Nodetool command to get dynamic snitch scores (#122)

* snitch scores

* handle when dynamic snitch not used

* formatting

src/java/org/apache/cassandra/tools/NodeProbe.java

@@ -63,6 +63,7 @@
 import org.apache.cassandra.gms.FailureDetectorMBean;
 import org.apache.cassandra.gms.Gossiper;
 import org.apache.cassandra.gms.GossiperMBean;
+import org.apache.cassandra.locator.DynamicEndpointSnitchMBean;
 import org.apache.cassandra.locator.EndpointSnitchInfoMBean;
 import org.apache.cassandra.metrics.CassandraMetricsRegistry;
 import org.apache.cassandra.metrics.ColumnFamilyMetrics.Sampler;
@@ -726,6 +727,18 @@ public void truncate(String keyspaceName, String cfName)
         }
     }
 
+    public DynamicEndpointSnitchMBean getDynamicEndpointSnitchProxy()
+    {
+        try
+        {
+            return JMX.newMBeanProxy(mbeanServerConn, new ObjectName("org.apache.cassandra.db:type=DynamicEndpointSnitch"), DynamicEndpointSnitchMBean.class);
+        }
+        catch (MalformedObjectNameException e)
+        {
+            throw new RuntimeException(e);
+        }
+    }
+
     public EndpointSnitchInfoMBean getEndpointSnitchInfoProxy()
     {
         try

src/java/org/apache/cassandra/tools/NodeTool.java

@@ -153,7 +153,8 @@ public int execute(String... args)
                 GetLoggingLevels.class,
                 FailureDetectorInfo.class,
                 RefreshSizeEstimates.class,
-                ForceTerminateRepairSessions.class
+                ForceTerminateRepairSessions.class,
+                DynamicEndpointSnitchStats.class
         );
 
         Cli.CliBuilder<Consumer<INodeProbeFactory>> builder = Cli.builder("nodetool");

src/java/org/apache/cassandra/tools/nodetool/DynamicEndpointSnitchStats.java

@@ -0,0 +1,64 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.cassandra.tools.nodetool;
+
+import static java.lang.String.format;
+import io.airlift.command.Command;
+
+import java.net.InetAddress;
+import java.util.List;
+import java.util.Map;
+
+import javax.management.InstanceNotFoundException;
+
+import org.apache.cassandra.locator.DynamicEndpointSnitch;
+import org.apache.cassandra.locator.DynamicEndpointSnitchMBean;
+import org.apache.cassandra.tools.NodeProbe;
+import org.apache.cassandra.tools.NodeTool.NodeToolCmd;
+
+@Command(name = "dynamicendpointsnitchstats", description = "Print the dynamic snitch configurations of a cluster and the current scores of all nodes")
+public class DynamicEndpointSnitchStats extends NodeToolCmd
+{
+    @Override
+    public void execute(NodeProbe probe)
+    {
+        try
+        {
+            DynamicEndpointSnitchMBean dynamicSnitchProxy = probe.getDynamicEndpointSnitchProxy();
+            // display snitch configuration
+            System.out.println("Dynamic Endpoint Snitch Configuration:");
+            System.out.println("\tUpdate Interval (ms): " + dynamicSnitchProxy.getUpdateInterval());
+            System.out.println("\tReset Interval (ms): " + dynamicSnitchProxy.getResetInterval());
+            System.out.println("\tBadness Threshold: " + dynamicSnitchProxy.getBadnessThreshold());
+            System.out.println("\tSubsnitch: " + dynamicSnitchProxy.getSubsnitchClassName());
+            System.out.println("\tSeverity: " + dynamicSnitchProxy.getSeverity());
+            // display snitch scores for each node
+            System.out.println("Dynamic Endpoint Snitch Scores:");
+            Map<InetAddress, Double> snitchScores = dynamicSnitchProxy.getScores();
+            for (InetAddress address : snitchScores.keySet())
+            {
+                System.out.println(format("\t%s: %s", address.getCanonicalHostName(), snitchScores.get(address)));
+            }
+        } catch (RuntimeException e) {
+            if ((e.getCause() instanceof InstanceNotFoundException)) {
+                System.out.println("Error getting DynamicEndpointSnitch proxy--Dynamic snitch may not be enabled on this cluster.");
+            }
+        }
+
+    }
+}