merge: Implement multi-flow stages in simulator (#110)

This pull request introduces the new `flow2` multi-flow simulator into the OpenDC codebase
and adjust all existing modules to make use of this new simulator.

The new simulator models flow as a network of components, which can each receive flow
from (potentially) multiple other components. In the previous simulator, the framework itself
supported only single flows between components and required re-implementation of many
components to support multiplexing flows.

Initial benchmarks show performance improvements in the range 2x–4x for large scale experiments
such as the Capelin benchmarks.

## Implementation Notes :hammer_and_pick:

* Add support for multi-flow stages
* Support flow transformations
* Add forwarding flow multiplexer
* Expose metrics on FlowMultiplexer
* Re-implement network sim using flow2
* Re-implement power sim using flow2 
* Re-implement compute sim using flow2
* Optimize workload implementation of SimTrace 
* Remove old flow simulator 
* Add log4j-core dependency 

## External Dependencies :four_leaf_clover:

* N/A

## Breaking API Changes :warning:

* Removal of the `org.opendc.simulator.flow` package. You should now use
   the new flow simulator located in `org.opendc.simulator.flow2`.
* `PowerModel` interface is replaced by the `CpuPowerModel` interface.
* `PowerDriver` interface is replaced by the `SimPsu` and `SimPsuFactory` interfaces.
* Removal of `SimTraceWorkload`. Instead, create a workload from a `SimTrace` using 
  `createWorkload(offset)`.
* `ScalingGovernor` has been split in a `ScalingGovernor` and `ScalingGovernorFactory`.
* All modules in `opendc-simulator` are now written in Java. This means that default 
   parameters are not supported anymore for these modules.

3 files changed, 8 insertions, 10 deletions

diff --git a/opendc-faas/opendc-faas-service/build.gradle.kts b/opendc-faas/opendc-faas-service/build.gradle.kts
index 34f5b7ea..8b371998 100644
--- a/opendc-faas/opendc-faas-service/build.gradle.kts
+++ b/opendc-faas/opendc-faas-service/build.gradle.kts
@@ -34,5 +34,6 @@ dependencies {
     implementation(libs.kotlin.logging)
 
     testImplementation(projects.opendcSimulator.opendcSimulatorCore)
+    testRuntimeOnly(libs.log4j.core)
     testRuntimeOnly(libs.log4j.slf4j)
 }
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 eba90cce..307ad5a5 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
@@ -42,10 +42,8 @@ import org.opendc.faas.simulator.workload.SimMetaFaaSWorkloadMapper
 import org.opendc.simulator.compute.SimBareMetalMachine
 import org.opendc.simulator.compute.SimMachine
 import org.opendc.simulator.compute.model.MachineModel
-import org.opendc.simulator.compute.power.ConstantPowerModel
-import org.opendc.simulator.compute.power.SimplePowerDriver
 import org.opendc.simulator.compute.runWorkload
-import org.opendc.simulator.flow.FlowEngine
+import org.opendc.simulator.flow2.FlowEngine
 import java.time.Clock
 import java.util.ArrayDeque
 import kotlin.coroutines.Continuation
@@ -87,10 +85,9 @@ public class SimFunctionDeployer(
         /**
          * The machine that will execute the workloads.
          */
-        public val machine: SimMachine = SimBareMetalMachine(
-            FlowEngine(scope.coroutineContext, clock),
-            model,
-            SimplePowerDriver(ConstantPowerModel(0.0))
+        public val machine: SimMachine = SimBareMetalMachine.create(
+            FlowEngine.create(scope.coroutineContext, clock).newGraph(),
+            model
         )
 
         /**
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 9970d93a..aac54f57 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
@@ -58,15 +58,15 @@ internal class SimFaaSServiceTest {
         val cpuNode = ProcessingNode("Intel", "Xeon", "amd64", 2)
 
         machineModel = MachineModel(
-            cpus = List(cpuNode.coreCount) { ProcessingUnit(cpuNode, it, 1000.0) },
-            memory = List(4) { MemoryUnit("Crucial", "MTA18ASF4G72AZ-3G2B1", 3200.0, 32_000) }
+            /*cpus*/ List(cpuNode.coreCount) { ProcessingUnit(cpuNode, it, 1000.0) },
+            /*memory*/ List(4) { MemoryUnit("Crucial", "MTA18ASF4G72AZ-3G2B1", 3200.0, 32_000) }
         )
     }
 
     @Test
     fun testSmoke() = runSimulation {
         val random = Random(0)
-        val workload = spyk(object : SimFaaSWorkload, SimWorkload by SimRuntimeWorkload(1000) {
+        val workload = spyk(object : SimFaaSWorkload, SimWorkload by SimRuntimeWorkload(1000, 1.0) {
             override suspend fun invoke() {
                 delay(random.nextInt(1000).toLong())
             }