add monotonic_count support

src/main/java/org/datadog/jmxfetch/App.java

@@ -511,6 +511,7 @@ private void fixBrokenInstances(Reporter reporter) {
         for (Instance instance : brokenInstanceMap.values()) {
             // Clearing rates aggregator so we won't compute wrong rates if we can reconnect
             reporter.clearRatesAggregator(instance.getName());
+            reporter.clearCountersAggregator(instance.getName());
 
             LOGGER.warn(
                     "Instance "

src/main/java/org/datadog/jmxfetch/reporter/Reporter.java

@@ -19,6 +19,8 @@ public abstract class Reporter {
     private HashMap<String, Integer> serviceCheckCount;
     private HashMap<String, HashMap<String, HashMap<String, Object>>> ratesAggregator =
             new HashMap<String, HashMap<String, HashMap<String, Object>>>();
+    private HashMap<String, HashMap<String, Long>> countersAggregator =
+            new HashMap<String, HashMap<String, Long>>();
 
     /** Reporter constructor. */
     public Reporter() {
@@ -38,18 +40,31 @@ public void clearRatesAggregator(String instanceName) {
         ratesAggregator.put(instanceName, new HashMap<String, HashMap<String, Object>>());
     }
 
+    /** Clears the counter aggregator for the provided instance name.  */
+    public void clearCountersAggregator(String instanceName) {
+        countersAggregator.put(instanceName, new HashMap<String, Long>());
+    }
+
     /** Submits the metrics in the implementing reporter. */
     public void sendMetrics(
             LinkedList<HashMap<String, Object>> metrics,
             String instanceName,
             boolean canonicalRate) {
         HashMap<String, HashMap<String, Object>> instanceRatesAggregator;
+        HashMap<String, Long> instanceCountersAggregator;
+
         if (ratesAggregator.containsKey(instanceName)) {
             instanceRatesAggregator = ratesAggregator.get(instanceName);
         } else {
             instanceRatesAggregator = new HashMap<String, HashMap<String, Object>>();
         }
 
+        if (countersAggregator.containsKey(instanceName)) {
+            instanceCountersAggregator = countersAggregator.get(instanceName);
+        } else {
+            instanceCountersAggregator = new HashMap<String, Long>();
+        }
+
         int loopCounter = App.getLoopCounter();
 
         String sendingMessage =
@@ -85,6 +100,28 @@ public void sendMetrics(
             // rates
             if ("gauge".equals(metricType) || "histogram".equals(metricType)) {
                 sendMetricPoint(metricType, metricName, currentValue, tags);
+            } else if ("monotonic_count".equals(metricType)) {
+                String key = generateId(metric);
+                if (!instanceCountersAggregator.containsKey(key)) {
+                    instanceCountersAggregator.put(key,  currentValue.longValue());
+                    continue;
+                }
+
+                long oldValue = instanceCountersAggregator.get(key);
+                long delta = currentValue.longValue() - oldValue;
+
+                if (Double.isNaN(delta) || Double.isInfinite(delta)) {
+                    continue;
+                }
+
+                instanceCountersAggregator.put(key, currentValue.longValue());
+
+                if (delta < 0) {
+                    LOGGER.info("Counter " + metricName + " has been reset - not submitting.");
+                    continue;
+                }
+                sendMetricPoint(metricType, metricName, delta, tags);
+
             } else { // The metric should be 'counter'
                 String key = generateId(metric);
                 if (!instanceRatesAggregator.containsKey(key)) {
@@ -118,6 +155,7 @@ public void sendMetrics(
         }
 
         ratesAggregator.put(instanceName, instanceRatesAggregator);
+        countersAggregator.put(instanceName, instanceCountersAggregator);
     }
 
     /** Submits service check. */

src/main/java/org/datadog/jmxfetch/reporter/StatsdReporter.java

@@ -35,7 +35,9 @@ protected void sendMetricPoint(
             this.statsDClient.stop();
             init();
         }
-        if (metricType.equals("histogram")) {
+        if (metricType.equals("monotonic_count")) {
+            statsDClient.count(metricName, (long) value, tags);
+        } else if (metricType.equals("histogram")) {
             statsDClient.histogram(metricName, value, tags);
         } else {
             statsDClient.gauge(metricName, value, tags);

src/test/java/org/datadog/jmxfetch/TestApp.java

@@ -7,6 +7,7 @@
 import java.io.File;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.LinkedList;
 import java.util.List;
@@ -716,7 +717,41 @@ public void testAppCanonicalRate() throws Exception {
         assertCoverage();
     }
 
-    /** Test JMX Service Discovery. */
+    /**
+     * Test counts.
+     */
+    @Test
+    public void testAppCount() throws Exception {
+        // We expose a few metrics through JMX
+        SimpleTestJavaApp testApp = new SimpleTestJavaApp();
+        registerMBean( testApp, "org.datadog.jmxfetch.test:type=SimpleTestJavaApp");
+
+        initApplication("jmx_count.yaml");
+
+        // First collection should not contain our count
+        run();
+        metrics = getMetrics();
+        assertEquals(13, metrics.size());
+
+        // Since our count is still equal to 0, we should report a delta equal to 0
+        run();
+        metrics = getMetrics();
+        assertEquals(14, metrics.size());
+        assertMetric("test.counter", 0, Collections.<String>emptyList(), 3);
+
+        // For the 3rd collection we increment the count to 5 so we should get a +5 delta
+        testApp.incrementCounter(5);
+        run();
+        metrics = getMetrics();
+        assertEquals(14, metrics.size());
+        assertMetric("test.counter", 5, Collections.<String>emptyList(), 3);
+
+        assertCoverage();
+    }
+
+    /** 
+     * Test JMX Service Discovery.
+     * */
     @Test
     public void testServiceDiscovery() throws Exception {
         // We expose a few metrics through JMX

src/test/resources/jmx_count.yaml

@@ -0,0 +1,13 @@
+init_config:
+
+instances:
+    -   process_name_regex: .*surefire.*
+        refresh_beans: 4
+        name: jmx_test_instance
+        conf:
+            - include:
+               domain: org.datadog.jmxfetch.test
+               attribute:
+                    ShouldBeCounter:
+                        metric_type: monotonic_count
+                        alias: test.counter