Using ConnectableFlux for hot stream REST endpoint - spring

Question

I'm trying to create a REST endpoint to subscribe to a hot stream using Reactor.
My test provider for the stream looks like this:
#Service
class TestProvider {
fun getStream(resourceId: String): ConnectableFlux<QData> {
return Flux.create<QData> {
for (i in 1..10) {
it.next(QData(LocalDateTime.now().toString(), "next"))
Thread.sleep(500L)
}
it.complete()
}.publish()
}
}
My service for the REST endpoint looks like this:
#Service
class DataService #Autowired constructor(
private val prv: TestProvider
) {
private val streams = mutableMapOf<String, ConnectableFlux<QData>>()
fun subscribe(resourceId: String): Flux<QData> {
val stream = getStream(resourceId)
return Flux.push { flux ->
stream.subscribe{
flux.next(it)
}
flux.complete()
}
}
private fun getStream(resourceId: String): ConnectableFlux<QData> {
if(streams.containsKey(resourceId).not()) {
streams.put(resourceId, createStream(resourceId))
}
return streams.get(resourceId)!!
}
private fun createStream(resourceId: String): ConnectableFlux<QData> {
val stream = prv.getStream(resourceId)
stream.connect()
return stream
}
}
The controller looks like this:
#RestController
class DataController #Autowired constructor(
private val dataService: DataService
): DataApi {
override fun subscribe(resourceId: String): Flux<QData> {
return dataService.subscribe(resourceId)
}
}
The API interface looks like this:
interface DataApi {
#ApiResponses(value = [
ApiResponse(responseCode = "202", description = "Client is subscribed", content = [
Content(mediaType = "application/json", array = ArraySchema(schema = Schema(implementation = QData::class)))
])
])
#GetMapping(path = ["/subscription/{resourceId}"], produces = [MediaType.APPLICATION_JSON_VALUE])
fun subscribe(
#Parameter(description = "The resource id for which quality data is subscribed for", required = true, example = "example",allowEmptyValue = false)
#PathVariable("resourceId", required = true) #NotEmpty resourceId: String
): Flux<QData>
}
Unfortunately, my curl delivers an empty array.
Does anyone has an idea what the issue is? Thanks in advance!

Answer 1

I had to run connect() async in DataService:
CompletableFuture.runAsync {
stream.connect()
}