Moving to metrics and deltas, fixes for Issue #1

src/main/java/org/elasticsearch/plugin/newrelic/agents/HttpAgent.java

@@ -23,6 +23,7 @@
 
 public class HttpAgent extends NodeAgent{
 
+
 
 	@Override
 	public void execute(NodeStats nodeStats) {

src/main/java/org/elasticsearch/plugin/newrelic/agents/NodeAgent.java

@@ -18,13 +18,16 @@
  */
 package org.elasticsearch.plugin.newrelic.agents;
 
+import java.util.HashMap;
+import java.util.Map;
 import java.util.concurrent.atomic.AtomicBoolean;
 
 import org.elasticsearch.action.admin.cluster.node.stats.NodeStats;
 import org.elasticsearch.common.logging.ESLogger;
 import org.elasticsearch.common.logging.ESLoggerFactory;
 import org.elasticsearch.plugin.newrelic.collector.MetricCollector;
 import org.elasticsearch.plugin.newrelic.collector.NewRelicCollector;
+import org.elasticsearch.plugin.newrelic.model.Metric;
 
 public abstract class NodeAgent {
 
@@ -34,6 +37,8 @@ public abstract class NodeAgent {
 
 	protected AtomicBoolean enabled = new AtomicBoolean(true);
 
+	protected Map<String, Metric> metrics = new HashMap<String, Metric>();
+
 	public void setCollector(MetricCollector collector) {
 		this.collector = collector;
 	}

src/main/java/org/elasticsearch/plugin/newrelic/model/Metric.java

@@ -0,0 +1,104 @@
+/*
+ * Licensed to ElasticSearch under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. ElasticSearch 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.elasticsearch.plugin.newrelic.model;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
+
+/**
+ * Not complete thread safe, but should suffice for the needs of the plugin.
+ * 
+ */
+public class Metric {
+
+	private Double current;
+	private Double last;
+	private final boolean delta;
+	private Double min;
+	private Double max;
+	private Lock lock = new ReentrantLock();
+
+	public Metric(){
+		this(0.0);
+	}
+
+	public Metric (Double current){
+		this(current,false);
+	}
+
+	public Metric(Double current, boolean delta) {
+		this.current = current;
+		this.delta = delta;
+		this.min = current;
+		this.max = current;
+	}
+
+	public void refresh(Double value){
+		try {
+			lock.lock();
+			last = current;
+			current = value;
+			if(value < min)
+				min = value;
+			if(value > max)
+				max = value;
+		} catch (Exception e) {
+			// TODO: handle exception
+		}finally {
+			lock.unlock();
+		}
+	}
+
+	public Double getValue(){
+		Double value = null;
+		try {
+			lock.lock();
+			if(delta){
+				value = (last == null) ? null : current-last;
+			}else{
+				value = current;
+			}
+		} catch (Exception e) {
+			// TODO: handle exception
+		} finally {
+			lock.unlock();
+		}
+		return value;
+	}
+
+	public Map<String, Object> getValues(){
+		Map<String,Object> values = new HashMap<String, Object>();
+		try {
+			lock.lock();
+			values.put("current",current);
+			values.put("last", last);
+			values.put("min", min);
+			values.put("max", max);
+			values.put("delta", delta);
+		} catch (Exception e) {
+			// TODO: handle exception
+		}finally{
+			lock.unlock();
+		}
+		return values;
+	}
+
+}

src/test/java/org/elasticsearch/plugin/newrelic/MetricTest.java

@@ -0,0 +1,55 @@
+/*
+ * Licensed to ElasticSearch under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. ElasticSearch 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.elasticsearch.plugin.newrelic;
+
+import junit.framework.Assert;
+
+import org.elasticsearch.plugin.newrelic.model.Metric;
+import org.junit.Test;
+
+public class MetricTest {
+
+	@Test
+	public void simpleMetric(){
+		Metric m = new Metric();
+		m.refresh(1.0);
+		Assert.assertEquals(1.0, m.getValue());
+		m.refresh(2.0);
+		Assert.assertEquals(2.0, m.getValue());
+	}
+
+	@Test
+	public void deltaMetric(){
+		Metric m = new Metric(1.0,true);
+		Assert.assertEquals(null, m.getValue());
+		m.refresh(3.0);
+		Assert.assertEquals(2.0, m.getValue());
+	}
+
+	@Test
+	public void deltaMetricValues(){
+		Metric m = new Metric(1.0,true);
+		Assert.assertEquals(null, m.getValue());
+		m.refresh(3.0);
+		Assert.assertEquals(2.0, m.getValue());
+
+		Assert.assertEquals(1.0, m.getValues().get("min"));
+		Assert.assertEquals(3.0, m.getValues().get("max"));
+	}
+}