How to manage configuration in NestJS with configmodule?

Configuration Management in NestJS

NestJS provides @nestjs/config — a module that loads environment variables from .env files and exposes them via a type-safe ConfigService.

Setup

bash

npm install @nestjs/config

typescript

// app.module.ts
import { ConfigModule } from '@nestjs/config';

@Module({
  imports: [
    ConfigModule.forRoot({
      isGlobal: true,     // no need to import in every module
      envFilePath: '.env',
      cache: true,        // cache values for performance
    }),
  ],
})
export class AppModule {}

Using ConfigService

typescript

import { Injectable } from '@nestjs/common';
import { ConfigService } from '@nestjs/config';

@Injectable()
export class DatabaseService {
  constructor(private configService: ConfigService) {}

  getConnectionString(): string {
    const host = this.configService.get<string>('DB_HOST');
    const port = this.configService.get<number>('DB_PORT', 5432); // default 5432
    const name = this.configService.get<string>('DB_NAME');
    return `postgres://${host}:${port}/${name}`;
  }
}

Typed Configuration (Namespaced)

typescript

// config/database.config.ts
import { registerAs } from '@nestjs/config';

export default registerAs('database', () => ({
  host: process.env.DB_HOST || 'localhost',
  port: parseInt(process.env.DB_PORT || '5432', 10),
  name: process.env.DB_NAME || 'mydb',
  password: process.env.DB_PASS,
}));

// app.module.ts
import databaseConfig from './config/database.config';

ConfigModule.forRoot({
  isGlobal: true,
  load: [databaseConfig],
})

// Usage:
const dbHost = this.configService.get<string>('database.host');
const dbPort = this.configService.get<number>('database.port');

Environment Validation with Joi

bash

npm install joi

typescript

import * as Joi from 'joi';

ConfigModule.forRoot({
  isGlobal: true,
  validationSchema: Joi.object({
    NODE_ENV: Joi.string().valid('development', 'production', 'test').required(),
    PORT: Joi.number().default(3000),
    DB_HOST: Joi.string().required(),
    DB_PORT: Joi.number().default(5432),
    DB_USER: Joi.string().required(),
    DB_PASS: Joi.string().required(),
    DB_NAME: Joi.string().required(),
    JWT_SECRET: Joi.string().min(32).required(),
  }),
  validationOptions: {
    allowUnknown: true,
    abortEarly: false, // show all errors at once
  },
})

If validation fails, the app refuses to start — catching missing env vars early.

Using Config in forRoot() (e.g., TypeORM)

typescript

TypeOrmModule.forRootAsync({
  imports: [ConfigModule],
  useFactory: (config: ConfigService) => ({
    type: 'postgres',
    host: config.get('DB_HOST'),
    port: config.get<number>('DB_PORT'),
    username: config.get('DB_USER'),
    password: config.get('DB_PASS'),
    database: config.get('DB_NAME'),
    autoLoadEntities: true,
    synchronize: config.get('NODE_ENV') !== 'production',
  }),
  inject: [ConfigService],
})

Multiple .env Files

typescript

ConfigModule.forRoot({
  envFilePath: [
    `.env.${process.env.NODE_ENV}.local`,
    `.env.${process.env.NODE_ENV}`,
    '.env.local',
    '.env',
  ],
})

Use ConfigModule.forRoot({ isGlobal: true }) to load .env once and make ConfigService available everywhere. Add validationSchema with Joi to validate required variables at startup. Use registerAs() for typed, namespaced config objects.

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