Fix InternalAutoDateHistogram reproducible failure

server/src/main/java/org/elasticsearch/search/aggregations/bucket/histogram/AutoDateHistogramAggregationBuilder.java

@@ -156,7 +156,7 @@ public int getNumBuckets() {
         return new AutoDateHistogramAggregatorFactory(name, config, numBuckets, roundings, context, parent, subFactoriesBuilder, metaData);
     }
 
-    private static Rounding createRounding(DateTimeUnit interval, DateTimeZone timeZone) {
+    static Rounding createRounding(DateTimeUnit interval, DateTimeZone timeZone) {
         Rounding.Builder tzRoundingBuilder = Rounding.builder(interval);
         if (timeZone != null) {
             tzRoundingBuilder.timeZone(timeZone);

server/src/main/java/org/elasticsearch/search/aggregations/bucket/histogram/InternalAutoDateHistogram.java

@@ -418,7 +418,7 @@ private BucketReduceResult addEmptyBuckets(BucketReduceResult currentResult, Red
             return currentResult;
         }
         int roundingIdx = getAppropriateRounding(list.get(0).key, list.get(list.size() - 1).key, currentResult.roundingIdx,
-                bucketInfo.roundingInfos);
+                bucketInfo.roundingInfos, targetBuckets);
         RoundingInfo roundingInfo = bucketInfo.roundingInfos[roundingIdx];
         Rounding rounding = roundingInfo.rounding;
         // merge buckets using the new rounding
@@ -447,8 +447,8 @@ private BucketReduceResult addEmptyBuckets(BucketReduceResult currentResult, Red
         return new BucketReduceResult(list, roundingInfo, roundingIdx);
     }
 
-    private int getAppropriateRounding(long minKey, long maxKey, int roundingIdx,
-                                              RoundingInfo[] roundings) {
+    static int getAppropriateRounding(long minKey, long maxKey, int roundingIdx,
+                                              RoundingInfo[] roundings, int targetBuckets) {
         if (roundingIdx == roundings.length - 1) {
             return roundingIdx;
         }
@@ -480,7 +480,7 @@ private int getAppropriateRounding(long minKey, long maxKey, int roundingIdx,
                 currentKey = currentRounding.nextRoundingValue(currentKey);
             }
             currentRoundingIdx++;
-        } while (requiredBuckets > (targetBuckets * roundings[roundingIdx].getMaximumInnerInterval())
+            } while (requiredBuckets > (targetBuckets * roundings[currentRoundingIdx-1].getMaximumInnerInterval())
                 && currentRoundingIdx < roundings.length);
         // The loop will increase past the correct rounding index here so we
         // need to subtract one to get the rounding index we need

server/src/test/java/org/elasticsearch/search/aggregations/bucket/histogram/InternalAutoDateHistogramTests.java

@@ -20,6 +20,7 @@
 package org.elasticsearch.search.aggregations.bucket.histogram;
 
 import org.elasticsearch.common.io.stream.Writeable;
+import org.elasticsearch.common.rounding.DateTimeUnit;
 import org.elasticsearch.search.DocValueFormat;
 import org.elasticsearch.search.aggregations.InternalAggregations;
 import org.elasticsearch.search.aggregations.ParsedMultiBucketAggregation;
@@ -28,7 +29,11 @@
 import org.elasticsearch.search.aggregations.pipeline.PipelineAggregator;
 import org.elasticsearch.test.InternalMultiBucketAggregationTestCase;
 import org.joda.time.DateTime;
+import org.joda.time.DateTimeZone;
 
+import java.time.Instant;
+import java.time.OffsetDateTime;
+import java.time.ZoneOffset;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashMap;
@@ -39,6 +44,8 @@
 import static org.elasticsearch.common.unit.TimeValue.timeValueHours;
 import static org.elasticsearch.common.unit.TimeValue.timeValueMinutes;
 import static org.elasticsearch.common.unit.TimeValue.timeValueSeconds;
+import static org.elasticsearch.search.aggregations.bucket.histogram.AutoDateHistogramAggregationBuilder.createRounding;
+import static org.hamcrest.Matchers.equalTo;
 
 public class InternalAutoDateHistogramTests extends InternalMultiBucketAggregationTestCase<InternalAutoDateHistogram> {
 
@@ -61,6 +68,7 @@ protected InternalAutoDateHistogram createTestInstance(String name,
         int nbBuckets = randomNumberOfBuckets();
         int targetBuckets = randomIntBetween(1, nbBuckets * 2 + 1);
         List<InternalAutoDateHistogram.Bucket> buckets = new ArrayList<>(nbBuckets);
+
         long startingDate = System.currentTimeMillis();
 
         long interval = randomIntBetween(1, 3);
@@ -77,18 +85,38 @@ protected InternalAutoDateHistogram createTestInstance(String name,
         return new InternalAutoDateHistogram(name, buckets, targetBuckets, bucketInfo, format, pipelineAggregators, metaData);
     }
 
+    /*
+    This test was added to reproduce a bug where getAppropriateRounding was only ever using the first innerIntervals
+    passed in, instead of using the interval associated with the loop.
+     */
+    public void testGetAppropriateRoundingUsesCorrectIntervals() {
+        RoundingInfo[] roundings = new RoundingInfo[6];
+        DateTimeZone timeZone = DateTimeZone.UTC;
+        // Since we pass 0 as the starting index to getAppropriateRounding, we'll also use
+        // an innerInterval that is quite large, such that targetBuckets * roundings[i].getMaximumInnerInterval()
+        // will be larger than the estimate.
+        roundings[0] = new RoundingInfo(createRounding(DateTimeUnit.SECOND_OF_MINUTE, timeZone),
+            1000L, 1000);
+        roundings[1] = new RoundingInfo(createRounding(DateTimeUnit.MINUTES_OF_HOUR, timeZone),
+            60 * 1000L, 1, 5, 10, 30);
+        roundings[2] = new RoundingInfo(createRounding(DateTimeUnit.HOUR_OF_DAY, timeZone),
+            60 * 60 * 1000L, 1, 3, 12);
+
+        OffsetDateTime timestamp = Instant.parse("2018-01-01T00:00:01.000Z").atOffset(ZoneOffset.UTC);
+        // We want to pass a roundingIdx of zero, because in order to reproduce this bug, we need the function
+        // to increment the rounding (because the bug was that the function would not use the innerIntervals
+        // from the new rounding.
+        int result = InternalAutoDateHistogram.getAppropriateRounding(timestamp.toEpochSecond()*1000,
+            timestamp.plusDays(1).toEpochSecond()*1000, 0, roundings, 25);
+        assertThat(result, equalTo(2));
+    }
+
     @Override
     protected void assertReduced(InternalAutoDateHistogram reduced, List<InternalAutoDateHistogram> inputs) {
-        int roundingIdx = 0;
-        for (InternalAutoDateHistogram histogram : inputs) {
-            if (histogram.getBucketInfo().roundingIdx > roundingIdx) {
-                roundingIdx = histogram.getBucketInfo().roundingIdx;
-            }
-        }
-        RoundingInfo roundingInfo = roundingInfos[roundingIdx];
 
         long lowest = Long.MAX_VALUE;
         long highest = 0;
+
         for (InternalAutoDateHistogram histogram : inputs) {
             for (Histogram.Bucket bucket : histogram.getBuckets()) {
                 long bucketKey = ((DateTime) bucket.getKey()).getMillis();
@@ -100,35 +128,72 @@ protected void assertReduced(InternalAutoDateHistogram reduced, List<InternalAut
                 }
             }
         }
+
+        int roundingIndex = reduced.getBucketInfo().roundingIdx;
+        RoundingInfo roundingInfo = roundingInfos[roundingIndex];
+
         long normalizedDuration = (highest - lowest) / roundingInfo.getRoughEstimateDurationMillis();
-        long innerIntervalToUse = 0;
-        for (int interval : roundingInfo.innerIntervals) {
-            if (normalizedDuration / interval < maxNumberOfBuckets()) {
-                innerIntervalToUse = interval;
+        long innerIntervalToUse = roundingInfo.innerIntervals[0];
+        int innerIntervalIndex = 0;
+
+        // First, try to calculate the correct innerInterval using the normalizedDuration.
+        // This handles cases where highest and lowest are further apart than the interval being used.
+        if (normalizedDuration != 0) {
+            for (int j = roundingInfo.innerIntervals.length-1; j >= 0; j--) {
+                int interval = roundingInfo.innerIntervals[j];
+                if (normalizedDuration / interval < reduced.getBuckets().size()) {
+                    innerIntervalToUse = interval;
+                    innerIntervalIndex = j;
+                }
+            }
+        }
+
+        long intervalInMillis = innerIntervalToUse * roundingInfo.getRoughEstimateDurationMillis();
+        int bucketCount = getBucketCount(lowest, highest, roundingInfo, intervalInMillis);
+
+        //Next, if our bucketCount is still above what we need, we'll go back and determine the interval
+        // based on a size calculation.
+        if (bucketCount > reduced.getBuckets().size()) {
+            for (int i = innerIntervalIndex; i < roundingInfo.innerIntervals.length; i++) {
+                long newIntervalMillis = roundingInfo.innerIntervals[i] * roundingInfo.getRoughEstimateDurationMillis();
+                if (getBucketCount(lowest, highest, roundingInfo, newIntervalMillis) <= reduced.getBuckets().size()) {
+                    innerIntervalToUse = roundingInfo.innerIntervals[i];
+                    intervalInMillis = innerIntervalToUse * roundingInfo.getRoughEstimateDurationMillis();
+                }
             }
         }
+
         Map<Long, Long> expectedCounts = new TreeMap<>();
-        long intervalInMillis = innerIntervalToUse*roundingInfo.getRoughEstimateDurationMillis();
         for (long keyForBucket = roundingInfo.rounding.round(lowest);
-             keyForBucket <= highest;
+             keyForBucket <= roundingInfo.rounding.round(highest);
              keyForBucket = keyForBucket + intervalInMillis) {
             expectedCounts.put(keyForBucket, 0L);
 
+            // Iterate through the input buckets, and for each bucket, determine if it's inside
+            // the range of the bucket in the outer loop. if it is, add the doc count to the total
+            // for that bucket.
+
             for (InternalAutoDateHistogram histogram : inputs) {
                 for (Histogram.Bucket bucket : histogram.getBuckets()) {
-                    long bucketKey = ((DateTime) bucket.getKey()).getMillis();
-                    long roundedBucketKey = roundingInfo.rounding.round(bucketKey);
+                    long roundedBucketKey = roundingInfo.rounding.round(((DateTime) bucket.getKey()).getMillis());
+                    long docCount = bucket.getDocCount();
                     if (roundedBucketKey >= keyForBucket
                         && roundedBucketKey < keyForBucket + intervalInMillis) {
-                        long count = bucket.getDocCount();
                         expectedCounts.compute(keyForBucket,
-                            (key, oldValue) -> (oldValue == null ? 0 : oldValue) + count);
+                            (key, oldValue) -> (oldValue == null ? 0 : oldValue) + docCount);
                     }
                 }
             }
         }
 
+        // If there is only a single bucket, and we haven't added it above, add a bucket with no documents.
+        // this step is necessary because of the roundedBucketKey < keyForBucket + intervalInMillis above.
+        if (roundingInfo.rounding.round(lowest) == roundingInfo.rounding.round(highest) && expectedCounts.isEmpty()) {
+            expectedCounts.put(roundingInfo.rounding.round(lowest), 0L);
+        }
 
+
+        // pick out the actual reduced values to the make the assertion more readable
         Map<Long, Long> actualCounts = new TreeMap<>();
         for (Histogram.Bucket bucket : reduced.getBuckets()) {
             actualCounts.compute(((DateTime) bucket.getKey()).getMillis(),
@@ -137,12 +202,16 @@ protected void assertReduced(InternalAutoDateHistogram reduced, List<InternalAut
         assertEquals(expectedCounts, actualCounts);
     }
 
-    @Override
-    @AwaitsFix(bugUrl = "https://github.com/elastic/elasticsearch/issues/32215")
-    public void testReduceRandom() {
-        super.testReduceRandom();
+    private int getBucketCount(long lowest, long highest, RoundingInfo roundingInfo, long intervalInMillis) {
+        int bucketCount = 0;
+        for (long keyForBucket = roundingInfo.rounding.round(lowest);
+             keyForBucket <= roundingInfo.rounding.round(highest);
+             keyForBucket = keyForBucket + intervalInMillis) {
+            bucketCount++;
+        }
+        return bucketCount;
     }
-    
+
     @Override
     protected Writeable.Reader<InternalAutoDateHistogram> instanceReader() {
         return InternalAutoDateHistogram::new;