compute: Migrate compute service simulator to OpenTelemetry

This change updates the compute service simulator to use OpenTelemetry
for reporting metrics of the (simulated) hosts as opposed to using
custom event flows.

This approach is more generic, flexible and possibly offers better
performance as we can collect metrics of all services in a single sweep,
as opposed to listening to several services and each invoking the
handlers.

1 files changed, 95 insertions, 22 deletions

diff --git a/simulator/opendc-compute/opendc-compute-simulator/src/main/kotlin/org/opendc/compute/simulator/SimHost.kt b/simulator/opendc-compute/opendc-compute-simulator/src/main/kotlin/org/opendc/compute/simulator/SimHost.kt
index 89784803..6d81aa7d 100644
--- a/simulator/opendc-compute/opendc-compute-simulator/src/main/kotlin/org/opendc/compute/simulator/SimHost.kt
+++ b/simulator/opendc-compute/opendc-compute-simulator/src/main/kotlin/org/opendc/compute/simulator/SimHost.kt
@@ -22,8 +22,9 @@
 
 package org.opendc.compute.simulator
 
+import io.opentelemetry.api.metrics.Meter
+import io.opentelemetry.api.metrics.common.Labels
 import kotlinx.coroutines.*
-import kotlinx.coroutines.flow.Flow
 import mu.KotlinLogging
 import org.opendc.compute.api.Flavor
 import org.opendc.compute.api.Server
@@ -36,7 +37,6 @@ import org.opendc.simulator.compute.model.MemoryUnit
 import org.opendc.simulator.compute.power.ConstantPowerModel
 import org.opendc.simulator.compute.power.MachinePowerModel
 import org.opendc.simulator.failures.FailureDomain
-import org.opendc.utils.flow.EventFlow
 import java.time.Clock
 import java.util.*
 import kotlin.coroutines.CoroutineContext
@@ -52,6 +52,7 @@ public class SimHost(
     override val meta: Map<String, Any>,
     context: CoroutineContext,
     clock: Clock,
+    meter: Meter,
     hypervisor: SimHypervisorProvider,
     powerModel: MachinePowerModel = ConstantPowerModel(0.0),
     private val mapper: SimWorkloadMapper = SimMetaWorkloadMapper(),
@@ -66,10 +67,6 @@ public class SimHost(
      */
     private val logger = KotlinLogging.logger {}
 
-    override val events: Flow<HostEvent>
-        get() = _events
-    internal val _events = EventFlow<HostEvent>()
-
     /**
      * The event listeners registered with this host.
      */
@@ -99,18 +96,13 @@ public class SimHost(
                 cpuUsage: Double,
                 cpuDemand: Double
             ) {
-                _events.emit(
-                    HostEvent.SliceFinished(
-                        this@SimHost,
-                        requestedWork,
-                        grantedWork,
-                        overcommittedWork,
-                        interferedWork,
-                        cpuUsage,
-                        cpuDemand,
-                        guests.size
-                    )
-                )
+                _cpuWork.record(requestedWork.toDouble())
+                _cpuWorkGranted.record(grantedWork.toDouble())
+                _cpuWorkOvercommit.record(overcommittedWork.toDouble())
+                _cpuWorkInterference.record(interferedWork.toDouble())
+                _cpuUsage.record(cpuUsage)
+                _cpuDemand.record(cpuDemand)
+                _cpuPower.record(machine.powerDraw.value)
             }
         }
     )
@@ -132,6 +124,87 @@ public class SimHost(
 
     override val model: HostModel = HostModel(model.cpus.size, model.memory.map { it.size }.sum())
 
+    /**
+     * The number of guests on the host.
+     */
+    private val _guests = meter.longUpDownCounterBuilder("guests.total")
+        .setDescription("Number of guests")
+        .setUnit("1")
+        .build()
+        .bind(Labels.of("host", uid.toString()))
+
+    /**
+     * The number of active guests on the host.
+     */
+    private val _activeGuests = meter.longUpDownCounterBuilder("guests.active")
+        .setDescription("Number of active guests")
+        .setUnit("1")
+        .build()
+        .bind(Labels.of("host", uid.toString()))
+
+    /**
+     * The CPU usage on the host.
+     */
+    private val _cpuUsage = meter.doubleValueRecorderBuilder("cpu.usage")
+        .setDescription("The amount of CPU resources used by the host")
+        .setUnit("MHz")
+        .build()
+        .bind(Labels.of("host", uid.toString()))
+
+    /**
+     * The CPU demand on the host.
+     */
+    private val _cpuDemand = meter.doubleValueRecorderBuilder("cpu.demand")
+        .setDescription("The amount of CPU resources the guests would use if there were no CPU contention or CPU limits")
+        .setUnit("MHz")
+        .build()
+        .bind(Labels.of("host", uid.toString()))
+
+    /**
+     * The requested work for the CPU.
+     */
+    private val _cpuPower = meter.doubleValueRecorderBuilder("power.usage")
+        .setDescription("The amount of power used by the CPU")
+        .setUnit("W")
+        .build()
+        .bind(Labels.of("host", uid.toString()))
+
+    /**
+     * The requested work for the CPU.
+     */
+    private val _cpuWork = meter.doubleValueRecorderBuilder("cpu.work.total")
+        .setDescription("The amount of work supplied to the CPU")
+        .setUnit("1")
+        .build()
+        .bind(Labels.of("host", uid.toString()))
+
+    /**
+     * The work actually performed by the CPU.
+     */
+    private val _cpuWorkGranted = meter.doubleValueRecorderBuilder("cpu.work.granted")
+        .setDescription("The amount of work performed by the CPU")
+        .setUnit("1")
+        .build()
+        .bind(Labels.of("host", uid.toString()))
+
+    /**
+     * The work that could not be performed by the CPU due to overcommitting resource.
+     */
+    private val _cpuWorkOvercommit = meter.doubleValueRecorderBuilder("cpu.work.overcommit")
+        .setDescription("The amount of work not performed by the CPU due to overcommitment")
+        .setUnit("1")
+        .build()
+        .bind(Labels.of("host", uid.toString()))
+
+    /**
+     * The work that could not be performed by the CPU due to interference.
+     */
+    private val _cpuWorkInterference = meter.doubleValueRecorderBuilder("cpu.work.interference")
+        .setDescription("The amount of work not performed by the CPU due to interference")
+        .setUnit("1")
+        .build()
+        .bind(Labels.of("host", uid.toString()))
+
     init {
         // Launch hypervisor onto machine
         scope.launch {
@@ -166,12 +239,11 @@ public class SimHost(
         require(canFit(server)) { "Server does not fit" }
         val guest = Guest(server, hypervisor.createMachine(server.flavor.toMachineModel()))
         guests[server] = guest
+        _guests.add(1)
 
         if (start) {
             guest.start()
         }
-
-        _events.emit(HostEvent.VmsUpdated(this, guests.count { it.value.state == ServerState.RUNNING }, availableMemory))
     }
 
     override fun contains(server: Server): Boolean {
@@ -191,6 +263,7 @@ public class SimHost(
     override suspend fun delete(server: Server) {
         val guest = guests.remove(server) ?: return
         guest.terminate()
+        _guests.add(-1)
     }
 
     override fun addListener(listener: HostListener) {
@@ -228,6 +301,7 @@ public class SimHost(
             }
         }
 
+        _activeGuests.add(1)
         listeners.forEach { it.onStateChanged(this, vm.server, vm.state) }
     }
 
@@ -238,9 +312,8 @@ public class SimHost(
             }
         }
 
+        _activeGuests.add(-1)
         listeners.forEach { it.onStateChanged(this, vm.server, vm.state) }
-
-        _events.emit(HostEvent.VmsUpdated(this@SimHost, guests.count { it.value.state == ServerState.RUNNING }, availableMemory))
     }
 
     override suspend fun fail() {