Comment Vibe API (Culture Amp SRE Technical Interview Code)

Welcome to the Culture Amp SRE Technical Interview code repository. This simple API and deployment IAC is the material we use to collaborate on with interviewees.

The Comment Vibe API is a small microservice for calculating sentiment using AFINN-165 for comments left on surveys.

It exposes an API using API Gateway V2 and AWS Lambda and persists survey comments in a DynamoDB table. The infrastructure is managed and deployed using the AWS CDK.

sre-tech-interview
├── ops                  AWS CDK project for deploying Comment Vibe
├── src                  Node.js application source code for Comment Vibe
├── Dockerfile           Builds AWS Lambda container image for Comment Vibe
├── docker-compose.yaml  Allows for Comment Vibe to be run locally for testing
├── openapi.yaml         OpenAPI documentation for Comment Vibe
└── readme.md            This document

Getting started

Requirements:

• Docker (or compatible), with Docker Compose v2 and above
• (optional) asdf or mise for easy tool installation -- this will install Node and Yarn using the .tool-versions file.
• Node 20
• Yarn 1.22.19

Tip

Consider a GitHub Codespace (or similar) that has this tooling installed if it's not readily available on the machine you're using for the interview.

Running in Docker

Comment Vibe can be run locally using Docker to imitate the AWS Lambda and DynamoDB infrastructure.

Build images:

$ docker compose build

Run local containers:

$ docker compose up

When the service starts, a container will run a command to create the necessary table. The status of this will be shown in the logs.

Follow on to the next section for details on running the API locally for development. Note that it is possible to communicate with the API in the container too, using a different payload.

Running the API locally

Tip

Running directly on the local host allows for an easier dev/test workflow than when all services are running in Docker. The local API instance relies on the local DynamoDB instance running in docker compose.

Install dependencies

$ yarn install

Run Express.js app locally

$ yarn start
yarn run v1.22.15
dotenv ts-node src/local.ts
Server started on port 3000

Tip

• Restart the yarn process to apply local changes.
• Use the examples from the next section against your local copy of the API when testing.

The API

Comment Vibe exposes two endpoints for use. See the OpenAPI specification for more complete details.

Comment on a survey: POST /comment/:surveyId

• Receives surveyId as parameter in path
• Receives new comment as JSON in the request body of a POST request
• Calculates sentiment field for the comment and saves it into the DynamoDB table
• Returns the comment with sentiment field set

# example request and response

$ HOST=http://localhost:3000
$ curl -X POST -H 'Content-Type: application/json' ${HOST}/comment/my-survey -d '{"content":"Today is a good day."}'

{
  "action": "add",
  "data": {
    "surveyId": "my-survey",
    "datetime": "2022-09-08T22:32:50.515Z",
    "content": "Today is a good day.",
    "sentiment": 3
  }
}

Reporting on a survey: GET /report/:surveyId

• Receives surveyId as parameter in path
• Queries DynamoDB for all comments for the given surveyId
• Buckets them based on sentiment and returns a basic report of the survey comments

# example request and response

$ HOST=http://localhost:3000
$ curl -X GET -H 'Content-Type: application/json' ${HOST}/report/my-survey

{
  "action": "report",
  "data": {
    "surveyId": "my-survey",
    "positiveCount": 1,
    "negativeCount": 0,
    "neutralCount": 0,
    "averageSentiment": 3
  }
}

Sending requests to the API in Docker Compose

The Lambda container expects to receive an AWS API Gateway v2 payload. See below for an example minimal request JSON for wrapping up a Comment Vibe request. See this reference for a complete example.

# adding a comment
curl -X POST http://localhost:9000/2015-03-31/functions/function/invocations -d '
{
  "version": "2.0",
  "headers": {
    "Content-Type": "application/json"
  },
  "rawPath": "/comment/my-survey",
  "body": "{\"content\":\"This survey was good.\"}",
  "requestContext": {
    "http": {
      "method": "POST"
    }
  }
}'

# reporting on a survey
curl -X POST http://localhost:9000/2015-03-31/functions/function/invocations -d '
{
  "version": "2.0",
  "headers": {
    "Content-Type": "application/json"
  },
  "rawPath": "/report/my-survey",
  "requestContext": {
    "http": {
      "method": "GET"
    }
  }
}'

Deploying to AWS with the CDK application

Requirements to run the CDK application:

• Node 16
• yarn

These can be installed using asdf, which will utilize the versions set in .tool-versions.

The CDK application is located in the ops directory

❯ cd ops

Install dependencies

❯ yarn install

Run Jest tests

❯ yarn test

Synth CloudFormation stack

❯ yarn cdk synth

Deploy the CloudFormation stack (the CDK app will use any valid credentials available in your terminal session)

❯ yarn cdk deploy