Histogram Aggregation on Up-Down-Counters results in wrong max

[pichlermarc]

What happened?

HistogramAggregation incorrectly assumes positive-only values, and therfore produces wrong max values on export.

Steps to Reproduce

1. Set up OTel JS Metrics
2. Create View that changes an UpDownCounter to have an ExplicitBucketHistogramAggregation
3. Create an UpDownCounter
4. Only add values -1

Expected Result

Exported metrics should have a maximum of < -1.

Actual Result

Exported metrics have a maximum of -1.

OpenTelemetry Setup Code

// Test for 'MeterProvider addView' in 'MeterProvider.test.ts'

it('with UP_DOWN_COUNTER and ExplicitBucketHistogramAggregation does export the correct min/max', async() => {
      const meterProvider = new MeterProvider({ resource: defaultResource });
      const reader = new TestMetricReader();
      meterProvider.addMetricReader(reader);

      meterProvider.addView({
        aggregation: new ExplicitBucketHistogramAggregation([1,3,4])
      },
      {
        instrument: {
          name: 'test-histogram'
        },
        meter: {
          name: 'meter1'
        }
      });

      // Create meter and instruments.
      const meter = meterProvider.getMeter('meter1', 'v1.0.0');
      const counter = meter.createUpDownCounter('test-histogram');

      // Record value.
      counter.add(-20);
      counter.add(-5);

      // Perform collection.
      const { resourceMetrics, errors } = await reader.collect();

      assert.strictEqual(errors.length, 0);
      // Results came only from one Meter.
      assert.strictEqual(resourceMetrics.scopeMetrics.length, 1);

      // InstrumentationScope matches the only created Meter.
      assertScopeMetrics(resourceMetrics.scopeMetrics[0], {
        name: 'meter1',
        version: 'v1.0.0'
      });

      // one metric collected
      assert.strictEqual(resourceMetrics.scopeMetrics[0].metrics.length, 1);

      const metric = resourceMetrics.scopeMetrics[0].metrics[0];
      assert.strictEqual(metric.dataPointType, DataPointType.HISTOGRAM);
      // eslint-disable-next-line @typescript-eslint/ban-ts-comment
      // @ts-ignore was asserted to be DataPointType.HISTOGRAM
      assert.strictEqual(metric.dataPoints[0].value.min, -20);
      // eslint-disable-next-line @typescript-eslint/ban-ts-comment
      // @ts-ignore was asserted to be DataPointType.HISTOGRAM
      assert.strictEqual(metric.dataPoints[0].value.max, -5);
    });

// test for Histogram.test.ts, 'HistogramAggregator merge'
it('with only negatives', () => {
      const aggregator = new HistogramAggregator([1, 10, 100], true);
      const prev = aggregator.createAccumulation([0, 0]);
      prev.record(-10);
      prev.record(-20);

      const delta = aggregator.createAccumulation([1, 1]);
      delta.record(-5);
      delta.record(-30);

      assert.deepStrictEqual(aggregator.merge(prev, delta).toPointValue(), {
        buckets: {
          boundaries: [1, 10, 100],
          counts: [4, 0, 0, 0]
        },
        count: 4,
        hasMinMax: true,
        max: -5,
        min: -30,
        sum: -65
      });
    });

package.json

"@opentelemetry/sdk-metrics-base": "0.30.0"

Relevant log output

No response

[pichlermarc]

Provided a fix in #3086.