compute: Implement filter scheduler

This pull request implements the filter scheduler modeled after the scheduler 
from [OpenStack](https://docs.openstack.org/nova/latest/user/filter-scheduler.html). 
The scheduler is functionally equivalent to the old allocation policies, but is more 
flexible and allows policies to be combined.

* A new interface, `ComputeScheduler` is introduced, which is used by the 
  `ComputeServiceImpl` to pick hosts to schedule on.
* `FilterScheduler` is implemented, which works by filtering and weighing the available hosts.

**Breaking API Changes**

* Removal of the `AllocationPolicy` interface and its implementations. 
   Users should migrate to the filter scheduler which offers the same functionality and more.

1 files changed, 9 insertions, 2 deletions

diff --git a/simulator/opendc-workflow/opendc-workflow-service/src/test/kotlin/org/opendc/workflow/service/WorkflowServiceIntegrationTest.kt b/simulator/opendc-workflow/opendc-workflow-service/src/test/kotlin/org/opendc/workflow/service/WorkflowServiceIntegrationTest.kt
index 46c0d835..be59c8d2 100644
--- a/simulator/opendc-workflow/opendc-workflow-service/src/test/kotlin/org/opendc/workflow/service/WorkflowServiceIntegrationTest.kt
+++ b/simulator/opendc-workflow/opendc-workflow-service/src/test/kotlin/org/opendc/workflow/service/WorkflowServiceIntegrationTest.kt
@@ -35,7 +35,10 @@ import org.junit.jupiter.api.DisplayName
 import org.junit.jupiter.api.Test
 import org.junit.jupiter.api.assertAll
 import org.opendc.compute.service.ComputeService
-import org.opendc.compute.service.scheduler.NumberOfActiveServersAllocationPolicy
+import org.opendc.compute.service.scheduler.FilterScheduler
+import org.opendc.compute.service.scheduler.filters.ComputeCapabilitiesFilter
+import org.opendc.compute.service.scheduler.filters.ComputeFilter
+import org.opendc.compute.service.scheduler.weights.ProvisionedCoresWeigher
 import org.opendc.compute.simulator.SimHost
 import org.opendc.format.environment.sc18.Sc18EnvironmentReader
 import org.opendc.format.trace.gwf.GwfTraceReader
@@ -84,7 +87,11 @@ internal class WorkflowServiceIntegrationTest {
             }
 
         val meter = MeterProvider.noop().get("opendc-compute")
-        val compute = ComputeService(coroutineContext, clock, meter, NumberOfActiveServersAllocationPolicy(), schedulingQuantum = 1000)
+        val computeScheduler = FilterScheduler(
+            filters = listOf(ComputeFilter(), ComputeCapabilitiesFilter()),
+            weighers = listOf(ProvisionedCoresWeigher() to -1.0)
+        )
+        val compute = ComputeService(coroutineContext, clock, meter, computeScheduler, schedulingQuantum = 1000)
 
         hosts.forEach { compute.addHost(it) }