I ve been trying to consume a subscription in Kotlin Multipl

Question

I ve been trying to consume a subscription in Kotlin Multiplatform and finding that I often have many missing elements in my flow The code I m using is in the thread

Neal Sanche · Answer

Graph is just a poor man s dependency graph where we set up the GraphQL subscription client

Neal Sanche · Answer

I ve set up code like this for the creation of the ApolloClient for the subscription handling This connects and does get one or two elements But if the elements come in too fast it seems I don t get them all When the server delays sending all of the elements do come in

Neal Sanche · Answer

What am I missing Am I doing it wrong

mbonnin · Answer

That s interesting Sounds like a `CONFLATED` channel somewhere Do you have a rough idea of the delay that makes everything work again Are we talking milliseconds or seconds

Neal Sanche · Answer

More than 100ms and works pretty reliably around 1s I have a little time to play with this today but then I have to move on

mbonnin · Answer

Do you mind opening an issue with your code in the repo pseudo code work too Make sure we can track this

Neal Sanche · Answer

I don t mind at all Since the GraphQL playground seems to be able to get all of the data I am going to focus on the KMP side and see where I ve gone wrong The server side is using graphql kotlin and the code I used for that is really small

mbonnin · Answer

Also quick question is this JVM native or both

Neal Sanche · Answer

The app will be iOS and Android so both

Neal Sanche · Answer

I have only tested on Android so far

Neal Sanche · Answer

Okay wrote Let me know if you want more information inside that report < mbonnin>

mbonnin · Answer

Thanks will look into it `graphql ws` is getting some attention lately I know < Doug Chappelle> has been looking into it too a couple of threads just above this one so looks like there might be something to do there

mbonnin · Answer

Alright that d be the `CONFLATED` I guess <https github com apollographql apollo android blob 818ff720fe982132e9e0d5bccd20e3aa112774a4 apollo runtime kotlin src commonMain kotlin com apollographql apollo network ws ApolloWebSocketNetworkTransport kt L180|https github com apollographql apollo android blob 818ff720fe982132e9e0d5bccd20e llographql apollo network ws ApolloWebSocketNetworkTransport kt>

Neal Sanche · Answer

Funny I was just looking at exactly that line

mbonnin · Answer

slightly smiling face

mbonnin · Answer

Not sure there is a reason for this I guess we should make it configurable somehow with the defaultcertainly to not drop items

Neal Sanche · Answer

I ll see if I can get set up to experiment with the different options on that webSocketConnection broadcast function

mbonnin · Answer

These days `SharedFlow` might be an option too I think it didn t exist at the time

Neal Sanche · Answer

That s true

mbonnin · Answer

Oh well there s more to it as the producer gets called from a okhttp non suspending callback <https github com apollographql apollo android blob 23e78fc09452e17ffe8d5da9a03f7c86b282fd38 apollo runtime kotlin src jvmMain kotlin com apollographql apollo network ws ApolloWebSocket kt L62|https github com apollographql apollo android blob 23e78fc09452e17ffe8d5da9a03f7 n kotlin com apollographql apollo network ws ApolloWebSocket kt>

mbonnin · Answer

Buffering will work to a certain extent but proper backpressure handling will require more work

Neal Sanche · Answer

I ve cloned the repo but not sure the easiest way to make small code changes publish to my local maven repo and try it in my code

mbonnin · Answer

Yep publishToMavenLocal works well

mbonnin · Answer

You can also include the build but tbh that might take longer in gradle sync compared to maven local

Neal Sanche · Answer

Okay `publishToMavenLocal` works Just doing that and testing a few things out here

Neal Sanche · Answer

So making ApolloWebSocketNetworkTransport kt 180 read ``` private val messageChannel BroadcastChannel lt ByteString gt = webSocketConnection broadcast Channel BUFFERED ``` works the way I d expect it to I get all of the data items delivered

mbonnin · Answer

Nice Want to submit a PR to make this a parameter of `ApolloWebSocketNetworkTransport` We can figure out the backpressure stuff later

Neal Sanche · Answer

Sure will give that a shot

Neal Sanche · Answer

Okay I ve made a PR <https github com apollographql apollo android pull 3096> and do let me know in the PR if you d prefer a different implementation I simply went for minimal changes and defaults to the current value

mbonnin · Answer

Looks good to me thank you so much for the contribution blush

Neal Sanche · Answer

You re welcome Looking forward to using it to finish this feature I m working on I ll keep my eye out for when it gets into the repo Thanks for your help with it