[2.0.0] CircuitBreaker.state() returns the wrong state.

[hoc081098]

Version

2.0.0

Reproduce

I've copied the sample code from https://arrow-kt.io/learn/resilience/circuitbreaker/#arrows-circuitbreaker, and added 2 lines to print the state of the CircuitBreaker.

Github link: https://github.com/hoc081098/kotlin_playground/blob/master/src/main/kotlin/com/hoc081098/kotlin_playground/arrowkt/circuit_breaker.kt

package com.hoc081098.kotlin_playground.arrowkt

import arrow.core.Either
import arrow.resilience.CircuitBreaker
import kotlin.time.Duration.Companion.seconds
import kotlin.time.ExperimentalTime
import kotlinx.coroutines.delay

@ExperimentalTime
suspend fun main(): Unit {
  val circuitBreaker = CircuitBreaker(
    openingStrategy = CircuitBreaker.OpeningStrategy.Count(2),
    resetTimeout = 2.seconds,
    exponentialBackoffFactor = 1.2,
    maxResetTimeout = 60.seconds,
  )

  // normal operation
  circuitBreaker.protectOrThrow { "I am in Closed: ${circuitBreaker.state()}" }.also(::println)

  // simulate service getting overloaded
  Either.catch {
    circuitBreaker.protectOrThrow { throw RuntimeException("Service overloaded") }
  }.also(::println)
  Either.catch {
    circuitBreaker.protectOrThrow { throw RuntimeException("Service overloaded") }
  }.also(::println)
  circuitBreaker.protectEither { }
    .also { println("I am Open and short-circuit with ${it}. ${circuitBreaker.state()}") }

  println(">>> state should be Open: ${circuitBreaker.state()}")
  // simulate reset timeout
  println("Service recovering . . .").also { delay(2500) }
  println(">>> state should be HalfOpen: ${circuitBreaker.state()}")

  // simulate test request success
  circuitBreaker.protectOrThrow {
    "I am running test-request in HalfOpen: ${circuitBreaker.state()}"
  }.also(::println)
  println("I am back to normal state closed ${circuitBreaker.state()}")
}

---

Console

I am in Closed: arrow.resilience.CircuitBreaker$State$Closed@5ccd43c2
Either.Left(java.lang.RuntimeException: Service overloaded)
Either.Left(java.lang.RuntimeException: Service overloaded)
I am Open and short-circuit with Either.Right(kotlin.Unit). arrow.resilience.CircuitBreaker$State$Closed@27ddd392
>>> state should be Open: arrow.resilience.CircuitBreaker$State$Closed@27ddd392
Service recovering . . .
>>> state should be HalfOpen: arrow.resilience.CircuitBreaker$State$Closed@27ddd392
I am running test-request in HalfOpen: arrow.resilience.CircuitBreaker$State$Closed@27ddd392
I am back to normal state closed arrow.resilience.CircuitBreaker$State$Closed@27ddd392

Process finished with exit code 0

We can see the line >>> state should be Open: arrow.resilience.CircuitBreaker$State$Closed@27ddd392
I think that CircuitBreaker.state() returns the wrong state.

[hoc081098]

I have just noticed that the example in docs seems to be wrong compared to the actual library source code.

Docs

🔀Closed
This is the state in which the circuit breaker starts.
Requests are made normally in this state:
When an exception occurs, it increments the failure counter.
When the failure counter reaches the given maxFailures threshold, the breaker moves to the Open state.
A successful request will reset the failure counter to zero.

Actual library source code

arrow/arrow-libs/resilience/arrow-resilience/src/commonMain/kotlin/arrow/resilience/CircuitBreaker.kt

Line 587 in 0245973

override fun shouldOpen(): Boolean = failuresCount > maxFailures

Should it be override fun shouldOpen(): Boolean = failuresCount >= maxFailures?

[hoc081098]

circuitBreaker.protectEither { }
    .also { println("I am Open and short-circuit with ${it}. ${circuitBreaker.state()}") }

gives output

I am Open and short-circuit with Either.Right(kotlin.Unit). arrow.resilience.CircuitBreaker$State$Closed@71ebc7d4

That means the CircuitBreaker does not reject the execution of the lambda (Either.Right(kotlin.Unit))