Kotlin version of com.codahale.metrics.SharedMetricRegistries

SharedMetricRegistries.kt

import com.codahale.metrics.MetricRegistry
import java.util.concurrent.ConcurrentHashMap

/**
 * A map of shared, named metric registries.
 */
object SharedMetricRegistries {
    private val REGISTRIES = ConcurrentHashMap<String, MetricRegistry>()

    @Volatile
    private var defaultRegistryName: String? = null

    val default: MetricRegistry
        get() = defaultRegistryName?.let { get(it) }
            ?: throw IllegalStateException("Default registry name has not been set.")

    fun clear() {
        REGISTRIES.clear()
    }

    fun names(): Set<String> = REGISTRIES.keys.toSet()

    fun remove(key: String) {
        REGISTRIES.remove(key)
    }

    fun set(name: String, registry: MetricRegistry): MetricRegistry? {
        return REGISTRIES.putIfAbsent(name, registry)
    }

    fun get(name: String): MetricRegistry {
        val existing = REGISTRIES[name]
        if (existing == null) {
            val created = MetricRegistry()
            return set(name, created) ?: return created
        }
        return existing
    }

    @Synchronized
    fun setDefault(name: String): MetricRegistry {
        val registry = get(name)
        return setDefault(name, registry)
    }

    fun setDefault(name: String, metricRegistry: MetricRegistry): MetricRegistry {
        if (defaultRegistryName == null) {
            defaultRegistryName = name
            set(name, metricRegistry)
            return metricRegistry
        }
        throw IllegalStateException("Default metric registry name is already set.")
    }
}