Drop summary and timer lines with a count of 0 (#3030)

Co-authored-by: Georg Pirklbauer <[email protected]>

Author: jonatan-ivanov

implementations/micrometer-registry-dynatrace/src/main/java/io/micrometer/dynatrace/v2/DynatraceExporterV2.java

@@ -174,6 +174,10 @@ Stream<String> toTimerLine(Timer meter) {
 
     private Stream<String> toSummaryLine(Meter meter, HistogramSnapshot histogramSnapshot, TimeUnit timeUnit) {
         long count = histogramSnapshot.count();
+        if (count < 1) {
+            logger.debug("Summary with 0 count dropped: %s", meter.getId().getName());
+            return Stream.empty();
+        }
         double total = (timeUnit != null) ? histogramSnapshot.total(timeUnit) : histogramSnapshot.total();
         double max = (timeUnit != null) ? histogramSnapshot.max(timeUnit) : histogramSnapshot.max();
         double min = (count == 1) ? max : minFromHistogramSnapshot(histogramSnapshot, timeUnit);
@@ -218,9 +222,13 @@ Stream<String> toFunctionCounterLine(FunctionCounter meter) {
     }
 
     Stream<String> toFunctionTimerLine(FunctionTimer meter) {
+        long count = (long) meter.count();
+        if (count < 1) {
+            logger.debug("Timer with 0 count dropped: %s", meter.getId().getName());
+            return Stream.empty();
+        }
         double total = meter.totalTime(getBaseTimeUnit());
         double average = meter.mean(getBaseTimeUnit());
-        long count = Double.valueOf(meter.count()).longValue();
 
         return createSummaryLine(meter, average, average, total, count);
     }

implementations/micrometer-registry-dynatrace/src/test/java/io/micrometer/dynatrace/v2/DynatraceExporterV2Test.java

@@ -230,6 +230,22 @@ void toTimerLine() {
         assertThat(lines.get(0)).isEqualTo("my.timer,dt.metrics.source=micrometer gauge,min=0.0,max=60.0,sum=90.0,count=3 " + clock.wallTime());
     }
 
+    @Test
+    void toTimerLine_DropIfCountIsZero() {
+        Timer timer = meterRegistry.timer("my.timer");
+        timer.record(Duration.ofMillis(60));
+        clock.add(config.step());
+
+        List<String> lines = exporter.toTimerLine(timer).collect(Collectors.toList());
+        assertThat(lines).hasSize(1);
+        assertThat(lines.get(0)).isEqualTo("my.timer,dt.metrics.source=micrometer gauge,min=60.0,max=60.0,sum=60.0,count=1 " + clock.wallTime());
+
+        clock.add(config.step());
+        // Before the update to drop zero count lines, this would contain 1 line (with count=0), which is not desired.
+        List<String> zeroCountLines = exporter.toTimerLine(timer).collect(Collectors.toList());
+        assertThat(zeroCountLines).isEmpty();
+    }
+
     @Test
     void toFunctionTimerLineShouldDropNanMean() {
         FunctionTimer functionTimer = new FunctionTimer() {
@@ -329,6 +345,22 @@ void testToDistributionSummaryLine() {
         assertThat(lines.get(0)).isEqualTo("my.summary,dt.metrics.source=micrometer gauge,min=0.0,max=5.4,sum=10.9,count=4 " + clock.wallTime());
     }
 
+    @Test
+    void testToDistributionSummaryLine_DropsLineIfCountIsZero() {
+        DistributionSummary summary = DistributionSummary.builder("my.summary").register(meterRegistry);
+        summary.record(3.1);
+        clock.add(config.step());
+
+        List<String> nonEmptyLines = exporter.toDistributionSummaryLine(summary).collect(Collectors.toList());
+        assertThat(nonEmptyLines).hasSize(1);
+        assertThat(nonEmptyLines.get(0)).isEqualTo("my.summary,dt.metrics.source=micrometer gauge,min=3.1,max=3.1,sum=3.1,count=1 " + clock.wallTime());
+
+        clock.add(config.step());
+        // Before the update to drop zero count lines, this would contain 1 line (with count=0), which is not desired.
+        List<String> zeroCountLines = exporter.toDistributionSummaryLine(summary).collect(Collectors.toList());
+        assertThat(zeroCountLines).isEmpty();
+    }
+
     @Test
     void toMeterLine() {
         Measurement m1 = new Measurement(() -> 23d, Statistic.VALUE);