Horizontal pod autoscaler from kubernetes

.github/workflows/update_documentation.yml

@@ -30,13 +30,13 @@ jobs:
           GITHUB_TOKEN: ${{ secrets.READ_PACKAGES }}
 
       - name: Upload JavaDoc as HTML
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         with:
           name: JavaDoc
           path: ./target/site/apidocs
 
       - name: Upload JavaDoc as JAR
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         with:
           name: JavaDocJar
           path: ./target/misim-javadoc.jar
@@ -50,12 +50,12 @@ jobs:
 
     steps:
       - name: Download JavaDoc Artifact
-        uses: actions/download-artifact@v3
+        uses: actions/download-artifact@v4
         with:
           name: JavaDoc
           path: ~/docs/
 
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           fetch-depth: 0
 

src/main/java/cambio/simulator/entities/patterns/HorizontalPodAutoscalingPolicy.java

@@ -0,0 +1,85 @@
+package cambio.simulator.entities.patterns;
+
+import cambio.simulator.entities.microservice.Microservice;
+import cambio.simulator.export.MultiDataPointReporter;
+import cambio.simulator.misc.TimeUtil;
+import cambio.simulator.parsing.JsonTypeName;
+import desmoj.core.simulator.TimeInstant;
+
+/**
+ * AN implementation based on Kubernetes
+ * <a href="https://github.com/kubernetes/kubernetes/blob/8caeec429ee1d2a9df7b7a41b21c626346b456fb/docs/design/horizontal-pod-autoscaler.md#autoscaling-algorithm">Horizontal Pod Autoscaler</a>.
+ *
+ * <p>
+ * By default, scale-up can only happen if there was no rescaling within the last 3 minutes. Scale-down will wait for 5
+ * minutes from the last rescaling. Moreover, any scaling will only be made if: avg(CurrentPodsConsumption) / Target
+ * drops below 0.9 or increases above 1.1 (10% tolerance)
+ *
+ * <p>
+ * TODO Maybe also include via adapter, upscaling/downscaling behavior not 100% as in Kubernetes, e.g. see
+ *      <a href="https://github.com/kubernetes/kubernetes/blob/master/pkg/apis/autoscaling/types.go#L113">HorizontalPodAutoscalerBehavior Implementation</a>
+ *      In particular, Kubernetes mentions different holdTimes for up- and downscaling, as well as a 30s evaluation
+ *      frequency (MiSim probably evaluates every time unit. Thus, reacts faster.)
+ */
+@JsonTypeName("hpa")
+public class HorizontalPodAutoscalingPolicy implements IAutoscalingPolicy {
+    private transient MultiDataPointReporter reporter = null;
+    private double targetUtilization = 0.8;
+    private int minInstances = 1;
+    private int maxInstances = Integer.MAX_VALUE;
+
+    /**
+     * Minimum time an instance has to run before it can be shutdown by down-scaling.
+     */
+    private double holdTime = 120;
+    private transient TimeInstant lastScaleUp = new TimeInstant(0);
+
+    @Override
+    public void apply(Microservice owner) {
+        if (reporter == null) {
+            reporter = new MultiDataPointReporter(String.format("AS[%s]_", owner.getPlainName()), owner.getModel());
+        }
+
+        TimeInstant presentTime = owner.presentTime();
+        int currentInstanceCount = owner.getInstancesCount();
+        double avg2Target = owner.getAverageRelativeUtilization() / targetUtilization;
+        // Tolerance area
+
+        int newInstanceCount = (int) Math.ceil(avg2Target * currentInstanceCount);
+
+        newInstanceCount = Math.min(newInstanceCount, maxInstances);
+        newInstanceCount = Math.max(minInstances, newInstanceCount);
+
+        if (currentInstanceCount < minInstances) { //starts minimum instances
+            owner.setInstancesCount(minInstances);
+            reporter.addDatapoint("Decision", presentTime, "Spawn");
+            reporter.addDatapoint("InstanceChange", presentTime, minInstances - currentInstanceCount);
+        } else if (currentInstanceCount > maxInstances) {
+            owner.setInstancesCount(maxInstances);
+            reporter.addDatapoint("Decision", presentTime, "Despawn");
+            reporter.addDatapoint("InstanceChange", presentTime, maxInstances - currentInstanceCount);
+        } else if (avg2Target > 0.9 && avg2Target < 1.1) {
+            // Tolerance area
+            reporter.addDatapoint("Decision", presentTime, "Hold");
+            reporter.addDatapoint("InstanceChange", presentTime, 0);
+        } else if (avg2Target > 1 && currentInstanceCount < maxInstances) {
+            owner.scaleToInstancesCount(newInstanceCount);
+            lastScaleUp = presentTime;
+            reporter.addDatapoint("Decision", presentTime, "Up");
+            reporter.addDatapoint("InstanceChange", presentTime, newInstanceCount - currentInstanceCount);
+        } else if (avg2Target < 1 && currentInstanceCount > minInstances && TimeUtil.subtract(presentTime,
+                lastScaleUp).getTimeAsDouble() > holdTime) {
+            owner.scaleToInstancesCount(newInstanceCount);
+            lastScaleUp = presentTime;
+            reporter.addDatapoint("Decision", presentTime, "Down");
+            reporter.addDatapoint("InstanceChange", presentTime, newInstanceCount - currentInstanceCount);
+        } else {
+            reporter.addDatapoint("Decision", presentTime, "Hold");
+            reporter.addDatapoint("InstanceChange", presentTime, 0);
+        }
+
+        if (owner.getInstancesCount() != currentInstanceCount) {
+            owner.sendTraceNote(String.format("Changed target instance count to %d", owner.getInstancesCount()));
+        }
+    }
+}

src/main/java/cambio/simulator/entities/patterns/ReactiveAutoscalingPolicy.java

@@ -39,26 +39,27 @@ public void apply(Microservice owner) {
         if (currentInstanceCount < minInstances) { //starts minimum instances
             owner.setInstancesCount(minInstances);
             reporter.addDatapoint("Decision", presentTime, "Spawn");
-            reporter.addDatapoint("InstanceChange", presentTime, minInstances-currentInstanceCount);
+            reporter.addDatapoint("InstanceChange", presentTime, minInstances - currentInstanceCount);
         } else if (currentInstanceCount > maxInstances) {
             owner.setInstancesCount(maxInstances);
             reporter.addDatapoint("Decision", presentTime, "Despawn");
-            reporter.addDatapoint("InstanceChange", presentTime, maxInstances-currentInstanceCount);
+            reporter.addDatapoint("InstanceChange", presentTime, maxInstances - currentInstanceCount);
         } else if (avg >= upperBound && currentInstanceCount < maxInstances) {
             double upScalingFactor = avg / (upperBound - 0.01);
-            int newInstanceCount = Math.min(maxInstances, (int) Math.max(1, Math.ceil(currentInstanceCount * upScalingFactor)));
+            int newInstanceCount = Math.min(maxInstances, (int) Math.max(1,
+                    Math.ceil(currentInstanceCount * upScalingFactor)));
             owner.scaleToInstancesCount(newInstanceCount);
             lastScaleUp = presentTime;
             reporter.addDatapoint("Decision", presentTime, "Up");
             reporter.addDatapoint("InstanceChange", presentTime, newInstanceCount - currentInstanceCount);
-        } else if (avg <= lowerBound
-                && currentInstanceCount > minInstances
-                && TimeUtil.subtract(presentTime, lastScaleUp).getTimeAsDouble() > holdTime) {
+        } else if (avg <= lowerBound && currentInstanceCount > minInstances && TimeUtil.subtract(presentTime,
+                lastScaleUp).getTimeAsDouble() > holdTime) {
             System.out.println(presentTime);
             System.out.println(lastScaleUp);
             System.out.println(holdTime);
             double downScaleFactor = Math.max(0.01, avg) / lowerBound;
-            int newInstanceCount = Math.max(minInstances, (int) Math.max(1, Math.ceil(currentInstanceCount * downScaleFactor)));
+            int newInstanceCount = Math.max(minInstances, (int) Math.max(1,
+                    Math.ceil(currentInstanceCount * downScaleFactor)));
             owner.scaleToInstancesCount(newInstanceCount);
             lastScaleUp = presentTime;
             reporter.addDatapoint("Decision", presentTime, "Down");