NestJS - How to use .env variables in main app module file for database connection

Question

I am working on my first NestJS application, which was working fine with hardcoded database connecting string in app.module.ts.

But then as per our requirements, I had to pick the database config values from environment files. For that, I followed the configuration documentation on the nestjs documentation website - https://docs.nestjs.com/techniques/configuration

But the issue is that I need to use the .env variables inside the same file for database connection, which is failing.

Here is my original code that was working fine:

@Module({   imports: [     MongooseModule.forRoot(`mongodb+srv://myusername:[email protected]?retryWrites=true&w=majority&db=dbname`, { useNewUrlParser: true, dbName: 'dbname' }),     ProductModule,     CategoryModule,   ],   controllers: [     AppController,     HealthCheckController,   ],   providers: [AppService, CustomLogger], }) 

Now, I wanted to pick those DB values from .env files which are like local.env, dev.env etc. depending on the environment. Now, my this code is not working:

@Module({   imports: [     ConfigModule.forRoot({ envFilePath: `${process.env.NODE_ENV}.env` }),     MongooseModule.forRoot(`mongodb+srv://${ConfigModule.get('DB_USER')}:${ConfigModule.get('DB_PASS')}@myhost.net?retryWrites=true&w=majority&db=dbname`, { useNewUrlParser: true, dbName: 'dbname' }),     ProductModule,     CategoryModule,   ],   controllers: [     AppController,     HealthCheckController,   ],   providers: [AppService, CustomLogger], }) 

Answer 1

From Nestjs docs here - https://docs.nestjs.com/techniques/configuration

These steps worked for me with MySQL and TypeORM.

1. Install Nestjs config module - npm i --save @nestjs/config. It relies on dotenv

2. Create a .env file in your root folder and add your key/value pairs e.g. DATABASE_USER=myusername

3. Open app.module.ts and import the config module

    import { ConfigModule } from '@nestjs/config'; 

4. Add below line to the imports section of app.module.ts. I added it a the first import. It will load the contents of the .env file automatically.

    ConfigModule.forRoot(), 

5. Then you can begin to use the env variables as per the usual process.env.<variable_name> in the database config section e.g.

    process.env.DATABASE_USER 

For more configuration of the ConfigModule, see the link above. You can use a custom file/path and set the module visible globally.

Answer 2

1. Keeping using ConfigModule

You need to set NODE_ENV in npm scripts so that it can be used to load an env file based on the env.

"scripts": {   "start:local": "NODE_ENV=local npm run start"   "start:dev": "NODE_ENV=dev npm run start" } 

Now you can just use the ConfigModule:

@Module({   imports: [     ConfigModule.forRoot({ envFilePath: `${process.env.NODE_ENV}.env` }),  MongooseModule.forRoot(`mongodb+srv://${process.env.DB_USER}:${process.env.DB_PASS}@myhost.net?retryWrites=true&w=majority&db=dbname`, { useNewUrlParser: true, dbName: 'dbname' })     ... }) 

2. Using dotenv

npm install dotenv 

Add some scripts to your package.json to set what env you are in.

"scripts": {   ...   "start:local": "NODE_ENV=local npm run start"   "start:dev": "NODE_ENV=dev npm run start" } 

Import dotenv in main.ts file. Make sure you do it at the top of the file.

require('dotenv').config({ path: `../${process.env.NODE_ENV}.env` }); 

3. Using env-cmd

You can use env-cmd npm package.

npm install env-cmd 

And add some commands for different envs in package.json, for example:

"scripts": {   ...   "start:local": "env-cmd -f local.env npm run start"   "start:dev": "env-cmd -f dev.env npm run start" } ... 

---

Now you can use the env variables, for example:

MongooseModule.forRoot(`mongodb+srv://${process.env.DB_USER}:${process.env.DB_PASS}@myhost.net?retryWrites=true&w=majority&db=dbname`, { useNewUrlParser: true, dbName: 'dbname' }) 

process.env.MONGO_CONNECTION_STRING