feat(compute): Add support for looking up hosts

This change adds the ability for users to lookup the `Host` on which a
`Server` is hosted (if any). This allows the user to potentially
interact with the `Host` directly, e.g., in order to obtain advanced
metrics.

3 files changed, 15 insertions, 17 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 2a1fbaa0..e8cd9e54 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
@@ -25,6 +25,7 @@ package org.opendc.compute.service
 import io.opentelemetry.api.metrics.Meter
 import io.opentelemetry.api.metrics.MeterProvider
 import org.opendc.compute.api.ComputeClient
+import org.opendc.compute.api.Server
 import org.opendc.compute.service.driver.Host
 import org.opendc.compute.service.internal.ComputeServiceImpl
 import org.opendc.compute.service.scheduler.ComputeScheduler
@@ -37,16 +38,11 @@ import kotlin.coroutines.CoroutineContext
  */
 public interface ComputeService : AutoCloseable {
     /**
-     * The hosts that are used by the compute service.
+     * The hosts that are registered with the "compute" service.
      */
     public val hosts: Set<Host>
 
     /**
-     * The number of hosts available in the system.
-     */
-    public val hostCount: Int
-
-    /**
      * Create a new [ComputeClient] to control the compute service.
      */
     public fun newClient(): ComputeClient
@@ -66,6 +62,11 @@ public interface ComputeService : AutoCloseable {
      */
     public override fun close()
 
+    /**
+     * Lookup the [Host] that currently hosts the specified [server].
+     */
+    public fun lookupHost(server: Server): Host?
+
     public companion object {
         /**
          * Construct a new [ComputeService] implementation.
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 144b6573..b7a47a06 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
@@ -154,9 +154,6 @@ internal class ComputeServiceImpl(
     override val hosts: Set<Host>
         get() = hostToView.keys
 
-    override val hostCount: Int
-        get() = hostToView.size
-
     init {
         val upState = Attributes.of(AttributeKey.stringKey("state"), "up")
         val downState = Attributes.of(AttributeKey.stringKey("state"), "down")
@@ -165,7 +162,7 @@ internal class ComputeServiceImpl(
             .setDescription("Number of hosts registered with the scheduler")
             .setUnit("1")
             .buildWithCallback { result ->
-                val total = hostCount
+                val total = hosts.size
                 val available = availableHosts.size.toLong()
 
                 result.record(available, upState)
@@ -322,6 +319,11 @@ internal class ComputeServiceImpl(
         }
     }
 
+    override fun lookupHost(server: Server): Host? {
+        val internal = requireNotNull(servers[server.uid]) { "Invalid server passed to lookupHost" }
+        return internal.host
+    }
+
     override fun close() {
         scope.cancel()
     }
diff --git a/opendc-compute/opendc-compute-service/src/test/kotlin/org/opendc/compute/service/ComputeServiceTest.kt b/opendc-compute/opendc-compute-service/src/test/kotlin/org/opendc/compute/service/ComputeServiceTest.kt
index 7b8d0fe2..eb106817 100644
--- a/opendc-compute/opendc-compute-service/src/test/kotlin/org/opendc/compute/service/ComputeServiceTest.kt
+++ b/opendc-compute/opendc-compute-service/src/test/kotlin/org/opendc/compute/service/ComputeServiceTest.kt
@@ -24,7 +24,6 @@ package org.opendc.compute.service
 
 import io.mockk.*
 import io.opentelemetry.api.metrics.MeterProvider
-import kotlinx.coroutines.ExperimentalCoroutinesApi
 import kotlinx.coroutines.delay
 import org.junit.jupiter.api.Assertions.assertEquals
 import org.junit.jupiter.api.Assertions.assertNull
@@ -48,10 +47,9 @@ import java.util.*
 /**
  * Test suite for the [ComputeService] interface.
  */
-@OptIn(ExperimentalCoroutinesApi::class)
 internal class ComputeServiceTest {
-    lateinit var scope: SimulationCoroutineScope
-    lateinit var service: ComputeService
+    private lateinit var scope: SimulationCoroutineScope
+    private lateinit var service: ComputeService
 
     @BeforeEach
     fun setUp() {
@@ -128,14 +126,12 @@ internal class ComputeServiceTest {
         every { host.model } returns HostModel(4 * 2600.0, 4, 2048)
         every { host.state } returns HostState.UP
 
-        assertEquals(0, service.hostCount)
         assertEquals(emptySet<Host>(), service.hosts)
 
         service.addHost(host)
 
         verify(exactly = 1) { host.addListener(any()) }
 
-        assertEquals(1, service.hostCount)
         assertEquals(1, service.hosts.size)
 
         service.removeHost(host)
@@ -150,7 +146,6 @@ internal class ComputeServiceTest {
         every { host.model } returns HostModel(4 * 2600.0, 4, 2048)
         every { host.state } returns HostState.DOWN
 
-        assertEquals(0, service.hostCount)
         assertEquals(emptySet<Host>(), service.hosts)
 
         service.addHost(host)