1 files changed, 93 insertions, 0 deletions
diff --git a/documentapi/src/main/java/com/yahoo/documentapi/messagebus/protocol/LegacyLoadBalancer.java b/documentapi/src/main/java/com/yahoo/documentapi/messagebus/protocol/LegacyLoadBalancer.java
new file mode 100644
index 00000000000..54e18302ef6
--- /dev/null
+++ b/documentapi/src/main/java/com/yahoo/documentapi/messagebus/protocol/LegacyLoadBalancer.java
@@ -0,0 +1,93 @@
+// Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.documentapi.messagebus.protocol;
+
+import com.yahoo.jrt.slobrok.api.Mirror;
+
+import java.util.List;
+
+/**
+ * Load balances over a set of nodes based on statistics gathered from those nodes.
+ *
+ * @author thomasg
+ */
+class LegacyLoadBalancer extends LoadBalancer {
+
+    static class LegacyNodeMetrics extends NodeMetrics {
+        double weight = 1.0;
+    }
+
+    private double position = 0.0;
+
+    public LegacyLoadBalancer(String cluster) {
+        super(cluster);
+    }
+
+    /**
+     * The load balancing operation: Returns a node choice from the given choices,
+     * based on previously gathered statistics on the nodes, and a running "position"
+     * which is increased by 1 on each call to this.
+     *
+     * @param choices the node choices, represented as Slobrok entries
+     * @return the chosen node, or null only if the given choices were zero
+     */
+    public Node getRecipient(List<Mirror.Entry> choices) {
+        if (choices.isEmpty()) return null;
+
+        double weightSum = 0.0;
+        Node selectedNode = null;
+        synchronized (this) {
+            for (Mirror.Entry entry : choices) {
+                LegacyNodeMetrics nodeMetrics = (LegacyNodeMetrics)getNodeMetrics(entry);
+
+                weightSum += nodeMetrics.weight;
+
+                if (weightSum > position) {
+                    selectedNode = new Node(entry, nodeMetrics);
+                    break;
+                }
+            }
+            if (selectedNode == null) { // Position>sum of all weights: Wrap around (but keep the remainder for some reason)
+                position -= weightSum;
+                selectedNode = new Node(choices.get(0), getNodeMetrics(choices.get(0)));
+            }
+            position += 1.0;
+            selectedNode.metrics.incSend();
+        }
+        return selectedNode;
+    }
+
+    protected NodeMetrics createNodeMetrics() {
+        return new LegacyNodeMetrics();
+    }
+
+    /** Scale weights such that ratios are preserved */
+    private void increaseWeights() {
+        for (NodeMetrics nodeMetrics : getNodeWeights()) {
+            LegacyNodeMetrics n = (LegacyNodeMetrics) nodeMetrics;
+            if (n == null) continue;
+            double want = n.weight * 1.01010101010101010101;
+            if (want >= 1.0) {
+                n.weight = want;
+            } else {
+                n.weight = 1.0;
+            }
+        }
+    }
+
+    public void received(Node node, boolean busy) {
+        if (busy) {
+            synchronized (this) {
+                LegacyNodeMetrics n = (LegacyNodeMetrics) node.metrics;
+                double wantWeight = n.weight - 0.01;
+                if (wantWeight < 1.0) {
+                    increaseWeights();
+                    n.weight = 1.0;
+                } else {
+                    n.weight = wantWeight;
+                }
+                node.metrics.incBusy();
+            }
+        }
+    }
+
+}