merge: Expose metrics directly to user (#80)

This pull request adds the ability to access the metrics of resources modeled
by the OpenDC Compute, Workflow, FaaS, and TensorFlow services directly from
their corresponding interfaces. Previously, users would have to interact with
OpenTelemetry to obtain these values, which is complex and provides
significant overhead.

With this pull request, users can access the metrics of all cloud resources
modeled by OpenDC via methods such as `getSchedulerStats()`, etc.

** Breaking Changes **

- `ComputeService.hostCount` removed in favour of `ComputeService.hosts.size`

2 files changed, 20 insertions, 6 deletions

diff --git a/opendc-faas/opendc-faas-simulator/src/main/kotlin/org/opendc/faas/simulator/SimFunctionDeployer.kt b/opendc-faas/opendc-faas-simulator/src/main/kotlin/org/opendc/faas/simulator/SimFunctionDeployer.kt
index 68233c1a..a3d0d34e 100644
--- a/opendc-faas/opendc-faas-simulator/src/main/kotlin/org/opendc/faas/simulator/SimFunctionDeployer.kt
+++ b/opendc-faas/opendc-faas-simulator/src/main/kotlin/org/opendc/faas/simulator/SimFunctionDeployer.kt
@@ -123,7 +123,6 @@ public class SimFunctionDeployer(
         /**
          * Start the function instance.
          */
-        @OptIn(InternalCoroutinesApi::class)
         internal fun start() {
             check(state == FunctionInstanceState.Provisioning) { "Invalid state of function instance" }
             job = scope.launch {
diff --git a/opendc-faas/opendc-faas-simulator/src/test/kotlin/org/opendc/faas/simulator/SimFaaSServiceTest.kt b/opendc-faas/opendc-faas-simulator/src/test/kotlin/org/opendc/faas/simulator/SimFaaSServiceTest.kt
index 0dc9ba87..792a8584 100644
--- a/opendc-faas/opendc-faas-simulator/src/test/kotlin/org/opendc/faas/simulator/SimFaaSServiceTest.kt
+++ b/opendc-faas/opendc-faas-simulator/src/test/kotlin/org/opendc/faas/simulator/SimFaaSServiceTest.kt
@@ -28,22 +28,25 @@ import io.opentelemetry.api.metrics.MeterProvider
 import kotlinx.coroutines.ExperimentalCoroutinesApi
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.yield
+import org.junit.jupiter.api.Assertions.assertEquals
 import org.junit.jupiter.api.BeforeEach
 import org.junit.jupiter.api.Test
 import org.junit.jupiter.api.assertAll
 import org.opendc.faas.service.FaaSService
 import org.opendc.faas.service.autoscaler.FunctionTerminationPolicyFixed
 import org.opendc.faas.service.router.RandomRoutingPolicy
-import org.opendc.faas.simulator.delay.ZeroDelayInjector
+import org.opendc.faas.simulator.delay.ColdStartModel
+import org.opendc.faas.simulator.delay.StochasticDelayInjector
 import org.opendc.faas.simulator.workload.SimFaaSWorkload
 import org.opendc.simulator.compute.model.MachineModel
 import org.opendc.simulator.compute.model.MemoryUnit
 import org.opendc.simulator.compute.model.ProcessingNode
 import org.opendc.simulator.compute.model.ProcessingUnit
-import org.opendc.simulator.compute.workload.SimFlopsWorkload
+import org.opendc.simulator.compute.workload.SimRuntimeWorkload
 import org.opendc.simulator.compute.workload.SimWorkload
 import org.opendc.simulator.core.runBlockingSimulation
 import java.time.Duration
+import java.util.*
 
 /**
  * A test suite for the [FaaSService] implementation under simulated conditions.
@@ -65,10 +68,15 @@ internal class SimFaaSServiceTest {
 
     @Test
     fun testSmoke() = runBlockingSimulation {
-        val workload = spyk(object : SimFaaSWorkload, SimWorkload by SimFlopsWorkload(1000) {
-            override suspend fun invoke() {}
+        val random = Random(0)
+        val workload = spyk(object : SimFaaSWorkload, SimWorkload by SimRuntimeWorkload(1000) {
+            override suspend fun invoke() {
+                delay(random.nextInt(1000).toLong())
+            }
         })
-        val deployer = SimFunctionDeployer(clock, this, machineModel, ZeroDelayInjector) { workload }
+
+        val delayInjector = StochasticDelayInjector(ColdStartModel.GOOGLE, random)
+        val deployer = SimFunctionDeployer(clock, this, machineModel, delayInjector) { workload }
         val service = FaaSService(
             coroutineContext, clock, MeterProvider.noop(), deployer, RandomRoutingPolicy(),
             FunctionTerminationPolicyFixed(coroutineContext, clock, timeout = Duration.ofMillis(10000))
@@ -84,8 +92,15 @@ internal class SimFaaSServiceTest {
 
         yield()
 
+        val funcStats = service.getFunctionStats(function)
+
         assertAll(
             { coVerify { workload.invoke() } },
+            { assertEquals(1, funcStats.totalInvocations) },
+            { assertEquals(1, funcStats.delayedInvocations) },
+            { assertEquals(0, funcStats.failedInvocations) },
+            { assertEquals(100.0, funcStats.waitTime.mean) },
+            { assertEquals(1285.0, funcStats.activeTime.mean) },
         )
     }
 }