Merge pull request #1921 from meeech/prisma-recipe-fix

Prisma recipe fix

Author: kamilmysliwiec

content/recipes/prisma.md

@@ -247,22 +247,27 @@ When setting up your NestJS application, you'll want to abstract away the Prisma
 Inside the `src` directory, create a new file called `prisma.service.ts` and add the following code to it:
 
 ```typescript
-import { Injectable, OnModuleInit, OnModuleDestroy } from '@nestjs/common';
+import { INestApplication, Injectable, OnModuleInit, OnModuleDestroy } from '@nestjs/common';
 import { PrismaClient } from '@prisma/client';
 
 @Injectable()
 export class PrismaService extends PrismaClient
-  implements OnModuleInit, OnModuleDestroy {
+  implements OnModuleInit {
+
   async onModuleInit() {
     await this.$connect();
   }
 
-  async onModuleDestroy() {
-    await this.$disconnect();
+  async enableShutdownHooks(app: INestApplication) {
+    this.$on('beforeExit', async () => {
+      await app.close();
+    });    
   }
 }
 ```
 
+> info **Note** The `onModuleInit` is optional — if you leave it out, Prisma will connect lazily on its first call to the database. We don't bother with `onModuleDestroy`, since Prisma has its own shutdown hooks where it will destroy the connection. For more info on `enableShutdownHooks`, please see [Issues with `enableShutdownHooks`](#issues-with-enableShutdownHooks)
+
 Next, you can write services that you can use to make database calls for the `User` and `Post` models from your Prisma schema.
 
 Still inside the `src` directory, create a new file called `user.service.ts` and add the following code to it:
@@ -516,6 +521,25 @@ This controller implements the following routes:
 
 - `/post/:id`: Delete a post by its `id`
 
+#### Issues with `enableShutdownHooks`
+
+Prisma interferes with NestJS `enableShutdownHooks`. Prisma listens for shutdown signals and will call `process.exit()` before your application shutdown hooks fire. To deal with this, you would need to add a listener for Prisma `beforeExit` event.
+
+```typescript
+// main.ts
+...
+import { PrismaService } from './services/prisma/prisma.service';
+...
+bootstrap() {
+  ...
+  const prismaService: PrismaService = app.get(PrismaService);
+  prismaService.enableShutdownHooks(app)
+  ...
+}
+```
+
+You can [read more](https://github.com/prisma/prisma/issues/2917#issuecomment-708340112) about Prisma handling of shutdown signal, and `beforeExit` event.
+
 #### Summary
 
 In this recipe, you learned how to use Prisma along with NestJS to implement a REST API. The controller that implements the routes of the API is calling a `PrismaService` which in turn uses Prisma Client to send queries to a database to fulfill the data needs of incoming requests.