Prerequisites

• AWS CLI

Setup

• Create nodejs lambda function in AWS console using the name firefly-error-test
• cd into the firefly-test directory and run the following commands, replacing region with the region in which your lambda function resides:

$ aws lambda update-function-code --function-name firefly-error-test --zip-file fileb://function.zip

• Navigate to the AWS parameter store and create a new parameter

Name: failureLambdaConfig
Value: {"isEnabled": true, "failureMode": "latency", "rate": 1, "minLatency": 100, "maxLatency": 400, "exceptionMsg": "Exception message!", "statusCode": 404, "diskSpace": 100, "denylist": ["s3.*.amazonaws.com", "dynamodb.*.amazonaws.com"]}

• Add the following environment variable to your function FAILURE_INJECTION_PARAM and set the value to failureLambdaConfig

Permissions

• Go to your function in the AWS console
• Navigate to Configuration > Permissions
• Click the functions role
• Click Add permissions and Create inline policy
• In the JSON editor paste the following
  • Replace region and account number with your relevant details
  • Run the following command aws sts get-caller-identity to get your account number

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": [
              "ssm:GetParameter",
              "ssm:GetParameters",
              "ssm:GetParametersByPath",
              "ssm:PutParameter",
              "ssm:DeleteParameter",
              "ssm:DeleteParameters"
            ],
            "Resource": [
              "arn:aws:ssm:<region>:<account-number>:parameter/failureLambdaConfig"
            ]
        }
    ]
}

• Click Review policy
• Provide the following name firefly-test-parameter-policy and click Create policy

Please see the failure-lambda module here for relevant instructions on adpating the parameter to create different error types.

Function invoker

• add the URL's that will invoke your aws lambdas (or any serverless function), to the array called FAAS_URLS
• set INTERVAL to the rate (in milliseconds) you want setTimeout to be called
• set VARIANCE to the maximum of your random time range (in milliseconds) for the function to be invoked