NestJS Configuration Standards

Priority: P1 (HIGH)

Setup

1. Library: Use @nestjs/config.
2. Initialization: Import ConfigModule.forRoot({ isGlobal: true }) in AppModule.

Validation

• Mandatory: Validate environment variables at startup.
• Tool: Use joi or custom validation class.
• Effect: app must crash immediately if required env var (e.g., DB_URL) missing.

// app.module.ts
ConfigModule.forRoot({
  validationSchema: Joi.object({
    NODE_ENV: Joi.string()
      .valid('development', 'production')
      .default('development'),
    PORT: Joi.number().default(3000),
    DATABASE_URL: Joi.string().required(),
  }),
});

Usage

• Injection: Inject ConfigService to access values.
• Typing: Avoid magic strings. Use type-safe getter helper or dedicated configuration object/interface.
• Secrets: Never commit .env files. Add .env* to .gitignore.

⚠️ Adding New Variables

When adding new environment variable to application, you MUST update all of following:

1. src/config/env.validation.ts: Add class property with appropriate class-validator decorators.
2. .env.example: Add placeholder value so other developers know about it.
3. .env.development / .env.test: Add actual development values.
4. CI/CD Pipelines & Infrastructure: You MUST map new variable in your deployment scripts (e.g., .github/workflows/*.yml, gitlab-ci.yml, Terraform, or Azure Pipelines). Most modern cloud platforms (Cloud Run, ECS, Kubernetes) require explicit mapping of secrets/env-vars into container runtime. Failure to this will cause production deployment to crash or silently fail.

Anti-Patterns

• No unchecked env vars: Validate all required variables at startup; app must crash if missing.
• No committed secrets: Add .env* to .gitignore; load values via ConfigService only.
• No new vars without CI/CD update: Always update env.validation.ts, .env.example, and pipeline manifests.