Fix LatencyMetrics parsing to take into account that getCount() retur…

…ns different reservoir values for 3.11/4.0 and 4.1/5.0. In latter, the reservoir stores in microseconds while in the first case, they are nanoseconds.

CHANGELOG.md

@@ -14,6 +14,7 @@ Changelog for Management API, new PRs should update the `main / unreleased` sect
 * [FEATURE] [#549](https://github.com/k8ssandra/management-api-for-apache-cassandra/issues/549) Add DSE 6.9.3 to the build matrix
 * [ENHANCEMENT] [#552](https://github.com/k8ssandra/management-api-for-apache-cassandra/issues/552) Improve "liveness" probe implementation
 * [BUGFIX] [#553](https://github.com/k8ssandra/management-api-for-apache-cassandra/issues/553) Fix CassandraTaskExports metric filtering to make it work with 5.0.x Major compactions
+* [BUGFIX] [#560](https://github.com/k8ssandra/management-api-for-apache-cassandra/issues/560) Fix LatencyMetrics bucketing on 4.1 and 5.0 as their reservoir stores the data in microseconds, not nano (unlike 3.11 and 4.0)
 
 ## v0.1.87 (2024-10-02)
 * [FEATURE] [#535](https://github.com/k8ssandra/management-api-for-apache-cassandra/issues/535) Add Cassandra 5.0.0 to the build matrix

management-api-agent-common/src/main/java/io/k8ssandra/metrics/builder/CassandraMetricRegistryListener.java

@@ -31,6 +31,8 @@
 import java.util.function.Supplier;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
+
+import org.apache.cassandra.utils.CassandraVersion;
 import org.apache.cassandra.utils.EstimatedHistogram;
 import org.apache.cassandra.utils.FBUtilities;
 import org.slf4j.LoggerFactory;
@@ -55,6 +57,8 @@ public class CassandraMetricRegistryListener implements MetricRegistryListener {
   private static final String SERVER_VERSION = FBUtilities.getReleaseVersionString();
   private static final int SERVER_PATCH_VERSION;
 
+  private boolean microLatencyBuckets = false;
+
   static {
     Matcher matcher = VERSION_PATTERN.matcher(SERVER_VERSION);
     if (matcher.matches()) {
@@ -83,6 +87,14 @@ public CassandraMetricRegistryListener(
     parser = CassandraMetricNameParser.getDefaultParser(config);
     cache = new ConcurrentHashMap<>();
 
+    CassandraVersion cassandraVersion =
+        new CassandraVersion(FBUtilities.getReleaseVersionString());
+
+    if(cassandraVersion.major > 4 || (cassandraVersion.major == 4 && cassandraVersion.minor > 0)) {
+      // 4.1 and up should use microsecond buckets
+      microLatencyBuckets = true;
+    }
+
     this.familyCache = familyCache;
   }
 
@@ -372,7 +384,7 @@ private void setTimerFiller(
               }
               buckets = (long[]) bucketOffsetField.get(snapshot);
             } catch (NoSuchFieldException | IllegalAccessException e) {
-              logger.debug("Unable to get bucketOffsets", e);
+//              logger.debug("Unable to get bucketOffsets", e);
               buckets = CassandraMetricsTools.DECAYING_BUCKETS;
             }
 
@@ -407,8 +419,9 @@ private void setTimerFiller(
           int outputIndex = 0; // output index
           long cumulativeCount = 0;
           for (int i = 0; i < buckets.length; i++) {
+            int offsetFix = microLatencyBuckets ? 1 : 1000;
             if (outputIndex < LATENCY_OFFSETS.length
-                && buckets[i] > (LATENCY_OFFSETS[outputIndex] * 1000)) {
+                && buckets[i] > (LATENCY_OFFSETS[outputIndex] * offsetFix)) {
               List<String> labelValues = new ArrayList<>(bucket.getLabelValues().size() + 1);
               int j = 0;
               for (; j < bucket.getLabelValues().size(); j++) {

management-api-agent-common/src/main/java/io/k8ssandra/metrics/builder/CassandraMetricsTools.java

@@ -63,7 +63,6 @@ public class CassandraMetricsTools {
   protected static final long[] DECAYING_BUCKETS = new EstimatedHistogram(165).getBucketOffsets();
 
   // Log linear buckets (these must match the collectd entry in types.db)
-  protected static final Pair<Long, String>[] LATENCY_BUCKETS;
   protected static final long[] LATENCY_OFFSETS = {
     35, 60, 103, 179, 310, 535, 924, 1597, 2759, 4768, 8239, 14237, 24601, 42510, 73457, 126934,
     219342, 379022, 654949, 1131752, 1955666, 3379391, 5839588, 10090808, 17436917
@@ -77,16 +76,6 @@ public class CassandraMetricsTools {
     }
   }
 
-  static {
-    LATENCY_BUCKETS = new Pair[LATENCY_OFFSETS.length];
-    for (int i = 0; i < LATENCY_BUCKETS.length; i++) {
-      // Latencies are reported in nanoseconds, so we convert the offsets from micros
-      // to nanos
-      LATENCY_BUCKETS[i] =
-          Pair.create(LATENCY_OFFSETS[i] * 1000, "bucket_" + Long.toString(LATENCY_OFFSETS[i]));
-    }
-  }
-
   private Map<String, CassandraMetricDefinition> metricDefinitions;
 
   public CassandraMetricsTools() {

management-api-agent-common/src/test/java/io/k8ssandra/metrics/builder/MetricsRegistryTest.java

@@ -5,8 +5,9 @@
  */
 package io.k8ssandra.metrics.builder;
 
-import static io.k8ssandra.metrics.builder.CassandraMetricsTools.LATENCY_BUCKETS;
+import static io.k8ssandra.metrics.builder.CassandraMetricsTools.LATENCY_OFFSETS;
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
 
 import com.codahale.metrics.Gauge;
@@ -22,6 +23,7 @@
 import java.util.concurrent.TimeUnit;
 import org.apache.cassandra.metrics.CassandraMetricsRegistry;
 import org.apache.cassandra.metrics.DefaultNameFactory;
+import org.apache.cassandra.metrics.LatencyMetrics;
 import org.junit.Test;
 
 public class MetricsRegistryTest {
@@ -125,7 +127,7 @@ public void timerTest() throws Exception {
 
     List<Collector.MetricFamilySamples> collect = exporter.collect();
 
-    HashMap<String, Double> bucketMap = new HashMap<>(LATENCY_BUCKETS.length + 1);
+    HashMap<String, Double> bucketMap = new HashMap<>(LATENCY_OFFSETS.length + 1);
     Double countValue = -1.0D;
     Double sumValue = -1.0D;
     for (Collector.MetricFamilySamples mfs : collect) {
@@ -140,15 +142,32 @@ public void timerTest() throws Exception {
       }
     }
 
-    assertEquals(LATENCY_BUCKETS.length + 1, bucketMap.keySet().size());
+    assertEquals(LATENCY_OFFSETS.length + 1, bucketMap.keySet().size());
     assertEquals(countValue, bucketMap.get("+Inf"));
     assertTrue(countValue > 0);
     assertTrue(sumValue > 0);
 
     registry.remove(createMetricName("test_timer"));
   }
 
-  private CassandraMetricsRegistry.MetricName createMetricName(String name) {
+  @Test
+  public void timerBucketTest() throws Exception {
+    CassandraMetricsRegistry registry = CassandraMetricsRegistry.Metrics;
+    Configuration config = new Configuration();
+    CassandraDropwizardExports exporter = new CassandraDropwizardExports(registry, config);
+
+    LatencyMetrics latencyMetrics = new LatencyMetrics("ClientRequest", "TimerTest");
+    latencyMetrics.addNano(TimeUnit.NANOSECONDS.convert(1, TimeUnit.MILLISECONDS));
+    latencyMetrics.addNano(TimeUnit.NANOSECONDS.convert(3, TimeUnit.MILLISECONDS));
+
+    List<Collector.MetricFamilySamples> collect = exporter.collect();
+    assertEquals(4000.0, collect.get(0).samples.get(0).value, 0.01);
+    assertEquals(1.0, collect.get(1).samples.get(7).value, 0.01);
+    assertEquals(2.0, collect.get(1).samples.get(9).value, 0.01);
+    assertEquals(2.0, collect.get(1).samples.get(collect.get(1).samples.size() - 1).value, 0.01);
+  }
+
+    private CassandraMetricsRegistry.MetricName createMetricName(String name) {
     return DefaultNameFactory.createMetricName("test", name, "test");
   }
 }