Idling applications

Idling applications
- Idling a single service
- Idling multiple services
Unidling applications

Cluster administrators can idle applications to reduce resource consumption. This is useful when the cluster is deployed on a public cloud where cost is related to resource consumption.

If any scalable resources are not in use, OKD discovers and idles them by scaling their replicas to 0. The next time network traffic is directed to the resources, the resources are unidled by scaling up the replicas, and normal operation continues.

Applications are made of services, as well as other scalable resources, such as deployment configs. The action of idling an application involves idling all associated resources.

Idling an application involves finding the scalable resources (deployment configurations, replication controllers, and others) associated with a service. Idling an application finds the service and marks it as idled, scaling down the resources to zero replicas.

You can use the oc idle command to idle a single service, or use the --resource-names-file option to idle multiple services.

Idling a single service

Procedure

To idle a single service, run:
```
$ oc idle <service>
```

Idling multiple services

Idling multiple services is helpful if an application spans across a set of services within a project, or when idling multiple services in conjunction with a script in order to idle multiple applications in bulk within the same project.

Procedure

Create a file containing a list of the services, each on their own line.
Idle the services using the --resource-names-file option:
```
$ oc idle --resource-names-file <filename>
```

The idle command is limited to a single project. For idling applications across a cluster, run the idle command for each project individually.

Unidling applications

Application services become active again when they receive network traffic and are scaled back up their previous state. This includes both traffic to the services and traffic passing through routes.

Applications can also be manually unidled by scaling up the resources.

Procedure

To scale up a DeploymentConfig, run:
```
$ oc scale --replicas=1 dc <dc_name>
```

Automatic unidling by a router is currently only supported by the default haproxy router.

Services do not support automatic unidling if you configure Kuryr-Kubernetes as an SDN.

In OKD 4.6, idled services do not become active again when they receive network traffic if they were idled while the leader ovnkube-master process was restarted or after the ovnkube-master leader changed. For more information, refer to Idled services cannot wake up automatically after restart of ovnkube-master in Red Hat OpenShift Container Platform 4.