Aggregations: Fix infinite loop in the histogram reduce logic.

The histogram reduce method can run into an infinite loop if the
Rounding.nextRoundingValue value is buggy, which happened to be the case for
DayTimeZoneRoundingFloor.

DayTimeZoneRoundingFloor is fixed, and the histogram reduce method has been
changed to fail instead of running into an infinite loop in case of a buffy
nextRoundingValue impl.

Close elastic#6965

src/main/java/org/elasticsearch/common/rounding/TimeZoneRounding.java

@@ -162,7 +162,7 @@ public long valueForKey(long time) {
 
         @Override
         public long nextRoundingValue(long value) {
-            return unit.field().roundCeiling(value + 1);
+            return unit.field().getDurationField().add(value, 1);
         }
 
         @Override
@@ -210,7 +210,7 @@ public long valueForKey(long key) {
 
         @Override
         public long nextRoundingValue(long value) {
-            return unit.field().roundCeiling(value + 1);
+            return unit.field().getDurationField().add(value, 1);
         }
 
         @Override
@@ -262,7 +262,7 @@ public long valueForKey(long time) {
 
         @Override
         public long nextRoundingValue(long value) {
-            return unit.field().getDurationField().getUnitMillis() + value;
+            return unit.field().getDurationField().add(value, 1);
         }
 
         @Override

src/main/java/org/elasticsearch/search/aggregations/bucket/histogram/InternalHistogram.java

@@ -320,10 +320,11 @@ public InternalAggregation reduce(ReduceContext reduceContext) {
                 B nextBucket = list.get(iter.nextIndex());
                 if (lastBucket != null) {
                     long key = emptyBucketInfo.rounding.nextRoundingValue(lastBucket.key);
-                    while (key != nextBucket.key) {
+                    while (key < nextBucket.key) {
                         iter.add(createBucket(key, 0, emptyBucketInfo.subAggregations, formatter));
                         key = emptyBucketInfo.rounding.nextRoundingValue(key);
                     }
+                    assert key == nextBucket.key;
                 }
                 lastBucket = iter.next();
             }

src/test/java/org/elasticsearch/search/aggregations/bucket/DateHistogramTests.java

@@ -1299,4 +1299,36 @@ public void singleValue_WithMultipleDateFormatsFromMapping() throws Exception {
         assertThat(bucket, Matchers.notNullValue());
         assertThat(bucket.getDocCount(), equalTo(5l));
     }
+
+    public void testIssue6965() {
+        SearchResponse response = client().prepareSearch("idx")
+                .addAggregation(dateHistogram("histo").field("date").preZone("+01:00").interval(DateHistogram.Interval.MONTH).minDocCount(0))
+                .execute().actionGet();
+
+        assertSearchResponse(response);
+
+
+        DateHistogram histo = response.getAggregations().get("histo");
+        assertThat(histo, notNullValue());
+        assertThat(histo.getName(), equalTo("histo"));
+        assertThat(histo.getBuckets().size(), equalTo(3));
+
+        DateTime key = new DateTime(2012, 1, 1, 0, 0, DateTimeZone.UTC);
+        DateHistogram.Bucket bucket = getBucket(histo, key);
+        assertThat(bucket, notNullValue());
+        assertThat(bucket.getKeyAsNumber().longValue(), equalTo(key.getMillis()));
+        assertThat(bucket.getDocCount(), equalTo(1l));
+
+        key = new DateTime(2012, 2, 1, 0, 0, DateTimeZone.UTC);
+        bucket = getBucket(histo, key);
+        assertThat(bucket, notNullValue());
+        assertThat(bucket.getKeyAsNumber().longValue(), equalTo(key.getMillis()));
+        assertThat(bucket.getDocCount(), equalTo(2l));
+
+        key = new DateTime(2012, 3, 1, 0, 0, DateTimeZone.UTC);
+        bucket = getBucket(histo, key);
+        assertThat(bucket, notNullValue());
+        assertThat(bucket.getKeyAsNumber().longValue(), equalTo(key.getMillis()));
+        assertThat(bucket.getDocCount(), equalTo(3l));
+    }
 }