How to know serverside a subscription was cancelled

[pbackx]

I'm creating a subscription that will continuously push data to the client. This is basically an endless loop as data will be coming into the system, whether a client is listening or not. On the backend resources are needed to make this work.

How can I know, server-side, that the client is no longer listening to the subscription? For instance, the connection was terminated or I believe there is also an unsubscribe method in most client.

I would need this to tear down the processing that is happening and avoid the server from eventually running out of resources.

[n1ru4l]

Here is an example of tearing down an example after the client disconnected. https://codesandbox.io/s/regression-subscription-not-closed-d8d5mj?file=/index.ts

import { createServer, Repeater } from "@graphql-yoga/node";

const server = createServer({
  schema: {
    typeDefs: /* GraphQL */ `
      type Query {
        hello: String
      }

      type Subscription {
        currentDate: String
      }
    `,
    resolvers: {
      Query: {
        hello: () => "Hello from Yoga!"
      },
      Subscription: {
        currentDate: {
          resolve: (value) => value,
          subscribe: () =>
            new Repeater(async (next, stop) => {
              console.log("Subscription starts");

              const interval = setInterval(() => {
                console.log("next");
                next(new Date().toString());
              }, 1000).unref();

              stop.then(() => {
                console.log("Subscription ends");
                clearInterval(interval);
              });
              await stop;
            })
        }
      }
    }
  }
});

server.start();

PLEASE NOTE that we are currently having a regression on the latest GraphQL Yoga version, that does not properly cleanup subscriptions. We are working on fixing it (#1399).

[pbackx]

Thanks, this is exactly what I was looking for!

[n1ru4l]

@pbackx Just wanna let you know that the subscription issue is now resolved!

[pbackx]

@n1ru4l I can confirm that it is indeed working as expected. Thanks again!

[deslee]

@n1ru4l I'm still seeing this problem on Cloudflare workers. I noticed the @graphql-yoga/common package is still at ^2.12.3. Does this mean that the fix hasn't been implemented on the common package yet?