Lambda update function memory

Introduction

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.

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.

note

• Kubernetes version 1.17 or later is required to execute this fault.
• 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
• 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: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
MEMORY_IN_MEGABYTES	Provide the value of the memory limit of a function in megabytes.	Minimum memory limit on a Lambda function is 128Mb and the maximum is 10240 Mb.
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.
CHAOS_INTERVAL	The interval (in seconds) between successive instance termination.	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 seconds	For example, 30 s.

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'