refactor: Use InstantSource as time source

This change updates the modules of OpenDC to always accept
the `InstantSource` interface as source of time. Previously we used
`java.time.Clock`, but this class is bound to a time zone which does not
make sense for our use-cases.

Since `java.time.Clock` implements `java.time.InstantSource`, it can be
used in places that require an `InstantSource` as parameter. Conversion
from `InstantSource` to `Clock` is also possible by invoking
`InstantSource#withZone`.

33 files changed, 76 insertions, 74 deletions

diff --git a/opendc-common/src/main/kotlin/org/opendc/common/util/Pacer.kt b/opendc-common/src/main/kotlin/org/opendc/common/util/Pacer.kt
index edf607d2..b6141db1 100644
--- a/opendc-common/src/main/kotlin/org/opendc/common/util/Pacer.kt
+++ b/opendc-common/src/main/kotlin/org/opendc/common/util/Pacer.kt
@@ -26,7 +26,7 @@ import kotlinx.coroutines.Delay
 import kotlinx.coroutines.DisposableHandle
 import kotlinx.coroutines.InternalCoroutinesApi
 import java.lang.Runnable
-import java.time.Clock
+import java.time.InstantSource
 import kotlin.coroutines.ContinuationInterceptor
 import kotlin.coroutines.CoroutineContext
 
@@ -40,7 +40,7 @@ import kotlin.coroutines.CoroutineContext
  */
 public class Pacer(
     private val context: CoroutineContext,
-    private val clock: Clock,
+    private val clock: InstantSource,
     private val quantum: Long,
     private val process: (Long) -> Unit
 ) {
diff --git a/opendc-common/src/main/kotlin/org/opendc/common/util/TimerScheduler.kt b/opendc-common/src/main/kotlin/org/opendc/common/util/TimerScheduler.kt
index 44d6010f..864512d3 100644
--- a/opendc-common/src/main/kotlin/org/opendc/common/util/TimerScheduler.kt
+++ b/opendc-common/src/main/kotlin/org/opendc/common/util/TimerScheduler.kt
@@ -25,7 +25,7 @@ package org.opendc.common.util
 import kotlinx.coroutines.Delay
 import kotlinx.coroutines.DisposableHandle
 import kotlinx.coroutines.InternalCoroutinesApi
-import java.time.Clock
+import java.time.InstantSource
 import java.util.ArrayDeque
 import java.util.PriorityQueue
 import kotlin.coroutines.ContinuationInterceptor
@@ -37,7 +37,7 @@ import kotlin.coroutines.CoroutineContext
  * @param context The [CoroutineContext] to run the tasks with.
  * @param clock The clock to keep track of the time.
  */
-public class TimerScheduler<T>(private val context: CoroutineContext, private val clock: Clock) {
+public class TimerScheduler<T>(private val context: CoroutineContext, private val clock: InstantSource) {
     /**
      * The [Delay] instance that provides scheduled execution of [Runnable]s.
      */
diff --git a/opendc-compute/opendc-compute-service/src/main/kotlin/org/opendc/compute/service/ComputeService.kt b/opendc-compute/opendc-compute-service/src/main/kotlin/org/opendc/compute/service/ComputeService.kt
index 85222c10..4ced9569 100644
--- a/opendc-compute/opendc-compute-service/src/main/kotlin/org/opendc/compute/service/ComputeService.kt
+++ b/opendc-compute/opendc-compute-service/src/main/kotlin/org/opendc/compute/service/ComputeService.kt
@@ -28,8 +28,8 @@ import org.opendc.compute.service.driver.Host
 import org.opendc.compute.service.internal.ComputeServiceImpl
 import org.opendc.compute.service.scheduler.ComputeScheduler
 import org.opendc.compute.service.telemetry.SchedulerStats
-import java.time.Clock
 import java.time.Duration
+import java.time.InstantSource
 import kotlin.coroutines.CoroutineContext
 
 /**
@@ -87,7 +87,7 @@ public interface ComputeService : AutoCloseable {
          */
         public operator fun invoke(
             context: CoroutineContext,
-            clock: Clock,
+            clock: InstantSource,
             scheduler: ComputeScheduler,
             schedulingQuantum: Duration = Duration.ofMinutes(5)
         ): ComputeService {
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 b377c3e3..2b755988 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
@@ -35,9 +35,9 @@ import org.opendc.compute.service.driver.HostListener
 import org.opendc.compute.service.driver.HostState
 import org.opendc.compute.service.scheduler.ComputeScheduler
 import org.opendc.compute.service.telemetry.SchedulerStats
-import java.time.Clock
 import java.time.Duration
 import java.time.Instant
+import java.time.InstantSource
 import java.util.ArrayDeque
 import java.util.Deque
 import java.util.Random
@@ -55,7 +55,7 @@ import kotlin.math.max
  */
 internal class ComputeServiceImpl(
     coroutineContext: CoroutineContext,
-    private val clock: Clock,
+    private val clock: InstantSource,
     private val scheduler: ComputeScheduler,
     schedulingQuantum: Duration
 ) : ComputeService, HostListener {
diff --git a/opendc-compute/opendc-compute-simulator/src/main/kotlin/org/opendc/compute/simulator/SimHost.kt b/opendc-compute/opendc-compute-simulator/src/main/kotlin/org/opendc/compute/simulator/SimHost.kt
index 5eccc6ec..a44ccc27 100644
--- a/opendc-compute/opendc-compute-simulator/src/main/kotlin/org/opendc/compute/simulator/SimHost.kt
+++ b/opendc-compute/opendc-compute-simulator/src/main/kotlin/org/opendc/compute/simulator/SimHost.kt
@@ -45,9 +45,9 @@ import org.opendc.simulator.compute.model.ProcessingNode
 import org.opendc.simulator.compute.model.ProcessingUnit
 import org.opendc.simulator.compute.workload.SimWorkload
 import org.opendc.simulator.compute.workload.SimWorkloads
-import java.time.Clock
 import java.time.Duration
 import java.time.Instant
+import java.time.InstantSource
 import java.util.UUID
 import java.util.function.Supplier
 
@@ -68,7 +68,7 @@ public class SimHost(
     override val uid: UUID,
     override val name: String,
     override val meta: Map<String, Any>,
-    private val clock: Clock,
+    private val clock: InstantSource,
     private val machine: SimBareMetalMachine,
     private val hypervisor: SimHypervisor,
     private val mapper: SimWorkloadMapper = DefaultWorkloadMapper,
diff --git a/opendc-compute/opendc-compute-simulator/src/main/kotlin/org/opendc/compute/simulator/failure/HostFault.kt b/opendc-compute/opendc-compute-simulator/src/main/kotlin/org/opendc/compute/simulator/failure/HostFault.kt
index 258ccc89..d34f70d7 100644
--- a/opendc-compute/opendc-compute-simulator/src/main/kotlin/org/opendc/compute/simulator/failure/HostFault.kt
+++ b/opendc-compute/opendc-compute-simulator/src/main/kotlin/org/opendc/compute/simulator/failure/HostFault.kt
@@ -23,7 +23,7 @@
 package org.opendc.compute.simulator.failure
 
 import org.opendc.compute.simulator.SimHost
-import java.time.Clock
+import java.time.InstantSource
 
 /**
  * Interface responsible for applying the fault to a host.
@@ -32,5 +32,5 @@ public interface HostFault {
     /**
      * Apply the fault to the specified [victims].
      */
-    public suspend fun apply(clock: Clock, victims: List<SimHost>)
+    public suspend fun apply(clock: InstantSource, victims: List<SimHost>)
 }
diff --git a/opendc-compute/opendc-compute-simulator/src/main/kotlin/org/opendc/compute/simulator/failure/HostFaultInjector.kt b/opendc-compute/opendc-compute-simulator/src/main/kotlin/org/opendc/compute/simulator/failure/HostFaultInjector.kt
index 5eff439f..afbb99d2 100644
--- a/opendc-compute/opendc-compute-simulator/src/main/kotlin/org/opendc/compute/simulator/failure/HostFaultInjector.kt
+++ b/opendc-compute/opendc-compute-simulator/src/main/kotlin/org/opendc/compute/simulator/failure/HostFaultInjector.kt
@@ -26,6 +26,7 @@ import org.apache.commons.math3.distribution.RealDistribution
 import org.opendc.compute.simulator.SimHost
 import org.opendc.compute.simulator.internal.HostFaultInjectorImpl
 import java.time.Clock
+import java.time.InstantSource
 import kotlin.coroutines.CoroutineContext
 
 /**
@@ -55,7 +56,7 @@ public interface HostFaultInjector : AutoCloseable {
          */
         public operator fun invoke(
             context: CoroutineContext,
-            clock: Clock,
+            clock: InstantSource,
             hosts: Set<SimHost>,
             iat: RealDistribution,
             selector: VictimSelector,
diff --git a/opendc-compute/opendc-compute-simulator/src/main/kotlin/org/opendc/compute/simulator/failure/StartStopHostFault.kt b/opendc-compute/opendc-compute-simulator/src/main/kotlin/org/opendc/compute/simulator/failure/StartStopHostFault.kt
index fc7cebfc..8bd25391 100644
--- a/opendc-compute/opendc-compute-simulator/src/main/kotlin/org/opendc/compute/simulator/failure/StartStopHostFault.kt
+++ b/opendc-compute/opendc-compute-simulator/src/main/kotlin/org/opendc/compute/simulator/failure/StartStopHostFault.kt
@@ -25,14 +25,14 @@ package org.opendc.compute.simulator.failure
 import kotlinx.coroutines.delay
 import org.apache.commons.math3.distribution.RealDistribution
 import org.opendc.compute.simulator.SimHost
-import java.time.Clock
+import java.time.InstantSource
 import kotlin.math.roundToLong
 
 /**
  * A type of [HostFault] where the hosts are stopped and recover after some random amount of time.
  */
 public class StartStopHostFault(private val duration: RealDistribution) : HostFault {
-    override suspend fun apply(clock: Clock, victims: List<SimHost>) {
+    override suspend fun apply(clock: InstantSource, victims: List<SimHost>) {
         for (host in victims) {
             host.fail()
         }
diff --git a/opendc-compute/opendc-compute-simulator/src/main/kotlin/org/opendc/compute/simulator/internal/Guest.kt b/opendc-compute/opendc-compute-simulator/src/main/kotlin/org/opendc/compute/simulator/internal/Guest.kt
index ca947625..02766cb1 100644
--- a/opendc-compute/opendc-compute-simulator/src/main/kotlin/org/opendc/compute/simulator/internal/Guest.kt
+++ b/opendc-compute/opendc-compute-simulator/src/main/kotlin/org/opendc/compute/simulator/internal/Guest.kt
@@ -32,15 +32,15 @@ import org.opendc.compute.simulator.SimWorkloadMapper
 import org.opendc.simulator.compute.SimMachineContext
 import org.opendc.simulator.compute.kernel.SimHypervisor
 import org.opendc.simulator.compute.kernel.SimVirtualMachine
-import java.time.Clock
 import java.time.Duration
 import java.time.Instant
+import java.time.InstantSource
 
 /**
  * A virtual machine instance that is managed by a [SimHost].
  */
 internal class Guest(
-    private val clock: Clock,
+    private val clock: InstantSource,
     val host: SimHost,
     private val hypervisor: SimHypervisor,
     private val mapper: SimWorkloadMapper,
diff --git a/opendc-compute/opendc-compute-simulator/src/main/kotlin/org/opendc/compute/simulator/internal/HostFaultInjectorImpl.kt b/opendc-compute/opendc-compute-simulator/src/main/kotlin/org/opendc/compute/simulator/internal/HostFaultInjectorImpl.kt
index f03bffe9..afc0b0d4 100644
--- a/opendc-compute/opendc-compute-simulator/src/main/kotlin/org/opendc/compute/simulator/internal/HostFaultInjectorImpl.kt
+++ b/opendc-compute/opendc-compute-simulator/src/main/kotlin/org/opendc/compute/simulator/internal/HostFaultInjectorImpl.kt
@@ -32,7 +32,7 @@ import org.opendc.compute.simulator.SimHost
 import org.opendc.compute.simulator.failure.HostFault
 import org.opendc.compute.simulator.failure.HostFaultInjector
 import org.opendc.compute.simulator.failure.VictimSelector
-import java.time.Clock
+import java.time.InstantSource
 import kotlin.coroutines.CoroutineContext
 import kotlin.math.roundToLong
 
@@ -40,7 +40,7 @@ import kotlin.math.roundToLong
  * Internal implementation of the [HostFaultInjector] interface.
  *
  * @param context The scope to run the fault injector in.
- * @param clock The [Clock] to keep track of simulation time.
+ * @param clock The [InstantSource] to keep track of simulation time.
  * @param hosts The set of hosts to inject faults into.
  * @param iat The inter-arrival time distribution of the failures (in hours).
  * @param selector The [VictimSelector] to select the host victims.
@@ -48,7 +48,7 @@ import kotlin.math.roundToLong
  */
 internal class HostFaultInjectorImpl(
     private val context: CoroutineContext,
-    private val clock: Clock,
+    private val clock: InstantSource,
     private val hosts: Set<SimHost>,
     private val iat: RealDistribution,
     private val selector: VictimSelector,
diff --git a/opendc-compute/opendc-compute-simulator/src/test/kotlin/org/opendc/compute/simulator/failure/HostFaultInjectorTest.kt b/opendc-compute/opendc-compute-simulator/src/test/kotlin/org/opendc/compute/simulator/failure/HostFaultInjectorTest.kt
index a65c37cf..54a5d1c8 100644
--- a/opendc-compute/opendc-compute-simulator/src/test/kotlin/org/opendc/compute/simulator/failure/HostFaultInjectorTest.kt
+++ b/opendc-compute/opendc-compute-simulator/src/test/kotlin/org/opendc/compute/simulator/failure/HostFaultInjectorTest.kt
@@ -30,8 +30,8 @@ import org.apache.commons.math3.random.Well19937c
 import org.junit.jupiter.api.Test
 import org.opendc.compute.simulator.SimHost
 import org.opendc.simulator.kotlin.runSimulation
-import java.time.Clock
 import java.time.Duration
+import java.time.InstantSource
 import kotlin.coroutines.CoroutineContext
 import kotlin.math.ln
 
@@ -100,7 +100,7 @@ class HostFaultInjectorTest {
     /**
      * Create a simple start stop fault injector.
      */
-    private fun createSimpleInjector(context: CoroutineContext, clock: Clock, hosts: Set<SimHost>): HostFaultInjector {
+    private fun createSimpleInjector(context: CoroutineContext, clock: InstantSource, hosts: Set<SimHost>): HostFaultInjector {
         val rng = Well19937c(0)
         val iat = LogNormalDistribution(rng, ln(24 * 7.0), 1.03)
         val selector = StochasticVictimSelector(LogNormalDistribution(rng, 1.88, 1.25))
diff --git a/opendc-experiments/opendc-experiments-base/src/main/kotlin/org/opendc/experiments/provisioner/Provisioner.kt b/opendc-experiments/opendc-experiments-base/src/main/kotlin/org/opendc/experiments/provisioner/Provisioner.kt
index 7fe3a2eb..66fcca22 100644
--- a/opendc-experiments/opendc-experiments-base/src/main/kotlin/org/opendc/experiments/provisioner/Provisioner.kt
+++ b/opendc-experiments/opendc-experiments-base/src/main/kotlin/org/opendc/experiments/provisioner/Provisioner.kt
@@ -25,7 +25,7 @@ package org.opendc.experiments.provisioner
 import org.opendc.experiments.MutableServiceRegistry
 import org.opendc.experiments.ServiceRegistry
 import org.opendc.experiments.internal.ServiceRegistryImpl
-import java.time.Clock
+import java.time.InstantSource
 import java.util.ArrayDeque
 import java.util.SplittableRandom
 import kotlin.coroutines.CoroutineContext
@@ -38,15 +38,15 @@ import kotlin.coroutines.CoroutineContext
  * down after the simulation completes.
  *
  * @param coroutineContext The [CoroutineContext] in which the environment is set up.
- * @param clock The simulation [Clock].
+ * @param clock The simulation clock represented as [InstantSource].
  * @param seed A seed for initializing the randomness of the environment.
  */
-public class Provisioner(coroutineContext: CoroutineContext, clock: Clock, seed: Long) : AutoCloseable {
+public class Provisioner(coroutineContext: CoroutineContext, clock: InstantSource, seed: Long) : AutoCloseable {
     /**
      * Implementation of [ProvisioningContext].
      */
     private val context = object : ProvisioningContext {
-        override val clock: Clock = clock
+        override val clock: InstantSource = clock
         override val coroutineContext: CoroutineContext = coroutineContext
         override val seeder: SplittableRandom = SplittableRandom(seed)
         override val registry: MutableServiceRegistry = ServiceRegistryImpl()
diff --git a/opendc-experiments/opendc-experiments-base/src/main/kotlin/org/opendc/experiments/provisioner/ProvisioningContext.kt b/opendc-experiments/opendc-experiments-base/src/main/kotlin/org/opendc/experiments/provisioner/ProvisioningContext.kt
index b8679872..7eec6fa4 100644
--- a/opendc-experiments/opendc-experiments-base/src/main/kotlin/org/opendc/experiments/provisioner/ProvisioningContext.kt
+++ b/opendc-experiments/opendc-experiments-base/src/main/kotlin/org/opendc/experiments/provisioner/ProvisioningContext.kt
@@ -23,7 +23,7 @@
 package org.opendc.experiments.provisioner
 
 import org.opendc.experiments.MutableServiceRegistry
-import java.time.Clock
+import java.time.InstantSource
 import java.util.SplittableRandom
 import java.util.random.RandomGenerator
 import kotlin.coroutines.CoroutineContext
@@ -40,9 +40,9 @@ public interface ProvisioningContext {
     public val coroutineContext: CoroutineContext
 
     /**
-     * The [Clock] tracking the virtual simulation time.
+     * The [InstantSource] tracking the virtual simulation time.
      */
-    public val clock: Clock
+    public val clock: InstantSource
 
     /**
      * A [SplittableRandom] instance used to seed the provisioners.
diff --git a/opendc-experiments/opendc-experiments-compute/src/main/kotlin/org/opendc/experiments/compute/FailureModel.kt b/opendc-experiments/opendc-experiments-compute/src/main/kotlin/org/opendc/experiments/compute/FailureModel.kt
index de2447c6..eb85dbb8 100644
--- a/opendc-experiments/opendc-experiments-compute/src/main/kotlin/org/opendc/experiments/compute/FailureModel.kt
+++ b/opendc-experiments/opendc-experiments-compute/src/main/kotlin/org/opendc/experiments/compute/FailureModel.kt
@@ -24,7 +24,7 @@ package org.opendc.experiments.compute
 
 import org.opendc.compute.service.ComputeService
 import org.opendc.compute.simulator.failure.HostFaultInjector
-import java.time.Clock
+import java.time.InstantSource
 import java.util.random.RandomGenerator
 import kotlin.coroutines.CoroutineContext
 
@@ -37,7 +37,7 @@ public interface FailureModel {
      */
     public fun createInjector(
         context: CoroutineContext,
-        clock: Clock,
+        clock: InstantSource,
         service: ComputeService,
         random: RandomGenerator
     ): HostFaultInjector
diff --git a/opendc-experiments/opendc-experiments-compute/src/main/kotlin/org/opendc/experiments/compute/FailureModels.kt b/opendc-experiments/opendc-experiments-compute/src/main/kotlin/org/opendc/experiments/compute/FailureModels.kt
index a77047b0..679e370a 100644
--- a/opendc-experiments/opendc-experiments-compute/src/main/kotlin/org/opendc/experiments/compute/FailureModels.kt
+++ b/opendc-experiments/opendc-experiments-compute/src/main/kotlin/org/opendc/experiments/compute/FailureModels.kt
@@ -31,8 +31,8 @@ import org.opendc.compute.simulator.SimHost
 import org.opendc.compute.simulator.failure.HostFaultInjector
 import org.opendc.compute.simulator.failure.StartStopHostFault
 import org.opendc.compute.simulator.failure.StochasticVictimSelector
-import java.time.Clock
 import java.time.Duration
+import java.time.InstantSource
 import java.util.random.RandomGenerator
 import kotlin.coroutines.CoroutineContext
 import kotlin.math.ln
@@ -47,7 +47,7 @@ public fun grid5000(failureInterval: Duration): FailureModel {
     return object : FailureModel {
         override fun createInjector(
             context: CoroutineContext,
-            clock: Clock,
+            clock: InstantSource,
             service: ComputeService,
             random: RandomGenerator
         ): HostFaultInjector {
diff --git a/opendc-experiments/opendc-experiments-compute/src/main/kotlin/org/opendc/experiments/compute/TraceHelpers.kt b/opendc-experiments/opendc-experiments-compute/src/main/kotlin/org/opendc/experiments/compute/TraceHelpers.kt
index f0e31932..16d28edb 100644
--- a/opendc-experiments/opendc-experiments-compute/src/main/kotlin/org/opendc/experiments/compute/TraceHelpers.kt
+++ b/opendc-experiments/opendc-experiments-compute/src/main/kotlin/org/opendc/experiments/compute/TraceHelpers.kt
@@ -29,7 +29,7 @@ import kotlinx.coroutines.delay
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.yield
 import org.opendc.compute.service.ComputeService
-import java.time.Clock
+import java.time.InstantSource
 import java.util.Random
 import kotlin.coroutines.coroutineContext
 import kotlin.math.max
@@ -45,7 +45,7 @@ import kotlin.math.max
  * @param interference A flag to indicate that VM interference needs to be enabled.
  */
 public suspend fun ComputeService.replay(
-    clock: Clock,
+    clock: InstantSource,
     trace: List<VirtualMachine>,
     seed: Long,
     submitImmediately: Boolean = false,
diff --git a/opendc-experiments/opendc-experiments-compute/src/main/kotlin/org/opendc/experiments/compute/telemetry/ComputeMetricReader.kt b/opendc-experiments/opendc-experiments-compute/src/main/kotlin/org/opendc/experiments/compute/telemetry/ComputeMetricReader.kt
index ac058171..f39f74bc 100644
--- a/opendc-experiments/opendc-experiments-compute/src/main/kotlin/org/opendc/experiments/compute/telemetry/ComputeMetricReader.kt
+++ b/opendc-experiments/opendc-experiments-compute/src/main/kotlin/org/opendc/experiments/compute/telemetry/ComputeMetricReader.kt
@@ -35,9 +35,9 @@ import org.opendc.experiments.compute.telemetry.table.HostTableReader
 import org.opendc.experiments.compute.telemetry.table.ServerInfo
 import org.opendc.experiments.compute.telemetry.table.ServerTableReader
 import org.opendc.experiments.compute.telemetry.table.ServiceTableReader
-import java.time.Clock
 import java.time.Duration
 import java.time.Instant
+import java.time.InstantSource
 
 /**
  * A helper class to collect metrics from a [ComputeService] instance and automatically export the metrics every
@@ -51,7 +51,7 @@ import java.time.Instant
  */
 public class ComputeMetricReader(
     scope: CoroutineScope,
-    clock: Clock,
+    clock: InstantSource,
     private val service: ComputeService,
     private val monitor: ComputeMonitor,
     private val exportInterval: Duration = Duration.ofMinutes(5)
diff --git a/opendc-experiments/opendc-experiments-faas/src/main/kotlin/org/opendc/experiments/faas/TraceHelpers.kt b/opendc-experiments/opendc-experiments-faas/src/main/kotlin/org/opendc/experiments/faas/TraceHelpers.kt
index c4001e2e..7a354d69 100644
--- a/opendc-experiments/opendc-experiments-faas/src/main/kotlin/org/opendc/experiments/faas/TraceHelpers.kt
+++ b/opendc-experiments/opendc-experiments-faas/src/main/kotlin/org/opendc/experiments/faas/TraceHelpers.kt
@@ -28,16 +28,16 @@ import kotlinx.coroutines.coroutineScope
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.launch
 import org.opendc.faas.service.FaaSService
-import java.time.Clock
+import java.time.InstantSource
 import kotlin.math.max
 
 /**
  * Run a simulation of the [FaaSService] by replaying the workload trace given by [trace].
  *
- * @param clock A [Clock] instance tracking simulation time.
+ * @param clock An [InstantSource] instance tracking simulation time.
  * @param trace The trace to simulate.
  */
-public suspend fun FaaSService.replay(clock: Clock, trace: List<FunctionTrace>) {
+public suspend fun FaaSService.replay(clock: InstantSource, trace: List<FunctionTrace>) {
     val client = newClient()
     try {
         coroutineScope {
diff --git a/opendc-experiments/opendc-experiments-tf20/src/main/kotlin/org/opendc/experiments/tf20/core/SimTFDevice.kt b/opendc-experiments/opendc-experiments-tf20/src/main/kotlin/org/opendc/experiments/tf20/core/SimTFDevice.kt
index eb308970..51f6e763 100644
--- a/opendc-experiments/opendc-experiments-tf20/src/main/kotlin/org/opendc/experiments/tf20/core/SimTFDevice.kt
+++ b/opendc-experiments/opendc-experiments-tf20/src/main/kotlin/org/opendc/experiments/tf20/core/SimTFDevice.kt
@@ -42,7 +42,7 @@ import org.opendc.simulator.flow2.FlowEngine
 import org.opendc.simulator.flow2.FlowStage
 import org.opendc.simulator.flow2.FlowStageLogic
 import org.opendc.simulator.flow2.OutPort
-import java.time.Clock
+import java.time.InstantSource
 import java.util.ArrayDeque
 import java.util.UUID
 import kotlin.coroutines.Continuation
@@ -58,7 +58,7 @@ public class SimTFDevice(
     override val uid: UUID,
     override val isGpu: Boolean,
     context: CoroutineContext,
-    clock: Clock,
+    clock: InstantSource,
     pu: ProcessingUnit,
     private val memory: MemoryUnit,
     powerModel: CpuPowerModel
diff --git a/opendc-experiments/opendc-experiments-tf20/src/main/kotlin/org/opendc/experiments/tf20/network/NetworkController.kt b/opendc-experiments/opendc-experiments-tf20/src/main/kotlin/org/opendc/experiments/tf20/network/NetworkController.kt
index 7d65a674..6fcdf513 100644
--- a/opendc-experiments/opendc-experiments-tf20/src/main/kotlin/org/opendc/experiments/tf20/network/NetworkController.kt
+++ b/opendc-experiments/opendc-experiments-tf20/src/main/kotlin/org/opendc/experiments/tf20/network/NetworkController.kt
@@ -24,14 +24,14 @@ package org.opendc.experiments.tf20.network
 
 import kotlinx.coroutines.channels.Channel
 import org.opendc.common.util.TimerScheduler
-import java.time.Clock
+import java.time.InstantSource
 import kotlin.coroutines.CoroutineContext
 
 /**
  * The network controller represents a simple network model between the worker and master nodes during
  * TensorFlow execution.
  */
-public class NetworkController(context: CoroutineContext, clock: Clock) : AutoCloseable {
+public class NetworkController(context: CoroutineContext, clock: InstantSource) : AutoCloseable {
     /**
      * The scheduler for the message.
      */
diff --git a/opendc-experiments/opendc-experiments-workflow/src/main/kotlin/org/opendc/experiments/workflow/TraceHelpers.kt b/opendc-experiments/opendc-experiments-workflow/src/main/kotlin/org/opendc/experiments/workflow/TraceHelpers.kt
index b622362a..2037dad4 100644
--- a/opendc-experiments/opendc-experiments-workflow/src/main/kotlin/org/opendc/experiments/workflow/TraceHelpers.kt
+++ b/opendc-experiments/opendc-experiments-workflow/src/main/kotlin/org/opendc/experiments/workflow/TraceHelpers.kt
@@ -42,7 +42,7 @@ import org.opendc.workflow.api.Task
 import org.opendc.workflow.api.WORKFLOW_TASK_CORES
 import org.opendc.workflow.api.WORKFLOW_TASK_DEADLINE
 import org.opendc.workflow.service.WorkflowService
-import java.time.Clock
+import java.time.InstantSource
 import java.util.UUID
 import kotlin.collections.HashMap
 import kotlin.collections.HashSet
@@ -110,7 +110,7 @@ public fun Trace.toJobs(): List<Job> {
 /**
  * Helper method to replay the specified list of [jobs] and suspend execution util all jobs have finished.
  */
-public suspend fun WorkflowService.replay(clock: Clock, jobs: List<Job>) {
+public suspend fun WorkflowService.replay(clock: InstantSource, jobs: List<Job>) {
     // Sort jobs by their arrival time
     val orderedJobs = jobs.sortedBy { it.metadata.getOrDefault("WORKFLOW_SUBMIT_TIME", Long.MAX_VALUE) as Long }
     if (orderedJobs.isEmpty()) {
diff --git a/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/FaaSService.kt b/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/FaaSService.kt
index 7b40d867..53706c57 100644
--- a/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/FaaSService.kt
+++ b/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/FaaSService.kt
@@ -30,8 +30,8 @@ import org.opendc.faas.service.internal.FaaSServiceImpl
 import org.opendc.faas.service.router.RoutingPolicy
 import org.opendc.faas.service.telemetry.FunctionStats
 import org.opendc.faas.service.telemetry.SchedulerStats
-import java.time.Clock
 import java.time.Duration
+import java.time.InstantSource
 import kotlin.coroutines.CoroutineContext
 
 /**
@@ -71,7 +71,7 @@ public interface FaaSService : AutoCloseable {
          */
         public operator fun invoke(
             context: CoroutineContext,
-            clock: Clock,
+            clock: InstantSource,
             deployer: FunctionDeployer,
             routingPolicy: RoutingPolicy,
             terminationPolicy: FunctionTerminationPolicy,
diff --git a/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/autoscaler/FunctionTerminationPolicyFixed.kt b/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/autoscaler/FunctionTerminationPolicyFixed.kt
index d579ad0c..f494adb1 100644
--- a/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/autoscaler/FunctionTerminationPolicyFixed.kt
+++ b/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/autoscaler/FunctionTerminationPolicyFixed.kt
@@ -25,8 +25,8 @@ package org.opendc.faas.service.autoscaler
 import org.opendc.common.util.TimerScheduler
 import org.opendc.faas.service.deployer.FunctionInstance
 import org.opendc.faas.service.deployer.FunctionInstanceState
-import java.time.Clock
 import java.time.Duration
+import java.time.InstantSource
 import kotlin.coroutines.CoroutineContext
 
 /**
@@ -36,7 +36,7 @@ import kotlin.coroutines.CoroutineContext
  */
 public class FunctionTerminationPolicyFixed(
     context: CoroutineContext,
-    clock: Clock,
+    clock: InstantSource,
     public val timeout: Duration
 ) : FunctionTerminationPolicy {
     /**
diff --git a/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/internal/FaaSServiceImpl.kt b/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/internal/FaaSServiceImpl.kt
index 901213af..3235ff1a 100644
--- a/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/internal/FaaSServiceImpl.kt
+++ b/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/internal/FaaSServiceImpl.kt
@@ -43,8 +43,8 @@ import org.opendc.faas.service.router.RoutingPolicy
 import org.opendc.faas.service.telemetry.FunctionStats
 import org.opendc.faas.service.telemetry.SchedulerStats
 import java.lang.IllegalStateException
-import java.time.Clock
 import java.time.Duration
+import java.time.InstantSource
 import java.util.ArrayDeque
 import java.util.Random
 import java.util.UUID
@@ -61,7 +61,7 @@ import kotlin.coroutines.resumeWithException
  */
 internal class FaaSServiceImpl(
     context: CoroutineContext,
-    private val clock: Clock,
+    private val clock: InstantSource,
     private val deployer: FunctionDeployer,
     private val routingPolicy: RoutingPolicy,
     private val terminationPolicy: FunctionTerminationPolicy,
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 307ad5a5..9ec26d5d 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
@@ -44,7 +44,7 @@ import org.opendc.simulator.compute.SimMachine
 import org.opendc.simulator.compute.model.MachineModel
 import org.opendc.simulator.compute.runWorkload
 import org.opendc.simulator.flow2.FlowEngine
-import java.time.Clock
+import java.time.InstantSource
 import java.util.ArrayDeque
 import kotlin.coroutines.Continuation
 import kotlin.coroutines.CoroutineContext
@@ -56,7 +56,7 @@ import kotlin.coroutines.resumeWithException
  */
 public class SimFunctionDeployer(
     context: CoroutineContext,
-    private val clock: Clock,
+    private val clock: InstantSource,
     private val model: MachineModel,
     private val delayInjector: DelayInjector,
     private val mapper: SimFaaSWorkloadMapper = SimMetaFaaSWorkloadMapper()
diff --git a/opendc-simulator/opendc-simulator-compute/src/main/java/org/opendc/simulator/compute/SimPsuFactories.java b/opendc-simulator/opendc-simulator-compute/src/main/java/org/opendc/simulator/compute/SimPsuFactories.java
index 52d04052..05b40cf8 100644
--- a/opendc-simulator/opendc-simulator-compute/src/main/java/org/opendc/simulator/compute/SimPsuFactories.java
+++ b/opendc-simulator/opendc-simulator-compute/src/main/java/org/opendc/simulator/compute/SimPsuFactories.java
@@ -22,7 +22,7 @@
 
 package org.opendc.simulator.compute;
 
-import java.time.Clock;
+import java.time.InstantSource;
 import org.jetbrains.annotations.NotNull;
 import org.opendc.simulator.compute.model.ProcessingUnit;
 import org.opendc.simulator.compute.power.CpuPowerModel;
@@ -117,7 +117,7 @@ public class SimPsuFactories {
         private final FlowStage stage;
         private final OutPort out;
         private final CpuPowerModel model;
-        private final Clock clock;
+        private final InstantSource clock;
 
         private double targetFreq;
         private double totalUsage;
diff --git a/opendc-simulator/opendc-simulator-compute/src/main/java/org/opendc/simulator/compute/kernel/SimHypervisor.java b/opendc-simulator/opendc-simulator-compute/src/main/java/org/opendc/simulator/compute/kernel/SimHypervisor.java
index 4ebcba71..a1623351 100644
--- a/opendc-simulator/opendc-simulator-compute/src/main/java/org/opendc/simulator/compute/kernel/SimHypervisor.java
+++ b/opendc-simulator/opendc-simulator-compute/src/main/java/org/opendc/simulator/compute/kernel/SimHypervisor.java
@@ -22,7 +22,7 @@
 
 package org.opendc.simulator.compute.kernel;
 
-import java.time.Clock;
+import java.time.InstantSource;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
@@ -253,7 +253,7 @@ public final class SimHypervisor implements SimWorkload {
         private final FlowMultiplexer multiplexer;
         private final FlowStage stage;
         private final List<ScalingGovernor> scalingGovernors;
-        private final Clock clock;
+        private final InstantSource clock;
         private final HvCounters counters;
 
         private long lastCounterUpdate;
@@ -526,7 +526,7 @@ public final class SimHypervisor implements SimWorkload {
         private final VmInterferenceMember interferenceMember;
         private final FlowStage stage;
         private final FlowMultiplexer multiplexer;
-        private final Clock clock;
+        private final InstantSource clock;
 
         private final List<VCpu> cpus;
         private final SimAbstractMachine.Memory memory;
diff --git a/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/flow2/FlowEngine.java b/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/flow2/FlowEngine.java
index 0ebb0da9..cfa5a48f 100644
--- a/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/flow2/FlowEngine.java
+++ b/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/flow2/FlowEngine.java
@@ -23,6 +23,7 @@
 package org.opendc.simulator.flow2;
 
 import java.time.Clock;
+import java.time.InstantSource;
 import java.util.ArrayList;
 import java.util.List;
 import kotlin.coroutines.ContinuationInterceptor;
@@ -57,17 +58,17 @@ public final class FlowEngine implements Runnable {
     private boolean active;
 
     private final CoroutineContext coroutineContext;
-    private final Clock clock;
+    private final InstantSource clock;
     private final Delay delay;
 
     /**
-     * Create a new {@link FlowEngine} instance using the specified {@link CoroutineContext} and {@link Clock}.
+     * Create a new {@link FlowEngine} instance using the specified {@link CoroutineContext} and {@link InstantSource}.
      */
-    public static FlowEngine create(CoroutineContext coroutineContext, Clock clock) {
+    public static FlowEngine create(CoroutineContext coroutineContext, InstantSource clock) {
         return new FlowEngine(coroutineContext, clock);
     }
 
-    FlowEngine(CoroutineContext coroutineContext, Clock clock) {
+    FlowEngine(CoroutineContext coroutineContext, InstantSource clock) {
         this.coroutineContext = coroutineContext;
         this.clock = clock;
 
@@ -78,7 +79,7 @@ public final class FlowEngine implements Runnable {
     /**
      * Obtain the (virtual) {@link Clock} driving the simulation.
      */
-    public Clock getClock() {
+    public InstantSource getClock() {
         return clock;
     }
 
diff --git a/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/flow2/FlowStage.java b/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/flow2/FlowStage.java
index ed5579ea..25f87e04 100644
--- a/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/flow2/FlowStage.java
+++ b/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/flow2/FlowStage.java
@@ -22,7 +22,7 @@
 
 package org.opendc.simulator.flow2;
 
-import java.time.Clock;
+import java.time.InstantSource;
 import java.util.HashMap;
 import java.util.Map;
 import org.slf4j.Logger;
@@ -67,7 +67,7 @@ public final class FlowStage {
      */
     int timerIndex = -1;
 
-    final Clock clock;
+    final InstantSource clock;
     private final FlowStageLogic logic;
     final FlowGraphInternal parentGraph;
     private final FlowEngine engine;
diff --git a/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/flow2/InPort.java b/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/flow2/InPort.java
index fba12aaf..16fed4eb 100644
--- a/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/flow2/InPort.java
+++ b/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/flow2/InPort.java
@@ -22,7 +22,7 @@
 
 package org.opendc.simulator.flow2;
 
-import java.time.Clock;
+import java.time.InstantSource;
 import java.util.Objects;
 
 /**
@@ -40,7 +40,7 @@ public final class InPort implements Inlet {
 
     OutPort output;
     private InHandler handler = InHandlers.noop();
-    private final Clock clock;
+    private final InstantSource clock;
     private final String name;
     private final FlowStage stage;
 
diff --git a/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/flow2/OutPort.java b/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/flow2/OutPort.java
index 332296a0..1f7ed4ee 100644
--- a/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/flow2/OutPort.java
+++ b/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/flow2/OutPort.java
@@ -22,7 +22,7 @@
 
 package org.opendc.simulator.flow2;
 
-import java.time.Clock;
+import java.time.InstantSource;
 import java.util.Objects;
 
 /**
@@ -42,7 +42,7 @@ public final class OutPort implements Outlet {
     private OutHandler handler = OutHandlers.noop();
     private final String name;
     private final FlowStage stage;
-    private final Clock clock;
+    private final InstantSource clock;
 
     OutPort(FlowStage stage, String name, int id) {
         this.name = name;
diff --git a/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/WorkflowService.kt b/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/WorkflowService.kt
index 2436c387..f0e86449 100644
--- a/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/WorkflowService.kt
+++ b/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/WorkflowService.kt
@@ -30,8 +30,8 @@ import org.opendc.workflow.service.scheduler.job.JobOrderPolicy
 import org.opendc.workflow.service.scheduler.task.TaskEligibilityPolicy
 import org.opendc.workflow.service.scheduler.task.TaskOrderPolicy
 import org.opendc.workflow.service.scheduler.telemetry.SchedulerStats
-import java.time.Clock
 import java.time.Duration
+import java.time.InstantSource
 import kotlin.coroutines.CoroutineContext
 
 /**
@@ -71,7 +71,7 @@ public interface WorkflowService : AutoCloseable {
          */
         public operator fun invoke(
             context: CoroutineContext,
-            clock: Clock,
+            clock: InstantSource,
             compute: ComputeClient,
             schedulingQuantum: Duration,
             jobAdmissionPolicy: JobAdmissionPolicy,
diff --git a/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/internal/WorkflowServiceImpl.kt b/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/internal/WorkflowServiceImpl.kt
index b1780896..20e30fd4 100644
--- a/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/internal/WorkflowServiceImpl.kt
+++ b/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/internal/WorkflowServiceImpl.kt
@@ -40,8 +40,8 @@ import org.opendc.workflow.service.scheduler.job.JobOrderPolicy
 import org.opendc.workflow.service.scheduler.task.TaskEligibilityPolicy
 import org.opendc.workflow.service.scheduler.task.TaskOrderPolicy
 import org.opendc.workflow.service.scheduler.telemetry.SchedulerStats
-import java.time.Clock
 import java.time.Duration
+import java.time.InstantSource
 import java.util.PriorityQueue
 import java.util.Queue
 import kotlin.coroutines.CoroutineContext
@@ -53,7 +53,7 @@ import kotlin.coroutines.resume
  */
 public class WorkflowServiceImpl(
     context: CoroutineContext,
-    private val clock: Clock,
+    private val clock: InstantSource,
     private val computeClient: ComputeClient,
     schedulingQuantum: Duration,
     jobAdmissionPolicy: JobAdmissionPolicy,