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Review follow-ups: DropAggregator comment + cumulative async reappearance test #23

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Merged
jack-berg merged 1 commit into from
Apr 7, 2026
Merged

Review follow-ups: DropAggregator comment + cumulative async reappearance test #23

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4 changes: 3 additions & 1 deletion ...etrics/src/main/java/io/opentelemetry/sdk/metrics/internal/aggregator/DropAggregator.java
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Original file line number Diff line number Diff line change
Expand Up @@ -52,9 +52,11 @@ public List<? extends ExemplarData> getExemplars() {

public static final Aggregator<PointData> INSTANCE = new DropAggregator();

// creationEpochNanos is 0 because DropAggregator never produces data points, so
// the start timestamp is irrelevant. A single shared HANDLE is safe to use.
private static final AggregatorHandle<PointData> HANDLE =
new AggregatorHandle<PointData>(
0, ExemplarReservoirFactory.noSamples(), /* isDoubleType= */ true) {
/* creationEpochNanos= */ 0, ExemplarReservoirFactory.noSamples(), /* isDoubleType= */ true) {
@Override
protected PointData doAggregateThenMaybeResetDoubles(
long startEpochNanos,
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67 changes: 67 additions & 0 deletions .../test/java/io/opentelemetry/sdk/metrics/internal/state/AsynchronousMetricStorageTest.java
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Expand Up @@ -335,6 +335,73 @@ void collect_CumulativeReportsCumulativeObservations(MemoryMode memoryMode) {
.hasAttributes(Attributes.builder().put("key", "value2").build())));
}

@ParameterizedTest
@EnumSource(MemoryMode.class)
void collect_CumulativeSeriesDisappearsAndReappears(MemoryMode memoryMode) {
setup(memoryMode);

Attributes attrA = Attributes.empty();
Attributes attrB = Attributes.builder().put("key", "b").build();

// Collection 1: both series reported. start time = instrument creation time (START_SECOND_NANOS)
testClock.advance(Duration.ofSeconds(10));
longCounterStorage.record(attrA, 1);
longCounterStorage.record(attrB, 2);
assertThat(longCounterStorage.collect(resource, scope, testClock.now()))
.hasLongSumSatisfying(
sum ->
sum.isCumulative()
.hasPointsSatisfying(
point ->
point
.hasStartEpochNanos(START_SECOND_NANOS)
.hasAttributes(attrA)
.hasValue(1),
point ->
point
.hasStartEpochNanos(START_SECOND_NANOS)
.hasAttributes(attrB)
.hasValue(2)));
registeredReader.setLastCollectEpochNanos(testClock.now());

// Collection 2: only attrA reported; attrB disappears and its handle is removed.
testClock.advance(Duration.ofSeconds(10));
longCounterStorage.record(attrA, 3);
assertThat(longCounterStorage.collect(resource, scope, testClock.now()))
.hasLongSumSatisfying(
sum ->
sum.isCumulative()
.hasPointsSatisfying(
point ->
point
.hasStartEpochNanos(START_SECOND_NANOS)
.hasAttributes(attrA)
.hasValue(3)));
registeredReader.setLastCollectEpochNanos(testClock.now());
long collectTime2 = testClock.now();

// Collection 3: attrB reappears. Its start time should be the time of the collection
// immediately preceding its reappearance (collectTime2), not the original creation time.
testClock.advance(Duration.ofSeconds(10));
longCounterStorage.record(attrA, 5);
longCounterStorage.record(attrB, 7);
assertThat(longCounterStorage.collect(resource, scope, testClock.now()))
.hasLongSumSatisfying(
sum ->
sum.isCumulative()
.hasPointsSatisfying(
point ->
point
.hasStartEpochNanos(START_SECOND_NANOS)
.hasAttributes(attrA)
.hasValue(5),
point ->
point
.hasStartEpochNanos(collectTime2)
.hasAttributes(attrB)
.hasValue(7)));
}

@ParameterizedTest
@EnumSource(MemoryMode.class)
void collect_DeltaComputesDiff(MemoryMode memoryMode) {
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