Move custom Flows to separate utility module

This change moves the custom Flow object we provide (e.g. EventFlow and
StateFlow) outside of the odcsim-api module into a separate opendc-utils
module.

This is in preparation for the removal of the odcsim components in OpenDC.

9 files changed, 214 insertions, 5 deletions

diff --git a/simulator/opendc/opendc-compute/build.gradle.kts b/simulator/opendc/opendc-compute/build.gradle.kts
index 0e44785e..a8852cba 100644
--- a/simulator/opendc/opendc-compute/build.gradle.kts
+++ b/simulator/opendc/opendc-compute/build.gradle.kts
@@ -32,6 +32,7 @@ plugins {
 dependencies {
     api(project(":odcsim:odcsim-api"))
     api(project(":opendc:opendc-core"))
+    implementation(project(":opendc:opendc-utils"))
     implementation("io.github.microutils:kotlin-logging:1.7.9")
 
     testImplementation(project(":opendc:opendc-simulator"))
diff --git a/simulator/opendc/opendc-compute/src/main/kotlin/com/atlarge/opendc/compute/metal/driver/SimpleBareMetalDriver.kt b/simulator/opendc/opendc-compute/src/main/kotlin/com/atlarge/opendc/compute/metal/driver/SimpleBareMetalDriver.kt
index c118cc3d..0c758e6b 100644
--- a/simulator/opendc/opendc-compute/src/main/kotlin/com/atlarge/opendc/compute/metal/driver/SimpleBareMetalDriver.kt
+++ b/simulator/opendc/opendc-compute/src/main/kotlin/com/atlarge/opendc/compute/metal/driver/SimpleBareMetalDriver.kt
@@ -24,8 +24,6 @@
 
 package com.atlarge.opendc.compute.metal.driver
 
-import com.atlarge.odcsim.flow.EventFlow
-import com.atlarge.odcsim.flow.StateFlow
 import com.atlarge.opendc.compute.core.Flavor
 import com.atlarge.opendc.compute.core.MemoryUnit
 import com.atlarge.opendc.compute.core.ProcessingUnit
@@ -57,6 +55,8 @@ import kotlinx.coroutines.intrinsics.startCoroutineCancellable
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.selects.SelectClause0
 import kotlinx.coroutines.selects.SelectInstance
+import org.opendc.utils.flow.EventFlow
+import org.opendc.utils.flow.StateFlow
 import java.lang.Exception
 import java.time.Clock
 import java.util.UUID
diff --git a/simulator/opendc/opendc-compute/src/main/kotlin/com/atlarge/opendc/compute/virt/driver/SimpleVirtDriver.kt b/simulator/opendc/opendc-compute/src/main/kotlin/com/atlarge/opendc/compute/virt/driver/SimpleVirtDriver.kt
index bd266208..fa172e6e 100644
--- a/simulator/opendc/opendc-compute/src/main/kotlin/com/atlarge/opendc/compute/virt/driver/SimpleVirtDriver.kt
+++ b/simulator/opendc/opendc-compute/src/main/kotlin/com/atlarge/opendc/compute/virt/driver/SimpleVirtDriver.kt
@@ -24,7 +24,6 @@
 
 package com.atlarge.opendc.compute.virt.driver
 
-import com.atlarge.odcsim.flow.EventFlow
 import com.atlarge.opendc.compute.core.Flavor
 import com.atlarge.opendc.compute.core.ProcessingUnit
 import com.atlarge.opendc.compute.core.Server
@@ -47,6 +46,7 @@ import kotlinx.coroutines.selects.SelectClause0
 import kotlinx.coroutines.selects.SelectInstance
 import kotlinx.coroutines.selects.select
 import mu.KotlinLogging
+import org.opendc.utils.flow.EventFlow
 import java.time.Clock
 import java.util.UUID
 import kotlin.math.ceil
diff --git a/simulator/opendc/opendc-compute/src/main/kotlin/com/atlarge/opendc/compute/virt/service/SimpleVirtProvisioningService.kt b/simulator/opendc/opendc-compute/src/main/kotlin/com/atlarge/opendc/compute/virt/service/SimpleVirtProvisioningService.kt
index 6b2cfc40..5e151cbb 100644
--- a/simulator/opendc/opendc-compute/src/main/kotlin/com/atlarge/opendc/compute/virt/service/SimpleVirtProvisioningService.kt
+++ b/simulator/opendc/opendc-compute/src/main/kotlin/com/atlarge/opendc/compute/virt/service/SimpleVirtProvisioningService.kt
@@ -1,6 +1,5 @@
 package com.atlarge.opendc.compute.virt.service
 
-import com.atlarge.odcsim.flow.EventFlow
 import com.atlarge.opendc.compute.core.Flavor
 import com.atlarge.opendc.compute.core.Server
 import com.atlarge.opendc.compute.core.ServerEvent
@@ -19,6 +18,7 @@ import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.launchIn
 import kotlinx.coroutines.flow.onEach
 import mu.KotlinLogging
+import org.opendc.utils.flow.EventFlow
 import java.time.Clock
 import kotlin.coroutines.Continuation
 import kotlin.coroutines.resume
diff --git a/simulator/opendc/opendc-utils/build.gradle.kts b/simulator/opendc/opendc-utils/build.gradle.kts
new file mode 100644
index 00000000..d66148c4
--- /dev/null
+++ b/simulator/opendc/opendc-utils/build.gradle.kts
@@ -0,0 +1,32 @@
+/*
+ * Copyright (c) 2020 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 = "Utilities used across OpenDC modules"
+
+/* Build configuration */
+plugins {
+    `kotlin-library-convention`
+}
+
+dependencies {
+    api("org.jetbrains.kotlinx:kotlinx-coroutines-core:${Library.KOTLINX_COROUTINES}")
+}
diff --git a/simulator/opendc/opendc-utils/src/main/kotlin/org/opendc/utils/flow/EventFlow.kt b/simulator/opendc/opendc-utils/src/main/kotlin/org/opendc/utils/flow/EventFlow.kt
new file mode 100644
index 00000000..948595b1
--- /dev/null
+++ b/simulator/opendc/opendc-utils/src/main/kotlin/org/opendc/utils/flow/EventFlow.kt
@@ -0,0 +1,96 @@
+/*
+ * Copyright (c) 2020 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.utils.flow
+
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.FlowPreview
+import kotlinx.coroutines.InternalCoroutinesApi
+import kotlinx.coroutines.channels.Channel
+import kotlinx.coroutines.channels.SendChannel
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.FlowCollector
+import kotlinx.coroutines.flow.consumeAsFlow
+
+/**
+ * A [Flow] that can be used to emit events.
+ */
+public interface EventFlow<T> : Flow<T> {
+    /**
+     * Emit the specified [event].
+     */
+    public fun emit(event: T)
+
+    /**
+     * Close the flow.
+     */
+    public fun close()
+}
+
+/**
+ * Creates a new [EventFlow].
+ */
+@Suppress("FunctionName")
+public fun <T> EventFlow(): EventFlow<T> = EventFlowImpl()
+
+/**
+ * Internal implementation of the [EventFlow] class.
+ */
+@OptIn(ExperimentalCoroutinesApi::class, FlowPreview::class)
+private class EventFlowImpl<T> : EventFlow<T> {
+    private var closed: Boolean = false
+    private val subscribers = HashMap<SendChannel<T>, Unit>()
+
+    override fun emit(event: T) {
+        synchronized(this) {
+            for ((chan, _) in subscribers) {
+                chan.offer(event)
+            }
+        }
+    }
+
+    override fun close() {
+        synchronized(this) {
+            closed = true
+
+            for ((chan, _) in subscribers) {
+                chan.close()
+            }
+        }
+    }
+
+    @InternalCoroutinesApi
+    override suspend fun collect(collector: FlowCollector<T>) {
+        val channel: Channel<T>
+        synchronized(this) {
+            if (closed) {
+                return
+            }
+
+            channel = Channel(Channel.UNLIMITED)
+            subscribers[channel] = Unit
+        }
+        channel.consumeAsFlow().collect(collector)
+    }
+
+    override fun toString(): String = "EventFlow"
+}
diff --git a/simulator/opendc/opendc-utils/src/main/kotlin/org/opendc/utils/flow/StateFlow.kt b/simulator/opendc/opendc-utils/src/main/kotlin/org/opendc/utils/flow/StateFlow.kt
new file mode 100644
index 00000000..996e7700
--- /dev/null
+++ b/simulator/opendc/opendc-utils/src/main/kotlin/org/opendc/utils/flow/StateFlow.kt
@@ -0,0 +1,79 @@
+/*
+ * Copyright (c) 2020 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.utils.flow
+
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.FlowPreview
+import kotlinx.coroutines.InternalCoroutinesApi
+import kotlinx.coroutines.channels.BroadcastChannel
+import kotlinx.coroutines.channels.ConflatedBroadcastChannel
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.FlowCollector
+import kotlinx.coroutines.flow.asFlow
+
+/**
+ * A [Flow] that contains a single value that changes over time.
+ *
+ * This class exists to implement the DataFlow/StateFlow functionality that will be implemented in `kotlinx-coroutines`
+ * in the future, but is not available yet.
+ * See: https://github.com/Kotlin/kotlinx.coroutines/pull/1354
+ */
+public interface StateFlow<T> : Flow<T> {
+    /**
+     * The current value of this flow.
+     *
+     * Setting a value that is [equal][Any.equals] to the previous one does nothing.
+     */
+    public var value: T
+}
+
+/**
+ * Creates a [StateFlow] with a given initial [value].
+ */
+@Suppress("FunctionName")
+public fun <T> StateFlow(value: T): StateFlow<T> = StateFlowImpl(value)
+
+/**
+ * Internal implementation of the [StateFlow] interface.
+ */
+@OptIn(ExperimentalCoroutinesApi::class, FlowPreview::class)
+private class StateFlowImpl<T>(initialValue: T) : StateFlow<T> {
+    /**
+     * The [BroadcastChannel] to back this flow.
+     */
+    private val chan = ConflatedBroadcastChannel(initialValue)
+
+    /**
+     * The internal [Flow] backing this flow.
+     */
+    private val flow = chan.asFlow()
+
+    public override var value: T = initialValue
+        set(value) {
+            chan.offer(value)
+            field = value
+        }
+
+    @InternalCoroutinesApi
+    override suspend fun collect(collector: FlowCollector<T>) = flow.collect(collector)
+}
diff --git a/simulator/opendc/opendc-workflows/build.gradle.kts b/simulator/opendc/opendc-workflows/build.gradle.kts
index 62c4bc25..f8a9a1f3 100644
--- a/simulator/opendc/opendc-workflows/build.gradle.kts
+++ b/simulator/opendc/opendc-workflows/build.gradle.kts
@@ -32,6 +32,7 @@ plugins {
 dependencies {
     api(project(":opendc:opendc-core"))
     api(project(":opendc:opendc-compute"))
+    implementation(project(":opendc:opendc-utils"))
 
     testImplementation(project(":opendc:opendc-simulator"))
     testImplementation(project(":opendc:opendc-format"))
diff --git a/simulator/opendc/opendc-workflows/src/main/kotlin/com/atlarge/opendc/workflows/service/StageWorkflowService.kt b/simulator/opendc/opendc-workflows/src/main/kotlin/com/atlarge/opendc/workflows/service/StageWorkflowService.kt
index aea27972..3a5b963c 100644
--- a/simulator/opendc/opendc-workflows/src/main/kotlin/com/atlarge/opendc/workflows/service/StageWorkflowService.kt
+++ b/simulator/opendc/opendc-workflows/src/main/kotlin/com/atlarge/opendc/workflows/service/StageWorkflowService.kt
@@ -24,7 +24,6 @@
 
 package com.atlarge.opendc.workflows.service
 
-import com.atlarge.odcsim.flow.EventFlow
 import com.atlarge.opendc.compute.core.Server
 import com.atlarge.opendc.compute.core.ServerEvent
 import com.atlarge.opendc.compute.core.ServerState
@@ -43,6 +42,7 @@ import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.launchIn
 import kotlinx.coroutines.flow.onEach
 import kotlinx.coroutines.launch
+import org.opendc.utils.flow.EventFlow
 import java.time.Clock
 import java.util.PriorityQueue
 import java.util.Queue