How to best handle long-running servers that reuse connections across requests?

[psteinroe]

Hey,

I am migrating a hono service from cf workers to a node service and need to replace something that was a simple http request before with multiple Redis connections. I am wondering what's the cleanest and most idiomatic way is. My current approach is simply declaring a variable outside of the handler and on first request initialise it. Its then passed to the context as usual.

let fnClient: FunctionsClient;

const app = new Hono<Env>();

app.use((c, next) => {
	if (!fnClient) {
		fnClient = new FunctionsClient({
			host: env("REDIS_HOST"),
			port: env("REDIS_PORT"),
		});
	}

	c.set("services", {
		logger,
		fnClient,
	});

	return next();
});

This feels a big sluggish for me. Is there a better way?

[maou-shonen]

I guess you're looking for something like this.

hono.js middleware can also be dependency injection!

import { Hono } from "hono"
import { createMiddleware } from "hono/factory"
import { Redis } from "ioredis"

const redisUrls = {
  default: "redis://127.0.0.1:6379",
  test1: "redis://127.0.0.1:16379",
  test2: "redis://127.0.0.1:26380",
}

type RedisKey = keyof typeof redisUrls

const clients = new Map<RedisKey, Redis>()

const useRedis = <ContextKey extends string = "redis">(
  redisKey: RedisKey,
  contextKey?: ContextKey,
) => {
  type Env = {
    Variables: {
      [key in ContextKey]: Redis
    }
  }

  contextKey ??= "redis" as ContextKey

  return createMiddleware<Env>(async (c, next) => {
    if (!clients.has(redisKey)) {
      const redisUrl = redisUrls[redisKey]
      clients.set(redisKey, new Redis(redisUrl))
    }

    const redis = clients.get(redisKey)!
    c.set(contextKey, redis)

    await next()
  })
}

const app = new Hono()
  .get("/", useRedis("default"), async (c) => {
    const redis = c.get("redis") // redis://127.0.0.1:6379
    return c.text("")
  })
  .get("/foo", useRedis("test1"), async (c) => {
    const redis = c.get("redis") // redis://127.0.0.1:16379
    return c.text("")
  })
  .get(
    "/multi",
    useRedis("test1", "redis1"),
    useRedis("test2", "redis2"),
    async (c) => {
      const redis1 = c.get("redis1") // redis://127.0.0.1:16380
      const redis2 = c.get("redis2") // redis://127.0.0.1:26380
      return c.text("")
    },
  )