R2 example

This tutorial builds a Worker that stores an object in a memory R2 bucket and returns the body on GET.

Prerequisites

• Install Peren so peren is on your PATH
• An empty project directory

Create the files

Create worker.js:

export default {
  async fetch(request, env) {
    const key = new URL(request.url).pathname.slice(1) || "message";
    if (request.method === "PUT") {
      await env.BUCKET.put(key, request.body, {
        customMetadata: { uploadedBy: "example" },
      });
      return new Response(null, { status: 204 });
    }
    const object = await env.BUCKET.get(key);
    if (object === null) {
      return Response.json(
        { provider: env.BUCKET.provider.kind, found: false },
        { status: 404 },
      );
    }
    return new Response(object.body, {
      headers: {
        "x-peren-r2-provider": env.BUCKET.provider.kind,
        "x-peren-r2-owner": object.customMetadata.uploadedBy ?? "",
      },
    });
  },
};

Create peren.toml:

[node]
node_id = "00000000-0000-0000-0000-000000000001"
advertise_addr = "127.0.0.1:7000"
listen = "127.0.0.1:7000"

[bucket]
kind = "memory"

[mtls]
ca_cert_path = "./certs/ca.pem"
leaf_cert_path = "./certs/leaf-cert.pem"
leaf_key_path = "./certs/leaf-key.pem"

[[services]]
name = "api"
worker_bundle_path = "worker.js"
compatibility_date = "2026-01-01"

[services.bindings.BUCKET]
type = "r2_bucket"
endpoint = "memory://demo"
bucket = "demo"
credential_scope = "demo"

[[sockets]]
name = "public"
listen = "127.0.0.1:8080"
service = "api"

An endpoint that starts with memory:// uses an in-process store. No access keys are required.

Run

peren devcert ./certs
peren dev peren.toml

peren dev binds loopback listeners on port 0 and uses a memory bucket for the session. Call the public: URL it prints. 54321 below stands for that port.

curl -X PUT http://127.0.0.1:54321/message --data "hello"
curl -i http://127.0.0.1:54321/message

PUT returns status 204 with an empty body. GET returns body hello with headers that include x-peren-r2-provider: memory and x-peren-r2-owner: example. Memory objects do not survive process restart.

Failure

A GET for a key that was never stored returns status 404 and:

{"provider":"memory","found":false}

Put the object first, or correct the path segment used as the key.

Next

S3 credentials, list and delete, and provider differences: R2.