faas: Rename opendc-serverless to opendc-faas

This change renames the opendc-serverless module to opendc-faas to
better distinguish between the two terms (Serverless and FaaS) and be
clearer about the intent of the module.

The opendc-faas module holds the code for the FaaS platform on top of
OpenDC. Although this is one approach of doing serverless, serverless
can also entail other services that will not be covered by this module.

28 files changed, 1948 insertions, 0 deletions

diff --git a/opendc-faas/build.gradle.kts b/opendc-faas/build.gradle.kts
new file mode 100644
index 00000000..2493639f
--- /dev/null
+++ b/opendc-faas/build.gradle.kts
@@ -0,0 +1,23 @@
+/*
+ * Copyright (c) 2021 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+description = "Function-as-a-Service (FaaS) platform for OpenDC"
diff --git a/opendc-faas/opendc-faas-api/build.gradle.kts b/opendc-faas/opendc-faas-api/build.gradle.kts
new file mode 100644
index 00000000..7362d949
--- /dev/null
+++ b/opendc-faas/opendc-faas-api/build.gradle.kts
@@ -0,0 +1,32 @@
+/*
+ * Copyright (c) 2021 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+description = "API for the OpenDC FaaS platform"
+
+/* Build configuration */
+plugins {
+    `kotlin-library-conventions`
+}
+
+dependencies {
+    api(platform(projects.opendcPlatform))
+}
diff --git a/opendc-faas/opendc-faas-api/src/main/kotlin/org/opendc/faas/api/FaaSClient.kt b/opendc-faas/opendc-faas-api/src/main/kotlin/org/opendc/faas/api/FaaSClient.kt
new file mode 100644
index 00000000..ebda4f90
--- /dev/null
+++ b/opendc-faas/opendc-faas-api/src/main/kotlin/org/opendc/faas/api/FaaSClient.kt
@@ -0,0 +1,74 @@
+/*
+ * Copyright (c) 2021 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package org.opendc.faas.api
+
+import java.util.*
+
+/**
+ * Client interface to the OpenDC FaaS platform.
+ */
+public interface FaaSClient : AutoCloseable {
+    /**
+     * Obtain the list of [FaaSFunction]s accessible by the requesting user.
+     */
+    public suspend fun queryFunctions(): List<FaaSFunction>
+
+    /**
+     * Obtain a [FaaSFunction] by its unique identifier.
+     *
+     * @param id The identifier of the flavor.
+     */
+    public suspend fun findFunction(id: UUID): FaaSFunction?
+
+    /**
+     * Obtain a [FaaSFunction] by its name.
+     *
+     * @param name The name of the function.
+     */
+    public suspend fun findFunction(name: String): FaaSFunction?
+
+    /**
+     * Create a new serverless function.
+     *
+     * @param name The name of the function.
+     * @param memorySize The memory allocated for the function in MB.
+     * @param labels The labels associated with the function.
+     * @param meta The metadata associated with the function.
+     */
+    public suspend fun newFunction(
+        name: String,
+        memorySize: Long,
+        labels: Map<String, String> = emptyMap(),
+        meta: Map<String, Any> = emptyMap()
+    ): FaaSFunction
+
+    /**
+     * Invoke the function with the specified [name].
+     */
+    public suspend fun invoke(name: String)
+
+    /**
+     * Release the resources associated with this client, preventing any further API calls.
+     */
+    public override fun close()
+}
diff --git a/opendc-faas/opendc-faas-api/src/main/kotlin/org/opendc/faas/api/FaaSFunction.kt b/opendc-faas/opendc-faas-api/src/main/kotlin/org/opendc/faas/api/FaaSFunction.kt
new file mode 100644
index 00000000..40f0092f
--- /dev/null
+++ b/opendc-faas/opendc-faas-api/src/main/kotlin/org/opendc/faas/api/FaaSFunction.kt
@@ -0,0 +1,70 @@
+/*
+ * Copyright (c) 2021 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package org.opendc.faas.api
+
+import java.util.UUID
+
+/**
+ * A serverless function instance.
+ */
+public interface FaaSFunction {
+    /**
+     * The unique identifier of the function.
+     */
+    public val uid: UUID
+
+    /**
+     * The name of the function.
+     */
+    public val name: String
+
+    /**
+     * The amount of memory allocated for this function in MB.
+     */
+    public val memorySize: Long
+
+    /**
+     * The identifying labels attached to the resource.
+     */
+    public val labels: Map<String, String>
+
+    /**
+     * The non-identifying metadata attached to the resource.
+     */
+    public val meta: Map<String, Any>
+
+    /**
+     * Invoke the serverless function.
+     */
+    public suspend operator fun invoke()
+
+    /**
+     * Request the function to be deleted.
+     */
+    public suspend fun delete()
+
+    /**
+     * Refresh the local state of this object.
+     */
+    public suspend fun refresh()
+}
diff --git a/opendc-faas/opendc-faas-service/build.gradle.kts b/opendc-faas/opendc-faas-service/build.gradle.kts
new file mode 100644
index 00000000..63bed8bc
--- /dev/null
+++ b/opendc-faas/opendc-faas-service/build.gradle.kts
@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) 2021 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+description = "FaaS service for OpenDC"
+
+/* Build configuration */
+plugins {
+    `kotlin-library-conventions`
+    `testing-conventions`
+    `jacoco-conventions`
+}
+
+dependencies {
+    api(platform(projects.opendcPlatform))
+    api(projects.opendcFaas.opendcFaasApi)
+    api(projects.opendcTelemetry.opendcTelemetryApi)
+    implementation(projects.opendcUtils)
+    implementation(libs.kotlin.logging)
+
+    testImplementation(projects.opendcSimulator.opendcSimulatorCore)
+    testRuntimeOnly(libs.log4j.slf4j)
+}
diff --git a/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/FaaSService.kt b/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/FaaSService.kt
new file mode 100644
index 00000000..7e716a34
--- /dev/null
+++ b/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/FaaSService.kt
@@ -0,0 +1,70 @@
+/*
+ * Copyright (c) 2021 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package org.opendc.faas.service
+
+import io.opentelemetry.api.metrics.Meter
+import org.opendc.faas.api.FaaSClient
+import org.opendc.faas.service.autoscaler.FunctionTerminationPolicy
+import org.opendc.faas.service.deployer.FunctionDeployer
+import org.opendc.faas.service.internal.FaaSServiceImpl
+import org.opendc.faas.service.router.RoutingPolicy
+import java.time.Clock
+import kotlin.coroutines.CoroutineContext
+
+/**
+ * The [FaaSService] hosts the service implementation of the OpenDC FaaS platform.
+ */
+public interface FaaSService : AutoCloseable {
+    /**
+     * Create a new [FaaSClient] to control the compute service.
+     */
+    public fun newClient(): FaaSClient
+
+    /**
+     * Terminate the lifecycle of the FaaS service, stopping all running function instances.
+     */
+    public override fun close()
+
+    public companion object {
+        /**
+         * Construct a new [FaaSService] implementation.
+         *
+         * @param context The [CoroutineContext] to use in the service.
+         * @param clock The clock instance to use.
+         * @param meter The meter to report metrics to.
+         * @param deployer the [FunctionDeployer] to use for deploying function instances.
+         * @param routingPolicy The policy to route function invocations.
+         * @param terminationPolicy The policy for terminating function instances.
+         */
+        public operator fun invoke(
+            context: CoroutineContext,
+            clock: Clock,
+            meter: Meter,
+            deployer: FunctionDeployer,
+            routingPolicy: RoutingPolicy,
+            terminationPolicy: FunctionTerminationPolicy,
+        ): FaaSService {
+            return FaaSServiceImpl(context, clock, meter, deployer, routingPolicy, terminationPolicy)
+        }
+    }
+}
diff --git a/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/FunctionObject.kt b/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/FunctionObject.kt
new file mode 100644
index 00000000..7c7621b8
--- /dev/null
+++ b/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/FunctionObject.kt
@@ -0,0 +1,139 @@
+/*
+ * Copyright (c) 2021 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package org.opendc.faas.service
+
+import io.opentelemetry.api.metrics.BoundLongCounter
+import io.opentelemetry.api.metrics.BoundLongUpDownCounter
+import io.opentelemetry.api.metrics.BoundLongValueRecorder
+import io.opentelemetry.api.metrics.Meter
+import io.opentelemetry.api.metrics.common.Labels
+import org.opendc.faas.service.deployer.FunctionInstance
+import java.util.*
+
+/**
+ * An [FunctionObject] represents the service's view of a serverless function.
+ */
+public class FunctionObject(
+    meter: Meter,
+    public val uid: UUID,
+    name: String,
+    allocatedMemory: Long,
+    labels: Map<String, String>,
+    meta: Map<String, Any>
+) : AutoCloseable {
+    /**
+     * The total amount of function invocations received by the function.
+     */
+    public val invocations: BoundLongCounter = meter.longCounterBuilder("function.invocations.total")
+        .setDescription("Number of function invocations")
+        .setUnit("1")
+        .build()
+        .bind(Labels.of("function", uid.toString()))
+
+    /**
+     * The amount of function invocations that could be handled directly.
+     */
+    public val timelyInvocations: BoundLongCounter = meter.longCounterBuilder("function.invocations.warm")
+        .setDescription("Number of function invocations handled directly")
+        .setUnit("1")
+        .build()
+        .bind(Labels.of("function", uid.toString()))
+
+    /**
+     * The amount of function invocations that were delayed due to function deployment.
+     */
+    public val delayedInvocations: BoundLongCounter = meter.longCounterBuilder("function.invocations.cold")
+        .setDescription("Number of function invocations that are delayed")
+        .setUnit("1")
+        .build()
+        .bind(Labels.of("function", uid.toString()))
+
+    /**
+     * The amount of function invocations that failed.
+     */
+    public val failedInvocations: BoundLongCounter = meter.longCounterBuilder("function.invocations.failed")
+        .setDescription("Number of function invocations that failed")
+        .setUnit("1")
+        .build()
+        .bind(Labels.of("function", uid.toString()))
+
+    /**
+     * The amount of instances for this function.
+     */
+    public val activeInstances: BoundLongUpDownCounter = meter.longUpDownCounterBuilder("function.instances.active")
+        .setDescription("Number of active function instances")
+        .setUnit("1")
+        .build()
+        .bind(Labels.of("function", uid.toString()))
+
+    /**
+     * The amount of idle instances for this function.
+     */
+    public val idleInstances: BoundLongUpDownCounter = meter.longUpDownCounterBuilder("function.instances.idle")
+        .setDescription("Number of idle function instances")
+        .setUnit("1")
+        .build()
+        .bind(Labels.of("function", uid.toString()))
+
+    /**
+     * The time that the function waited.
+     */
+    public val waitTime: BoundLongValueRecorder = meter.longValueRecorderBuilder("function.time.wait")
+        .setDescription("Time the function has to wait before being started")
+        .setUnit("ms")
+        .build()
+        .bind(Labels.of("function", uid.toString()))
+
+    /**
+     * The time that the function was running.
+     */
+    public val activeTime: BoundLongValueRecorder = meter.longValueRecorderBuilder("function.time.active")
+        .setDescription("Time the function was running")
+        .setUnit("ms")
+        .build()
+        .bind(Labels.of("function", uid.toString()))
+
+    /**
+     * The instances associated with this function.
+     */
+    public val instances: MutableList<FunctionInstance> = mutableListOf()
+
+    public var name: String = name
+        private set
+
+    public var memorySize: Long = allocatedMemory
+        private set
+
+    public val labels: MutableMap<String, String> = labels.toMutableMap()
+
+    public val meta: MutableMap<String, Any> = meta.toMutableMap()
+
+    override fun close() {
+        instances.forEach(FunctionInstance::close)
+        instances.clear()
+    }
+
+    override fun equals(other: Any?): Boolean = other is FunctionObject && uid == other.uid
+
+    override fun hashCode(): Int = uid.hashCode()
+}
diff --git a/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/autoscaler/FunctionTerminationPolicy.kt b/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/autoscaler/FunctionTerminationPolicy.kt
new file mode 100644
index 00000000..2ab3638b
--- /dev/null
+++ b/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/autoscaler/FunctionTerminationPolicy.kt
@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) 2021 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package org.opendc.faas.service.autoscaler
+
+import org.opendc.faas.service.deployer.FunctionInstance
+import org.opendc.faas.service.deployer.FunctionInstanceListener
+
+/**
+ * A management policy that is responsible for downscaling the active function instances for a function.
+ */
+public interface FunctionTerminationPolicy : FunctionInstanceListener {
+    /**
+     * Enqueue the specified [instance] to be scheduled for termination a
+     */
+    public fun enqueue(instance: FunctionInstance)
+}
diff --git a/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/autoscaler/FunctionTerminationPolicyFixed.kt b/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/autoscaler/FunctionTerminationPolicyFixed.kt
new file mode 100644
index 00000000..1e224ed1
--- /dev/null
+++ b/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/autoscaler/FunctionTerminationPolicyFixed.kt
@@ -0,0 +1,65 @@
+/*
+ * Copyright (c) 2021 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package org.opendc.faas.service.autoscaler
+
+import org.opendc.faas.service.deployer.FunctionInstance
+import org.opendc.faas.service.deployer.FunctionInstanceState
+import org.opendc.utils.TimerScheduler
+import java.time.Clock
+import kotlin.coroutines.CoroutineContext
+
+/**
+ * A [FunctionTerminationPolicy] that terminates idle function instances after a fixed keep-alive time.
+ *
+ * @param timeout The idle timeout after which the function instance is terminated.
+ */
+public class FunctionTerminationPolicyFixed(
+    context: CoroutineContext,
+    clock: Clock,
+    public val timeout: Long
+) : FunctionTerminationPolicy {
+    /**
+     * The [TimerScheduler] used to schedule the function terminations.
+     */
+    private val scheduler = TimerScheduler<FunctionInstance>(context, clock)
+
+    override fun enqueue(instance: FunctionInstance) {
+        // Cancel the existing timeout timer
+        scheduler.cancel(instance)
+    }
+
+    override fun onStateChanged(instance: FunctionInstance, newState: FunctionInstanceState) {
+        when (newState) {
+            FunctionInstanceState.Active -> scheduler.cancel(instance)
+            FunctionInstanceState.Idle -> schedule(instance)
+            else -> {}
+        }
+    }
+
+    /**
+     * Schedule termination for the specified [instance].
+     */
+    private fun schedule(instance: FunctionInstance) {
+        scheduler.startSingleTimer(instance, delay = timeout) { instance.close() }
+    }
+}
diff --git a/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/autoscaler/FunctionTerminationPolicyNull.kt b/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/autoscaler/FunctionTerminationPolicyNull.kt
new file mode 100644
index 00000000..957e569b
--- /dev/null
+++ b/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/autoscaler/FunctionTerminationPolicyNull.kt
@@ -0,0 +1,34 @@
+/*
+ * Copyright (c) 2021 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package org.opendc.faas.service.autoscaler
+
+import org.opendc.faas.service.deployer.FunctionInstance
+
+/**
+ * A [FunctionTerminationPolicy] that never terminates function instances.
+ */
+public class FunctionTerminationPolicyNull : FunctionTerminationPolicy {
+    override fun enqueue(instance: FunctionInstance) {
+        // No-op
+    }
+}
diff --git a/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/deployer/FunctionDeployer.kt b/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/deployer/FunctionDeployer.kt
new file mode 100644
index 00000000..049f1cc7
--- /dev/null
+++ b/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/deployer/FunctionDeployer.kt
@@ -0,0 +1,43 @@
+/*
+ * Copyright (c) 2021 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package org.opendc.faas.service.deployer
+
+import org.opendc.faas.service.FunctionObject
+
+/**
+ * A [FunctionDeployer] is responsible for ensuring that an instance of an arbitrary function, a [FunctionInstance],
+ * is deployed.
+ *
+ * The function deployer should combines the configuration stored in the function registry, the parameters supplied by
+ * the requester, and other factors into a decision of how the function should be deployed, including how many and
+ * what kind of resources it should receive.
+ *
+ * Though it decides how the function instance should be deployed, the deployment of the function instance itself is
+ * delegated to the Resource Orchestration Layer.
+ */
+public interface FunctionDeployer {
+    /**
+     * Deploy the specified [function].
+     */
+    public fun deploy(function: FunctionObject, listener: FunctionInstanceListener): FunctionInstance
+}
diff --git a/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/deployer/FunctionInstance.kt b/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/deployer/FunctionInstance.kt
new file mode 100644
index 00000000..a8b04df4
--- /dev/null
+++ b/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/deployer/FunctionInstance.kt
@@ -0,0 +1,55 @@
+/*
+ * Copyright (c) 2021 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package org.opendc.faas.service.deployer
+
+import org.opendc.faas.service.FunctionObject
+
+/**
+ * A [FunctionInstance] is a a self-contained worker—typically a container—capable of handling function executions.
+ *
+ * Multiple, concurrent function instances can exists for a single function, for scalability purposes.
+ */
+public interface FunctionInstance : AutoCloseable {
+    /**
+     * The state of the instance.
+     */
+    public val state: FunctionInstanceState
+
+    /**
+     * The [FunctionObject] that is represented by this instance.
+     */
+    public val function: FunctionObject
+
+    /**
+     * Invoke the function instance.
+     *
+     * This method will suspend execution util the function instance has returned.
+     */
+    public suspend fun invoke()
+
+    /**
+     * Indicate to the resource manager that the instance is not needed anymore and may be cleaned up by the resource
+     * manager.
+     */
+    public override fun close()
+}
diff --git a/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/deployer/FunctionInstanceListener.kt b/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/deployer/FunctionInstanceListener.kt
new file mode 100644
index 00000000..20e280a2
--- /dev/null
+++ b/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/deployer/FunctionInstanceListener.kt
@@ -0,0 +1,33 @@
+/*
+ * Copyright (c) 2021 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package org.opendc.faas.service.deployer
+
+/**
+ * Listener interface for events originating from a [FunctionInstance].
+ */
+public interface FunctionInstanceListener {
+    /**
+     * This method is invoked when the state of a [FunctionInstance] has changed.
+     */
+    public fun onStateChanged(instance: FunctionInstance, newState: FunctionInstanceState) {}
+}
diff --git a/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/deployer/FunctionInstanceState.kt b/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/deployer/FunctionInstanceState.kt
new file mode 100644
index 00000000..2b6b6eba
--- /dev/null
+++ b/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/deployer/FunctionInstanceState.kt
@@ -0,0 +1,48 @@
+/*
+ * Copyright (c) 2021 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package org.opendc.faas.service.deployer
+
+/**
+ * This enumeration describes the states of a [FunctionInstance].
+ */
+public enum class FunctionInstanceState {
+    /**
+     * The function instance is currently being provisioned.
+     */
+    Provisioning,
+
+    /**
+     * The function instance is idle and ready to execute.
+     */
+    Idle,
+
+    /**
+     * The function instance is executing.
+     */
+    Active,
+
+    /**
+     * The function instance is released and cannot be used anymore.
+     */
+    Deleted
+}
diff --git a/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/internal/FaaSFunctionImpl.kt b/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/internal/FaaSFunctionImpl.kt
new file mode 100644
index 00000000..bd7f13f6
--- /dev/null
+++ b/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/internal/FaaSFunctionImpl.kt
@@ -0,0 +1,70 @@
+/*
+ * Copyright (c) 2021 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package org.opendc.faas.service.internal
+
+import org.opendc.faas.api.FaaSFunction
+import org.opendc.faas.service.FunctionObject
+import java.util.*
+
+/**
+ * A [FaaSFunction] implementation that is passed to clients.
+ */
+internal class FaaSFunctionImpl(
+    private val service: FaaSServiceImpl,
+    private val state: FunctionObject
+) : FaaSFunction {
+    override val uid: UUID = state.uid
+
+    override var name: String = state.name
+        private set
+
+    override var memorySize: Long = state.memorySize
+        private set
+
+    override var labels: Map<String, String> = state.labels.toMap()
+        private set
+
+    override var meta: Map<String, Any> = state.meta.toMap()
+        private set
+
+    override suspend fun delete() {
+        service.delete(state)
+    }
+
+    override suspend fun invoke() {
+        service.invoke(state)
+    }
+
+    override suspend fun refresh() {
+        name = state.name
+        memorySize = state.memorySize
+        labels = state.labels
+        meta = state.meta
+    }
+
+    override fun equals(other: Any?): Boolean = other is FaaSFunctionImpl && uid == other.uid
+
+    override fun hashCode(): Int = uid.hashCode()
+
+    override fun toString(): String = "FaaSFunction[uid=$uid,name=$name]"
+}
diff --git a/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/internal/FaaSServiceImpl.kt b/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/internal/FaaSServiceImpl.kt
new file mode 100644
index 00000000..b169436f
--- /dev/null
+++ b/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/internal/FaaSServiceImpl.kt
@@ -0,0 +1,304 @@
+/*
+ * Copyright (c) 2021 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package org.opendc.faas.service.internal
+
+import io.opentelemetry.api.metrics.Meter
+import kotlinx.coroutines.*
+import kotlinx.coroutines.intrinsics.startCoroutineCancellable
+import mu.KotlinLogging
+import org.opendc.faas.api.FaaSClient
+import org.opendc.faas.api.FaaSFunction
+import org.opendc.faas.service.FaaSService
+import org.opendc.faas.service.FunctionObject
+import org.opendc.faas.service.autoscaler.FunctionTerminationPolicy
+import org.opendc.faas.service.deployer.FunctionDeployer
+import org.opendc.faas.service.deployer.FunctionInstance
+import org.opendc.faas.service.deployer.FunctionInstanceListener
+import org.opendc.faas.service.deployer.FunctionInstanceState
+import org.opendc.faas.service.router.RoutingPolicy
+import org.opendc.utils.TimerScheduler
+import java.lang.IllegalStateException
+import java.time.Clock
+import java.util.*
+import kotlin.coroutines.Continuation
+import kotlin.coroutines.CoroutineContext
+import kotlin.coroutines.resumeWithException
+
+/**
+ * Implementation of the [FaaSService] interface.
+ *
+ * This component acts as the function router from the SPEC RG Reference Architecture for FaaS and is responsible
+ * for routing incoming requests or events to the correct [FunctionInstance]. If no [FunctionInstance] is available,
+ * this component queues the events to await the deployment of new instances.
+ */
+internal class FaaSServiceImpl(
+    context: CoroutineContext,
+    private val clock: Clock,
+    private val meter: Meter,
+    private val deployer: FunctionDeployer,
+    private val routingPolicy: RoutingPolicy,
+    private val terminationPolicy: FunctionTerminationPolicy
+) : FaaSService, FunctionInstanceListener {
+    /**
+     * The [CoroutineScope] of the service bounded by the lifecycle of the service.
+     */
+    private val scope = CoroutineScope(context + Job())
+
+    /**
+     * The logger instance of this server.
+     */
+    private val logger = KotlinLogging.logger {}
+
+    /**
+     * The [TimerScheduler] to use for scheduling the scheduler cycles.
+     */
+    private val scheduler: TimerScheduler<Unit> = TimerScheduler(scope.coroutineContext, clock)
+
+    /**
+     * The [Random] instance used to generate unique identifiers for the objects.
+     */
+    private val random = Random(0)
+
+    /**
+     * The registered functions for this service.
+     */
+    private val functions = mutableMapOf<UUID, FunctionObject>()
+    private val functionsByName = mutableMapOf<String, FunctionObject>()
+
+    /**
+     * The queue of invocation requests.
+     */
+    private val queue = ArrayDeque<InvocationRequest>()
+
+    /**
+     * The total amount of function invocations received by the service.
+     */
+    private val _invocations = meter.longCounterBuilder("service.invocations.total")
+        .setDescription("Number of function invocations")
+        .setUnit("1")
+        .build()
+
+    /**
+     * The amount of function invocations that could be handled directly.
+     */
+    private val _timelyInvocations = meter.longCounterBuilder("service.invocations.warm")
+        .setDescription("Number of function invocations handled directly")
+        .setUnit("1")
+        .build()
+
+    /**
+     * The amount of function invocations that were delayed due to function deployment.
+     */
+    private val _delayedInvocations = meter.longCounterBuilder("service.invocations.cold")
+        .setDescription("Number of function invocations that are delayed")
+        .setUnit("1")
+        .build()
+
+    override fun newClient(): FaaSClient {
+        return object : FaaSClient {
+            private var isClosed: Boolean = false
+
+            /**
+             * Exposes a [FunctionObject] to a client-exposed [FaaSFunction] instance.
+             */
+            private fun FunctionObject.asClientFunction(): FaaSFunction {
+                return FaaSFunctionImpl(this@FaaSServiceImpl, this)
+            }
+
+            override suspend fun queryFunctions(): List<FaaSFunction> {
+                check(!isClosed) { "Client is already closed" }
+
+                return functions.values.map { it.asClientFunction() }
+            }
+
+            override suspend fun findFunction(id: UUID): FaaSFunction? {
+                check(!isClosed) { "Client is already closed" }
+
+                return functions[id]?.asClientFunction()
+            }
+
+            override suspend fun findFunction(name: String): FaaSFunction? {
+                check(!isClosed) { "Client is already closed" }
+
+                return functionsByName[name]?.asClientFunction()
+            }
+
+            override suspend fun newFunction(
+                name: String,
+                memorySize: Long,
+                labels: Map<String, String>,
+                meta: Map<String, Any>
+            ): FaaSFunction {
+                check(!isClosed) { "Client is already closed" }
+                require(name !in functionsByName) { "Function with same name exists" }
+
+                val uid = UUID(clock.millis(), random.nextLong())
+                val function = FunctionObject(
+                    meter,
+                    uid,
+                    name,
+                    memorySize,
+                    labels,
+                    meta
+                )
+
+                functionsByName[name] = function
+                functions[uid] = function
+
+                return function.asClientFunction()
+            }
+
+            override suspend fun invoke(name: String) {
+                check(!isClosed) { "Client is already closed" }
+
+                val func = requireNotNull(functionsByName[name]) { "Unknown function" }
+                this@FaaSServiceImpl.invoke(func)
+            }
+
+            override fun close() {
+                isClosed = true
+            }
+        }
+    }
+
+    /**
+     * Indicate that a new scheduling cycle is needed due to a change to the service's state.
+     */
+    private fun schedule() {
+        // Bail out in case we have already requested a new cycle or the queue is empty.
+        if (scheduler.isTimerActive(Unit) || queue.isEmpty()) {
+            return
+        }
+
+        val quantum = 100
+
+        // We assume that the provisioner runs at a fixed slot every time quantum (e.g t=0, t=60, t=120).
+        // This is important because the slices of the VMs need to be aligned.
+        // We calculate here the delay until the next scheduling slot.
+        val delay = quantum - (clock.millis() % quantum)
+
+        scheduler.startSingleTimer(Unit, delay, ::doSchedule)
+    }
+
+    /**
+     * Run a single scheduling iteration.
+     */
+    @OptIn(InternalCoroutinesApi::class)
+    private fun doSchedule() {
+        try {
+            while (queue.isNotEmpty()) {
+                val (submitTime, function, cont) = queue.poll()
+
+                val instances = function.instances
+
+                // Check if there exists an instance of the function
+                val activeInstance = if (instances.isNotEmpty()) {
+                    routingPolicy.select(instances, function)
+                } else {
+                    null
+                }
+
+                val instance = if (activeInstance != null) {
+                    _timelyInvocations.add(1)
+                    function.timelyInvocations.add(1)
+
+                    activeInstance
+                } else {
+                    val instance = deployer.deploy(function, this)
+                    instances.add(instance)
+                    terminationPolicy.enqueue(instance)
+
+                    function.idleInstances.add(1)
+
+                    _delayedInvocations.add(1)
+                    function.delayedInvocations.add(1)
+
+                    instance
+                }
+
+                suspend {
+                    val start = clock.millis()
+                    function.waitTime.record(start - submitTime)
+                    function.idleInstances.add(-1)
+                    function.activeInstances.add(1)
+                    try {
+                        instance.invoke()
+                    } catch (e: Throwable) {
+                        logger.debug(e) { "Function invocation failed" }
+                        function.failedInvocations.add(1)
+                    } finally {
+                        val end = clock.millis()
+                        function.activeTime.record(end - start)
+                        function.idleInstances.add(1)
+                        function.activeInstances.add(-1)
+                    }
+                }.startCoroutineCancellable(cont)
+            }
+        } catch (cause: Throwable) {
+            logger.error(cause) { "Exception occurred during scheduling cycle" }
+        }
+    }
+
+    suspend fun invoke(function: FunctionObject) {
+        check(function.uid in functions) { "Function does not exist (anymore)" }
+
+        _invocations.add(1)
+        function.invocations.add(1)
+
+        return suspendCancellableCoroutine { cont ->
+            if (!queue.add(InvocationRequest(clock.millis(), function, cont))) {
+                cont.resumeWithException(IllegalStateException("Failed to enqueue request"))
+            } else {
+                schedule()
+            }
+        }
+    }
+
+    fun delete(function: FunctionObject) {
+        functions.remove(function.uid)
+        functionsByName.remove(function.name)
+    }
+
+    override fun close() {
+        scope.cancel()
+
+        // Stop all function instances
+        for ((_, function) in functions) {
+            function.close()
+        }
+    }
+
+    override fun onStateChanged(instance: FunctionInstance, newState: FunctionInstanceState) {
+        terminationPolicy.onStateChanged(instance, newState)
+
+        if (newState == FunctionInstanceState.Deleted) {
+            val function = instance.function
+            function.instances.remove(instance)
+        }
+    }
+
+    /**
+     * A request to invoke a function.
+     */
+    private data class InvocationRequest(val timestamp: Long, val function: FunctionObject, val cont: Continuation<Unit>)
+}
diff --git a/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/router/RandomRoutingPolicy.kt b/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/router/RandomRoutingPolicy.kt
new file mode 100644
index 00000000..5bd9d4d3
--- /dev/null
+++ b/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/router/RandomRoutingPolicy.kt
@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) 2021 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package org.opendc.faas.service.router
+
+import org.opendc.faas.service.FunctionObject
+import org.opendc.faas.service.deployer.FunctionInstance
+import kotlin.random.Random
+
+/**
+ * A [RoutingPolicy] that selects a random function instance.
+ */
+public class RandomRoutingPolicy(private val random: Random = Random(0)) : RoutingPolicy {
+    override fun select(instances: List<FunctionInstance>, function: FunctionObject): FunctionInstance {
+        return instances.random(random)
+    }
+}
diff --git a/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/router/RoutingPolicy.kt b/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/router/RoutingPolicy.kt
new file mode 100644
index 00000000..e99e329a
--- /dev/null
+++ b/opendc-faas/opendc-faas-service/src/main/kotlin/org/opendc/faas/service/router/RoutingPolicy.kt
@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) 2021 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package org.opendc.faas.service.router
+
+import org.opendc.faas.service.FunctionObject
+import org.opendc.faas.service.deployer.FunctionInstance
+
+/**
+ * A [RoutingPolicy] decides to which [FunctionInstance] a function invocation should be routed.
+ */
+public interface RoutingPolicy {
+    /**
+     * Select the instance to which the request should be routed to.
+     */
+    public fun select(instances: List<FunctionInstance>, function: FunctionObject): FunctionInstance?
+}
diff --git a/opendc-faas/opendc-faas-service/src/test/kotlin/org/opendc/faas/service/FaaSServiceTest.kt b/opendc-faas/opendc-faas-service/src/test/kotlin/org/opendc/faas/service/FaaSServiceTest.kt
new file mode 100644
index 00000000..6b99684a
--- /dev/null
+++ b/opendc-faas/opendc-faas-service/src/test/kotlin/org/opendc/faas/service/FaaSServiceTest.kt
@@ -0,0 +1,186 @@
+/*
+ * Copyright (c) 2021 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package org.opendc.faas.service
+
+import io.mockk.*
+import io.opentelemetry.api.metrics.MeterProvider
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import org.junit.jupiter.api.Assertions.*
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.assertDoesNotThrow
+import org.junit.jupiter.api.assertThrows
+import org.opendc.faas.api.FaaSFunction
+import org.opendc.faas.service.deployer.FunctionDeployer
+import org.opendc.faas.service.deployer.FunctionInstance
+import org.opendc.faas.service.deployer.FunctionInstanceState
+import org.opendc.simulator.core.runBlockingSimulation
+import java.util.*
+
+/**
+ * Test suite for the [FaaSService] implementation.
+ */
+@OptIn(ExperimentalCoroutinesApi::class)
+internal class FaaSServiceTest {
+
+    @Test
+    fun testClientState() = runBlockingSimulation {
+        val meter = MeterProvider.noop().get("opendc-faas")
+        val service = FaaSService(coroutineContext, clock, meter, mockk(), mockk(), mockk())
+
+        val client = assertDoesNotThrow { service.newClient() }
+        assertDoesNotThrow { client.close() }
+
+        assertThrows<IllegalStateException> { client.queryFunctions() }
+        assertThrows<IllegalStateException> { client.newFunction("test", 128) }
+        assertThrows<IllegalStateException> { client.invoke("test") }
+        assertThrows<IllegalStateException> { client.findFunction(UUID.randomUUID()) }
+        assertThrows<IllegalStateException> { client.findFunction("name") }
+    }
+
+    @Test
+    fun testClientInvokeUnknown() = runBlockingSimulation {
+        val meter = MeterProvider.noop().get("opendc-faas")
+        val service = FaaSService(coroutineContext, clock, meter, mockk(), mockk(), mockk())
+
+        val client = service.newClient()
+
+        assertThrows<IllegalArgumentException> { client.invoke("test") }
+    }
+
+    @Test
+    fun testClientFunctionCreation() = runBlockingSimulation {
+        val meter = MeterProvider.noop().get("opendc-faas")
+        val service = FaaSService(coroutineContext, clock, meter, mockk(), mockk(), mockk())
+
+        val client = service.newClient()
+
+        val function = client.newFunction("test", 128)
+
+        assertEquals("test", function.name)
+    }
+
+    @Test
+    fun testClientFunctionQuery() = runBlockingSimulation {
+        val meter = MeterProvider.noop().get("opendc-faas")
+        val service = FaaSService(coroutineContext, clock, meter, mockk(), mockk(), mockk())
+
+        val client = service.newClient()
+
+        assertEquals(emptyList<FaaSFunction>(), client.queryFunctions())
+
+        val function = client.newFunction("test", 128)
+
+        assertEquals(listOf(function), client.queryFunctions())
+    }
+
+    @Test
+    fun testClientFunctionFindById() = runBlockingSimulation {
+        val meter = MeterProvider.noop().get("opendc-faas")
+        val service = FaaSService(coroutineContext, clock, meter, mockk(), mockk(), mockk())
+
+        val client = service.newClient()
+
+        assertEquals(emptyList<FaaSFunction>(), client.queryFunctions())
+
+        val function = client.newFunction("test", 128)
+
+        assertNotNull(client.findFunction(function.uid))
+    }
+
+    @Test
+    fun testClientFunctionFindByName() = runBlockingSimulation {
+        val meter = MeterProvider.noop().get("opendc-faas")
+        val service = FaaSService(coroutineContext, clock, meter, mockk(), mockk(), mockk())
+
+        val client = service.newClient()
+
+        assertEquals(emptyList<FaaSFunction>(), client.queryFunctions())
+
+        val function = client.newFunction("test", 128)
+
+        assertNotNull(client.findFunction(function.name))
+    }
+
+    @Test
+    fun testClientFunctionDuplicateName() = runBlockingSimulation {
+        val meter = MeterProvider.noop().get("opendc-faas")
+        val service = FaaSService(coroutineContext, clock, meter, mockk(), mockk(), mockk())
+
+        val client = service.newClient()
+
+        client.newFunction("test", 128)
+
+        assertThrows<IllegalArgumentException> { client.newFunction("test", 128) }
+    }
+
+    @Test
+    fun testClientFunctionDelete() = runBlockingSimulation {
+        val meter = MeterProvider.noop().get("opendc-faas")
+        val service = FaaSService(coroutineContext, clock, meter, mockk(), mockk(), mockk())
+
+        val client = service.newClient()
+        val function = client.newFunction("test", 128)
+        assertNotNull(client.findFunction(function.uid))
+        function.delete()
+        assertNull(client.findFunction(function.uid))
+
+        // Delete should be idempotent
+        function.delete()
+    }
+
+    @Test
+    fun testClientFunctionCannotInvokeDeleted() = runBlockingSimulation {
+        val meter = MeterProvider.noop().get("opendc-faas")
+        val service = FaaSService(coroutineContext, clock, meter, mockk(), mockk(), mockk())
+
+        val client = service.newClient()
+        val function = client.newFunction("test", 128)
+        assertNotNull(client.findFunction(function.uid))
+        function.delete()
+
+        assertThrows<IllegalStateException> { function.invoke() }
+    }
+
+    @Test
+    fun testClientFunctionInvoke() = runBlockingSimulation {
+        val meter = MeterProvider.noop().get("opendc-faas")
+        val deployer = mockk<FunctionDeployer>()
+        val service = FaaSService(coroutineContext, clock, meter, deployer, mockk(), mockk(relaxUnitFun = true))
+
+        every { deployer.deploy(any(), any()) } answers {
+            object : FunctionInstance {
+                override val state: FunctionInstanceState = FunctionInstanceState.Idle
+                override val function: FunctionObject = it.invocation.args[0] as FunctionObject
+
+                override suspend fun invoke() {}
+
+                override fun close() {}
+            }
+        }
+
+        val client = service.newClient()
+        val function = client.newFunction("test", 128)
+
+        function.invoke()
+    }
+}
diff --git a/opendc-faas/opendc-faas-simulator/build.gradle.kts b/opendc-faas/opendc-faas-simulator/build.gradle.kts
new file mode 100644
index 00000000..fed1862d
--- /dev/null
+++ b/opendc-faas/opendc-faas-simulator/build.gradle.kts
@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2021 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+description = "Simulator for the OpenDC FaaS platform"
+
+/* Build configuration */
+plugins {
+    `kotlin-library-conventions`
+    `testing-conventions`
+    `jacoco-conventions`
+}
+
+dependencies {
+    api(platform(projects.opendcPlatform))
+    api(projects.opendcFaas.opendcFaasService)
+    api(projects.opendcSimulator.opendcSimulatorCompute)
+
+    testImplementation(projects.opendcSimulator.opendcSimulatorCore)
+    testRuntimeOnly(libs.slf4j.simple)
+}
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
new file mode 100644
index 00000000..602f1678
--- /dev/null
+++ b/opendc-faas/opendc-faas-simulator/src/main/kotlin/org/opendc/faas/simulator/SimFunctionDeployer.kt
@@ -0,0 +1,179 @@
+/*
+ * Copyright (c) 2021 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package org.opendc.faas.simulator
+
+import kotlinx.coroutines.*
+import kotlinx.coroutines.channels.Channel
+import org.opendc.faas.service.FunctionObject
+import org.opendc.faas.service.deployer.FunctionDeployer
+import org.opendc.faas.service.deployer.FunctionInstance
+import org.opendc.faas.service.deployer.FunctionInstanceListener
+import org.opendc.faas.service.deployer.FunctionInstanceState
+import org.opendc.faas.simulator.delay.DelayInjector
+import org.opendc.faas.simulator.workload.SimFaaSWorkloadMapper
+import org.opendc.simulator.compute.SimBareMetalMachine
+import org.opendc.simulator.compute.SimMachine
+import org.opendc.simulator.compute.SimMachineModel
+import org.opendc.simulator.compute.power.ConstantPowerModel
+import org.opendc.simulator.compute.power.SimplePowerDriver
+import org.opendc.simulator.resources.SimResourceInterpreter
+import java.time.Clock
+import java.util.ArrayDeque
+import kotlin.coroutines.Continuation
+import kotlin.coroutines.resume
+import kotlin.coroutines.resumeWithException
+
+/**
+ * A [FunctionDeployer] that uses that simulates the [FunctionInstance]s.
+ */
+public class SimFunctionDeployer(
+    private val clock: Clock,
+    private val scope: CoroutineScope,
+    private val model: SimMachineModel,
+    private val delayInjector: DelayInjector,
+    private val mapper: SimFaaSWorkloadMapper
+) : FunctionDeployer {
+
+    override fun deploy(function: FunctionObject, listener: FunctionInstanceListener): Instance {
+        val instance = Instance(function, listener)
+        instance.start()
+        return instance
+    }
+
+    /**
+     * A simulated [FunctionInstance].
+     */
+    public inner class Instance(override val function: FunctionObject, private val listener: FunctionInstanceListener) :
+        FunctionInstance {
+        /**
+         * The workload associated with this instance.
+         */
+        private val workload = mapper.createWorkload(function)
+
+        /**
+         * The machine that will execute the workloads.
+         */
+        public val machine: SimMachine = SimBareMetalMachine(
+            SimResourceInterpreter(scope.coroutineContext, clock),
+            model,
+            SimplePowerDriver(ConstantPowerModel(0.0))
+        )
+
+        /**
+         * The job associated with the lifecycle of the instance.
+         */
+        private var job: Job? = null
+
+        /**
+         * The invocation request queue.
+         */
+        private val queue = ArrayDeque<InvocationRequest>()
+
+        /**
+         * A channel used to signal that new invocations have been enqueued.
+         */
+        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" }
+            return suspendCancellableCoroutine { cont ->
+                queue.add(InvocationRequest(cont))
+                chan.trySend(Unit)
+            }
+        }
+
+        override fun close() {
+            state = FunctionInstanceState.Deleted
+            stop()
+            machine.close()
+        }
+
+        override fun toString(): String = "FunctionInstance[state=$state]"
+
+        /**
+         * Start the function instance.
+         */
+        @OptIn(InternalCoroutinesApi::class)
+        internal fun start() {
+            check(state == FunctionInstanceState.Provisioning) { "Invalid state of function instance" }
+            job = scope.launch {
+                delay(delayInjector.getColdStartDelay(this@Instance))
+
+                launch {
+                    try {
+                        machine.run(workload)
+                    } finally {
+                        state = FunctionInstanceState.Deleted
+                    }
+                }
+
+                while (isActive) {
+                    if (queue.isEmpty()) {
+                        chan.receive()
+                    }
+
+                    state = FunctionInstanceState.Active
+                    while (queue.isNotEmpty()) {
+                        val request = queue.poll()
+                        try {
+                            workload.invoke()
+                            request.cont.resume(Unit)
+                        } catch (cause: CancellationException) {
+                            request.cont.resumeWithException(cause)
+                            throw cause
+                        } catch (cause: Throwable) {
+                            request.cont.resumeWithException(cause)
+                        }
+                    }
+                    state = FunctionInstanceState.Idle
+                }
+            }
+        }
+
+        /**
+         * Stop the function instance.
+         */
+        private fun stop() {
+            val job = job
+
+            if (job != null) {
+                this.job = null
+                job.cancel()
+            }
+        }
+    }
+
+    /**
+     * A function invocation request.
+     */
+    private data class InvocationRequest(val cont: Continuation<Unit>)
+}
diff --git a/opendc-faas/opendc-faas-simulator/src/main/kotlin/org/opendc/faas/simulator/delay/ColdStartModel.kt b/opendc-faas/opendc-faas-simulator/src/main/kotlin/org/opendc/faas/simulator/delay/ColdStartModel.kt
new file mode 100644
index 00000000..624067be
--- /dev/null
+++ b/opendc-faas/opendc-faas-simulator/src/main/kotlin/org/opendc/faas/simulator/delay/ColdStartModel.kt
@@ -0,0 +1,69 @@
+/*
+ * Copyright (c) 2021 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package org.opendc.faas.simulator.delay
+
+/**
+ * Model parameters for the cold start times of serverless services.
+ */
+public enum class ColdStartModel {
+    // Min and max memory values from [Peeking Behind The Curtains of Serverless Platforms][2018],
+    // other values deduced from linear curve.
+    LAMBDA {
+        override fun coldStartParam(provisionedMemory: Int): Pair<Double, Double> {
+            return when (provisionedMemory) {
+                128 -> Pair(265.21, 354.43)
+                256 -> Pair(261.46, 334.23)
+                512 -> Pair(257.71, 314.03)
+                1024 -> Pair(253.96, 293.83)
+                1536 -> Pair(250.07, 273.63)
+                2048 -> Pair(246.11, 253.43)
+                else -> Pair(0.0, 1.0)
+            }
+        }
+    },
+    AZURE {
+        // Azure by default uses 1.5gb memory to instantiate functions
+        override fun coldStartParam(provisionedMemory: Int): Pair<Double, Double> {
+            return Pair(242.66, 340.67)
+        }
+    },
+
+    GOOGLE {
+        override fun coldStartParam(provisionedMemory: Int): Pair<Double, Double> {
+            return when (provisionedMemory) {
+                128 -> Pair(493.04, 345.8)
+                256 -> Pair(416.59, 301.5)
+                512 -> Pair(340.14, 257.2)
+                1024 -> Pair(263.69, 212.9)
+                1536 -> Pair(187.24, 168.6)
+                2048 -> Pair(110.77, 124.3)
+                else -> Pair(0.0, 1.0)
+            }
+        }
+    };
+
+    /**
+     * Obtain the stochastic parameters for the cold start models.
+     */
+    public abstract fun coldStartParam(provisionedMemory: Int): Pair<Double, Double>
+}
diff --git a/opendc-faas/opendc-faas-simulator/src/main/kotlin/org/opendc/faas/simulator/delay/DelayInjector.kt b/opendc-faas/opendc-faas-simulator/src/main/kotlin/org/opendc/faas/simulator/delay/DelayInjector.kt
new file mode 100644
index 00000000..c1df682c
--- /dev/null
+++ b/opendc-faas/opendc-faas-simulator/src/main/kotlin/org/opendc/faas/simulator/delay/DelayInjector.kt
@@ -0,0 +1,37 @@
+/*
+ * Copyright (c) 2021 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package org.opendc.faas.simulator.delay
+
+import org.opendc.faas.service.deployer.FunctionInstance
+
+/**
+ * An interface for modeling the delay caused by function cold starts.
+ */
+public interface DelayInjector {
+    /**
+     * Returns the cold start delay duration sampled from a normal distribution, the distribution is
+     * initialized using custom mean and standard deviation based on provisioned memory, language and
+     * failure model
+     */
+    public fun getColdStartDelay(instance: FunctionInstance): Long
+}
diff --git a/opendc-faas/opendc-faas-simulator/src/main/kotlin/org/opendc/faas/simulator/delay/StochasticDelayInjector.kt b/opendc-faas/opendc-faas-simulator/src/main/kotlin/org/opendc/faas/simulator/delay/StochasticDelayInjector.kt
new file mode 100644
index 00000000..9442e2d3
--- /dev/null
+++ b/opendc-faas/opendc-faas-simulator/src/main/kotlin/org/opendc/faas/simulator/delay/StochasticDelayInjector.kt
@@ -0,0 +1,37 @@
+/*
+ * Copyright (c) 2021 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package org.opendc.faas.simulator.delay
+
+import org.opendc.faas.service.deployer.FunctionInstance
+import java.util.*
+import kotlin.math.abs
+
+/*
+ * Interface for instance deployment delay estimation.
+ */
+public class StochasticDelayInjector(private val model: ColdStartModel, private val random: Random) : DelayInjector {
+    override fun getColdStartDelay(instance: FunctionInstance): Long {
+        val (mean, sd) = model.coldStartParam(instance.function.memorySize.toInt())
+        return abs(random.nextGaussian() * sd + mean).toLong()
+    }
+}
diff --git a/opendc-faas/opendc-faas-simulator/src/main/kotlin/org/opendc/faas/simulator/delay/ZeroDelayInjector.kt b/opendc-faas/opendc-faas-simulator/src/main/kotlin/org/opendc/faas/simulator/delay/ZeroDelayInjector.kt
new file mode 100644
index 00000000..0e318764
--- /dev/null
+++ b/opendc-faas/opendc-faas-simulator/src/main/kotlin/org/opendc/faas/simulator/delay/ZeroDelayInjector.kt
@@ -0,0 +1,29 @@
+/*
+ * Copyright (c) 2021 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package org.opendc.faas.simulator.delay
+
+import org.opendc.faas.service.deployer.FunctionInstance
+
+public object ZeroDelayInjector : DelayInjector {
+    override fun getColdStartDelay(instance: FunctionInstance): Long = 0
+}
diff --git a/opendc-faas/opendc-faas-simulator/src/main/kotlin/org/opendc/faas/simulator/workload/SimFaaSWorkload.kt b/opendc-faas/opendc-faas-simulator/src/main/kotlin/org/opendc/faas/simulator/workload/SimFaaSWorkload.kt
new file mode 100644
index 00000000..aaee26c0
--- /dev/null
+++ b/opendc-faas/opendc-faas-simulator/src/main/kotlin/org/opendc/faas/simulator/workload/SimFaaSWorkload.kt
@@ -0,0 +1,35 @@
+/*
+ * Copyright (c) 2021 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package org.opendc.faas.simulator.workload
+
+import org.opendc.simulator.compute.workload.SimWorkload
+
+/**
+ * A model for a serverless function workload, which may be invoked multiple times.
+ */
+public interface SimFaaSWorkload : SimWorkload {
+    /**
+     * This method is invoked when an active function instance is invoked.
+     */
+    public suspend fun invoke()
+}
diff --git a/opendc-faas/opendc-faas-simulator/src/main/kotlin/org/opendc/faas/simulator/workload/SimFaaSWorkloadMapper.kt b/opendc-faas/opendc-faas-simulator/src/main/kotlin/org/opendc/faas/simulator/workload/SimFaaSWorkloadMapper.kt
new file mode 100644
index 00000000..b22dd659
--- /dev/null
+++ b/opendc-faas/opendc-faas-simulator/src/main/kotlin/org/opendc/faas/simulator/workload/SimFaaSWorkloadMapper.kt
@@ -0,0 +1,37 @@
+/*
+ * Copyright (c) 2021 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package org.opendc.faas.simulator.workload
+
+import org.opendc.faas.api.FaaSFunction
+import org.opendc.faas.service.FunctionObject
+
+/**
+ * A [SimFaaSWorkloadMapper] is responsible for mapping a [FaaSFunction] to a [SimFaaSWorkload] that
+ * can be simulated.
+ */
+public fun interface SimFaaSWorkloadMapper {
+    /**
+     * Map the specified [function] to a [SimFaaSWorkload] that can be simulated.
+     */
+    public fun createWorkload(function: FunctionObject): SimFaaSWorkload
+}
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
new file mode 100644
index 00000000..ceb91e75
--- /dev/null
+++ b/opendc-faas/opendc-faas-simulator/src/test/kotlin/org/opendc/faas/simulator/SimFaaSServiceTest.kt
@@ -0,0 +1,91 @@
+/*
+ * Copyright (c) 2021 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package org.opendc.faas.simulator
+
+import io.mockk.coVerify
+import io.mockk.spyk
+import io.opentelemetry.api.metrics.MeterProvider
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.delay
+import kotlinx.coroutines.yield
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.assertAll
+import org.opendc.faas.service.FaaSService
+import org.opendc.faas.service.autoscaler.FunctionTerminationPolicyFixed
+import org.opendc.faas.service.router.RandomRoutingPolicy
+import org.opendc.faas.simulator.delay.ZeroDelayInjector
+import org.opendc.faas.simulator.workload.SimFaaSWorkload
+import org.opendc.simulator.compute.SimMachineModel
+import org.opendc.simulator.compute.model.MemoryUnit
+import org.opendc.simulator.compute.model.ProcessingNode
+import org.opendc.simulator.compute.model.ProcessingUnit
+import org.opendc.simulator.compute.workload.SimFlopsWorkload
+import org.opendc.simulator.compute.workload.SimWorkload
+import org.opendc.simulator.core.runBlockingSimulation
+
+/**
+ * A test suite for the [FaaSService] implementation under simulated conditions.
+ */
+@OptIn(ExperimentalCoroutinesApi::class)
+internal class SimFaaSServiceTest {
+
+    private lateinit var machineModel: SimMachineModel
+
+    @BeforeEach
+    fun setUp() {
+        val cpuNode = ProcessingNode("Intel", "Xeon", "amd64", 2)
+
+        machineModel = SimMachineModel(
+            cpus = List(cpuNode.coreCount) { ProcessingUnit(cpuNode, it, 1000.0) },
+            memory = List(4) { MemoryUnit("Crucial", "MTA18ASF4G72AZ-3G2B1", 3200.0, 32_000) }
+        )
+    }
+
+    @Test
+    fun testSmoke() = runBlockingSimulation {
+        val meter = MeterProvider.noop().get("opendc-faas")
+        val workload = spyk(object : SimFaaSWorkload, SimWorkload by SimFlopsWorkload(1000) {
+            override suspend fun invoke() {}
+        })
+        val deployer = SimFunctionDeployer(clock, this, machineModel, ZeroDelayInjector) { workload }
+        val service = FaaSService(
+            coroutineContext, clock, meter, deployer, RandomRoutingPolicy(),
+            FunctionTerminationPolicyFixed(coroutineContext, clock, timeout = 10000)
+        )
+
+        val client = service.newClient()
+
+        val function = client.newFunction("test", 128)
+        function.invoke()
+        delay(2000)
+
+        service.close()
+
+        yield()
+
+        assertAll(
+            { coVerify { workload.invoke() } },
+        )
+    }
+}