typescript 37 lines · 8 steps

Validating env config at boot in NestJS

A NestJS ConfigModule that loads environment files and validates every variable with a Joi schema before the app starts.

Explained by highlit
NestJS Intermediate configuration schema-validation environment-variables fail-fast dependency-injection
1import { Module } from '@nestjs/common';
2import { ConfigModule } from '@nestjs/config';
3import * as Joi from 'joi';
4 
5@Module({
6 imports: [
7 ConfigModule.forRoot({
8 isGlobal: true,
9 cache: true,
10 expandVariables: true,
11 envFilePath: [`.env.${process.env.NODE_ENV ?? 'development'}`, '.env'],
12 validationSchema: Joi.object({
13 NODE_ENV: Joi.string()
14 .valid('development', 'test', 'staging', 'production')
15 .default('development'),
16 PORT: Joi.number().port().default(3000),
17 DATABASE_URL: Joi.string().uri({ scheme: ['postgres', 'postgresql'] }).required(),
18 DATABASE_POOL_SIZE: Joi.number().integer().min(1).max(50).default(10),
19 REDIS_URL: Joi.string().uri({ scheme: ['redis', 'rediss'] }).required(),
20 JWT_SECRET: Joi.string().min(32).required(),
21 JWT_EXPIRES_IN: Joi.string().default('15m'),
22 SMTP_HOST: Joi.string().hostname().required(),
23 SMTP_PORT: Joi.number().port().default(587),
24 SMTP_FROM: Joi.string().email().required(),
25 STRIPE_SECRET_KEY: Joi.string().pattern(/^sk_(test|live)_/).required(),
26 LOG_LEVEL: Joi.string()
27 .valid('error', 'warn', 'info', 'debug', 'verbose')
28 .default('info'),
29 }),
30 validationOptions: {
31 abortEarly: false,
32 allowUnknown: true,
33 },
34 }),
35 ],
36})
37export class AppConfigModule {}
01 / 01
STEP 01

Walkthrough

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Three takeaways
  1. 1Validating environment variables at startup turns silent misconfiguration into an immediate, descriptive crash.
  2. 2A single global config module lets every provider read validated settings without re-importing configuration everywhere.
  3. 3Layering env files by NODE_ENV keeps per-environment overrides separate while sharing a common base.

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