build: Flatten project structure

This change updates the project structure to become flattened. 
Previously, the simulator, frontend and API each lived into their own directory. 

With this change, all modules of the project live in the top-level directory of 
the repository.

4 files changed, 270 insertions, 0 deletions

diff --git a/opendc-simulator/opendc-simulator-failures/src/main/kotlin/org/opendc/simulator/failures/CorrelatedFaultInjector.kt b/opendc-simulator/opendc-simulator-failures/src/main/kotlin/org/opendc/simulator/failures/CorrelatedFaultInjector.kt
new file mode 100644
index 00000000..0e15f338
--- /dev/null
+++ b/opendc-simulator/opendc-simulator-failures/src/main/kotlin/org/opendc/simulator/failures/CorrelatedFaultInjector.kt
@@ -0,0 +1,129 @@
+/*
+ * 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.simulator.failures
+
+import kotlinx.coroutines.*
+import java.time.Clock
+import kotlin.math.exp
+import kotlin.math.max
+import kotlin.random.Random
+import kotlin.random.asJavaRandom
+
+/**
+ * A [FaultInjector] that injects fault in the system which are correlated to each other. Failures do not occur in
+ * isolation, but will trigger other faults.
+ */
+public class CorrelatedFaultInjector(
+    private val coroutineScope: CoroutineScope,
+    private val clock: Clock,
+    private val iatScale: Double,
+    private val iatShape: Double,
+    private val sizeScale: Double,
+    private val sizeShape: Double,
+    private val dScale: Double,
+    private val dShape: Double,
+    random: Random = Random(0)
+) : FaultInjector {
+    /**
+     * The active failure domains that have been registered.
+     */
+    private val active = mutableSetOf<FailureDomain>()
+
+    /**
+     * The [Job] that awaits the nearest fault in the system.
+     */
+    private var job: Job? = null
+
+    /**
+     * The [Random] instance to use.
+     */
+    private val random: java.util.Random = random.asJavaRandom()
+
+    /**
+     * Enqueue the specified [FailureDomain] to fail some time in the future.
+     */
+    override fun enqueue(domain: FailureDomain) {
+        active += domain
+
+        // Clean up the domain if it finishes
+        domain.scope.coroutineContext[Job]!!.invokeOnCompletion {
+            this@CorrelatedFaultInjector.coroutineScope.launch {
+                active -= domain
+
+                if (active.isEmpty()) {
+                    job?.cancel()
+                    job = null
+                }
+            }
+        }
+
+        if (job != null) {
+            return
+        }
+
+        job = this.coroutineScope.launch {
+            while (active.isNotEmpty()) {
+                ensureActive()
+
+                // Make sure to convert delay from hours to milliseconds
+                val d = lognvariate(iatScale, iatShape) * 3.6e6
+
+                // Handle long overflow
+                if (clock.millis() + d <= 0) {
+                    return@launch
+                }
+
+                delay(d.toLong())
+
+                val n = lognvariate(sizeScale, sizeShape).toInt()
+                val targets = active.shuffled(random).take(n)
+
+                for (failureDomain in targets) {
+                    active -= failureDomain
+                    failureDomain.fail()
+                }
+
+                val df = max(lognvariate(dScale, dShape) * 6e4, 15 * 6e4)
+
+                // Handle long overflow
+                if (clock.millis() + df <= 0) {
+                    return@launch
+                }
+
+                delay(df.toLong())
+
+                for (failureDomain in targets) {
+                    failureDomain.recover()
+
+                    // Re-enqueue machine to be failed
+                    enqueue(failureDomain)
+                }
+            }
+
+            job = null
+        }
+    }
+
+    // XXX We should extract this in some common package later on.
+    private fun lognvariate(scale: Double, shape: Double) = exp(scale + shape * random.nextGaussian())
+}
diff --git a/opendc-simulator/opendc-simulator-failures/src/main/kotlin/org/opendc/simulator/failures/FailureDomain.kt b/opendc-simulator/opendc-simulator-failures/src/main/kotlin/org/opendc/simulator/failures/FailureDomain.kt
new file mode 100644
index 00000000..dc3006e8
--- /dev/null
+++ b/opendc-simulator/opendc-simulator-failures/src/main/kotlin/org/opendc/simulator/failures/FailureDomain.kt
@@ -0,0 +1,47 @@
+/*
+ * MIT License
+ *
+ * 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.simulator.failures
+
+import kotlinx.coroutines.CoroutineScope
+
+/**
+ * A logical or physical component in a computing environment which may fail.
+ */
+public interface FailureDomain {
+    /**
+     * The lifecycle of the failure domain to which a [FaultInjector] will attach.
+     */
+    public val scope: CoroutineScope
+
+    /**
+     * Fail the domain externally.
+     */
+    public suspend fun fail()
+
+    /**
+     * Resume the failure domain.
+     */
+    public suspend fun recover()
+}
diff --git a/opendc-simulator/opendc-simulator-failures/src/main/kotlin/org/opendc/simulator/failures/FaultInjector.kt b/opendc-simulator/opendc-simulator-failures/src/main/kotlin/org/opendc/simulator/failures/FaultInjector.kt
new file mode 100644
index 00000000..a866260c
--- /dev/null
+++ b/opendc-simulator/opendc-simulator-failures/src/main/kotlin/org/opendc/simulator/failures/FaultInjector.kt
@@ -0,0 +1,33 @@
+/*
+ * 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.simulator.failures
+
+/**
+ * An interface for stochastically injecting faults into a running system.
+ */
+public interface FaultInjector {
+    /**
+     * Enqueue the specified [FailureDomain] into the queue as candidate for failure injection in the future.
+     */
+    public fun enqueue(domain: FailureDomain)
+}
diff --git a/opendc-simulator/opendc-simulator-failures/src/main/kotlin/org/opendc/simulator/failures/UncorrelatedFaultInjector.kt b/opendc-simulator/opendc-simulator-failures/src/main/kotlin/org/opendc/simulator/failures/UncorrelatedFaultInjector.kt
new file mode 100644
index 00000000..b3bd737e
--- /dev/null
+++ b/opendc-simulator/opendc-simulator-failures/src/main/kotlin/org/opendc/simulator/failures/UncorrelatedFaultInjector.kt
@@ -0,0 +1,61 @@
+/*
+ * 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.simulator.failures
+
+import kotlinx.coroutines.delay
+import kotlinx.coroutines.launch
+import java.time.Clock
+import kotlin.math.ln1p
+import kotlin.math.pow
+import kotlin.random.Random
+
+/**
+ * A [FaultInjector] that injects uncorrelated faults into the system, meaning that failures of the subsystems are
+ * independent.
+ */
+public class UncorrelatedFaultInjector(
+    private val clock: Clock,
+    private val alpha: Double,
+    private val beta: Double,
+    private val random: Random = Random(0)
+) : FaultInjector {
+    /**
+     * Enqueue the specified [FailureDomain] to fail some time in the future.
+     */
+    override fun enqueue(domain: FailureDomain) {
+        domain.scope.launch {
+            val d = random.weibull(alpha, beta) * 1e3 // Make sure to convert delay to milliseconds
+
+            // Handle long overflow
+            if (clock.millis() + d <= 0) {
+                return@launch
+            }
+
+            delay(d.toLong())
+            domain.fail()
+        }
+    }
+
+    // XXX We should extract this in some common package later on.
+    private fun Random.weibull(alpha: Double, beta: Double) = (beta * (-ln1p(-nextDouble())).pow(1.0 / alpha))
+}