Hello, I'm using resilience4j and I'm trying to fi...

# coroutines

[obobo]

Hello,
I'm using resilience4j and I'm trying to figure out a pattern: I want to a function call in a circuit breaker, but this function suspends, so the compiler won't let me do it.

decorateCheckedSupplier(circuitBreaker) {
  suspendingFunction() // compiler complains
}

How would I handle this? I've realized that I can wrap the suspendingFunction call in an async block, but then the circuitbreaker returns a Deferred and always succeeds, which is not what I want. What I want, I think, is to have be able to call a suspending function from an arbitrary lambda.

[streetsofboston]

Do you need the result of the suspendingFunction ?
If not, wrap it in a launch: `launch { suspendingFunction() }’.
If you need to wait for the result, wrap it in a runBlocking instead.

[obobo]

Yeah, I need the result -- so runBlocking is the choice here?

[streetsofboston]

Yep. runBlocking should be used to bridge non-suspend code that can block/wait with suspend code.

[gildor]

Does this API provide any async API? If so just write coroutine adapter, so it will convert callback API to suspend function, so you can use it from coroutine

[marcoferrer]

This is possible using resilience4js adapters for reactor and the corotines reactor integration. We do it in production and it works really well. I can provide an example in a few minutes

[marcoferrer]

suspend fun doSomethingSuspending(){}

fun CoroutineScope.test(){
    //using mono coroutine builder from coroutines reactor
    mono{ doSomethingSuspending() }
        .withCircuitBreaker(circuitBreaker)
        .awaitFirst()
}

fun <T> Mono<T>.withCircuitBreaker(circuitBreaker: CircuitBreaker): Mono<T> =
    this.transform(CircuitBreakerOperator.of(circuitBreaker))

[marcoferrer]

with these deps

"io.github.resilience4j:resilience4j-circuitbreaker"
"io.github.resilience4j:resilience4j-reactor"
"org.jetbrains.kotlinx:kotlinx-coroutines-reactor"