Adding onOperation outside of SubscriptionServer constructor

[findlay-hannam]

I have an express server with the apollo middleware integration. I needed to integrate with a SSE API in the back-end, so I'm adding subscriptions.

I've set up subscriptions using installSubscriptionHandlers. When a client subscribes to the graphql, I want to use the variables to execute a function which will be used by the subscription.

I think onOperation is the best way to go about this, but I can't see a way to register the hooks, or specify the url, while using installSubscriptionHandlers. Is this level of control possible? Or is there some other method I should be using?

[glasser]

Just to let you know, we are currently planning to remove the surface-level direct integration between subscriptions-transport-ws and apollo-server in AS v3; ie, installSubscriptionHandlers is going away. Given that installSubscriptionHandlers already seems to not support your use case, I'd suggest ignoring it and integrating subscriptions-transport-ws with your http server directly, or perhaps using graphql-ws which I've heard is more actively maintained.