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* The use of `CoroutineContext` and `Clock` as parameters of classes has been replaced 
  by the `Dispatcher` interface.
* The use of `Clock` has been replaced by `InstantSource` which does not carry time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* The use of `Random` and `SplittableRandom` as parameter type has been replaced 
   by `RandomGenerator`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, 18 insertions, 18 deletions

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..07b43b6d 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
@@ -22,6 +22,7 @@
 
 package org.opendc.workflow.service
 
+import org.opendc.common.Dispatcher
 import org.opendc.compute.api.ComputeClient
 import org.opendc.workflow.api.Job
 import org.opendc.workflow.service.internal.WorkflowServiceImpl
@@ -30,9 +31,7 @@ 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 kotlin.coroutines.CoroutineContext
 
 /**
  * A service for cloud workflow execution.
@@ -59,9 +58,7 @@ public interface WorkflowService : AutoCloseable {
         /**
          * Construct a new [WorkflowService] implementation.
          *
-         * @param context The [CoroutineContext] to use in the service.
-         * @param clock The clock instance to use.
-         * @param meterProvider The meter provider to use.
+         * @param dispatcher A [Dispatcher] to schedule future events.
          * @param compute The "Compute" client to use.
          * @param schedulingQuantum The scheduling quantum to use (minimum duration between scheduling cycles).
          * @param jobAdmissionPolicy The job admission policy to use.
@@ -70,8 +67,7 @@ public interface WorkflowService : AutoCloseable {
          * @param taskOrderPolicy The task order policy to use.
          */
         public operator fun invoke(
-            context: CoroutineContext,
-            clock: Clock,
+            dispatcher: Dispatcher,
             compute: ComputeClient,
             schedulingQuantum: Duration,
             jobAdmissionPolicy: JobAdmissionPolicy,
@@ -80,8 +76,7 @@ public interface WorkflowService : AutoCloseable {
             taskOrderPolicy: TaskOrderPolicy
         ): WorkflowService {
             return WorkflowServiceImpl(
-                context,
-                clock,
+                dispatcher,
                 compute,
                 schedulingQuantum,
                 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..01c1f565 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
@@ -26,6 +26,8 @@ import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.cancel
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.suspendCancellableCoroutine
+import org.opendc.common.Dispatcher
+import org.opendc.common.asCoroutineDispatcher
 import org.opendc.common.util.Pacer
 import org.opendc.compute.api.ComputeClient
 import org.opendc.compute.api.Image
@@ -40,11 +42,10 @@ 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
 import kotlin.coroutines.resume
 
 /**
@@ -52,8 +53,7 @@ import kotlin.coroutines.resume
  * Datacenter Scheduling.
  */
 public class WorkflowServiceImpl(
-    context: CoroutineContext,
-    private val clock: Clock,
+    dispatcher: Dispatcher,
     private val computeClient: ComputeClient,
     schedulingQuantum: Duration,
     jobAdmissionPolicy: JobAdmissionPolicy,
@@ -64,7 +64,12 @@ public class WorkflowServiceImpl(
     /**
      * The [CoroutineScope] of the service bounded by the lifecycle of the service.
      */
-    private val scope = CoroutineScope(context + kotlinx.coroutines.Job())
+    private val scope = CoroutineScope(dispatcher.asCoroutineDispatcher() + kotlinx.coroutines.Job())
+
+    /**
+     * The [InstantSource] representing the clock of this service.
+     */
+    private val clock = dispatcher.timeSource
 
     /**
      * The incoming jobs ready to be processed by the scheduler.
@@ -149,7 +154,7 @@ public class WorkflowServiceImpl(
     /**
      * The [Pacer] to use for scheduling the scheduler cycles.
      */
-    private val pacer = Pacer(scope.coroutineContext, clock, schedulingQuantum.toMillis()) { doSchedule() }
+    private val pacer = Pacer(dispatcher, schedulingQuantum.toMillis()) { doSchedule() }
 
     private val jobAdmissionPolicy: JobAdmissionPolicy.Logic
     private val taskEligibilityPolicy: TaskEligibilityPolicy.Logic
diff --git a/opendc-workflow/opendc-workflow-service/src/test/kotlin/org/opendc/workflow/service/WorkflowServiceTest.kt b/opendc-workflow/opendc-workflow-service/src/test/kotlin/org/opendc/workflow/service/WorkflowServiceTest.kt
index b165418a..e5e05a92 100644
--- a/opendc-workflow/opendc-workflow-service/src/test/kotlin/org/opendc/workflow/service/WorkflowServiceTest.kt
+++ b/opendc-workflow/opendc-workflow-service/src/test/kotlin/org/opendc/workflow/service/WorkflowServiceTest.kt
@@ -70,7 +70,7 @@ internal class WorkflowServiceTest {
         val computeService = "compute.opendc.org"
         val workflowService = "workflow.opendc.org"
 
-        Provisioner(coroutineContext, clock, seed = 0L).use { provisioner ->
+        Provisioner(dispatcher, seed = 0L).use { provisioner ->
             val scheduler: (ProvisioningContext) -> ComputeScheduler = {
                 FilterScheduler(
                     filters = listOf(ComputeFilter(), VCpuFilter(1.0), RamFilter(1.0)),
@@ -103,7 +103,7 @@ internal class WorkflowServiceTest {
                 Paths.get(checkNotNull(WorkflowServiceTest::class.java.getResource("/trace.gwf")).toURI()),
                 format = "gwf"
             )
-            service.replay(clock, trace.toJobs())
+            service.replay(timeSource, trace.toJobs())
 
             val metrics = service.getSchedulerStats()
 
@@ -119,7 +119,7 @@ internal class WorkflowServiceTest {
                 },
                 { assertEquals(0, metrics.tasksRunning, "Not all started tasks finished") },
                 { assertEquals(metrics.tasksSubmitted, metrics.tasksFinished, "Not all started tasks finished") },
-                { assertEquals(45977707L, clock.millis()) { "Total duration incorrect" } }
+                { assertEquals(45977707L, timeSource.millis()) { "Total duration incorrect" } }
             )
         }
     }