer to the Register an existing OpenStack based cloud to Krake for useful information about Cloud attributes.

rok infra cloud register --global-metric electricity_cost_1 1 --global-metric green_energy_ratio_1 10 --type openstack --url <os-auth-url> --project <os-project-name> --username <os-username> --password <os-password> --infra-provider im-provider os-cloud-1
rok infra cloud register --global-metric electricity_cost_1 10 --global-metric green_energy_ratio_1 1 --type openstack --url <os-auth-url> --project <os-project-name> --username <os-username> --password <os-password> --infra-provider im-provider os-cloud-2

Tip

You do not need access to the two OpenStack projects for os-cloud-1 and os-cloud-2 registration. It is possible to register one OpenStack project two times in Krake with different metrics. Do not use this setup in the production environment!

The clouds os-cloud-1/-2 have been defined with the following weights for the two static metrics:

os-cloud-1 os-cloud-2 Value

electricity_cost_1 Weight: 1 Weight: 10 0.9

green_energy_ratio_1 Weight: 10 Weight: 1 0.1

Score 1.9 9.1

As the score of os-cloud-2 is higher, it will been chosen, and the Cluster will be spawned on it. The score is computed like the following:

\[10 \cdot 0.9 + 1 \cdot 0.1 = 9.1\]

Scheduling of a Cluster¶

Create the my-cluster cluster and check it is actually spawned on the second cloud:

rok kube cluster create -f rak/functionals/im-cluster.yaml my-cluster
rok kube cluster get my-cluster  -o json | jq .status.running_on  # Cluster is running on "os-cloud-2"

Note

You can observe the scheduler logs in DEBUG mode to gather additional understanding of the scheduling mechanism.

Cleanup¶

Delete the Cluster, both Clouds and the InfrastructureProvider.

rok kube cluster delete my-cluster
rok infra cloud delete os-cloud-1
rok infra cloud delete os-cloud-2
rok infra provider delete im-provider