/print-service

Primary LanguageTypeScript

Print service

Web system to store, manage and print DOCX templates. Supplied with the frontend control panel.

Technologies overview

  • Latest & greatest NodeJS (v16 atm)
  • Core – modern yet popular NestJS framework:
    • Highly active community
    • Large plugins base
  • 100% latest TypeScript-powered
  • GraphQL Web API (NestJS feature):
    • Versatile request-response communication
    • Metadata, errors and extensions (warnings)
    • Schema-first approach – schema is a source of truth for all underlying layers
  • Database – PostgreSQL
  • ORM – TypeORM (by NestJS):
    • Auto-generates described schemas
    • Strongly typed
    • Create/update/remove etc. events triggers
  • Template files actual storage – file-system mount point:
    • Can be a dedicated hard drive, network disk or just a local directory – just provide a path as an ENV variable
    • Human-readable file structure – all files/foldres are named in respect to user input (with a proper sanitizing, of course) so the storage can be easily observed just by looking at a file explorer. Kept in-sync with possible renaming.
  • Templates filling (fields substitution): Docxtemplater package – time-proven solution
  • Printing to PDF by LibreOffice:
    • On-demand execution by native NodeJS child_process API as a separate forked non-blocking process
    • Easily installable by any popular Linux package manager
    • Convenient CLI
    • 3rd-party fonts support
    • Free & open modular software
  • Print jobs queue:
    • Powered by Redis DB
    • NestJS-recommended Bull queue NodeJS package
    • Asynchronous running
    • Full support for distributed multi-instance configurations and unexpected processes crashes
    • Set number of attempts
    • Straightforward monitoring by any 3rd-party tool, shipped with Web GUI Bull-board
  • Background job for a temp files/jobs cleanups
  • Server-sent events (SSE) API to notify clients about requested jobs progress/results
  • Simple HTML home page is returned on root URL endpont to help a user find their way
  • Documentation by Compodoc:
    • Complete Web static assets folder generation based on developer JSDocs (utilize existing controller)
    • Zero-touching dependencies/relations graphs rendering
  • Docker/Kubernetes proof-of-concept configuration provided (see a diagram below):
    • Ingress Nginx is catching requests at the entrance and route them to corresponding services. Also, acts as a load-balancer
    • Deployment of each service (front- and backend) describes a number of instances (replicas) and hydrates containers with ENV variables

Kubernetes cluster architecture

diagram

Install & build

This project is a NestJS project and fully compilant with its CLI. Refer to Nest documentation on how to perform common tasks.

Running the app

Development mode:

$ npm run prebuild && NODE_ENV=development npm run start:dev

In production, intended to be deployed on the Kubernetes cluster (see a diagram above):

$ kubectl apply -f k8s/prod -f k8s/ingress.yaml -f k8s/service.yaml

Useful commands

These commands were used on different stages of development

Create new TemplateFile via curl:

$ curl -X POST -F 'operations={"query":"mutation CreateTemplateFile($file:Upload!) {\n  createTemplateFile(file:$file data:{templateTypeId:\"b1c1d8aa-5f07-4475-8719-a6dbb669b13e\"})\n {id title}}", "variables":{"file":null}}' -F 'map={"0":["variables.file"]}' -F '0=@/Users/chufyrev/Pictures/IMG_3184.JPG' http://localhost/api/graphql

Build a Docker image:

# development
$ docker build -t print-service .

# production
$ docker build -t print-service-prod -f Dockerfile.prod .

Run the development Docker container:

$ docker-compose up

Shutdown a cluster:

$ kubectl delete -f k8s/prod -f k8s/ingress.yaml -f k8s/service.yaml

Connect to service logs stream:

$ kubectl logs -f -lapp=print-service --all-containers=true

List pods:

$ kubectl get pods

Execute a command inside the particular pod:

$ kubectl exec print-service-deployment-797f9f96b6-847qc -- ls

Generate docs:

$ npx @compodoc/compodoc -p tsconfig.json -d docs --silent

Useful links

Roadmap

See TODO and in-place TODOs to get a look on what can be improved in the future.