Syn Flood Scenarios

This scenario generates a substantial amount of TCP traffic directed at one or more Kubernetes services within the cluster to test the server’s resiliency under extreme traffic conditions. It can also target hosts outside the cluster by specifying a reachable IP address or hostname. This scenario leverages the distributed nature of Kubernetes clusters to instantiate multiple instances of the same pod against a single host, significantly increasing the effectiveness of the attack. The configuration also allows for the specification of multiple node selectors, enabling Kubernetes to schedule the attacker pods on a user-defined subset of nodes to make the test more realistic.

The attacker container source code is available here.

How to Run Syn Flood Scenarios

Choose your preferred method to run syn flood scenarios:

Example scenario file: syn_flood.yaml

Sample scenario config

packet-size: 120 # hping3 packet size
window-size: 64 # hping 3 TCP window size
duration: 10 # chaos scenario duration
namespace: default # namespace where the target service(s) are deployed
target-service: target-svc # target service name (if set target-service-label must be empty)
target-port: 80 # target service TCP port
target-service-label : "" # target service label, can be used to target multiple target at the same time
                          # if they have the same label set (if set target-service must be empty)
number-of-pods: 2 # number of attacker pod instantiated per each target
image: quay.io/krkn-chaos/krkn-syn-flood # syn flood attacker container image
attacker-nodes: # this will set the node affinity to schedule the attacker node. Per each node label selector
                # can be specified multiple values in this way the kube scheduler will schedule the attacker pods
                # in the best way possible based on the provided labels. Multiple labels can be specified
  kubernetes.io/hostname:
    - host_1
    - host_2
  kubernetes.io/os:
    - linux

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:
        - syn_flood_scenarios:
            - scenarios/<scenario_name>.yaml

Note

You can specify multiple scenario files of the same type by adding additional paths to the list:

kraken:
    chaos_scenarios:
        - syn_flood_scenarios:
            - scenarios/syn-flood-1.yaml
            - scenarios/syn-flood-2.yaml
            - scenarios/syn-flood-3.yaml

You can also combine multiple different scenario types in the same config.yaml file. Scenario types can be specified in any order, and you can include the same scenario type multiple times:

kraken:
    chaos_scenarios:
        - syn_flood_scenarios:
            - scenarios/syn-flood.yaml
        - pod_disruption_scenarios:
            - scenarios/pod-kill.yaml
        - network_chaos_scenarios:
            - scenarios/network-chaos.yaml
        - syn_flood_scenarios:  # Same type can appear multiple times
            - scenarios/syn-flood-2.yaml

Run

python run_kraken.py --config config/config.yaml

Syn Flood scenario

This scenario simulates a user-defined surge of TCP SYN requests directed at one or more services deployed within the cluster or an external target reachable by the cluster. For more details, please refer to 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 \
  -e TARGET_PORT=<target_port> \
  -e NAMESPACE=<target_namespace> \
  -e TOTAL_CHAOS_DURATION=<duration> \
  -e TARGET_SERVICE=<target_service> \
  -e NUMBER_OF_PODS=10 \
  -e NODE_SELECTORS=<key>=<value>;<key>=<othervalue> \
  -d containers.krkn-chaos.dev/krkn-chaos/krkn-hub:syn-flood

$ podman logs -f <container_name or container_id>

$ podman inspect <container-name or container-id> \
  --format "{{.State.ExitCode}}"

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 environment 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 \
  -e TARGET_PORT=<target_port> \
  -e NAMESPACE=<target_namespace> \
  -e TOTAL_CHAOS_DURATION=<duration> \
  -e TARGET_SERVICE=<target_service> \
  -e NUMBER_OF_PODS=10 \
  -e NODE_SELECTORS=<key>=<value>;<key>=<othervalue> \
  -d containers.krkn-chaos.dev/krkn-chaos/krkn-hub:syn-flood

$ docker logs -f <container_name or container_id>

$ docker inspect <container-name or container-id> \
  --format "{{.State.ExitCode}}"

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
PACKET_SIZE	The size in bytes of the SYN packet	120
WINDOW_SIZE	The TCP window size between packets in bytes	64
TOTAL_CHAOS_DURATION	The number of seconds the chaos will last	120
NAMESPACE	The namespace containing the target service and where the attacker pods will be deployed	default
TARGET_SERVICE	The service name (or the hostname/IP address in case an external target will be hit) that will be affected by the attack. Must be empty if TARGET_SERVICE_LABEL will be set
TARGET_PORT	The TCP port that will be targeted by the attack
TARGET_SERVICE_LABEL	The label that will be used to select one or more services. Must be left empty if TARGET_SERVICE variable is set
NUMBER_OF_PODS	The number of attacker pods that will be deployed	2
IMAGE	The container image that will be used to perform the scenario	quay.io/krkn-chaos/krkn-syn-flood:latest
NODE_SELECTORS	The node selectors are used to guide the cluster on where to deploy attacker pods. You can specify one or more labels in the format key=value;key=value2 (even using the same key) to choose one or more node categories. If left empty, the pods will be scheduled on any available node, depending on the cluster’s capacity.

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:syn-flood

krknctl run syn-flood [--<parameter> <value>]

Can also set any global variable listed here

Scenario specific parameters:

Parameter	Description	Type	Required	Default
`--packet-size`	The size in bytes of the SYN packet	number	No	120
`--window-size`	The TCP window size between packets in bytes	number	No	64
`--chaos-duration`	The number of seconds the chaos will last	number	No	120
`--namespace`	The namespace containing the target service and where the attacker pods will be deployed	string	No	default
`--target-service`	The service name (or the hostname/IP address in case an external target will be hit) that will be affected by the attack.Must be empty if TARGET_SERVICE_LABEL will be set	string	No
`--target-port`	The TCP port that will be targeted by the attack	number	Yes
`--target-service-label`	The label that will be used to select one or more services.Must be left empty if TARGET_SERVICE variable is set	string	No
`--number-of-pods`	The number of attacker pods that will be deployed	number	No	2
`--image`	The container image that will be used to perform the scenario	string	No	quay.io/krkn-chaos/krkn-syn-flood:latest
`--node-selectors`	The node selectors are used to guide the cluster on where to deploy attacker pods. You can specify one or more labels in the format key=value;key=value2 (even using the same key) to choose one or more node categories. If left empty, the pods will be scheduled on any available node, depending on the cluster s capacity.	string	No

To see all available scenario options

krknctl run syn-flood --help