Application Outage Scenarios

1: Application Outage Scenarios using Krkn
2: Application outage Scenario using Krkn-hub
3: Application Outage Scenarios using Krknctl

Application outages

Scenario to block the traffic ( Ingress/Egress ) of an application matching the labels for the specified duration of time to understand the behavior of the service/other services which depend on it during downtime. This helps with planning the requirements accordingly, be it improving the timeouts or tweaking the alerts etc. You can add in your applications URL into the [health checks section](../../krkn/config.md#health-checks) of the config to track the downtime of your application during this scenario

Rollback Scenario Support

Krkn supports rollback for Application outages. For more details, please refer to the Rollback Scenarios documentation.

1 - Application Outage Scenarios using Krkn

Sample scenario config

application_outage:                                  # Scenario to create an outage of an application by blocking traffic
  duration: 600                                      # Duration in seconds after which the routes will be accessible
  namespace: <namespace-with-application>            # Namespace to target - all application routes will go inaccessible if pod selector is empty
  pod_selector: {app: foo}                           # Pods to target
  exclude_label: ""                                  # Optional label selector to exclude pods. Supports dict, string, or list format
  block: [Ingress, Egress]                           # It can be Ingress or Egress or Ingress, Egress

Debugging steps in case of failures

Kraken creates a network policy blocking the ingress/egress traffic to create an outage, in case of failures before reverting back the network policy, you can delete it manually by executing the following commands to stop the outage:

$ oc delete networkpolicy/kraken-deny -n <targeted-namespace>

How to Use Plugin Name

Add the plugin name to the list of chaos_scenarios section in the config/config.yaml file

kraken:
    kubeconfig_path: ~/.kube/config                     # Path to kubeconfig
    .. 
    chaos_scenarios:
        - application_outages_scenarios:
            - scenarios/<scenario_name>.yaml

2 - Application outage Scenario using Krkn-hub

This scenario disrupts the traffic to the specified application to be able to understand the impact of the outage on the dependent service/user experience. Refer docs for more details.

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 --pull=always -v <path-to-kube-config>:/home/krkn/.kube/config:Z -d containers.krkn-chaos.dev/krkn-chaos/krkn-hub:application-outages
$ 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:application-outages
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:application-outages

$ 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 -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
DURATION	Duration in seconds after which the routes will be accessible	600
NAMESPACE	Namespace to target - all application routes will go inaccessible if pod selector is empty ( Required )	No default
POD_SELECTOR	Pods to target. For example “{app: foo}”	No default
EXCLUDE_LABEL	Pods to exclude after getting list of pods from POD_SELECTOR to target. For example “{app: foo}”	No default
BLOCK_TRAFFIC_TYPE	It can be Ingress or Egress or Ingress, Egress ( needs to be a list )	[Ingress, Egress]

Note

Defining the NAMESPACE parameter is required for running this scenario while the pod_selector is optional. In case of using pod selector to target a particular application, make sure to define it using the following format with a space between key and value: “{key: value}”.

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 --env-host=true --pull=always -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:application-outages

Demo

See a demo of this scenario:

3 - Application Outage Scenarios using Krknctl

krknctl run application-outages (optional: --<parameter>:<value>)

Can also set any global variable listed here

Scenario specific parameters:

Parameter	Description	Type	Required	Default
--namespace	Namespace to target - all application routes will go inaccessible if pod selector is empty	string	True
--chaos-duration	Set chaos duration (in sec) as desired	number	False	600
--pod-selector	Pods to target. For example “{app: foo}”	string	False
--exclude-label	Pods to exclude after using pod-selector to target. For example “{app: foo}”	string	False
--block-traffic-type	It can be [Ingress] or [Egress] or [Ingress, Egress]	string	False	“[Ingress, Egress]”

To see all available scenario options

krknctl run application-outages --help