Franco Romano Losada Comments

Franco Romano Losada

•Created by Franco Romano Losada on 4/9/2025 in #workers-help

Reusing DB instance with process.env

Cloudflare Workers are designed to be super fast and lightweight. So when possible, they reuse the same isolate (kind of like a lightweight V8 sandbox) between requests. That means top-level variables can persist between invocations, but you should not rely on them for request-specific logic or state, especially for I/O objects. 🧠 What’s Really Going On in Cloudflare Workers When you do something like: let db; export function initDb() { db = drizzle(...); } You’re creating a shared global variable. And while it may seem isolated per request in theory, Cloudflare does reuse the execution context between requests when it can.

Okay, is this is what you mean I get it now 😄

17 replies

CDCloudflare Developers

•Created by Franco Romano Losada on 4/9/2025 in #workers-help

Reusing DB instance with process.env

But that means memory is shared across requests?

17 replies

CDCloudflare Developers

•Created by Franco Romano Losada on 4/9/2025 in #workers-help

Reusing DB instance with process.env

Do you mind explaining to me why this doesn't work?

import { drizzle } from "drizzle-orm/postgres-js";
import postgres from "postgres";

import * as schema from "./schema";

export type DBClient = ReturnType<typeof drizzle<typeof schema>>;

let db: DBClient;

export function initDb(
  connectionString: string,
) {
  if (!connectionString) {
    throw new Error("No connection string provided");
  }

  const queryClient = postgres(connectionString);
  db = drizzle({
    client: queryClient,
    schema,
    logger: false,
    casing: "snake_case",
  });

  return db;
}

export { db, schema };

import { drizzle } from "drizzle-orm/postgres-js";
import postgres from "postgres";

import * as schema from "./schema";

export type DBClient = ReturnType<typeof drizzle<typeof schema>>;

let db: DBClient;

export function initDb(
  connectionString: string,
) {
  if (!connectionString) {
    throw new Error("No connection string provided");
  }

  const queryClient = postgres(connectionString);
  db = drizzle({
    client: queryClient,
    schema,
    logger: false,
    casing: "snake_case",
  });

  return db;
}

export { db, schema };

Where initDb is called in a middleware, before anything imports the db. Why the console yields:

Error: Cannot perform I/O on behalf of a different request. I/O objects (such as streams, request/response bodies, and others) created in the context of one request handler cannot be accessed from a different request’s handler. This is a limitation of Cloudflare Workers which allows us to improve overall performance.

From my POV, I'm building the db client once in the middleware and then importing it where its used. This would make working with workers much better. I mean, it works but sometimes it breaks when two requests to the server are done almost at the same time. I thought that a worker is a traditional serverless instance, where the files are initiated by request. So, the first request runs middleware and initiates the db for that specific worker, then different files imports it and the next requests do the same thing, like isolated code. req -> middleware creates db connection -> file imports it -> res | -> req -> middleware creates db connection -> file imports it -> res | same

17 replies

CDCloudflare Developers

•Created by Franco Romano Losada on 4/9/2025 in #workers-help

Reusing DB instance with process.env

Thats better, thank you

17 replies

CDCloudflare Developers

•Created by Franco Romano Losada on 4/9/2025 in #workers-help

Reusing DB instance with process.env

Mmm yes, Im usingn it. Maybe I didn’t explain myself well. I want to create the connection once and then import the db in any place as clean as possible without having to pass the created instance all over the places. im not sure this solves that without caching the output of the function

17 replies

CDCloudflare Developers

•Created by Franco Romano Losada on 4/9/2025 in #workers-help

Reusing DB instance with process.env

Thanks a ton. Im wondering, do you do something under the hood with the connection? Or should I memoize it?

17 replies

CDCloudflare Developers

•Created by Franco Romano Losada on 4/9/2025 in #workers-help

Reusing DB instance with process.env

Thanks

17 replies

CDCloudflare Developers

•Created by Franco Romano Losada on 4/9/2025 in #workers-help

Reusing DB instance with process.env

But that means that I have to pass it around or calling the func is enough?

17 replies

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