Lambda toggle event mapping state

Introduction

Lambda toggle event mapping state toggles (or sets) the event source mapping state to disable for a Lambda function during a specific duration. Toggling between different states of event source mapping from a Lambda function may lead to failures when updating the database on an event trigger. This can break the service and impact its delivery.

Use cases

Lambda toggle event mapping:

• Checks the performance of the running application when the event source mapping is not enabled. This may cause missing entries in a database.
• Determines if the application has proper error handling or auto recovery actions configured.

note

• Kubernetes version 1.17 or later is required to execute this fault.
• AWS Lambda event source mapping must be healthy and attached to the Lambda function.
• Kubernetes secret must have the AWS access configuration(key) in the CHAOS_NAMESPACE. A secret file looks like this:

  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
• Harness recommends using the same secret name, that is, cloud-secret. Otherwise, you must update the AWS_SHARED_CREDENTIALS_FILE environment variable in the fault template and you won't be able to use the default health check probes.
• Go to AWS named profile for chaos to use a different profile for AWS faults.
• Go to superset permission/policy to execute all AWS faults.
• Go to common tunables and AWS-specific tunables to tune the common tunables for all faults and AWS-specific tunables.

Below is an example AWS policy to execute the fault.

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": [
                "lambda:ListEventSourceMappings",
                "lambda:DeleteEventSourceMapping",
                "lambda:UpdateEventSourceMapping",
                "lambda:CreateEventSourceMapping",
                "lambda:UpdateFunctionConfiguration",
                "lambda:GetFunctionConcurrency",
                "lambda:GetFunction",
                "lambda:DeleteFunctionConcurrency",
                "lambda:PutFunctionConcurrency"
            ],
            "Resource": "*"
        }
    ]
}

Fault tunables

Mandatory tunables

Tunable	Description	Notes
FUNCTION_NAME	Function name of the target lambda function. It supports single function name.	For example, test-function
EVENT_UUIDS	Provide the UUID for the target event source mapping.	You can provide multiple values as comma-separated values. For example, id1,id2
REGION	The region name of the target lambda function	For example, us-east-2

Optional tunables

Tunable	Description	Notes
TOTAL_CHAOS_DURATION	Duration that you specify, through which chaos is injected into the target resource (in seconds).	Default: 30 s.
SEQUENCE	It defines sequence of chaos execution for multiple instance	Default value: parallel. Supported: serial, parallel
RAMP_TIME	Period to wait before and after injection of chaos in sec	For example, 30 s.

Multiple event source mapping

Toggle between multiple event source mapping for a specific duration. Tune it by using EVENT_UUIDS environment variable that takes the UUID of the events as a comma-separated value.

The following YAML snippet illustrates the use of this environment variable:

# contains the removal of multiple event source mapping
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: lambda-toggle-event-mapping-state
    spec:
      components:
        env:
        # provide UUIDS of event source mapping
        - name: EVENT_UUIDS
          value: 'id1,id2'
        # provide the function name for the chaos
        - name: FUNCTION_NAME
          value: 'chaos-function'