Description

pgkit module for Nest.

Contents

• nestjs-pgkit
  • Installation
  • Basic import
  • Multiple databases
  • Async configuration
  • License

Installation

npm

npm i --save nestjs-pgkit @pgkit/client

yarn

yarn add nestjs-pgkit @pgkit/client

Basic import

Once the installation process is complete, we can import the PgKitModule into the root AppModule.

app.module.ts

import { Module } from "@nestjs/common";
import { PgKitModule } from "nestjs-pgkit";

@Module({
  imports: [
    PgKitModule.forRoot({
      connectionUri: "postgres://user:password@localhost:5432/test",
    }),
  ],
})
export class AppModule {}

The forRoot() method supports configuration properties described below.

PgKit options
connectionUri	Connection URI
PgKitModule options
name	Connection client name. Used to inject different db connections (default: default)
toRetry	Function that determines whether the module should attempt to connect upon failure (err: any) => boolean err parameter is error that was thrown
verboseRetryLog	If true, will show verbose error messages on each connection retry (default: false)
retryAttempts	Number of attempts to connect to the database (default: 10)
retryDelay	Delay between connection retry attempts (ms) (default: 3000)

Once this is done, the pgkit client will be available to inject across the entire project (without needing to import any modules), for example:

app.service.ts

import { Injectable } from "@nestjs/common";

import { Client, sql } from "@pgkit/client";
import { InjectClient } from "nestjs-pgkit";

@Injectable()
export class AppService {
  constructor(
    @InjectClient()
    private readonly client: Client,
  ) {}

  getGreeting(): Promise<string> {
    return this.client.oneFirst<string>(sql`SELECT 'Hello World!';`);
  }
}

Multiple databases

Some projects require multiple database connections. This can also be achieved with this module. To work with multiple clients, first create the clients. In this case, client naming becomes mandatory.

@Module({
  imports: [
    PgKitModule.forRoot({
      connectionUri: "postgres://user:password@users_db_host:5432/users",
    }),
    PgKitModule.forRoot({
      name: "ALBUMS_CLIENT",
      connectionUri: "postgres://user:password@albums_db_host:5432/albums",
    }),
  ],
})
export class AppModule {}

Notice If you don't set the name for a client, its name is set to default. Please note that you shouldn't have multiple clients without a name, or with the same name, otherwise they will get overridden.

Now you can inject the pgkit client for a given client name:

@Injectable()
export class AlbumsService {
  constructor(
    @InjectClient()
    private usersClient: Client,
    @InjectClient("ALBUMS_CLIENT")
    private albumsClient: Client,
  ) {}
}

Async configuration

You may want to pass your PgKitModule options asynchronously instead of statically. In this case, use the forRootAsync() method, which provides several ways to deal with async configuration.

One approach is to use a factory function:

PgKitModule.forRootAsync({
  useFactory: () => ({
    connectionUri: "postgres://user:password@users_db_host:5432/users",
  }),
});

Our factory behaves like any other asynchronous provider (e.g., it can be async and it's able to inject dependencies through inject).

PgKitModule.forRootAsync({
  imports: [ConfigModule],
  useFactory: (configService: ConfigService) => ({
    connectionUri: configService.get("DATABASE_URL"),
  }),
  inject: [ConfigService],
});

Alternatively, you can use the useClass syntax:

PgKitModule.forRootAsync({
  useClass: PgKitConfigService,
});

The construction above will instantiate PgKitConfigService inside PgKitModule and use it to provide an options object by calling createPgKitOptions(). Note that this means that the PgKitConfigService has to implement the PgKitOptionsFactory interface, as shown below:

@Injectable()
class PgKitConfigService implements PgKitOptionsFactory {
  createPgKitOptions(): PgKitModuleOptions {
    return {
      connectionUri: "postgres://user:password@users_db_host:5432/users",
    };
  }
}

In order to prevent the creation of PgKitConfigService inside PgKitModule and use a provider imported from a different module, you can use the useExisting syntax.

PgKitModule.forRootAsync({
  imports: [ConfigModule],
  useExisting: ConfigService,
});

This construction works the same as useClass with one critical difference - PgKitModule will lookup imported modules to reuse an existing ConfigService instead of instantiating a new one.

Make sure that the name property is defined at the same level as the useFactory, useClass, or useValue property. This will allow Nest to properly register the pool under the appropriate injection token.

PgKitModule.forRootAsync({
  name: "ALBUMS_CLIENT",
  useFactory: () => ({
    connectionUri: postgresConnectionUri,
  }),
})

MIT license