Add default MethodName CollectStatsMetric in service log when MethodName is not provided

Author: yujias0706

src/main/java/com/amazon/opendistro/elasticsearch/performanceanalyzer/collectors/StatsCollector.java

@@ -26,6 +26,7 @@
 import java.io.InputStream;
 import java.text.SimpleDateFormat;
 import java.util.Date;
+import java.util.HashMap;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
@@ -52,6 +53,12 @@ public class StatsCollector extends PerformanceAnalyzerMetricsCollector {
   private Map<String, AtomicInteger> counters = new ConcurrentHashMap<>();
   private Date objectCreationTime = new Date();
 
+  private static final Map<String, String> DEFAULT_STATS_DATA = new HashMap<>();
+
+  static {
+    DEFAULT_STATS_DATA.put("MethodName", "CollectStatsMetric");
+  }
+
   private List<StatExceptionCode> defaultExceptionCodes = new Vector<>();
 
   public static StatsCollector instance() {
@@ -149,7 +156,7 @@ public void collectMetrics(long startTime) {
     }
 
     writeStats(
-        metadata, currentCounters, null, null, objectCreationTime.getTime(), new Date().getTime());
+        metadata, currentCounters, DEFAULT_STATS_DATA, null, objectCreationTime.getTime(), new Date().getTime());
     collectAndWriteRcaStats();
     objectCreationTime = new Date();
   }