From a4544615dfcbd80122e75c1ba6288a4f17bb4389 Mon Sep 17 00:00:00 2001
From: Jonathan Ellis <jbellis@apache.org>
Date: Fri, 11 Jul 2014 23:49:36 -0500
Subject: [PATCH] Fix range merging when DES scores are zero patch by thobbs;
 reviewed by jbellis for CASSANDRA-7535

---
 CHANGES.txt                                                | 1 +
 .../apache/cassandra/locator/DynamicEndpointSnitch.java    | 7 ++++++-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/CHANGES.txt b/CHANGES.txt
index d39cf63a29..e1c89220bf 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -1,4 +1,5 @@
 2.0.10
+ * Fix range merging when DES scores are zero (CASSANDRA-7535)
  * Warn when SSL certificates have expired (CASSANDRA-7528)
  * Workaround JVM NPE on JMX bind failure (CASSANDRA-7254)
  * Fix race in FileCacheService RemovalListener (CASSANDRA-7278)
diff --git a/src/java/org/apache/cassandra/locator/DynamicEndpointSnitch.java b/src/java/org/apache/cassandra/locator/DynamicEndpointSnitch.java
index c76a196da5..32f52eec58 100644
--- a/src/java/org/apache/cassandra/locator/DynamicEndpointSnitch.java
+++ b/src/java/org/apache/cassandra/locator/DynamicEndpointSnitch.java
@@ -45,6 +45,11 @@ public class DynamicEndpointSnitch extends AbstractEndpointSnitch implements ILa
     private int UPDATE_INTERVAL_IN_MS = DatabaseDescriptor.getDynamicUpdateInterval();
     private int RESET_INTERVAL_IN_MS = DatabaseDescriptor.getDynamicResetInterval();
     private double BADNESS_THRESHOLD = DatabaseDescriptor.getDynamicBadnessThreshold();
+
+    // the score for a merged set of endpoints must be this much worse than the score for separate endpoints to
+    // warrant not merging two ranges into a single range
+    private double RANGE_MERGING_PREFERENCE = 1.5;
+
     private String mbeanName;
     private boolean registered = false;
 
@@ -320,7 +325,7 @@ public class DynamicEndpointSnitch extends AbstractEndpointSnitch implements ILa
         if (maxMerged < 0 || maxL1 < 0 || maxL2 < 0)
             return true;
 
-        return maxMerged < maxL1 + maxL2;
+        return maxMerged <= (maxL1 + maxL2) * RANGE_MERGING_PREFERENCE;
     }
 
     // Return the max score for the endpoint in the provided list, or -1.0 if no node have a score.