The error The script will never generate a response on Cloudflare Workers.

[aiji42]

Issue workflow progress

Progress of the issue based on the Contributor Workflow

• 1. The issue provides a reproduction available on Github, Stackblitz or CodeSandbox

Make sure to fork this template and run yarn generate in the terminal.

Please make sure Mesh package versions under package.json matches yours.

• 2. A failing test has been provided
• 3. A local solution has been provided
• 4. A pull request is pending review

---

Describe the bug

I have deployed and running graphql-mesh on Cloudflare Workers.
When accesses increase, the status 500 error The script will never generate a response is returned at a high frequency.

After investigating the cause, I found it mentioned here that storing a Promise in a global level variable and using it causes the error. This is due to the fact that the Cloudflare Workers runtime is V8 isolate.

Eventually I came to the conclusion that the script (.mesh/index.ts) generated by the mesh build was the cause.

let meshInstance$: Promise<MeshInstance<MeshContext>>;
// ^^^^^^
export function getBuiltMesh(): Promise<MeshInstance<MeshContext>> {
  if (meshInstance$ == null) {
    meshInstance$ = getMeshOptions().then(meshOptions => getMesh<MeshContext>(meshOptions)).then(mesh => {
      const id$ = mesh.pubsub.subscribe('destroy', () => {
        meshInstance$ = undefined;
        id$.then(id => mesh.pubsub.unsubscribe(id)).catch(err => console.error(err));
      });
      return mesh;
    });
  }
  return meshInstance$;
}

My Worker code is as follows.

import { getBuiltMesh } from "../.mesh";
import { createServer } from "@graphql-yoga/common";
import { useDisableIntrospection } from "@envelop/disable-introspection";

export default {
  async fetch(
    request: Request,
    env: Env,
    ctx: ExecutionContext
  ): Promise<Response> {
    const mesh = await getBuiltMesh();
    const server = createServer({
      plugins: mesh.plugins,
      graphiql: {
        endpoint: "/graphql",
      }
    });

    return server.fetch(request);
  },
};

To Reproduce
Steps to reproduce the behavior:

1. Generate .mesh by mesh build.
2. Deploy the above code to Cloudflare Wokers.
3. Access a large amount of data using benchmark tools.

Expected behavior

Expect to be able to access it without error.

Environment:

• @graphql-mesh/cli: 0.75.3
• @graphql-mesh/graphql: 0.29.5
• @graphql-mesh/transform-naming-convention: 0.10.61
• @graphql-mesh/transform-prefix: 0.11.60
• @graphql-yoga/common: 2.12.3
• graphql: 16.5.0
• Runtime: Cloudflare Workers

Additional context

Using DO (Durable Objects) would have solved the problem, but I would like to know if there is a way to get it running stably without using DO.

[samdenty]

I've ran into this and am tracking it here cloudflare/workers-rs#255

[ardatan]

Did you see our example?
https://github.com/Urigo/graphql-mesh/blob/master/examples/cloudflare-workers/src/index.ts#L3

[samdenty]

oh this isn't wasm, nvm then!

[ardatan]

Just checking @samdenty . Your issue has been fixed right?

[alibombaye]

Hello, I'm seeing the same error when running a mesh gateway hosted on cloudflare. We are currently running some load tests to see if it is fit for purpose and occasionally see the same error as mentioned above.

@ardatan I have followed the same as the example and I still get the same.

[ardatan]

Could you create a new issue with a reproduction? Thanks!