Nestjs resolve custom startup dependency - node.js

Question

I have this factory which resolves redis:
import {RedisClient} from "redis";
export const RedisProvider = {
provide: 'RedisToken',
useFactory: async () => {
return new Promise((resolve, reject) => {
let redisClient = new RedisClient({
host: 'resolver_redis'
});
redisClient.on('ready', function () {
resolve(redisClient);
});
});
}
};
But in addition to that, i wanna check if a specific key exists in redis, and if its not i want to retrive it using microservices, but for that i need to inject the microservices "client", i wanna change it to someting like that:
import {RedisClient} from "redis";
export const RedisProvider = {
provide: 'RedisToken',
useFactory: async () => {
return new Promise((resolve, reject) => {
let redisClient = new RedisClient({
host: 'resolver_redis'
});
redisClient.on('ready', async function () {
let campaigns = await redisClient.get('campaigns');
if ( ! campaigns) {
// Note: "client" is not available in this scope
client.send('get:campaigns').subscribe(async function (campaigns) {
await redisClient.set('campaigns', campaigns);
resolve(redisClient);
});
}
else {
resolve(redisClient);
}
});
});
}
};
the only problem is that i dont have access to the "client", or do i?
it can also be anther provider if it makes more sense, but then i will also need priority for loading the providers, i am doing this because the application requires this data for startup stuff

Answer 1

I don't recommend adding more logic in providers factory, since it could be more controlled in the consumer of this provider ie: the services
in your services code you could do something like this
import { Component, Inject, OnModuleInit } from '#nestjs/common';
...
#Component()
export class MyService implements OnModuleInit {
constructor(#Inject(REDIS_TOKEN) private readonly redis: RedisClient) {}
onModuleInit() {
const campaigns = await this.redis.get('campaigns');
...
}
}
I assume that REDIS_TOKEN is constant saved on constants.ts file and equal to RedisToken.
this will be more controlled.
the code of checking for the campaigns key will be executed once your Module init.
for more information about Module Lifecycle checkout: Modules Lifecycle