Detecting connection changes

[hognevevle]

Hi there!

Is there a way to detect when a (re)connection and connection loss has occured? I've tried onMessage, but it doesn't seem to give me anything there.

[enisdenjo]

Not really, because each connection (in "distinct connection mode", default) is a separate connection and its therefore hard to provide a centralised dispatcher of this event.

You could theoretically used the retry callback which controls the reconnections.

Out of curiosity, what are you trying to achieve? What is the use-case?

[hognevevle]

Thanks for confirming @enisdenjo .

I understand how it could be challenging..

I don't think retry will let me do what I need, since I have no easy way of knowing if the retry will be successful or not, I'll just know that something intends to retry.

We're using graphql-sse for subscriptions, and "regular" http for queries/mutations. Our use case is that whenever a client's connection is lost and then reestablished, we want to refetch all active queries to make sure the client's state is updated (because subscription messages sent via SSE were likely not delivered while the connection was gone). 🤔

[hognevevle]

@enisdenjo What about the keepalive-messages sent from the server - would we be able to monitor these somehow? If so, I'd imagine we could detect connection loss if we don't see any keepalives for some given time. Then, if we start seeing them again, we'll know connection is back up and we can make sure to refetch all the (potentially) missed data.

As far as I can see, the client discards keepalive-messages by default. Is there a way they can be exposed instead?

[hognevevle]

Or perhaps adding a callback that fires every time the subscription is established?

[enisdenjo]

Hey sorry for the late reply. I am a tad busy at the moment - but I haven't forgotten about this! Will revisit after my time frees up. Thanks for understanding!

[enisdenjo]

Hey @hognevevle, I'll start by apologising for such a long wait. Nevertheless, I bear great news! With v2.4.0, we have more sophisticated event listeners (including what was discussed here).

Please consult the description of #84 for explanation with examples.

[hognevevle]

This is really awesome, thank you so much! 🙏🥳

[enisdenjo]

You're very welcome! Would appreciate it if you can try it out and report back whether this works for you as intended. Thanks!