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Lambda update function memory

Lambda update function memory causes the memory of a Lambda function to update to a specific value for a certain duration. This fault:

  • Determines a safe overall memory limit value for the function. Smaller the memory limit, higher will be the time taken by the Lambda function under load.

Lambda Update Function Memory

Use cases​

Lambda update function memory:

  • Helps build resilience to unexpected scenarios such as hitting a memory limit with the Lambda function, that slows down the service and impacts its delivery. Running out of memory due to smaller limits interrupts the flow of the given function.
  • Checks the performance of the application (or service) running with a new memory limit.

Prerequisites​

  • Kubernetes >= 1.17
  • Access to operate AWS Lambda functions.
  • Lambda function must be up and running.
  • 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
tip

HCE recommends that you use the same secret name, that is, cloud-secret. Otherwise, you will need to update the AWS_SHARED_CREDENTIALS_FILE environment variable in the fault template with the new secret name and you won't be able to use the default health check probes.

Below is an example AWS policy to execute the fault.

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

Mandatory tunables​

Tunable Description Notes
FUNCTION_NAME Function name of the target Lambda function. It supports single function name. For example, test-function
MEMORY_IN_MEGABYTES Provide the value of the memory limit of a function in megabytes. Minimum (128MB) and the maximum (10240 MB) memory limit on a Lambda function. For more information, go to memory limit.
REGION 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. For more information, go to duration of the chaos.
CHAOS_INTERVAL The interval (in seconds) between successive instance termination. Default: 30 s. For more information, go to chaos interval.
AWS_SHARED_CREDENTIALS_FILE Path to the AWS secret credentials. Default: /tmp/cloud_config.yml.
SEQUENCE It defines sequence of chaos execution for multiple instance Default: parallel. Supports serial and parallel. For more information, go to sequence of chaos execution.
RAMP_TIME Period to wait before and after injection of chaos in seconds For example, 30 s. For more information, go to ramp time.

Memory limit​

Updates the Lambda function memory limit to a different value. Tune it by using MEMORY_IN_MEGABYTES environment variable.

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

# contains the memory limit value for the lambda function
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: lambda-update-function-memory
    spec:
      components:
        env:
        # provide the function memory limit
        - name: MEMORY_IN_MEGABYTES
          value: '10'
        # provide the function name for memory limit chaos
        - name: FUNCTION_NAME
          value: 'chaos-function'