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ECS container IO stress

ECS container IO stress disrupts the state of infrastructure resources. It induces stress on the AWS ECS container using Amazon SSM Run command, which is carried out using SSM docs which is in-built into the fault.

  • It causes I/O stress on the containers of the ECS task using the given CLUSTER_NAME environment variable for a specific duration.
  • To select the Task Under Chaos (TUC), use the servie name associated with the task. If you provide the service name along with the cluster name, all the tasks associated with the given service will be selected as chaos targets.
  • It tests the ECS task sanity (service availability) and recovery of the task containers subject to I/O stress.

ECS Container IO Stress

Usage

View fault usage
File system read and write can evict the application (task container) and impact its delivery. These issues are also known as noisy neighbour problems. Injecting a rogue process into a target container starves the main microservice process (typically pid 1) of the resources allocated to it (where the limits are defined). This slows down the application traffic or exhausts the resources leading to eviction of all task containers. This fault determines how a container recovers from such a memory exhaustion.

Prerequisites

  • Kubernetes >= 1.17
  • ECS container metadata is enabled (disabled by default). To enable it, refer to this docs. If your task is running from before, you may need to restart it to get the metadata directory.
  • You and the ECS cluster instances have a role with the required AWS access to perform the SSM and ECS operations. Refer to systems manager docs.
  • Create a Kubernetes secret that has the AWS access configuration(key) in the CHAOS_NAMESPACE. Below is a sample secret file:
apiVersion: v1
kind: Secret
metadata:
name: cloud-secret
type: Opaque
stringData:
cloud_config.yml: |-
# Add the cloud AWS credentials respectively
[default]
aws_access_key_id = XXXXXXXXXXXXXXXXXXX
aws_secret_access_key = XXXXXXXXXXXXXXX
  • If you change the secret key name (from cloud_config.yml), ensure that you update the AWS_SHARED_CREDENTIALS_FILE environment variable in the chaos experiment with the new name.

Permissions required

Here is an example AWS policy to execute the fault.

View policy for the fault
{
"Version": "2012-10-17",
"Statement": [
{
"Sid": "VisualEditor0",
"Effect": "Allow",
"Action": [
"ecs:UpdateContainerInstancesState",
"ecs:RegisterContainerInstance",
"ecs:ListContainerInstances",
"ecs:DeregisterContainerInstance",
"ecs:DescribeContainerInstances",
"ecs:ListTasks",
"ecs:DescribeClusters"

],
"Resource": "*"
},
{
"Effect": "Allow",
"Action": [
"ssm:GetDocument",
"ssm:DescribeDocument",
"ssm:GetParameter",
"ssm:GetParameters",
"ssm:SendCommand",
"ssm:CancelCommand",
"ssm:CreateDocument",
"ssm:DeleteDocument",
"ssm:GetCommandInvocation",
"ssm:UpdateInstanceInformation",
"ssm:DescribeInstanceInformation"
],
"Resource": "*"
},
{
"Effect": "Allow",
"Action": [
"ec2messages:AcknowledgeMessage",
"ec2messages:DeleteMessage",
"ec2messages:FailMessage",
"ec2messages:GetEndpoint",
"ec2messages:GetMessages",
"ec2messages:SendReply"
],
"Resource": "*"
},
{
"Effect": "Allow",
"Action": [
"ec2:DescribeInstances"
],
"Resource": [
"*"
]
}
]
}

Refer to the superset permission/policy to execute all AWS faults.

Default validations

The ECS container instance should be in a healthy state.

Fault tunables

Fault tunables

Mandatory fields

Variables Description Notes
CLUSTER_NAME Name of the target ECS cluster. For example, cluster-1.
REGION Region name of the target ECS cluster For example, us-east-1.

Optional fields

Variables Description Notes
TOTAL_CHAOS_DURATION Duration that you specify, through which chaos is injected into the target resource (in seconds). Defaults to 30s.
CHAOS_INTERVAL Interval between successive instance terminations (in seconds). Defaults to 30s.
AWS_SHARED_CREDENTIALS_FILE Path to the AWS secret credentials. Defaults to /tmp/cloud_config.yml.
FILESYSTEM_UTILIZATION_BYTES Memory consumed during I/O stress (in GB). Defaults to 1.
VOLUME_MOUNT_PATH Location that points to the volume mount path used in I/O stress. Defaults to /tmp.
NUMBER_OF_WORKERS Number of workers for memory stress. Defaults to 1.
SEQUENCE Sequence of chaos execution for multiple instances Defaults to parallel. Supports serial sequence as well.
RAMP_TIME Period to wait before and after injecting chaos (in seconds). For example, 30s.

Fault examples

Common and AWS-specific tunables

Refer to the common attributes and AWS-specific tunables to tune the common tunables for all faults and aws specific tunables.

File system utilization percentage

It specifies the amount of free space available in the ECS container (in percentage). You can tune it using the FILESYSTEM_UTILIZATION_PERCENTAGE environment variable.

Use the following example to tune it:

# stress the i/o of the targeted pod with FILESYSTEM_UTILIZATION_PERCENTAGE of total free space 
# it is mutually exclusive with the FILESYSTEM_UTILIZATION_BYTES.
# if both are provided then it will use FILESYSTEM_UTILIZATION_PERCENTAGE for stress
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
name: engine-nginx
spec:
engineState: "active"
annotationCheck: "false"
chaosServiceAccount: litmus-admin
experiments:
- name: ecs-container-io-stress
spec:
components:
env:
# percentage of free space of file system, need to be stressed
- name: FILESYSTEM_UTILIZATION_PERCENTAGE
value: '10' #in GB
- name: TOTAL_CHAOS_DURATION
VALUE: '60'

File system utilization bytes

It specifies the amount of free space available in the ECS container (in gigabytes). You can tune it using the FILESYSTEM_UTILIZATION_BYTES environment variable.

The FILESYSTEM_UTILIZATION_BYTES and FILESYSTEM_UTILIZATION_PERCENTAGE environment variables are mutually exclusive. If values for both variables are provided, FILESYSTEM_UTILIZATION_PERCENTAGE takes precedence.

Use the following example to tune it:

# stress the i/o of the targeted pod with FILESYSTEM_UTILIZATION_PERCENTAGE of total free space 
# it is mutually exclusive with the FILESYSTEM_UTILIZATION_BYTES.
# if both are provided then it will use FILESYSTEM_UTILIZATION_PERCENTAGE for stress
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
name: engine-nginx
spec:
engineState: "active"
annotationCheck: "false"
chaosServiceAccount: litmus-admin
experiments:
- name: ecs-container-io-stress
spec:
components:
env:
# size of io to be stressed
- name: FILESYSTEM_UTILIZATION_BYTES
value: '1' #in GB
- name: TOTAL_CHAOS_DURATION
VALUE: '60'

Mount path

It specfiies the ;ocation that points to the volume mount path used in I/O stress. You can tune it using the VOLUME_MOUNT_PATH environment variable.

Use the following example to tune it:

# provide the volume mount path, which needs to be filled
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
name: engine-nginx
spec:
engineState: "active"
annotationCheck: "false"
chaosServiceAccount: litmus-admin
experiments:
- name: ecs-container-io-stress
spec:
components:
env:
# path need to be stressed/filled
- name: VOLUME_MOUNT_PATH
value: '/some-dir-in-container'
- name: TOTAL_CHAOS_DURATION
VALUE: '60'

Workers for stress

It specifies the worker's count to apply stress. You can tune it using the NUMBER_OF_WORKERS environment variable.

Use the following example to tune it:

# number of workers for the stress
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
name: engine-nginx
spec:
engineState: "active"
annotationCheck: "false"
chaosServiceAccount: litmus-admin
experiments:
- name: ecs-container-io-stress
spec:
components:
env:
# number of io workers
- name: NUMBER_OF_WORKERS
value: '4'
- name: TOTAL_CHAOS_DURATION
VALUE: '60'