CPU Hog Scenario
Overview
The CPU Hog scenario is designed to create CPU pressure on one or more nodes in your Kubernetes/OpenShift cluster for a specified duration. This scenario helps you test how your cluster and applications respond to high CPU utilization.
How It Works
The scenario deploys a stress workload pod on targeted nodes. These pods use stress-ng to consume CPU resources according to your configuration. The workload runs for a specified duration and then terminates, allowing you to observe your cluster’s behavior under CPU stress.
When to Use
Use the CPU Hog scenario to:
- Test your cluster’s ability to handle CPU resource contention
- Validate that CPU resource limits and quotas are properly configured
- Evaluate the impact of CPU pressure on application performance
- Test whether your monitoring and alerting systems properly detect CPU saturation
- Verify that the Kubernetes scheduler correctly handles CPU-constrained nodes
- Simulate scenarios where rogue pods consume excessive CPU without limits
Key Configuration Options
In addition to the common hog scenario options, CPU Hog scenarios support:
| Option | Type | Description |
|---|
cpu-load-percentage | number | The percentage of CPU that will be consumed by the hog |
cpu-method | string | The CPU load strategy adopted by stress-ng (see stress-ng documentation for available options) |
Usage
Select your deployment method to get started:
1 - CPU Hog Scenarios using Krkn
To enable this plugin add the pointer to the scenario input file scenarios/kube/cpu-hog.yml as described in the
Usage section.
cpu-hog options
In addition to the common hog scenario options, you can specify the below options in your scenario configuration to specificy the amount of CPU to hog on a certain worker node
| Option | Type | Description |
|---|
cpu-load-percentage | number | the amount of cpu that will be consumed by the hog |
cpu-method | string | reflects the cpu load strategy adopted by stress-ng, please refer to the stress-ng documentation for all the available options |
Usage
To enable hog scenarios edit the kraken config file, go to the section kraken -> chaos_scenarios of the yaml structure
and add a new element to the list named hog_scenarios then add the desired scenario
pointing to the hog.yaml file.
kraken:
...
chaos_scenarios:
- hog_scenarios:
- scenarios/kube/cpu-hog.yml
2 - CPU Hog Scenario using Krkn-Hub
This scenario hogs the cpu on the specified node on a Kubernetes/OpenShift cluster for a specified duration. For more information refer the following documentation.
Run
If enabling Cerberus to monitor the cluster and pass/fail the scenario post chaos, refer docs. Make sure to start it before injecting the chaos and set CERBERUS_ENABLED environment variable for the chaos injection container to autoconnect.
$ podman run --name=<container_name> --net=host --pull=always --env-host=true -v <path-to-kube-config>:/home/krkn/.kube/config:Z -d containers.krkn-chaos.dev/krkn-chaos/krkn-hub:node-cpu-hog
$ podman logs -f <container_name or container_id> # Streams Kraken logs
$ podman inspect <container-name or container-id> --format "{{.State.ExitCode}}" # Outputs exit code which can considered as pass/fail for the scenario
Note
–env-host: This option is not available with the remote Podman client, including Mac and Windows (excluding WSL2) machines.
Without the –env-host option you’ll have to set each enviornment variable on the podman command line like -e <VARIABLE>=<value>$ docker run $(./get_docker_params.sh) --name=<container_name> --net=host --pull=always -v <path-to-kube-config>:/home/krkn/.kube/config:Z -d containers.krkn-chaos.dev/krkn-chaos/krkn-hub:node-cpu-hog
OR
$ docker run -e <VARIABLE>=<value> --net=host --pull=always -v <path-to-kube-config>:/home/krkn/.kube/config:Z -d containers.krkn-chaos.dev/krkn-chaos/krkn-hub:node-cpu-hog
$ docker logs -f <container_name or container_id> # Streams Kraken logs
$ docker inspect <container-name or container-id> --format "{{.State.ExitCode}}" # Outputs exit code which can considered as pass/fail for the scenario
Tip
Because the container runs with a non-root user, ensure the kube config is globally readable before mounting it in the container. You can achieve this with the following commands:
kubectl config view --flatten > ~/kubeconfig && chmod 444 ~/kubeconfig && docker run $(./get_docker_params.sh) --name=<container_name> --net=host --pull=always -v ~kubeconfig:/home/krkn/.kube/config:Z -d containers.krkn-chaos.dev/krkn-chaos/krkn-hub:<scenario>Supported parameters
The following environment variables can be set on the host running the container to tweak the scenario/faults being injected:
Example if –env-host is used:
export <parameter_name>=<value>
OR on the command line like example:
-e <VARIABLE>=<value>
See list of variables that apply to all scenarios here that can be used/set in addition to these scenario specific variables
| Parameter | Description | Default |
|---|
| TOTAL_CHAOS_DURATION | Set chaos duration (in sec) as desired | 60 |
| NODE_CPU_CORE | Number of cores (workers) of node CPU to be consumed | 2 |
| NODE_CPU_PERCENTAGE | Percentage of total cpu to be consumed | 50 |
| NAMESPACE | Namespace where the scenario container will be deployed | default |
| NODE_SELECTOR | Defines the node selector for choosing target nodes. If not specified, one schedulable node in the cluster will be chosen at random. If multiple nodes match the selector, all of them will be subjected to stress. If number-of-nodes is specified, that many nodes will be randomly selected from those identified by the selector. | "" |
| TAINTS | List of taints for which tolerations need to created. Example: [“node-role.kubernetes.io/master:NoSchedule”] | [] |
| NUMBER_OF_NODES | Restricts the number of selected nodes by the selector | "" |
| IMAGE | The container image of the stress workload | quay.io/krkn-chaos/krkn-hog |
Note
In case of using custom metrics profile or alerts profile when CAPTURE_METRICS or ENABLE_ALERTS is enabled, mount the metrics profile from the host on which the container is run using podman/docker under /home/krkn/kraken/config/metrics-aggregated.yaml and /home/krkn/kraken/config/alerts.For example:
$ podman run --name=<container_name> --net=host --pull=always --env-host=true -v <path-to-custom-metrics-profile>:/home/krkn/kraken/config/metrics-aggregated.yaml -v <path-to-custom-alerts-profile>:/home/krkn/kraken/config/alerts -v <path-to-kube-config>:/home/krkn/.kube/config:Z -d containers.krkn-chaos.dev/krkn-chaos/krkn-hub:node-cpu-hog
Demo
You can find a link to a demo of the scenario here
3 - Node CPU Hog using Krknctl
krknctl run node-cpu-hog (optional: --<parameter>:<value> )
Can also set any global variable listed here
| Parameter | Description | Type | Default |
|---|
--chaos-duration | Set chaos duration (in secs) as desired | number | 60 |
--cores | Number of cores (workers) of node CPU to be consumed | number | |
--cpu-percentage | Percentage of total cpu to be consumed | number | 50 |
--namespace | Namespace where the scenario container will be deployed | string | default |
--node-selector | Node selector where the scenario containers will be scheduled in the format “=”. NOTE: Will be instantiated a container per each node selected with the same scenario options. If left empty a random node will be selected | string | |
--taints | List of taints for which tolerations need to created. For example [“node-role.kubernetes.io/master:NoSchedule”]" | string | [] |
--number-of-nodes | restricts the number of selected nodes by the selector | number | |
--image | The hog container image. Can be changed if the hog image is mirrored on a private repository | string | quay.io/krkn-chaos/krkn-hog |
To see all available scenario options
krknctl run node-cpu-hog --help
