nestjs-deployment

name	nestjs-deployment
description	Docker builds, Memory tuning, and Graceful shutdown. Use when containerizing NestJS apps, tuning memory, or implementing graceful shutdown. (triggers: Dockerfile, k8s/**, helm/**, Dockerfile, max-old-space-size, shutdown hooks)

Deployment & Ops Standards

Priority: P1 (OPERATIONAL)

Docker optimization and production deployment standards for NestJS applications.

Docker Optimization

• Multi-Stage Builds: Mandatory.
  1. Build Stage: Install devDependencies, build NestJS (nest build).
  2. Run Stage: Copy only dist and node_modules (pruned), use node:alpine.
• Security: Do not run as root.
  • Dockerfile: USER node.

Runtime Tuning (Node.js)

• Memory Config: Container memory != Node memory.
  • Rule: Explicitly set Max Old Space.
  • Command: node --max-old-space-size=XXX dist/main
  • Calculation: Set to ~75-80% of Kubernetes Limit. (Limit: 1GB -> OldSpace: 800MB).
• Graceful Shutdown:
  • Signal: Listen to SIGTERM.
  • NestJS: app.enableShutdownHooks() is mandatory.
  • Sleep: Add a "Pre-Stop" sleep in K8s (5-10s) to allow Load Balancer to drain connections before Node process stops accepting traffic.

Init Patterns

• Database Migrations:
  • Anti-Pattern: Running migration in main.ts on startup.
  • Pro Pattern: Use an Init Container in Kubernetes that runs npm run typeorm:migration:run before the app container starts.

Environment Variables & CI/CD

• CI/CD Pipelines (GitHub, GitLab, Azure, etc.):
  • If you modify src/config/env.validation.ts to add a new environment variable, you MUST map it explicitly in your deployment pipeline/infrastructure-as-code.
  • Platform Context:
    • Cloud Run/ECS: Variables must be explicitly passed in the service definition.
    • Kubernetes: New variables must be added to the Deployment manifest or ConfigMap/Secret.
    • Lambda/Serverless: Must be added to serverless.yml or provider console.
  • Fundamental Rule: Application code configuration changes are "breaking changes" for the infrastructure layer. Never assume environment inheritance.

Anti-Patterns

• No migrations in main.ts: Use K8s Init Containers or pre-deploy CI steps for migration runs.
• No root user in Docker: Always add USER node to Dockerfile; running as root is a security risk.
• No unbounded Node heap: Set --max-old-space-size to ~75% of container memory limit.