serverless: Add support for custom termination policies

This change adds support for custom termination policies for function
instances. This allows the user to build different strategies for
downscaling function instances after they become idle.

2 files changed, 17 insertions, 5 deletions

diff --git a/opendc-serverless/opendc-serverless-simulator/src/main/kotlin/org/opendc/serverless/simulator/SimFunctionDeployer.kt b/opendc-serverless/opendc-serverless-simulator/src/main/kotlin/org/opendc/serverless/simulator/SimFunctionDeployer.kt
index 2945a279..0605eaac 100644
--- a/opendc-serverless/opendc-serverless-simulator/src/main/kotlin/org/opendc/serverless/simulator/SimFunctionDeployer.kt
+++ b/opendc-serverless/opendc-serverless-simulator/src/main/kotlin/org/opendc/serverless/simulator/SimFunctionDeployer.kt
@@ -27,6 +27,7 @@ import kotlinx.coroutines.channels.Channel
 import org.opendc.serverless.service.FunctionObject
 import org.opendc.serverless.service.deployer.FunctionDeployer
 import org.opendc.serverless.service.deployer.FunctionInstance
+import org.opendc.serverless.service.deployer.FunctionInstanceListener
 import org.opendc.serverless.service.deployer.FunctionInstanceState
 import org.opendc.serverless.simulator.delay.DelayInjector
 import org.opendc.serverless.simulator.workload.SimServerlessWorkloadMapper
@@ -53,8 +54,8 @@ public class SimFunctionDeployer(
     private val mapper: SimServerlessWorkloadMapper
 ) : FunctionDeployer {
 
-    override fun deploy(function: FunctionObject): Instance {
-        val instance = Instance(function)
+    override fun deploy(function: FunctionObject, listener: FunctionInstanceListener): Instance {
+        val instance = Instance(function, listener)
         instance.start()
         return instance
     }
@@ -62,7 +63,7 @@ public class SimFunctionDeployer(
     /**
      * A simulated [FunctionInstance].
      */
-    public inner class Instance(override val function: FunctionObject) : FunctionInstance {
+    public inner class Instance(override val function: FunctionObject, private val listener: FunctionInstanceListener) : FunctionInstance {
         /**
          * The workload associated with this instance.
          */
@@ -89,6 +90,13 @@ public class SimFunctionDeployer(
         private val chan = Channel<Unit>(Channel.RENDEZVOUS)
 
         override var state: FunctionInstanceState = FunctionInstanceState.Provisioning
+            set(value) {
+                if (field != value) {
+                    listener.onStateChanged(this, value)
+                }
+
+                field = value
+            }
 
         override suspend fun invoke() {
             check(state != FunctionInstanceState.Deleted) { "Function instance has been released" }
@@ -119,7 +127,7 @@ public class SimFunctionDeployer(
                     try {
                         machine.run(workload)
                     } finally {
-                        state = FunctionInstanceState.Terminated
+                        state = FunctionInstanceState.Deleted
                     }
                 }
 
diff --git a/opendc-serverless/opendc-serverless-simulator/src/test/kotlin/org/opendc/serverless/simulator/SimServerlessServiceTest.kt b/opendc-serverless/opendc-serverless-simulator/src/test/kotlin/org/opendc/serverless/simulator/SimServerlessServiceTest.kt
index 9592d870..6afa1b65 100644
--- a/opendc-serverless/opendc-serverless-simulator/src/test/kotlin/org/opendc/serverless/simulator/SimServerlessServiceTest.kt
+++ b/opendc-serverless/opendc-serverless-simulator/src/test/kotlin/org/opendc/serverless/simulator/SimServerlessServiceTest.kt
@@ -32,6 +32,7 @@ import org.junit.jupiter.api.BeforeEach
 import org.junit.jupiter.api.Test
 import org.junit.jupiter.api.assertAll
 import org.opendc.serverless.service.ServerlessService
+import org.opendc.serverless.service.autoscaler.FunctionTerminationPolicyFixed
 import org.opendc.serverless.service.router.RandomRoutingPolicy
 import org.opendc.serverless.simulator.delay.ZeroDelayInjector
 import org.opendc.serverless.simulator.workload.SimServerlessWorkload
@@ -68,7 +69,10 @@ internal class SimServerlessServiceTest {
             override suspend fun invoke() {}
         })
         val deployer = SimFunctionDeployer(clock, this, machineModel, ZeroDelayInjector) { workload }
-        val service = ServerlessService(coroutineContext, clock, meter, deployer, RandomRoutingPolicy())
+        val service = ServerlessService(
+            coroutineContext, clock, meter, deployer, RandomRoutingPolicy(),
+            FunctionTerminationPolicyFixed(coroutineContext, clock, timeout = 10000)
+        )
 
         val client = service.newClient()