ParserController.kt

package example.controller

import arrow.fx.reactor.FluxK
import arrow.fx.reactor.extensions.fluxk.async.effect
import arrow.fx.reactor.value
import example.ParserService
import org.springframework.web.bind.annotation.GetMapping
import org.springframework.web.bind.annotation.RequestParam
import org.springframework.web.bind.annotation.RestController
import reactor.core.publisher.Flux


@RestController
class ParserController(
        private val parserService: ParserService
) {

    @GetMapping("/parse")
    fun parse(@RequestParam("keys") keys: Set<String>) = FluxK(Flux.fromIterable(keys)).flatMap { i ->
        effect {
            parserService.parse(i)
        }
    }.value()

}

ParserService.kt

package example.service

import arrow.core.Option
import arrow.extension
import arrow.typeclasses.Show
import org.springframework.stereotype.Component
import reactor.core.publisher.Mono
import java.util.*

interface ParserService {
    suspend fun parse(semKey: String): ParseResult
}

data class ParseResult(val type: String) {
    companion object
}

@extension
interface ResultShow : Show<ParseResult> {
    override fun ParseResult.show(): String {
        return "ParseResult: {type - $type}"
    }
}

data class ParseConfig(val resolveLocation: Boolean, val locale: Option<Locale>)


@Component
class ReactiveParserService : ParserService {

    override suspend fun parse(key: String): ParseResult {
        val sample = aux()
        val x = certainClient()
        return ParseResult(key + sample)
    }

    suspend fun aux(): Int = 3

    fun certainClient() : Mono<Int> = Mono.just(1)

}