NestJS Prisma: start application even if prisma can't connect to database

Question

I'm trying to prevent prisma from from shutting my app down even if it fails to connect to the database, so that my health-check endpoint can still be reached. The error I get is this:

          throw new PrismaClientInitializationError(error2.message, this.config.clientVersion, error2.error_code);
                ^
Error: Can't reach database server at `postgres`:`5432`

Please make sure your database server is running at `postgres`:`5432`.
    at startFn (/home/my_name/my_folder/my-service/node_modules/@prisma/client/runtime/index.js:27186:17)
    at Proxy.onModuleInit (/home/my_name/my_folder/my-service/src/services/prisma.ts:12:5)

which makes sense, because my database is shut off. But this crashes my nest application. The prisma docs say that the PrismaClientInitializationError is returned whenprisma.$connect runs, or if a query is run.

The obvious solution to me was to wrap this.$connect with a try catch to prevent it from crashing and burning. So here is my attempt in my PrismaService - the file that the error above is complaining about my-service/src/services/prisma:

import { INestApplication, Injectable, OnModuleInit } from '@nestjs/common';
import { PrismaClient, Prisma } from '@prisma/client';

@Injectable()
export class PrismaService
  extends PrismaClient<Prisma.PrismaClientOptions, 'query' | 'error'>
  implements OnModuleInit
{
  constructor() {
    try {
      super();
    } catch (e) {
      console.log(e);
    }
  }
  async onModuleInit() {
    this.$on('error', (event) => {
      console.log(event.target);
    });
    try {
      await this.$connect();
    } catch (e) {
      console.log(e);
    }
  }

  async enableShutdownHooks(app: INestApplication) {
    this.$on('beforeExit', async () => {
      await app.close();
    });
  }
}

It's littered with console logs, and none of them log anything to the console. In fact, I found that even if I delete this.$connect if my database is up and running then prisma still connects to the database. If my database is not running I still get the same error message as above.

My question is, where do I need to put a try catch in order to prevent prisma from breaking my app?

And to satisfy my curiosity, why is the prisma client seemingly initializing itself even if I don't run this.$connect

Answer 1

This issue has seemingly resolved itself. and my error handling now works. I'm suspecting that because I was using docker compose with mounted volumes some sort of caching was getting in the way and not registering that I had put a try/catch there