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`.

9 files changed, 19 insertions, 18 deletions

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))