Absinthe: Subscription documents resolve based on incorrect context

[davidye]

Environment

• Elixir version (elixir -v): 1.6.2
• Absinthe version (mix deps | grep absinthe): 1.4.9
• Client Framework and version (Relay, Apollo, etc): Relay

Expected behavior

My schema has a room node that contains a user field. This field resolves to the current user based on context.user_id.

When multiple clients with unique context.user_id values subscribe to a room_update subscription, and a mutation triggers the subscription publication, each client should receive a different value for the user field.

Actual behavior

Each client receives the same value for the user field. When logging the context in the user field resolver, context.user_id is the same for each client.

Note: In the case where the subscription is published to only one client, the user field does resolve correctly.

[davidye]

I've created a repo for this issue based off absinthe-tutorial: https://github.com/davidye/absinthe_tutorial

Steps

1. Run the app and load http://localhost:4000/api/graphiql
2. Set URL as http://localhost:4000/api
3. Set WS URL as ws://localhost:4000/socket
4. Run two or more subscriptions

subscription {
  roomUpdated(name:"absinthe") {
    name
    random
  }
}

5) Run this mutation

mutation {
  updateRoom(name:"absinthe") {
    name
    random
  }
}

Expected

Each subscription is assigned a random value in its context: https://github.com/davidye/absinthe_tutorial/blob/master/lib/blog_web/channels/user_socket.ex#L24-L26

Room query resolves room.random from context: https://github.com/davidye/absinthe_tutorial/blob/master/lib/blog_web/resolvers/rooms.ex#L11-L16

When the mutation is run, each subscription should return a different value for roomUpdated.random

Actual

When the mutation is run, each subscription receives the same value for roomUpdated.random

[benwilson512]

Thanks for the example, I've confirmed the issue and am investigating now.

[davidye]

Seems like the issue is in BatchResolver, I was able to fix it locally by setting this line: https://github.com/absinthe-graphql/absinthe/blob/266728e8a78c6d2fb6f14bf03740e92b2c393e99/lib/absinthe/pipeline/batch_resolver.ex#L21 to

  context: nil

And removing references to ctx in that file.

[benwilson512]

Yeah, this is a product of an effort to try to get dataloader to work across multiple document sets. In the short term I think I can go one step up and group the documents by those with equivalent contexts, and then pass those groups in to the batch resolver one at a time. This should prevent contexts from leaking.

[benwilson512]

See https://github.com/absinthe-graphql/absinthe/pull/529

[samsondav]

This issue is affecting us too, currently blocking a feature we need. LMK if there's anything I can do to help :)

[benwilson512]

Fixed in Absinthe v1.4.10

[samsondav]

❤️ 💚 💙 💛