Some subscriptions remain open after a websocket has been closed

[andreasdamm-shure]

Expected Behaviour
When a client closes a websocket then all subscriptions (i.e. async iterables) on the server side need to have their return method called (if defined) regardless of whether the client sent an unsubscribe message before closing the websocket.

Actual Behaviour
Some subscriptions remain open on the server after the websocket has been closed.

Debug Information
When a subscription request is received, the asynchronous subscribe resolver of the executable schema is ultimately called.

graphql-ws/src/server.ts

Line 797 in e2603be

const maybeResult = await onOperation?.(

Once the returned promise is resolved a subscription entry is made in ctx.subscriptions.

graphql-ws/src/server.ts

Line 812 in e2603be

ctx.subscriptions[id] = operationResult;

If the promise is resolved after the websocket close handler has been called the an entry is still made in ctx.subscriptions and its return method will never be called.

Depending on the subscription object leakage of memory and resources can ensue.

Further Information
Here is an example program: post-close-subscription-bug.zip

Run yarn install followed by yarn start and open a browser window for http://localhost:4000/graphql. Start a subscription in that window :--

subscription {
  never
}

then close the browser window (without stopping the subscription first) within less than five seconds of establishing the subscription.

Open another browser window for http://localhost:4000/graphql and run

query {
  count
}

A count of 1 should be returned.

Repeating the same process but waiting at least five seconds before closing the subscription browser window should not lead to an increase of the count.

[enisdenjo]

Wow great catch! I've managed to create a failing test replicating what you've described. Thanks for reporting it! Fix coming soon.

[enisdenjo]

🎉 This issue has been resolved in version 5.15.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀