---
layout: pattern
title: Serverless
folder: serverless
permalink: /patterns/serverless/
categories: Architectural
tags:
- Cloud distributed
---
## Serverless
Serverless eliminates the need to plan for infrastructure and let's you focus on your
application.
Following are optimization katas you should be aware of while building a serverless
applications
* The Lean function
* Concise logic - Use functions to transform, not transport (utilize some of the
integration available from the provider to transport), and make sure you read only
what you need
* Efficient/single purpose code - avoid conditional/routing logic and break down
into individual functions, avoid "fat"/monolithic functions and control the
dependencies in the function deployment package to reduce the load time for your
function
* ephemeral environment - Utilize container start for expensive initializations
* Eventful Invocations
* Succinct payloads - Scrutinize the event as much as possible, and watch for
payload constraints (async - 128K)
* resilient routing - Understand retry policies and leverage dead letter queues
(SQS or SNS for replays) and remember retries count as invocations
* concurrent execution - lambda thinks of it's scale in terms of concurrency and
its not request based/duration based. Lambda will spin up the number of instances
based on the request.
* Coordinated calls
* Decoupled via APIs - best practice to setup your application is to have API's as
contracts that ensures separation of concerns
* scale-matched downstream - make sure when Lambda is calling downstream
components, you are matching scale configuration to it (by specifying max
concurrency based on downstream services)
* secured - Always ask a question, do I need a VPC?
* Serviceful operations
* Automated - use automated tools to manage and maintain the stack
* monitored applications - use monitoring services to get holistic view of your
serverless applications
## Intent
Whether to reduce your infrastructure costs, shrink the time you spend on ops tasks,
simplify your deployment processes, reach infinite scalability, serverless cuts time
to market in half.
## Explanation
Serverless computing is a cloud computing execution model in which the cloud provider
dynamically manages the allocation of machine resources. Pricing is based on the
actual amount of resources consumed by an application, rather than on pre-purchased
units of capacity.
## Class diagram
## Serverless framework
[Serverless](https://serverless.com/) is a toolkit for deploying and operating serverless architectures.
## (Function as a Service or "FaaS")
The term ‘Serverless’ is confusing since with such applications there are both server
hardware and server processes running somewhere, but the difference to normal
approaches is that the organization building and supporting a ‘Serverless’ application
is not looking after the hardware or the processes - they are outsourcing this to a vendor.
Some of the Serverless Cloud Providers are
...
Anything that triggers an Lambda Function to execute is regarded by the Framework as
an Event. Most of the Serverless Cloud Providers support following Events
- Http
- PubSub Events
- scheduled
AWS supports processing event generated from AWS Services (S3/Cloudwatch/etc) and
using aws as a compute engine is our first choice.
## (Backend as a Service or "BaaS")
This example creates a backend for ‘persons’ collection which uses DynamoDB NoSQL
database service also provided by Amazon.
## AWS lambda function implementation
[AWS Lambda SDK](https://aws.amazon.com/sdk-for-java/) provides pre-defined interface
`com.amazonaws.services.lambda.runtime
.RequestHandler` to implement our lambda function.
```java
public class LambdaInfoApiHandler implements RequestHandler<Map<String, Object>, ApiGatewayResponse> {
private static final Logger LOG = Logger.getLogger(LambdaInfoApiHandler.class);
private static final Integer SUCCESS_STATUS_CODE = 200;
@Override
public ApiGatewayResponse handleRequest(Map<String, Object> input, Context context) {
}
}
```
handleRequest method is where the function code is implemented. Context provides
useful information about Lambda execution environment. AWS Lambda function needs a
deployment package. This package is either a .zip or .jar file that contains all the
dependencies of the function.
`serverless.yml` contains configuration to manage deployments for your functions.
## Run example in local
# Pre-requisites
* Node.js v6.5.0 or later.
* Serverless CLI v1.9.0 or later. You can run npm install -g serverless to install it.
* An AWS account. If you don't already have one, you can sign up for a free trial that includes 1 million free Lambda requests per month.
* [Set-up](https://serverless.com/framework/docs/providers/aws/guide/credentials/) your Provider Credentials. Watch the video on setting up credentials
# build and deploy
* `cd serverless`
* `mvn clean package`
* `serverless deploy --stage=dev --verbose`
Based on the configuration in `serverless.yml` serverless framework creates following
resources
* CloudFormation stack for S3 (ServerlessDeploymentBucket)
* IAM Role (IamRoleLambdaExecution)
* CloudWatch (log groups)
* API Gateway (ApiGatewayRestApi)
* Lambda function
* DynamoDB collection
The command will print out Stack Outputs which looks something like this
```yaml
endpoints:
GET - https://xxxxxxxxx.execute-api.us-east-1.amazonaws.com/dev/info
POST - https://xxxxxxxxx.execute-api.us-east-1.amazonaws.com/dev/api/person
GET - https://xxxxxxxxx.execute-api.us-east-1.amazonaws.com/dev/api/person/{id}
```
```yaml
CurrentTimeLambdaFunctionQualifiedArn: arn:aws:lambda:us-east-1:xxxxxxxxxxx:function:lambda-info-http-endpoint-dev-currentTime:4
ServiceEndpoint: https://xxxxxxxxx.execute-api.us-east-1.amazonaws.com/dev
ServerlessDeploymentBucketName: lambda-info-http-endpoin-serverlessdeploymentbuck-2u8uz2i7cap2
```
access the endpoint to invoke the function.
Use the following cURL commands to test the endpoints
```cURL
curl -X GET \
https://xxxxxxxxx.execute-api.us-east-1.amazonaws.com/dev/info \
-H 'cache-control: no-cache'
```
```cURL
curl -X POST \
https://xxxxxxxxx.execute-api.us-east-1.amazonaws.com/dev/api/person \
-H 'cache-control: no-cache' \
-H 'content-type: application/json' \
-d '{
"firstName": "Thor",
"lastName": "Odinson",
"address": {
"addressLineOne": "1 Odin ln",
"addressLineTwo": "100",
"city": "Asgard",
"state": "country of the Gods",
"zipCode": "00001"
}
}'
```
```cURL
curl -X GET \
https://xxxxxxxxx.execute-api.us-east-1.amazonaws.com/dev/api/person/{id} \
-H 'cache-control: no-cache'
```
## Credits
* [serverless docs](https://serverless.com/framework/docs/)
* [Serverless Architectures](https://martinfowler.com/articles/serverless.html)
* [Serverless Black Belt](https://youtu.be/oQFORsso2go)