refactor(model-server): implement metrics via generated base class

Use the generated base class from the OpenAPI generator to implement the
metrics API.

Author: languitar

model-server-openapi/specifications/model-server-operative.yaml

@@ -22,6 +22,8 @@ paths:
   /metrics:
     get:
       operationId: getMetrics
+      tags:
+        - metrics
       responses:
         "200":
           $ref: '#/components/responses/200'

model-server/src/main/kotlin/org/modelix/model/server/Main.kt

@@ -65,7 +65,7 @@ import org.modelix.model.server.handlers.HistoryHandler
 import org.modelix.model.server.handlers.HttpException
 import org.modelix.model.server.handlers.IdsApiImpl
 import org.modelix.model.server.handlers.KeyValueLikeModelServer
-import org.modelix.model.server.handlers.MetricsHandler
+import org.modelix.model.server.handlers.MetricsApiImpl
 import org.modelix.model.server.handlers.ModelReplicationServer
 import org.modelix.model.server.handlers.RepositoriesManager
 import org.modelix.model.server.handlers.RepositoryOverview
@@ -179,7 +179,7 @@ object Main {
             val historyHandler = HistoryHandler(localModelClient, repositoriesManager)
             val contentExplorer = ContentExplorer(localModelClient, repositoriesManager)
             val modelReplicationServer = ModelReplicationServer(repositoriesManager, localModelClient, inMemoryModels)
-            val metricsHandler = MetricsHandler()
+            val metricsApi = MetricsApiImpl()
 
             val configureNetty: NettyApplicationEngine.Configuration.() -> Unit = {
                 this.responseWriteTimeoutSeconds = cmdLineArgs.responseWriteTimeoutSeconds
@@ -217,7 +217,7 @@ object Main {
                 contentExplorer.init(this)
                 jsonModelServer.init(this)
                 modelReplicationServer.init(this)
-                metricsHandler.init(this)
+                metricsApi.init(this)
                 routing {
                     IdsApiImpl(repositoriesManager, localModelClient).installRoutes(this)
 

model-server/src/main/kotlin/org/modelix/model/server/handlers/MetricsHandler.kt renamed to model-server/src/main/kotlin/org/modelix/model/server/handlers/MetricsApiImpl.kt

@@ -17,13 +17,13 @@
 package org.modelix.model.server.handlers
 
 import io.ktor.server.application.Application
+import io.ktor.server.application.ApplicationCall
 import io.ktor.server.application.call
 import io.ktor.server.application.install
 import io.ktor.server.metrics.micrometer.MicrometerMetrics
-import io.ktor.server.resources.get
 import io.ktor.server.response.respond
-import io.ktor.server.routing.Route
 import io.ktor.server.routing.routing
+import io.ktor.util.pipeline.PipelineContext
 import io.micrometer.core.instrument.binder.jvm.ClassLoaderMetrics
 import io.micrometer.core.instrument.binder.jvm.JvmGcMetrics
 import io.micrometer.core.instrument.binder.jvm.JvmInfoMetrics
@@ -35,9 +35,12 @@ import io.micrometer.core.instrument.binder.system.UptimeMetrics
 import io.micrometer.core.instrument.distribution.DistributionStatisticConfig
 import io.micrometer.prometheusmetrics.PrometheusConfig
 import io.micrometer.prometheusmetrics.PrometheusMeterRegistry
-import org.modelix.api.operative.Paths
+import org.modelix.api.operative.MetricsApi
 
-class MetricsHandler {
+/**
+ * REST API implementation for providing micrometer metrics.
+ */
+class MetricsApiImpl : MetricsApi() {
 
     private val appMicrometerRegistry = PrometheusMeterRegistry(PrometheusConfig.DEFAULT)
 
@@ -63,14 +66,12 @@ class MetricsHandler {
             }
 
             routing {
-                installHandlers()
+                installRoutes(this)
             }
         }
     }
 
-    private fun Route.installHandlers() {
-        get<Paths.getMetrics> {
-            call.respond(appMicrometerRegistry.scrape())
-        }
+    override suspend fun PipelineContext<Unit, ApplicationCall>.getMetrics() {
+        call.respond(appMicrometerRegistry.scrape())
     }
 }