[Bug?]: GraphQL subscription not receiving data with many receivers

[jordanlavenant]

What's not working?

When sending data through a GraphQL subscription with multiple receivers registered (tabs opened on a page listening to the subscription), we observed that some of the tabs don't receive the data.

It appears that it only happens for the sixth and above tab, so we are guessing it is due to a limit to the number of receiver.

It happens both when using in-memory store and redis store

The expected behavior is that all receivers should receive the data correctly.

How do we reproduce the bug?

• Clone the POC
• Start the dev server
• Open tab on the sender page /sender
• Open a dozen tab on the receiver page /receiver
• Send a message
• Observe not all tabs receiving the data

What's your environment? (If it applies)

System:
    OS: Linux 6.8 Ubuntu 24.04.1 LTS 24.04.1 LTS (Noble Numbat)
    Shell: 5.2.21 - /bin/bash
  Binaries:
    Node: 20.16.0 - /tmp/xfs-6054f827/node
    Yarn: 4.4.0 - /tmp/xfs-6054f827/yarn
  npmPackages:
    @redwoodjs/core: 8.4.1 => 8.4.1 
    @redwoodjs/project-config: 8.4.1 => 8.4.1 
  redwood.toml:
    [web]
      title = "Redwood App"
      port = 8910
      apiUrl = "/.redwood/functions" # You can customize graphql and dbauth urls individually too: see https://redwoodjs.com/docs/app-configuration-redwood-toml#api-paths
      includeEnvironmentVariables = [
        # Add any ENV vars that should be available to the web side to this array
        # See https://redwoodjs.com/docs/environment-variables#web
      ]
    [api]
      port = 8911
    [browser]
      open = true
    [notifications]
      versionUpdates = ["latest"]

Are you interested in working on this?

• I'm interested in working on this