Memory Hog Scenario

• 1: Memory Hog Scenarios using Krkn
• 2: Memory Hog Scenario using Krkn-Hub

1 - Memory Hog Scenarios using Krkn

To enable this plugin add the pointer to the scenario input file scenarios/arcaflow/memory-hog/input.yaml as described in the Usage section. This scenario takes a list of objects named input_list with the following properties:

• kubeconfig : string the kubeconfig needed by the deployer to deploy the sysbench plugin in the target cluster
• namespace : string the namespace where the scenario container will be deployed Note: this parameter will be automatically filled by kraken if the kubeconfig_path property is correctly set
• node_selector : key-value map the node label that will be used as nodeSelector by the pod to target a specific cluster node
• duration : string stop stress test after N seconds. One can also specify the units of time in seconds, minutes, hours, days or years with the suffix s, m, h, d or y.
• vm_bytes : string N bytes per vm process or percentage of memory used (using the % symbol). The size can be expressed in units of Bytes, KBytes, MBytes and GBytes using the suffix b, k, m or g.
• vm_workers : int Number of VM stressors to be run (0 means 1 stressor per CPU)

To perform several load tests in the same run simultaneously (eg. stress two or more nodes in the same run) add another item to the input_list with the same properties (and eventually different values eg. different node_selectors to schedule the pod on different nodes). To reduce (or increase) the parallelism change the value parallelism in workload.yaml file

Usage

To enable arcaflow 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 arcaflow_scenarios then add the desired scenario pointing to the input.yaml file.

kraken:
    ...
    chaos_scenarios:
        - arcaflow_scenarios:
            - scenarios/arcaflow/cpu-hog/input.yaml

input.yaml

The implemented scenarios can be found in scenarios/arcaflow/<scenario_name> folder. The entrypoint of each scenario is the input.yaml file. In this file there are all the options to set up the scenario accordingly to the desired target

config.yaml

The arcaflow config file. Here you can set the arcaflow deployer and the arcaflow log level. The supported deployers are:

• Docker
• Podman (podman daemon not needed, suggested option)
• Kubernetes

The supported log levels are:

• debug
• info
• warning
• error

workflow.yaml

This file contains the steps that will be executed to perform the scenario against the target. Each step is represented by a container that will be executed from the deployer and its options. Note that we provide the scenarios as a template, but they can be manipulated to define more complex workflows. To have more details regarding the arcaflow workflows architecture and syntax it is suggested to refer to the Arcaflow Documentation.

This edit is no longer in quay image Working on fix in ticket: https://issues.redhat.com/browse/CHAOS-494 This will effect all versions 4.12 and higher of OpenShift

2 - Memory Hog Scenario using Krkn-Hub

This scenario hogs the memory 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 --env-host=true -v <path-to-kube-config>:/home/krkn/.kube/config:Z -d quay.io/krkn-chaos/krkn-hub:node-memory-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

$ docker run $(./get_docker_params.sh) --name=<container_name> --net=host -v <path-to-kube-config>:/home/krkn/.kube/config:Z -d quay.io/krkn-chaos/krkn-hub:node-memory-hog
OR 
$ docker run -e <VARIABLE>=<value> --net=host -v <path-to-kube-config>:/home/krkn/.kube/config:Z -d quay.io/krkn-chaos/krkn-hub:node-memory-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

Supported parameters

The following environment variables can be set on the host running the container to tweak the scenario/faults being injected:

example: export <parameter_name>=<value>

See list of variables that apply to all scenarios here that can be used/set in addition to these scenario specific variables

$ podman run --name=<container_name> --net=host --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 quay.io/krkn-chaos/krkn-hub:node-memory-hog

Demo

You can find a link to a demo of the scenario here