HonoJs: Best way to start a Twitter SDK connection in Hono with CloudFlare?

Question

In an old-school server environment, you initialize an SDK (like the Twitter SDK) when the server starts up, using dotenv to read secrets and tokens from your .env file like so:

import dotenv from 'dotenv';
import {Client} from 'twitter-api-sdk';

dotenv.config();
const twitterClient = new Client (TWITTER_SECRET_INFO);

And then you would use the twitterClient object to get data in one of the route handlers.

What's the best practice for initializing something like the twitter client in Hono with Cloudflare?

In the old service worker framework, I could have treated the secret info as a global environment variable much like in Node/Express, but in the new module worker code you have to access the environment variables as a parameter passed to a function call. It looks like Hono manages this by passing contexts to methods like .use/.get/.post.

Ideally, though, I wouldn't reinitialize the twitter connection on every request, especially since I'm just getting public info with a token, not dealing with any user login/password info.

Is there any way to do this in Hono/Cloudflare, or do I have to initialize the Twitter client middle ware each request? I looked at the Hono class constructer, but from what I can tell, all it does is take a router config object.

And from what I can tell of the cloudflare docs, module workers have the same issue. Whereas constants in a service worker were declared outside the route handler, it looks like everything in a module worker is declared inside a fetch handler. Is there anyway to initialize once during the life of the worker and not for each request?

Answer 1

In principle you could initialize the client on the first request:

let twitterClient = null;

export default {
  async fetch(req, env, ctx) {
    if (!twitterClient) {
      twitterClient = new Client(env.TWITTER_SECRET_INFO);
    }
    // ... normal code ...
  }
}

That said, though, is creating a new client actually expensive?

Constructing the client does not "initialize a connection". The client presumably makes requests by calling fetch(). The fetch() API doesn't expose any way to control the underlying connections used; each fetch() operates effectively independently. But, the Workers Runtime will automatically reuse connections behind the scenes, when possible. It could even reuse the same connection for two completely unrelated Workers, if they are contacting the same destination host. So it may be that even creating a new client with every request, you're already getting good connection reuse.

That said, perhaps the client has to do some sort of key exchange upfront, e.g. exchanging a long-lived refresh token for an access token. That is annoying to have to repeat on every request. So in that sense, maybe caching it in a global helps.

However, note that Workers creates LOTS of instances of your Worker around the world. You may find if you curl your Worker several times in a row, each request lands on a different instance. You may find that caching in global state does not actually have much impact unless you have a large amount of traffic.

Caching may be more effective if you use the Cache API to store cached values into the colo-wide cache. Unfortunately, client libraries designed for Node environments may not provide the right hooks to do this.

One final note: Note that putting live resources (things that are not just plain data structures) into the global scope can be dangerous on Workers, because in general a Promise created on behalf of one incoming request cannot be awaited in the context of some other request. So if that twitter client does do some sort of upfront key exchange and tries to have all requests wait for that to complete, you may find that if you receive multiple requests at once before the initial key exchange finishes, all except the first request end up failing. To be honest, I would recommend creating a new client for every request unless you see a measurable performance problem from this.