feat(telemetry): Report provisioning time of virtual machines

This change adds support for collecting the provisioning time of virtual
machines in addition to their boot time.

2 files changed, 26 insertions, 3 deletions

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 2a07a208..292feabe 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
@@ -26,6 +26,7 @@ import io.opentelemetry.api.common.AttributeKey
 import io.opentelemetry.api.common.Attributes
 import io.opentelemetry.api.metrics.Meter
 import io.opentelemetry.api.metrics.MeterProvider
+import io.opentelemetry.api.metrics.ObservableLongMeasurement
 import kotlinx.coroutines.*
 import mu.KotlinLogging
 import org.opendc.compute.api.*
@@ -173,6 +174,12 @@ internal class ComputeServiceImpl(
                 result.observe(available, upState)
                 result.observe(total - available, downState)
             }
+
+        meter.gaugeBuilder("system.time.provision")
+            .setDescription("The most recent timestamp where the server entered a provisioned state")
+            .setUnit("1")
+            .ofLongs()
+            .buildWithCallback(::collectProvisionTime)
     }
 
     override fun newClient(): ComputeClient {
@@ -324,8 +331,10 @@ internal class ComputeServiceImpl(
 
     internal fun schedule(server: InternalServer): SchedulingRequest {
         logger.debug { "Enqueueing server ${server.uid} to be assigned to host." }
+        val now = clock.millis()
+        val request = SchedulingRequest(server, now)
 
-        val request = SchedulingRequest(server, clock.millis())
+        server.lastProvisioningTimestamp = now
         queue.add(request)
         _serversPending.add(1)
         requestSchedulingCycle()
@@ -501,4 +510,13 @@ internal class ComputeServiceImpl(
             requestSchedulingCycle()
         }
     }
+
+    /**
+     * Collect the timestamp when each server entered its provisioning state most recently.
+     */
+    private fun collectProvisionTime(result: ObservableLongMeasurement) {
+        for ((_, server) in servers) {
+            result.observe(server.lastProvisioningTimestamp, server.attributes)
+        }
+    }
 }
diff --git a/opendc-compute/opendc-compute-service/src/main/kotlin/org/opendc/compute/service/internal/InternalServer.kt b/opendc-compute/opendc-compute-service/src/main/kotlin/org/opendc/compute/service/internal/InternalServer.kt
index 05a7e1bf..f1b92c66 100644
--- a/opendc-compute/opendc-compute-service/src/main/kotlin/org/opendc/compute/service/internal/InternalServer.kt
+++ b/opendc-compute/opendc-compute-service/src/main/kotlin/org/opendc/compute/service/internal/InternalServer.kt
@@ -55,7 +55,7 @@ internal class InternalServer(
     /**
      * The attributes of a server.
      */
-    internal val attributes: Attributes = Attributes.builder()
+    @JvmField internal val attributes: Attributes = Attributes.builder()
         .put(ResourceAttributes.HOST_NAME, name)
         .put(ResourceAttributes.HOST_ID, uid.toString())
         .put(ResourceAttributes.HOST_TYPE, flavor.name)
@@ -70,7 +70,12 @@ internal class InternalServer(
     /**
      * The [Host] that has been assigned to host the server.
      */
-    internal var host: Host? = null
+    @JvmField internal var host: Host? = null
+
+    /**
+     * The most recent timestamp when the server entered a provisioning state.
+     */
+    @JvmField internal var lastProvisioningTimestamp: Long = Long.MIN_VALUE
 
     /**
      * The current scheduling request.