Refactor clearing collectors

observability/prometheus-backend/src/main/scala/sttp/client4/prometheus/PrometheusBackend.scala

@@ -14,6 +14,7 @@ import sttp.model.StatusCode
 import scala.collection.mutable
 
 object PrometheusBackend {
+ // TODO: Refactor metrics names according to Prometheus/OpenTelemetry standards
  val DefaultHistogramName = "sttp_request_latency"
  val DefaultRequestsInProgressGaugeName = "sttp_requests_in_progress"
  val DefaultSuccessCounterName = "sttp_requests_success_count"
@@ -121,15 +122,10 @@ object PrometheusBackend {
  /** Clear cached collectors (gauges and histograms) both from the given collector registry, and from the backend.
  */
  def clear(prometheusRegistry: PrometheusRegistry): Unit = {
- unregister(prometheusRegistry, histograms)
- histograms.remove(prometheusRegistry)
- unregister(prometheusRegistry, gauges)
- gauges.remove(prometheusRegistry)
- unregister(prometheusRegistry, counters)
- counters.remove(prometheusRegistry)
- unregister(prometheusRegistry, summaries)
- summaries.remove(prometheusRegistry)
- ()
+ clear(prometheusRegistry, histograms)
+ clear(prometheusRegistry, gauges)
+ clear(prometheusRegistry, counters)
+ clear(prometheusRegistry, summaries)
  }
 
  /*
@@ -138,11 +134,13 @@ object PrometheusBackend {
  Hence, we need to store a global cache o created histograms/gauges, so that we can properly re-use them.
  */
 
- private def unregister[T <: Collector](prometheusRegistry: PrometheusRegistry, collectors: mutable.WeakHashMap[PrometheusRegistry, ConcurrentHashMap[String, T]]): Unit =
+ private def clear[T <: Collector](prometheusRegistry: PrometheusRegistry, collectors: mutable.WeakHashMap[PrometheusRegistry, ConcurrentHashMap[String, T]]): Unit = {
  collectors
  .getOrElse(prometheusRegistry, new ConcurrentHashMap[String, T]())
  .values()
  .forEach(c => prometheusRegistry.unregister(c))
+ collectors.remove(prometheusRegistry)
+ }
 
  private val histograms = new mutable.WeakHashMap[PrometheusRegistry, ConcurrentHashMap[String, Histogram]]
  private val gauges = new mutable.WeakHashMap[PrometheusRegistry, ConcurrentHashMap[String, Gauge]]
@@ -154,6 +152,7 @@ object PrometheusBackend {
  prometheusRegistry: PrometheusRegistry
  ): ConcurrentHashMap[String, T] =
  cache.synchronized {
+ // TODO remove synchronized and improve caching
  cache.getOrElseUpdate(prometheusRegistry, new ConcurrentHashMap[String, T]())
  }
  final case class RequestCollectors(maybeTimer: Option[Timer], maybeGauge: Option[GaugeDataPoint])