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Software, tips and labs about FaaS and Serverless technology


Software, tips and labs about FaaS and Serverless technology

Cleuton Sampaio

Lambda vs gRPS vs Choreography vs HTTP / REST

I always say that 80% of your code is boilerplate. Ok, it may be overkill (and it certainly is), but part of your source code, where you have invested a lot of time and effort is related to infrastructure, not functionality. What do I mean by * infrastructure *? All that is required for your code to provide the desired service. And usually this * infrastructure * code is boilerplate, ie copy and paste with some changes, for example:

Boilerplate but not harmless!

Despite being boilerplate this code is not simple and not harmless! Big problems can arise if you inadvertently make a mistake or change something. Therefore, you need to know what you are doing and to know all the technologies involved in order to avoid problems.

I estimate a developer will waste between 50% and 80% of his time and effort (and cost) concerned with infrastructure code, including study, proof of concept, and so on.

To demonstrate what I am saying, and show an alternative, I decided to post this article.


This is a very simple example of application. A Pojo Java that verifies the digital signature of a text. I have already created many versions of this small component, and I will compare them here.

It’s a very simple code indeed. Let’s look at the main file:

    public String myHandler(String textAndSignature, Context context) throws InvalidKeyException, KeyStoreException, NoSuchAlgorithmException, CertificateException, NoSuchProviderException, SignatureException, IOException, DecoderException {
    	// Comment following two lines to run locally:
        LambdaLogger logger = context.getLogger();
        logger.log("received : " + textAndSignature);
        String [] parameters = textAndSignature.split(":");
        String returnValue = "";
		returnValue =  "Signature is " + verify(parameters[1],parameters[0],"*","meucertificado","teste001");
		// Comment following line to run locally:
        return returnValue;
	public static boolean verify(String hexSignature, String texto,
			String keystorePath, String alias, String keystorePassword) 
					throws KeyStoreException, NoSuchAlgorithmException, 
							CertificateException, IOException, InvalidKeyException, 
							NoSuchProviderException, DecoderException, SignatureException {
		boolean resultado = false;
		InputStream keystoreLocation = null;
		if (!keystorePath.equals("*")) {
			FileInputStream fisKs = new FileInputStream(keystorePath);
			keystoreLocation = fisKs;
		else {
			InputStream isKs = SignatureVerifier.class.getClassLoader().getResourceAsStream("minhakeystore.jks");
			keystoreLocation = isKs;
	    KeyStore keystore = KeyStore.getInstance(KeyStore.getDefaultType());
	    keystore.load(keystoreLocation, keystorePassword.toCharArray()); certificate = keystore.getCertificate(alias);
	    PublicKey pubKey = certificate.getPublicKey();
		Signature sig = Signature.getInstance("MD5withRSA", "SunRsaSign"); 
		Hex hex = new Hex();
		byte [] textContent = texto.getBytes("UTF-8");
		byte [] signature = (byte[]) hex.decode(hexSignature);
		resultado = sig.verify(signature);
		return resultado;

Total: 66 lines!

The verify() method takes two strings: a text and a digital signature from it, and verifies the signature using a keystore that I included in the project.

Nothing could be simpler, could it? This is actually the code to make this small module available as a function [Lambda in AWS!] ( optional.html). Note that there is virtually no boilerplate code here.

This is a perfect example of FaaS!

Now let’s look at other options of exposing the same code, and comparing everything.

RESTful Service

In this repository we have a RESTful version of this same service. Here, I used Dropwizard to create a Java JAX-RS application. Let’s look at the numbers of this version:

You can download the repository and test. There is even a python client for this.

The essential code to verify the signature has 66 lines, this version has 248 lines! In other words, the essential code is about 26% of the lines of code in this option. This is because I greatly simplified the RESTful service!


In this release, I created a gRPC based service and needed to create a load balancing engine using Apache Zookeeper, but I will not consider this when count the lines of code, but I will have to consider the client lines of code, after all, it’s part of the infrastructure. Although it is necessary, it is not essential. You can see this version in this folder. Here are the numbers:

Comparing to the 66 lines of essential code, we see that the ratio has expanded a lot: only 15% represents the essential code. I didn’t even count the customer lines!

Service choreograpy

I implemented an example using service choreography, with asynchronous messaging and RabbitMQ. I created a worker and a client, but I will only count worker lines:

Here the relationship has improved a lot. The essential code is 43% of the total code.

How to Make a Lambda Available in Java

Compile the source code with the command:

mvn clean package shade: shade

This will produce an Uber jar that you can load into the AWS console. Go to console and go to lambda functionality:

Select Create Role and indicate which is Runtime. Then upload your jar:

Finally, set up a test event:

You can perform your function and evaluate the results:

The example project has everything needed to create a uber jar for AWS Lambda. And you can use another product, such as API Gateway to expose your role to the world.


Less code, less complexity! You can expose functions in less than 1 minute! That is the beauty of FaaS.