update

src/main/java/ext/Ext.kt

@@ -5,6 +5,9 @@ import io.ktor.client.*
 import io.ktor.client.engine.cio.*
 import io.ktor.client.plugins.contentnegotiation.*
 import io.ktor.serialization.kotlinx.json.*
+import io.micrometer.core.instrument.*
+import io.micrometer.core.instrument.Timer
+import io.micrometer.core.instrument.Metrics as Micrometer
 import jakarta.persistence.Query
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.withContext
@@ -22,6 +25,7 @@ import java.time.LocalDate
 import java.time.LocalDateTime
 import java.time.format.DateTimeFormatter
 import java.util.*
+import java.util.concurrent.ConcurrentHashMap
 import kotlin.reflect.KCallable
 import kotlin.reflect.KClass
 import kotlin.reflect.KMutableProperty1
@@ -214,3 +218,45 @@ val <S> Pair<*, S>.r get() = component2()
 
 // Database
 val Query.exec get() = resultList.map { (it as Array<*>).toList() }
+
+// Metrics
+object Metrics {
+    @PublishedApi
+    internal inline fun <reified T : Any> expandLabels(labels: T): Array<String> {
+        return T::class.memberProperties.flatMap { prop ->
+            listOf(prop.name, prop.get(labels)?.toString() ?: throw IllegalArgumentException("Missing value for label ${prop.name}"))
+        }.toTypedArray()
+    }
+
+    @PublishedApi
+    internal data class MetricCacheKey(val metricName: String, val labels: Any)
+
+    @PublishedApi
+    internal val counterCache = ConcurrentHashMap<MetricCacheKey, Counter>()
+
+    inline fun <reified T : Any> counter(metricName: String): (T) -> Counter {
+        return { labels ->
+            counterCache.computeIfAbsent(MetricCacheKey(metricName, labels)) {
+                Counter
+                    .builder(metricName)
+                    .tags(*expandLabels(labels))
+                    .register(Micrometer.globalRegistry)
+            }
+        }
+    }
+
+    @PublishedApi
+    internal val timerCache = ConcurrentHashMap<MetricCacheKey, Timer>()
+
+    inline fun <reified T : Any> timer(metricName: String): (T) -> Timer {
+        return { labels ->
+            timerCache.computeIfAbsent(MetricCacheKey(metricName, labels)) {
+                Timer
+                    .builder(metricName)
+                    .publishPercentiles(0.5, 0.75, 0.90, 0.95, 0.99)
+                    .tags(*expandLabels(labels))
+                    .register(Micrometer.globalRegistry)
+            }
+        }
+    }
+}