feat(server): replace OpenTelemetry with Micrometer (#1823)

To test locally, follow these steps after installing docker and docker
compose:

1. Execute `./gradlew jit-binding-server:publishImageToLocalRegistry`
2. Create `docker-compose.yml` with the following content:
```
services:
  github-workflows-kt:
    image: github-workflows-kt-jit-binding-server 
    ports:
      - "8080:8080"
    environment:
      - GITHUB_TOKEN
    networks:
      prometheus:

  grafana:
    image: grafana/grafana:11.5.0
    ports:
      - "3000:3000"
    volumes:
      - ./datasources.yaml:/etc/grafana/provisioning/datasources/datasources.yaml
    networks:
      prometheus:

  prometheus:
    image: prom/prometheus:v3.1.0
    configs:
      - source: prometheus
        target: /etc/prometheus/prometheus.yml
    ports:
      - "9090:9090"
    command:
      - "--config.file=/etc/prometheus/prometheus.yml"
      - "--web.enable-remote-write-receiver"
    networks:
      prometheus:

networks:
  prometheus:

configs:
  prometheus:
    file: prometheus.yml
```

3. Create `.env` on the same folder as docker-compose:

```
GITHUB_TOKEN=XXX
```
where XXX is a generated github token with access to public repositories

4. Create `prometheus.yml` on the same folder as docker-compose:

```
global:
  scrape_interval: 5s

scrape_configs:
  - job_name: 'ktor-app'
    metrics_path: '/metrics'
    static_configs:
      - targets: ['github-workflows-kt:8080'] 

```
5. Create `datasources.yaml` on the same folder as docker-compose:
```
apiVersion: 1
datasources:
  - name: Prometheus
    type: prometheus
    url: http://prometheus:9090/
    access: proxy
    isDefault: true
```
6. Execute `docker compose up -d`


- Workflows should be accessible on port 8080
- Prometheus should be accessible on port 9090
- Grafana should be accessible on port 3000

Author: LeoColman

jit-binding-server/build.gradle.kts

@@ -16,10 +16,9 @@ dependencies {
     implementation("io.ktor:ktor-serialization-kotlinx-json")
     implementation("io.ktor:ktor-server-call-logging")
     implementation("io.ktor:ktor-server-call-id")
-    implementation("io.opentelemetry.instrumentation:opentelemetry-ktor-3.0:2.10.0-alpha")
-    implementation("io.opentelemetry:opentelemetry-sdk:1.47.0")
-    implementation("io.opentelemetry:opentelemetry-exporter-otlp:1.47.0")
-    implementation("io.opentelemetry:opentelemetry-exporter-logging:1.47.0")
+    implementation("io.ktor:ktor-server-metrics-micrometer")
+    implementation("io.micrometer:micrometer-registry-prometheus:1.14.4")
+    
     implementation("io.github.reactivecircus.cache4k:cache4k:0.14.0")
     implementation("io.github.oshai:kotlin-logging:7.0.4")
     implementation(platform("org.apache.logging.log4j:log4j-bom:2.24.3"))

jit-binding-server/src/main/kotlin/io/github/typesafegithub/workflows/jitbindingserver/InternalRoutes.kt

@@ -3,8 +3,13 @@ package io.github.typesafegithub.workflows.jitbindingserver
 import io.ktor.server.response.respondText
 import io.ktor.server.routing.Routing
 import io.ktor.server.routing.get
+import io.micrometer.prometheusmetrics.PrometheusMeterRegistry
+
+fun Routing.internalRoutes(prometheusRegistry: PrometheusMeterRegistry) {
+    get("/metrics") {
+        call.respondText(prometheusRegistry.scrape())
+    }
 
-fun Routing.internalRoutes() {
     get("/status") {
         call.respondText("OK")
     }

jit-binding-server/src/main/kotlin/io/github/typesafegithub/workflows/jitbindingserver/Main.kt

@@ -7,7 +7,20 @@ import io.ktor.server.engine.embeddedServer
 import io.ktor.server.netty.Netty
 import io.ktor.server.response.respondText
 import io.ktor.server.routing.routing
+import io.micrometer.prometheusmetrics.PrometheusConfig
+import io.micrometer.prometheusmetrics.PrometheusMeterRegistry
+import java.time.Duration
 
+private val prometheusRegistry =
+    PrometheusMeterRegistry(
+        object : PrometheusConfig {
+            override fun get(key: String): String? = null
+
+            override fun prefix(): String = "github-actions-binding-server"
+
+            override fun step() = Duration.ofSeconds(10)
+        },
+    )
 private val logger =
     System
         /*
@@ -25,10 +38,10 @@ fun main() {
         logger.error(throwable) { "Uncaught exception in thread $thread" }
     }
     embeddedServer(Netty, port = 8080) {
-        installPlugins()
+        installPlugins(prometheusRegistry)
 
         routing {
-            internalRoutes()
+            internalRoutes(prometheusRegistry)
 
             artifactRoutes()
             metadataRoutes()

jit-binding-server/src/main/kotlin/io/github/typesafegithub/workflows/jitbindingserver/OpenTelemetryConfig.kt

@@ -3,13 +3,14 @@ package io.github.typesafegithub.workflows.jitbindingserver
 import io.ktor.http.HttpHeaders
 import io.ktor.server.application.Application
 import io.ktor.server.application.install
+import io.ktor.server.metrics.micrometer.MicrometerMetrics
 import io.ktor.server.plugins.callid.CallId
 import io.ktor.server.plugins.callid.callIdMdc
 import io.ktor.server.plugins.callid.generate
 import io.ktor.server.plugins.calllogging.CallLogging
-import io.opentelemetry.instrumentation.ktor.v3_0.server.KtorServerTracing
+import io.micrometer.prometheusmetrics.PrometheusMeterRegistry
 
-fun Application.installPlugins() {
+fun Application.installPlugins(prometheusRegistry: PrometheusMeterRegistry) {
     install(CallId) {
         generate(15, "abcdefghijklmnopqrstuvwxyz0123456789")
         replyToHeader(HttpHeaders.XRequestId)
@@ -19,7 +20,7 @@ fun Application.installPlugins() {
         callIdMdc("request-id")
     }
 
-    install(KtorServerTracing) {
-        setOpenTelemetry(buildOpenTelemetryConfig("github-actions-bindings"))
+    install(MicrometerMetrics) {
+        registry = prometheusRegistry
     }
 }