I currently use a lambda that returns a mock response one out of ten times. It is integrated with AWS API gateway. The lambda implementation is as below:

def lambda_handler(event, context):
    body = json.loads(event['body'])
    if random.random() < 0.1: // Failure response
        response_body = {
            "error": "Something went wrong!"
        }
        return_value = {
            "isBase64Encoded": False,
            "statusCode": 400,
            "headers": {},
            "body": json.dumps(response_body)
        }
        logger.info(return_value)
        return return_value
    else: // Success response
        return_value = {
            "isBase64Encoded": False,
            "statusCode": 200,
            "headers": {},
            "body": json.dumps({})
        }
        logger.info(return_value)
        return return_value

Is it possible to achieve this directly using AWS API Gateway mock integration without the use of a lambda?

We tried using VTL in integration request, but the random number generation and wiring the value with response was tricky.

Integration Request

{
#set ($random = $math.getRandom(1,10))
#if($random < 1)
  "statusCode" : 400,
#else
  "statusCode" : 200,
#end
  "body" : "[1,2,3]"
}

Integration Response – Default 200

#set($inputRoot = $input.path('$'))
{
    "status" : "success",
    "prop" : "$inputRoot"
}

Integration Response – 4xx

HTTP status regex – 4d{2}

{
    "statusCode": 400,
    "message": "Go ahead without me"
}