feat(compute): Track provisioning response time

This change adds a metric for the provisioning time of virtual machines
by the compute service.

3 files changed, 19 insertions, 5 deletions

diff --git a/opendc-compute/opendc-compute-service/build.gradle.kts b/opendc-compute/opendc-compute-service/build.gradle.kts
index e0e48b0f..33cafc45 100644
--- a/opendc-compute/opendc-compute-service/build.gradle.kts
+++ b/opendc-compute/opendc-compute-service/build.gradle.kts
@@ -35,6 +35,7 @@ dependencies {
     api(projects.opendcTelemetry.opendcTelemetryApi)
     implementation(projects.opendcUtils)
     implementation(libs.kotlin.logging)
+    implementation(libs.opentelemetry.semconv)
 
     testImplementation(projects.opendcSimulator.opendcSimulatorCore)
     testRuntimeOnly(libs.log4j.slf4j)
diff --git a/opendc-compute/opendc-compute-service/src/main/kotlin/org/opendc/compute/service/internal/ComputeServiceImpl.kt b/opendc-compute/opendc-compute-service/src/main/kotlin/org/opendc/compute/service/internal/ComputeServiceImpl.kt
index d7a7e8f8..8c043142 100644
--- a/opendc-compute/opendc-compute-service/src/main/kotlin/org/opendc/compute/service/internal/ComputeServiceImpl.kt
+++ b/opendc-compute/opendc-compute-service/src/main/kotlin/org/opendc/compute/service/internal/ComputeServiceImpl.kt
@@ -22,7 +22,9 @@
 
 package org.opendc.compute.service.internal
 
+import io.opentelemetry.api.common.Attributes
 import io.opentelemetry.api.metrics.Meter
+import io.opentelemetry.semconv.resource.attributes.ResourceAttributes
 import kotlinx.coroutines.*
 import mu.KotlinLogging
 import org.opendc.compute.api.*
@@ -160,6 +162,15 @@ internal class ComputeServiceImpl(
         .build()
 
     /**
+     * The response time of the service.
+     */
+    private val _schedulerDuration = meter.histogramBuilder("scheduler.duration")
+        .setDescription("End to end latency for a server to be scheduled (in multiple attempts)")
+        .ofLongs()
+        .setUnit("ms")
+        .build()
+
+    /**
      * The [TimerScheduler] to use for scheduling the scheduler cycles.
      */
     private var timerScheduler: TimerScheduler<Unit> = TimerScheduler(scope.coroutineContext, clock)
@@ -325,7 +336,7 @@ internal class ComputeServiceImpl(
     internal fun schedule(server: InternalServer): SchedulingRequest {
         logger.debug { "Enqueueing server ${server.uid} to be assigned to host." }
 
-        val request = SchedulingRequest(server)
+        val request = SchedulingRequest(server, clock.millis())
         queue.add(request)
         _submittedServers.add(1)
         _waitingServers.add(1)
@@ -368,6 +379,7 @@ internal class ComputeServiceImpl(
      * Run a single scheduling iteration.
      */
     private fun doSchedule() {
+        val now = clock.millis()
         while (queue.isNotEmpty()) {
             val request = queue.peek()
 
@@ -402,6 +414,7 @@ internal class ComputeServiceImpl(
             // Remove request from queue
             queue.poll()
             _waitingServers.add(-1)
+            _schedulerDuration.record(now - request.submitTime, Attributes.of(ResourceAttributes.HOST_ID, server.uid.toString()))
 
             logger.info { "Assigned server $server to host $host." }
 
@@ -430,7 +443,7 @@ internal class ComputeServiceImpl(
     /**
      * A request to schedule an [InternalServer] onto one of the [Host]s.
      */
-    internal data class SchedulingRequest(val server: InternalServer) {
+    internal data class SchedulingRequest(val server: InternalServer, val submitTime: Long) {
         /**
          * A flag to indicate that the request is cancelled.
          */
diff --git a/opendc-compute/opendc-compute-service/src/test/kotlin/org/opendc/compute/service/InternalServerTest.kt b/opendc-compute/opendc-compute-service/src/test/kotlin/org/opendc/compute/service/InternalServerTest.kt
index 20ea8d20..28fd8217 100644
--- a/opendc-compute/opendc-compute-service/src/test/kotlin/org/opendc/compute/service/InternalServerTest.kt
+++ b/opendc-compute/opendc-compute-service/src/test/kotlin/org/opendc/compute/service/InternalServerTest.kt
@@ -102,7 +102,7 @@ class InternalServerTest {
         val image = mockk<InternalImage>()
         val server = InternalServer(service, uid, "test", flavor, image, mutableMapOf(), mutableMapOf())
 
-        every { service.schedule(any()) } answers { ComputeServiceImpl.SchedulingRequest(it.invocation.args[0] as InternalServer) }
+        every { service.schedule(any()) } answers { ComputeServiceImpl.SchedulingRequest(it.invocation.args[0] as InternalServer, 0) }
 
         server.start()
 
@@ -160,7 +160,7 @@ class InternalServerTest {
         val flavor = mockk<InternalFlavor>()
         val image = mockk<InternalImage>()
         val server = InternalServer(service, uid, "test", flavor, image, mutableMapOf(), mutableMapOf())
-        val request = ComputeServiceImpl.SchedulingRequest(server)
+        val request = ComputeServiceImpl.SchedulingRequest(server, 0)
 
         every { service.schedule(any()) } returns request
 
@@ -223,7 +223,7 @@ class InternalServerTest {
         val flavor = mockk<InternalFlavor>()
         val image = mockk<InternalImage>()
         val server = InternalServer(service, uid, "test", flavor, image, mutableMapOf(), mutableMapOf())
-        val request = ComputeServiceImpl.SchedulingRequest(server)
+        val request = ComputeServiceImpl.SchedulingRequest(server, 0)
 
         every { service.schedule(any()) } returns request