Passing parameters to AWS Lambda

You can pass ES cluster endpoint to Lambda function as an environment variable. Here is a snippet of CloudFormation template for such function:

"mylambda": {
  "Type": "AWS::Lambda::Function",
  "Properties": {
    "Handler": "index.handler",
    "Role": { "Fn::GetAtt" : ["LambdaExecutionRole", "Arn"] },
    "Code": {
      "S3Bucket": "my-lambda-functions-bucket",
      "S3Key": "mylambda.zip"
    },
    "Runtime": "nodejs4.3",
    "Timeout": "25",
    "Environment": {
       "Variables": {
         "ESENDPOINT": { "Fn::GetAtt": ["ESDOMAINRESOURCE", "DomainEndpoint"] }
       }
    }
  }
}