efumagal / geo-3d-otel

Go HTTP server to calculate distance between 3D points

geo-3d-otel

Introduction

A simple HTTP client to serve APIs to calculate distance between 3D points.
Implemented using Fiber and instrumented using OpenTelemetry.

CI/CD

GitHub action

When pushing to main the Publish Docker image to GHCR is triggered:

• Build the Docker image and push it to ghcr.io registry
• Scan the docker image using Snyk
• Update kustomization.yaml with the newly generated Docker image

K8s manifest Kustomize

For this example I'm using Kustomize to build the K8s manifest, this is different than what I'm currently doing on real projects where I use Helm Charts. In order to keep everything in one repo the K8S manifests are kept in kustomize folder, unless using a monorepo they should probably be decoupled as the app code should be agnostic to the way is deployed. Similarly the files used by Flux are stored in fluxCD.

In this case there are 4 manifests:

• Deployment Standard deployment with liveness/readiness, using a secret for the Honeycomb token. The secrets are added using Sealed secrets.
• Service
• HPA In order to scale out when needed, Average CPU > 80%, min 2, max 6 pods
• Namespace

Flux

Flux is deployed on a local K8s cluster, and changes in the kustomize folder in this repo will trigger the reconciliation.
On a real project there may be different variants for each env (deployment, staging, production).

An example of a merge can be seen in CICD Video Recording.

Observability

The code is instrumented with OpenTelemetry and in this particular example the traces and metrics are exported to Honeycomb.io.
Otel Fiber is used for HTTP calls, plus there are some custom spans created to check specific operations.

Heatmap of HTTP calls during a load test:

Single trace:

Run Locally

go run main.go

The webserver runs on port 8080.

APIs

• GET /health Used for liveness/readiness probes
• GET /hello Returns a hello World HTML page
• GET /distance Calculates distance between two randomly generated 3D points
• POST /action/cpu-load Used to generate some CPU load for testing HPA

Geo3D.postman_collection can be imported in Postman to try the endpoints implemented.

Testing

The Go code should have unit tests, this was not done for time constraints but it is a crucial part in guranteeing the correctness of the application.

Load test

Pre-requiste K6

The script Load test K6 script can be used to generate some load and test performance and instrumentation.

k6 run load_distance.js

TO DOs

• For this example the K8s cluster is a local one (provided by Docker Desktop) and FluxCD was deployed manually. With more time I could write a Terraform script to set up AWS EKS and bootstrap FluxCD.
• For a real app consider structuring the Go code using DDD/Hexagonal pattern and separate the source code in a separate folder.
• Run Docker build and push only on related code changes
• Add unit tests and run them on PRs
• In case of a real app use REST and generate OpenAPI specs

Notes

• Before deploying on production there will be probably be some functional/system automated tests