[PREVIEW] MODCLUSTER-449 Implement ramp-up when starting new nodes

container/tomcat/src/main/java/org/jboss/modcluster/container/tomcat/ModClusterListener.java

@@ -73,6 +73,7 @@ public class ModClusterListener extends ModClusterConfig implements TomcatConnec
     private float decayFactor = DynamicLoadBalanceFactorProvider.DEFAULT_DECAY_FACTOR;
     private int history = DynamicLoadBalanceFactorProvider.DEFAULT_HISTORY;
     private double capacity = LoadMetric.DEFAULT_CAPACITY;
+    private boolean rampUp = false;
 
     public ModClusterListener() {
         ModClusterService service = new ModClusterService(this, this);
@@ -102,7 +103,7 @@ public LoadMetric run() {
 
         metric.setCapacity(this.capacity);
 
-        DynamicLoadBalanceFactorProvider provider = new DynamicLoadBalanceFactorProvider(Collections.singleton(metric));
+        DynamicLoadBalanceFactorProvider provider = new DynamicLoadBalanceFactorProvider(Collections.singleton(metric), rampUp);
 
         provider.setDecayFactor(this.decayFactor);
         provider.setHistory(this.history);
@@ -254,6 +255,14 @@ public void setLoadMetricCapacity(String capacity) {
         this.capacity = Double.parseDouble(capacity);
     }
 
+    public boolean isRampUp() {
+        return rampUp;
+    }
+
+    public void setRampUp(boolean rampUp) {
+        this.rampUp = rampUp;
+    }
+
     // ---------------------------------------- ModClusterServiceMBean ----------------------------------------
 
     @Override

core/src/main/java/org/jboss/modcluster/load/impl/DynamicLoadBalanceFactorProvider.java

@@ -51,8 +51,19 @@ public class DynamicLoadBalanceFactorProvider implements LoadBalanceFactorProvid
     private volatile int history = DEFAULT_HISTORY;
 
     public DynamicLoadBalanceFactorProvider(Set<LoadMetric> metrics) {
+        this(metrics, false);
+    }
+
+    public DynamicLoadBalanceFactorProvider(Set<LoadMetric> metrics, boolean rampUp) {
         for (LoadMetric metric : metrics) {
-            this.loadHistory.put(metric, new ArrayList<Double>(this.history + 1));
+            ArrayList<Double> history = new ArrayList<>(this.history + 1);
+            if (rampUp) {
+                // If ramping up is enabled pre-populate the list with *full* load
+                for (int i = 0; i < this.history; i++) {
+                    history.add(0d);
+                }
+            }
+            this.loadHistory.put(metric, history);
         }
     }
 

core/src/test/java/org/jboss/modcluster/load/impl/DynamicLoadBalanceFactorProviderTest.java

@@ -75,4 +75,27 @@ public void getLoadBalanceFactorWithFloatDecayFactor() throws Exception {
         assertEquals(64, provider.getLoadBalanceFactor(engine)); // 100-(0.3*100/1.5+0.4*100)/(100/1.5+100)*100 = 64
         assertEquals(57, provider.getLoadBalanceFactor(engine)); // 100-(0.3*100/(1.5^2)+0.4*100/1.5+0.5*100)/(100/(1.5^2)+100/1.5+100)*100 = 57.3684
     }
+
+    @Test
+    public void getLoadBalanceFactorRampUpTime() throws Exception {
+        Engine engine = mock(Engine.class);
+
+        Set<LoadMetric> metrics = new HashSet<>();
+        LoadMetric metric = mock(LoadMetric.class);
+        when(metric.getWeight()).thenReturn(LoadMetric.DEFAULT_WEIGHT);
+        when(metric.getCapacity()).thenReturn(LoadMetric.DEFAULT_CAPACITY);
+        when(metric.getLoad(engine)).thenReturn(1d);
+        metrics.add(metric);
+
+        DynamicLoadBalanceFactorProvider provider = new DynamicLoadBalanceFactorProvider(metrics, true);
+        provider.setHistory(3);
+        provider.setDecayFactor(1f);
+
+        assertEquals(75, provider.getLoadBalanceFactor(engine));
+        assertEquals(50, provider.getLoadBalanceFactor(engine));
+        assertEquals(25, provider.getLoadBalanceFactor(engine));
+        assertEquals(1, provider.getLoadBalanceFactor(engine));
+        assertEquals(1, provider.getLoadBalanceFactor(engine));
+    }
+
 }