merge: Increase minimum Java version to 17 (#115)

This pull request increases the minimum version of Java required by OpenDC to 17.
This new version of Java introduces several new features compared to our old minimum 
version (11), which we attempt to apply in this conversion.

## Implementation Notes :hammer_and_pick:

* Increase minimum Java version to Java 17 
* Use RandomGenerator as randomness source 
* Add common dispatcher interface 
* Add compatibility with Kotlin coroutines
* Use InstantSource as time source
* Re-implement SimulationScheduler as Dispatcher 
* Replace use of CoroutineContext by Dispatcher 

## External Dependencies :four_leaf_clover:

* Java 17

## Breaking API Changes :warning:

* The use of `CoroutineContext` and `Clock` as parameters of classes has been replaced 
  by the `Dispatcher` interface.
* The use of `Clock` has been replaced by `InstantSource` which does not carry time
   zone info.
* The use of `Random` and `SplittableRandom` as parameter type has been replaced 
   by `RandomGenerator`

3 files changed, 10 insertions, 12 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 307ad5a5..47b4d4fa 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
@@ -31,6 +31,8 @@ import kotlinx.coroutines.delay
 import kotlinx.coroutines.isActive
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.suspendCancellableCoroutine
+import org.opendc.common.Dispatcher
+import org.opendc.common.asCoroutineDispatcher
 import org.opendc.faas.service.FunctionObject
 import org.opendc.faas.service.deployer.FunctionDeployer
 import org.opendc.faas.service.deployer.FunctionInstance
@@ -44,10 +46,8 @@ 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.util.ArrayDeque
 import kotlin.coroutines.Continuation
-import kotlin.coroutines.CoroutineContext
 import kotlin.coroutines.resume
 import kotlin.coroutines.resumeWithException
 
@@ -55,8 +55,7 @@ import kotlin.coroutines.resumeWithException
  * A [FunctionDeployer] that uses that simulates the [FunctionInstance]s.
  */
 public class SimFunctionDeployer(
-    context: CoroutineContext,
-    private val clock: Clock,
+    private val dispatcher: Dispatcher,
     private val model: MachineModel,
     private val delayInjector: DelayInjector,
     private val mapper: SimFaaSWorkloadMapper = SimMetaFaaSWorkloadMapper()
@@ -64,7 +63,7 @@ public class SimFunctionDeployer(
     /**
      * The [CoroutineScope] of this deployer.
      */
-    private val scope = CoroutineScope(context + Job())
+    private val scope = CoroutineScope(dispatcher.asCoroutineDispatcher() + Job())
 
     override fun deploy(function: FunctionObject, listener: FunctionInstanceListener): Instance {
         val instance = Instance(function, listener)
@@ -86,7 +85,7 @@ public class SimFunctionDeployer(
          * The machine that will execute the workloads.
          */
         public val machine: SimMachine = SimBareMetalMachine.create(
-            FlowEngine.create(scope.coroutineContext, clock).newGraph(),
+            FlowEngine.create(dispatcher).newGraph(),
             model
         )
 
diff --git a/opendc-faas/opendc-faas-simulator/src/main/kotlin/org/opendc/faas/simulator/delay/StochasticDelayInjector.kt b/opendc-faas/opendc-faas-simulator/src/main/kotlin/org/opendc/faas/simulator/delay/StochasticDelayInjector.kt
index d3b31bb9..de7b4aa5 100644
--- a/opendc-faas/opendc-faas-simulator/src/main/kotlin/org/opendc/faas/simulator/delay/StochasticDelayInjector.kt
+++ b/opendc-faas/opendc-faas-simulator/src/main/kotlin/org/opendc/faas/simulator/delay/StochasticDelayInjector.kt
@@ -23,13 +23,13 @@
 package org.opendc.faas.simulator.delay
 
 import org.opendc.faas.service.deployer.FunctionInstance
-import java.util.Random
+import java.util.random.RandomGenerator
 import kotlin.math.abs
 
 /*
  * Interface for instance deployment delay estimation.
  */
-public class StochasticDelayInjector(private val model: ColdStartModel, private val random: Random) : DelayInjector {
+public class StochasticDelayInjector(private val model: ColdStartModel, private val random: RandomGenerator) : DelayInjector {
     override fun getColdStartDelay(instance: FunctionInstance): Long {
         val (mean, sd) = model.coldStartParam(instance.function.memorySize.toInt())
         return abs(random.nextGaussian() * sd + mean).toLong()
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 6baee7ea..be133ded 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
@@ -73,13 +73,12 @@ internal class SimFaaSServiceTest {
         })
 
         val delayInjector = StochasticDelayInjector(ColdStartModel.GOOGLE, random)
-        val deployer = SimFunctionDeployer(coroutineContext, clock, machineModel, delayInjector) { workload }
+        val deployer = SimFunctionDeployer(dispatcher, machineModel, delayInjector) { workload }
         val service = FaaSService(
-            coroutineContext,
-            clock,
+            dispatcher,
             deployer,
             RandomRoutingPolicy(),
-            FunctionTerminationPolicyFixed(coroutineContext, clock, timeout = Duration.ofMillis(10000))
+            FunctionTerminationPolicyFixed(dispatcher, timeout = Duration.ofMillis(10000))
         )
 
         val client = service.newClient()