Using extension packages (read replica)

[MorenoMdz]

First, thanks for the solid work here!

I would like to see if it is already possible to use this service with read replicas and or see if it would be possible to add support for this extension.

https://github.com/prisma/extension-read-replicas

Thank you!

[marcjulian]

Hi @MorenoMdz, this is already possible with Prisma Client Extension. I have added it to the Extensions Example.

nestjs-prisma/examples/extensions/src/prisma.extension.ts

Lines 1 to 38 in 407de1b

	import { Prisma, PrismaClient } from '@prisma/client';
	// used for Read Replicas example
	import { readReplicas } from '@prisma/extension-read-replicas';
	export const extendedPrismaClient = new PrismaClient<
	Prisma.PrismaClientOptions,
	'query' | 'info' | 'warn' | 'error'
	>({
	log: [
	{ level: 'query', emit: 'event' },
	{ level: 'info', emit: 'event' },
	{ level: 'warn', emit: 'event' },
	{ level: 'error', emit: 'event' },
	],
	})
	// FIXME - `$on()` returns void
	// .$on('error', (e) => {})
	.$extends({
	model: {
	user: {
	findByEmail: async (email: string) => {
	console.log('extension findByEmail');
	return extendedPrismaClient.user.findFirstOrThrow({
	where: { email },
	});
	},
	},
	},
	})
	// Read Replicas example, change datasource prodiver (prisma/schema.prisma) to a supported database
	// More details in the blog - https://www.prisma.io/blog/read-replicas-prisma-client-extension-f66prwk56wow
	// .$extends(
	// readReplicas({
	// url: 'postgres://localhost:5432/prisma',
	// }),
	// );
	export type extendedPrismaClient = typeof extendedPrismaClient;

Let me know if this helps you. I will add a section to the docs too.

[marcjulian]

Checkout the new section for Read Replica in the docs.

[MorenoMdz]

This is great, I will give it a shot today, thanks again @marcjulian !

[MorenoMdz]

@marcjulian I might have to redo our setup, currently we have a PrismaConfigService.ts which we inject in all our services:

import { Injectable } from '@nestjs/common'
import { ConfigService } from '@nestjs/config'
import { PrismaOptionsFactory, PrismaServiceOptions } from 'nestjs-prisma'
import { getEnvironment, isProduction, isDevelopment } from './utils'

@Injectable()
export class PrismaConfigService implements PrismaOptionsFactory {
  constructor(private configService: ConfigService) {}

  createPrismaOptions(): PrismaServiceOptions | Promise<PrismaServiceOptions> {
    const environment = getEnvironment()
    const isProd = environment === 'production'
    const urlSuffix = isProduction()
      ? '_PROD'
      : // When running locally, and we want to use the DEV database
      isDevelopment() || process.env.FIREBASE_ENV === 'DEV'
      ? '_DEV'
      : ''
    const DB_URL = this.configService.get(`DATABASE_URL${urlSuffix}`)

    return {
      prismaOptions: {
        log: isProd ? undefined : ['info', 'query'],
        datasources: {
          db: {
            url: DB_URL,
          },
        },
      },
      explicitConnect: this.configService.get('DB_EXPLICIT_CONNECT') || false,
    }
  }
}

And then the app.module is initialized like this:

... 
imports: [
    PrismaModule.forRootAsync({
      isGlobal: true,
      useClass: PrismaConfigService,
    }),
    ...
    ]

Should I just redo the setup and or try to plug in the extensions on top of this at the App.module imports section?

[marcjulian]

You will need to use CustomPrismaModule instead of PrismaModule. The reason is, that PrismaModule provides PrismaService which is extended by the default PrismaClient and it cannot be used together with $extends.

Use CustomPrismaModule and inject your ConfigService which you can access in the factory method and pass any options directly to your PrismaClient instance.

import { Module } from '@nestjs/common';
import { CustomPrismaModule } from 'nestjs-prisma';
import { AppController } from './app.controller';
import { AppService } from './app.service';
import { extendedPrismaClient } from './prisma.extension';

@Module({
  imports: [
    CustomPrismaModule.forRootAsync({
      name: 'PrismaService',
      useFactory: (config: ConfigService) => {
        const options = {};
        return extendedPrismaClient(options);
      },
      inject: [ConfigService],
      // import ConfigModule when `isGlobal` not true
      // imports: [ConfigModule],
    }),
    ConfigModule.forRoot({
      isGlobal: true,
    }),
  ],
  controllers: [AppController],
  providers: [AppService],
})
export class AppModule {}

import { Prisma, PrismaClient } from '@prisma/client';
// used for Read Replicas example
import { readReplicas } from '@prisma/extension-read-replicas';

// add more parameters like read replicas urls
export const extendedPrismaClient = (options?: Prisma.PrismaClientOptions, ...) =>
  new PrismaClient<
    Prisma.PrismaClientOptions,
    'query' | 'info' | 'warn' | 'error'
  >(options)
// .$extends(
//   readReplicas({
//     url: 'postgres://localhost:5432/prisma',
//   }),
// );

// add ReturnType because extendedPrismaClient is now a function
export type extendedPrismaClient = ReturnType<typeof extendedPrismaClient>;

Let me know if that helps. I might need to update the docs to make it more clear to use CustomPrismaModule and CustomPrismaService when using $extends.

[MorenoMdz]

Thanks again for the response. I am still not sure I get how to configure this with our current setup.

1. Do I keep the current PrismaConfigService file that is creating the Prisma client options as well as defining the DB_URL? If so, ideally we want to define the read replica URL here too instead of at the extension file. What I am not sure is when using an extension, where do we configure the base Prisma settings? Would I have the setup in all three places, the PrismaConfigService, App module, and the new Prisma extension file?

2. Do I have to change all places that are currently loading the PrismaService to access the db to use CustomPrismaService<extendedPrismaClient> instead? Seems very verbose, shouldn't PrismaService already access the instance of the custom service everywhere?

Also, the way we have been injecting the Prisma service in our services is like private prisma: PrismaService I would assume that @Inject('PrismaService') is the same?

[marcjulian]

To clear it up a bit more.

PrismaModule and PrismaService

1. PrismaService has only access to the default PrismaClient, it does not work with $extends at all.
   Because PrismaService extends PrismaClient, the PrismaClient is created and it cannot be $extends further.

import { Inject, Injectable, Optional } from '@nestjs/common';
import { PrismaClient } from '@prisma/client';
import { PrismaServiceOptions } from './interfaces';
import { PRISMA_SERVICE_OPTIONS } from './prisma.constants';

@Injectable()
export class PrismaService extends PrismaClient {
  constructor(
    @Optional()
    @Inject(PRISMA_SERVICE_OPTIONS)
    private readonly prismaServiceOptions: PrismaServiceOptions = {},
  ) {
    super(prismaServiceOptions.prismaOptions);

    ...
  }
 
  ...
}

2. PrismaModule allows passing options to the PrismaClient via forRoot or forRootAsync. forRootAsync allows to pass a config class e.g. PrismaConfigService
3. Use PrismaService to access the database

CustomPrismaModule and CustomPrismaService

1. Use CustomPrismaModule and CustomPrismaService when you need to use $extends(...)

import { PrismaClientLike } from './custom-prisma-options';
import { Inject, Injectable } from '@nestjs/common';
import { CUSTOM_PRISMA_CLIENT } from './custom-prisma.constants';

@Injectable()
export class CustomPrismaService<Client extends PrismaClientLike> {
  constructor(
    @Inject(CUSTOM_PRISMA_CLIENT)
    public client: Client,
  ) {}
}

CustomPrismaService gives you access to your extended PrismaClient.

2. You have access to the PrismaClient instance directly and you can pass your options to it new PrismaClient(YOUR_OPTIONS)
3. Use CustomPrismaService to access the database
4. You can provide a config class to CustomPrismaModule

import { ExtendedPrismaConfigService } from './extended-prisma-config.service';

// app.module.ts
CustomPrismaModule.forRootAsync({
      name: 'PrismaService',
      useClass: ExtendedPrismaConfigService,
})


// extended-prisma-config.service.ts
import { Injectable } from '@nestjs/common';
import { CustomPrismaClientFactory } from 'nestjs-prisma';
import { extendedPrismaClient } from './prisma.extension';

@Injectable()
export class ExtendedPrismaConfigService
  implements CustomPrismaClientFactory<extendedPrismaClient>
{
  constructor() {
    // inject config service here
  }

  createPrismaClient(): extendedPrismaClient {
    return extendedPrismaClient;
  }
}

❌ CustomPrismaModule does not provide the extended PrismaClient for PrismaService, you must use CustomPrismaService

I will move this into a discussion as this might help others too.