Java on the AWS cloud using Lambda, Api Gateway and CloudFormation

On a previous post we implemented a java based aws lambda function and deployed it using CloudFormation.

Since we have our lambda function set up we will integrate it with a http endpoint using AWS API Gateway.

Amazon API Gateway is a fully managed service that makes it easy for developers to create, publish, maintain, monitor, and secure APIs at any scale. With a few clicks in the AWS Management Console, you can create an API that acts as a “front door” for applications to access data, business logic, or functionality from your back-end services, such as workloads running on Amazon Elastic Compute Cloud (Amazon EC2), code running on AWS Lambda, or any Web application

For this example imagine API gateway as if it is an HTTP Connector.

We will change our original function in order to implement a division.

package com.gkatzioura.deployment.lambda;

import com.amazonaws.services.lambda.runtime.Context;
import com.amazonaws.services.lambda.runtime.RequestHandler;

import java.math.BigDecimal;
import java.util.Map;
import java.util.logging.Logger;

/**
 * Created by gkatzioura on 9/10/2016.
 */
public class RequestFunctionHandler implements RequestHandler<Map<String,String>,String> {

    private static final String NUMERATOR_KEY = "numerator";
    private static final String DENOMINATOR_KEY = "denominator";

    private static final Logger LOGGER = Logger.getLogger(RequestFunctionHandler.class.getName());

    public String handleRequest(Map <String,String> values, Context context) {

        LOGGER.info("Handling request");

        if(!values.containsKey(NUMERATOR_KEY)||!values.containsKey(DENOMINATOR_KEY)) {
            return "You need both numberator and denominator";
        }

        try {
            BigDecimal numerator = new BigDecimal(values.get(NUMERATOR_KEY));
            BigDecimal denominator= new BigDecimal(values.get(DENOMINATOR_KEY));
            return  numerator.divide(denominator).toString();
        } catch (Exception e) {
            return "Please provide valid values";
        }
    }

}

Then we will change our lambda code and update it on s3.

aws s3 cp build/distributions/JavaLambdaDeployment.zip s3://lambda-functions/JavaLambdaDeployment.zip

Next step is to update our CloudFormation template and add the api gateway forwarding requests to our lambda function.

First we have to declare our Rest api

    "AGRA16PAA": {
      "Type": "AWS::ApiGateway::RestApi",
      "Properties": {"Name": "CalculationApi"}
    }

Then we need to add a rest resource. Inside the DependsOn element we can see the id of our rest api. Therefore cloudwatch will create the resource after the rest api has been created.

"AGR2JDQ8": {
      "Type": "AWS::ApiGateway::Resource",
      "Properties": {
        "RestApiId": {"Ref": "AGRA16PAA"},
        "ParentId": {
          "Fn::GetAtt": ["AGRA16PAA","RootResourceId"]
        },
        "PathPart": "divide"
      },
      "DependsOn": [
        "AGRA16PAA"
      ]
    }

Another crucial part is to add a permission in order to be able to invoke our lambda function.

    "LPI6K5": {
      "Type": "AWS::Lambda::Permission",
      "Properties": {
        "Action": "lambda:invokeFunction",
        "FunctionName": {"Fn::GetAtt": ["LF9MBL", "Arn"]},
        "Principal": "apigateway.amazonaws.com",
        "SourceArn": {"Fn::Join": ["",
          ["arn:aws:execute-api:", {"Ref": "AWS::Region"}, ":", {"Ref": "AWS::AccountId"}, ":", {"Ref": "AGRA16PAA"}, "/*"]
        ]}
      }
    }

Last step would be to add the api gateway method in order to be able to invoke our lambda function from the api gateway. Furthermore we will add an api gateway deployment instruction.

"Deployment": {
      "Type": "AWS::ApiGateway::Deployment",
      "Properties": {
        "RestApiId": { "Ref": "AGRA16PAA" },
        "Description": "First Deployment",
        "StageName": "StagingStage"
      },
      "DependsOn" : ["AGM25KFD"]
    },
    "AGM25KFD": {
      "Type": "AWS::ApiGateway::Method",
      "Properties": {
        "AuthorizationType": "NONE",
        "HttpMethod": "POST",
        "ResourceId": {"Ref": "AGR2JDQ8"},
        "RestApiId": {"Ref": "AGRA16PAA"},
        "Integration": {
          "Type": "AWS",
          "IntegrationHttpMethod": "POST",
          "IntegrationResponses": [{"StatusCode": 200}],
          "Uri": {
            "Fn::Join": [
              "",
              [
                "arn:aws:apigateway:",
                {"Ref": "AWS::Region"},
                ":lambda:path/2015-03-31/functions/",
                {"Fn::GetAtt": ["LF9MBL", "Arn"]},
                "/invocations"
              ]
            ]
          }
        },
        "MethodResponses": [{
          "StatusCode": 200
        }]
      }

So we ended up with our new cloudwatch configuration.

{
  "AWSTemplateFormatVersion": "2010-09-09",
  "Resources": {
    "LF9MBL": {
      "Type": "AWS::Lambda::Function",
      "Properties": {
        "Code": {
          "S3Bucket": "lambda-functions",
          "S3Key": "JavaLambdaDeployment.zip"
        },
        "FunctionName": "SimpleRequest",
        "Handler": "com.gkatzioura.deployment.lambda.RequestFunctionHandler",
        "MemorySize": 128,
        "Role": "arn:aws:iam::274402012893:role/lambda_basic_execution",
        "Runtime": "java8"
      }
    },
    "Deployment": {
      "Type": "AWS::ApiGateway::Deployment",
      "Properties": {
        "RestApiId": { "Ref": "AGRA16PAA" },
        "Description": "First Deployment",
        "StageName": "StagingStage"
      },
      "DependsOn" : ["AGM25KFD"]
    },
    "AGM25KFD": {
      "Type": "AWS::ApiGateway::Method",
      "Properties": {
        "AuthorizationType": "NONE",
        "HttpMethod": "POST",
        "ResourceId": {"Ref": "AGR2JDQ8"},
        "RestApiId": {"Ref": "AGRA16PAA"},
        "Integration": {
          "Type": "AWS",
          "IntegrationHttpMethod": "POST",
          "IntegrationResponses": [{"StatusCode": 200}],
          "Uri": {
            "Fn::Join": [
              "",
              [
                "arn:aws:apigateway:",
                {"Ref": "AWS::Region"},
                ":lambda:path/2015-03-31/functions/",
                {"Fn::GetAtt": ["LF9MBL","Arn"]},
                "/invocations"
              ]
            ]
          }
        },
        "MethodResponses": [{"StatusCode": 200}]
      },
      "DependsOn": ["LF9MBL","AGR2JDQ8","LPI6K5"]
    },
    "AGR2JDQ8": {
      "Type": "AWS::ApiGateway::Resource",
      "Properties": {
        "RestApiId": {"Ref": "AGRA16PAA"},
        "ParentId": {
          "Fn::GetAtt": ["AGRA16PAA","RootResourceId"]
        },
        "PathPart": "divide"
      },
      "DependsOn": ["AGRA16PAA"]
    },
    "AGRA16PAA": {
      "Type": "AWS::ApiGateway::RestApi",
      "Properties": {
        "Name": "CalculationApi"
      }
    },
    "LPI6K5": {
      "Type": "AWS::Lambda::Permission",
      "Properties": {
        "Action": "lambda:invokeFunction",
        "FunctionName": {"Fn::GetAtt": ["LF9MBL", "Arn"]},
        "Principal": "apigateway.amazonaws.com",
        "SourceArn": {"Fn::Join": ["",
          ["arn:aws:execute-api:", {"Ref": "AWS::Region"}, ":", {"Ref": "AWS::AccountId"}, ":", {"Ref": "AGRA16PAA"}, "/*"]
        ]}
      }
    }
 }
}

Last but not least, we have to update our previous cloudformation stack.

So we uploaded our latest template

aws s3 cp cloudformationjavalambda2.template s3://cloudformation-templates/cloudformationjavalambda2.template

And all we have to do is to update our stack.

aws cloudformation update-stack --stack-name JavaLambdaStack --template-url https://s3.amazonaws.com/cloudformation-templates/cloudformationjavalambda2.template

Our stack has just been updated.
We can got to our api gateway endpoint and try to issue a post.

curl -H "Content-Type: application/json" -X POST -d '{"numerator":1,"denominator":"2"}' https://{you api gateway endpoint}/StagingStage/divide
"0.5"

You can find the sourcecode on github.

Java on the AWS cloud using Lambda

Amazon Web Services gets more popular by the day. Java is a first class citizen on AWS and it is pretty easy to get started.
Deploying your application is a bit different, but still easy and convenient.

AWS Lambda is a compute service where you can upload your code to AWS Lambda and the service can run the code on your behalf using AWS infrastructure. After you upload your code and create what we call a Lambda function, AWS Lambda takes care of provisioning and managing the servers that you use to run the code.

Actually think of lambda as running a task that needs up to five minutes to finish. In case of simple actions or jobs that are not time consuming, and don’t require a huge framework, AWS lambda is the way to go. Also AWS lambda is great for horizontal scaling.

The most stripped down example would be to create a lambda function that responds to a request.

We shall implement the RequestHandler interface.

package com.gkatzioura.deployment.lambda;

import com.amazonaws.services.lambda.runtime.Context;
import com.amazonaws.services.lambda.runtime.RequestHandler;

import java.util.Map;
import java.util.logging.Logger;

/**
 * Created by gkatzioura on 9/10/2016.
 */
public class RequestFunctionHandler implements RequestHandler<Map<String,String>,String> {

    private static final Logger LOGGER = Logger.getLogger(RequestFunctionHandler.class.getName());

    public String handleRequest(Map <String,String> values, Context context) {

        LOGGER.info("Handling request");

        return "You invoked a lambda function";
    }

}

Somehow RequestHandler is like a controller.

To proceed we will have to create a jar file with the dependencies needed, therefore we will create a custom gradle task

apply plugin: 'java'

repositories {
    mavenCentral()
}

dependencies {
    compile (
            'com.amazonaws:aws-lambda-java-core:1.1.0',
            'com.amazonaws:aws-lambda-java-events:1.1.0'
    )
}

task buildZip(type: Zip) {
    from compileJava
    from processResources
    into('lib') {
        from configurations.runtime
    }
}

build.dependsOn buildZip

Then we should build

gradle build

Now we have to upload our code to our lambda function.

I have a s3 bucket on amazon for lambda functions only. Supposing that our bucket is called lambda-functions (I am pretty sure it is already reserved).
We will use aws cli wherever possible.

aws s3 cp build/distributions/JavaLambdaDeployment.zip s3://lambda-functions/JavaLambdaDeployment.zip

Now instead of creating a lambda function the manual way we are going to do so by creating a cloud formation template.

{
  "AWSTemplateFormatVersion": "2010-09-09",
  "Resources": {
    "LF9MBL": {
      "Type": "AWS::Lambda::Function",
      "Properties": {
        "Code": {
          "S3Bucket": "lambda-functions",
          "S3Key" : "JavaLambdaDeployment.zip",
        },
        "FunctionName": "SimpleRequest",
        "Handler": "com.gkatzioura.deployment.lambda.RequestFunctionHandler",
        "MemorySize": 128,
        "Role":"arn:aws:iam::274402012893:role/lambda_basic_execution",
        "Runtime":"java8"
      },
      "Metadata": {
        "AWS::CloudFormation::Designer": {
          "id": "66b2b325-f19a-4d7d-a7a9-943dd8cd4a5c"
        }
      }
    }
  }
}

Next step is to upload our cloudformation template to an s3 bucket. Personally I use a separate bucket for my templates. Supposing that our bucket is called cloudformation-templates

aws s3 cp cloudformationjavalambda.template s3://cloudformation-templates/cloudformationjavalambda.template

Next step is to create our cloudformation stack using the template specified

aws cloudformation create-stack --stack-name JavaLambdaStack --template-url https://s3.amazonaws.com/cloudformation-templates/cloudformationjavalambda.template

In order to check we shall invoke the lambda function through the amazon cli

aws lambda invoke --invocation-type RequestResponse --function-name SimpleRequest --region eu-west-1 --log-type Tail --payload '{}' outputfile.txt

And the result is the expected

"You invoked a lambda function"

You can find the source code on github.