typescript 35 lines · 6 steps

Provide a Redis client with a NestJS factory

A NestJS module wires a connected Redis client into the DI container using an async factory provider.

Explained by highlit

NestJS Intermediate dependency-injection async-factory redis provider-tokens configuration

1import { Module } from '@nestjs/common';
2import { ConfigModule, ConfigService } from '@nestjs/config';
3import { createClient, RedisClientType } from 'redis';
4 
5export const REDIS_CLIENT = Symbol('REDIS_CLIENT');
6 
7@Module({
8  imports: [ConfigModule],
9  providers: [
10    {
11      provide: REDIS_CLIENT,
12      inject: [ConfigService],
13      useFactory: async (config: ConfigService): Promise<RedisClientType> => {
14        const client: RedisClientType = createClient({
15          url: config.getOrThrow<string>('REDIS_URL'),
16          socket: {
17            connectTimeout: 5_000,
18            reconnectStrategy: (retries) => Math.min(retries * 100, 3_000),
19          },
20        });
21 
22        client.on('error', (err) => {
23          console.error('Redis client error', err);
24        });
25 
26        await client.connect();
27        await client.ping();
28 
29        return client;
30      },
31    },
32  ],
33  exports: [REDIS_CLIENT],
34})
35export class RedisModule {}

01 / 01

STEP 01

Walkthrough

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Three takeaways

1A Symbol injection token gives non-class dependencies a collision-proof identity in the DI container.
2useFactory can be async, letting a provider await connection setup before it becomes available.
3Exporting a provider lets other modules consume the same shared, already-connected instance.

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