[GitHub] [kafka] mjsax commented on a change in pull request #8697: KAFKA-9983: KIP-613, add INFO level e2e latency metrics

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mjsax commented on a change in pull request #8697:
URL: https://github.com/apache/kafka/pull/8697#discussion_r429499547



##########
File path: clients/src/test/java/org/apache/kafka/common/metrics/MetricsTest.java
##########
@@ -492,6 +493,52 @@ public void testPercentiles() {
         assertEquals(75, (Double) p75.metricValue(), 1.0);
     }
 
+    @Test
+    public void testPercentilesWithRandomNumbersAndLinearBucketing() {
+        long seed = new Random().nextLong();
+        int sizeInBytes = 1000 * 1000;   // 1MB
+        long maximumValue = 1000 * 24 * 60 * 60 * 1000L; // if values are ms, max is 1000 days
+
+        try {
+            Random prng = new Random(seed);
+            int numberOfValues = 5000 + prng.nextInt(10_000);  // ranges is [5000, 15000]
+
+            Percentiles percs = new Percentiles(sizeInBytes,
+                                                maximumValue,
+                                                BucketSizing.LINEAR,
+                                                new Percentile(metrics.metricName("test.p90", "grp1"), 90),
+                                                new Percentile(metrics.metricName("test.p99", "grp1"), 99));
+            MetricConfig config = new MetricConfig().eventWindow(50).samples(2);
+            Sensor sensor = metrics.sensor("test", config);
+            sensor.add(percs);
+            Metric p90 = this.metrics.metrics().get(metrics.metricName("test.p90", "grp1"));
+            Metric p99 = this.metrics.metrics().get(metrics.metricName("test.p99", "grp1"));
+
+            final List<Long> values = new ArrayList<>(numberOfValues);
+            // record two windows worth of sequential values
+            for (int i = 0; i < numberOfValues; ++i) {
+                long value = Math.abs(prng.nextLong()) % maximumValue;
+                values.add(value);
+                sensor.record(value);
+            }
+
+            Collections.sort(values);
+
+            int p90Index = (int)Math.ceil(((double)(90 * numberOfValues)) / 100);
+            int p99Index = (int)Math.ceil(((double)(99 * numberOfValues)) / 100);
+
+            double expectedP90 = values.get(p90Index - 1);
+            double expectedP99 = values.get(p99Index - 1);
+
+            assertEquals(expectedP90, (Double) p90.metricValue(), expectedP90 / 10);

Review comment:
       Let's see...
   
   But I am wondering if the condition is right? Should it be:
   ```
   assertTrue("Expected +/- 10% accuracy for exact value of " + expectedP90, expectedP90 * 0.9 <= (Double) p90.metricValue() && (Double) p90.metricValue() <= expectedP90 * 1.1);
   ```




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