For long task timers fixes the percentiles above interpolatable line

without this change for the provided test one of the histogram buckets gets removed and an ArrayIndexOutOfBoundsException is thrown
with this change the exception is not thrown anymore

fixes gh-3877

Author: marcingrzejszczak

Diff for: micrometer-core/src/main/java/io/micrometer/core/instrument/internal/DefaultLongTaskTimer.java

@@ -141,7 +141,7 @@ public HistogramSnapshot takeSnapshot() {
         CountAtBucket[] countAtBucketsArr = new CountAtBucket[0];
 
         List<Double> percentilesAboveInterpolatableLine = percentilesRequested.stream()
-            .filter(p -> p * (activeTasks.size() + 1) > activeTasks.size())
+            .filter(p -> p * (activeTasks.size() + 1) >= activeTasks.size())
             .collect(Collectors.toList());
 
         percentilesRequested.removeAll(percentilesAboveInterpolatableLine);

Diff for: micrometer-test/src/main/java/io/micrometer/core/tck/DefaultLongTaskTimerTest.java

@@ -24,19 +24,35 @@
 import io.micrometer.core.instrument.internal.DefaultLongTaskTimer;
 import io.micrometer.core.instrument.simple.SimpleConfig;
 import io.micrometer.core.instrument.simple.SimpleMeterRegistry;
-import org.junit.jupiter.api.DisplayName;
-import org.junit.jupiter.api.Test;
+
+import java.io.ByteArrayOutputStream;
+
+import java.io.PrintStream;
+
+import org.junit.jupiter.api.*;
 
 import java.time.Duration;
 import java.util.Arrays;
 import java.util.List;
 import java.util.concurrent.TimeUnit;
 
 import static io.micrometer.core.instrument.MockClock.clock;
-import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.*;
 
 public class DefaultLongTaskTimerTest {
 
+    final ByteArrayOutputStream myErr = new ByteArrayOutputStream();
+
+    @BeforeEach
+    void setup() {
+        System.setErr(new PrintStream(myErr));
+    }
+
+    @AfterAll
+    static void cleanup() {
+        System.setErr(System.err);
+    }
+
     @Test
     @DisplayName("supports sending histograms of active task duration")
     void histogram() {
@@ -97,4 +113,29 @@ protected LongTaskTimer newLongTaskTimer(Meter.Id id,
         }
     }
 
+    @Test
+    void histogramToStringNotThrowingException() throws InterruptedException {
+        SimpleMeterRegistry simpleMeterRegistry = new SimpleMeterRegistry();
+
+        LongTaskTimer timer = LongTaskTimer.builder("jobrunr.jobs")
+            .publishPercentiles(0.25, 0.5, 0.75, 0.8, 0.9, 0.95)
+            .publishPercentileHistogram()
+            .register(simpleMeterRegistry);
+        LongTaskTimer.Sample start = timer.start();
+        Thread.sleep(10);
+
+        assertThatNoException().isThrownBy(() -> {
+            simpleMeterRegistry.getMetersAsString();
+            String standardOutput = myErr.toString();
+            assertThat(standardOutput).doesNotContain("ArrayIndexOutOfBoundsException");
+        });
+
+        assertThatNoException().isThrownBy(() -> {
+            start.stop();
+            simpleMeterRegistry.getMetersAsString();
+            String standardOutput = myErr.toString();
+            assertThat(standardOutput).doesNotContain("ArrayIndexOutOfBoundsException");
+        });
+    }
+
 }