HWKMETRICS-160 Fix Intermittent test failures in GraphiteITest

When EmbeddedJMXTrans is stopped, it collects and sends metrics one last time after the schedulers have
been shut down. So two data points can have very close timestamps. But Graphite only supports second
resolution. So it is possible that two points with the same timestamp (see #getTimestamp logic) are sent
to the server. Consequently, when building the expected data set, we need to check if one metric has two
points with the same timestamp, and, in this case, keep the older one only.

clients/ptranslator/src/test/java/org/hawkular/metrics/clients/ptrans/fullstack/GraphiteITest.java

@@ -19,13 +19,15 @@
 
 import static java.util.concurrent.TimeUnit.MILLISECONDS;
 import static java.util.concurrent.TimeUnit.SECONDS;
-import static java.util.stream.Collectors.toList;
+import static java.util.stream.Collectors.groupingBy;
 
 import static org.junit.Assert.assertEquals;
 
 import java.util.ArrayList;
 import java.util.Collections;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 import java.util.Properties;
 
 import org.hawkular.metrics.clients.ptrans.ConfigurationKey;
@@ -73,16 +75,28 @@ protected void stopSource() throws Exception {
 
     @Override
     protected List<Point> getExpectedData() {
-        List<QueryResult> results = ListAppenderWriter.results;
-        return results.stream()
-                      .map(this::queryResultToPoint)
-                      .collect(toList());
+        // When EmbeddedJMXTrans is stopped, it collects and sends metrics one last time after the schedulers have
+        // been shut down. So two data points can have very close timestamps. But Graphite only supports second
+        // resolution. So it is possible that two points with the same timestamp (see #getTimestamp logic) are sent
+        // to the server. Consequently, when building the expected data set, we need to check if one metric has two
+        // points with the same timestamp, and, in this case, keep the older one only.
+        List<Point> points = new ArrayList<>();
+        ListAppenderWriter.results.stream().collect(groupingBy(QueryResult::getName)).entrySet().forEach(entry -> {
+            Map<Long, QueryResult> resultByTimestamp = new HashMap<>();
+            entry.getValue().forEach(result -> resultByTimestamp.put(getTimestamp(result), result));
+            resultByTimestamp.values().stream().map(this::queryResultToPoint).forEach(points::add);
+        });
+        return points;
+    }
+
+    private long getTimestamp(QueryResult result) {
+        return MILLISECONDS.convert(result.getEpoch(SECONDS), SECONDS);
     }
 
     private Point queryResultToPoint(QueryResult result) {
         return new Point(
                 result.getName(),
-                MILLISECONDS.convert(result.getEpoch(SECONDS), SECONDS),
+                getTimestamp(result),
                 Double.valueOf(String.valueOf(result.getValue()))
         );
     }