feat: enforce minimum max size

open-telemetry · Dec 20, 2022 · f40abac · f40abac
1 parent b710d4f
commit f40abac
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Showing 2 changed files with 20 additions and 2 deletions.
diff --git a/packages/sdk-metrics/src/aggregator/ExponentialHistogram.ts b/packages/sdk-metrics/src/aggregator/ExponentialHistogram.ts
@@ -24,7 +24,7 @@ import {
   DataPointType,
   ExponentialHistogramMetricData,
 } from '../export/MetricData';
-import { HrTime } from '@opentelemetry/api';
+import { diag, HrTime } from '@opentelemetry/api';
 import { InstrumentDescriptor, InstrumentType } from '../InstrumentDescriptor';
 import { Maybe } from '../utils';
 import { AggregationTemporality } from '../export/AggregationTemporality';
@@ -68,6 +68,7 @@ class HighLow {
 
 export class ExponentialHistogramAccumulation implements Accumulation {
   static DEFAULT_MAX_SIZE = 160;
+  static MIN_MAX_SIZE = 2;
 
   constructor(
     public startTime: HrTime = startTime,
@@ -81,7 +82,14 @@ export class ExponentialHistogramAccumulation implements Accumulation {
     private _positive = new Buckets(),
     private _negative = new Buckets(),
     private _mapping: Mapping = LogarithmMapping.get(LogarithmMapping.MAX_SCALE)
-  ) {}
+  ) {
+    if (this._maxSize < ExponentialHistogramAccumulation.MIN_MAX_SIZE) {
+      diag.warn(`Exponential Histogram Max Size set to ${this._maxSize}, \
+                changing to the minimum size of: \
+                ${ExponentialHistogramAccumulation.MIN_MAX_SIZE}`);
+      this._maxSize = ExponentialHistogramAccumulation.MIN_MAX_SIZE;
+    }
+  }
 
   /**
    * record updates a histogram with a single count

diff --git a/packages/sdk-metrics/test/aggregator/ExponentialHistogram.test.ts b/packages/sdk-metrics/test/aggregator/ExponentialHistogram.test.ts
@@ -530,6 +530,16 @@ describe('ExponentialHistogramAccumulation', () => {
       assert.deepStrictEqual(pv.negative.bucketCounts, acc.negative().counts());
     });
   });
+
+  describe('min max size', () => {
+    it('auto-corrects to min max', () => {
+      const acc: any = new ExponentialHistogramAccumulation([0, 0], 0);
+      assert.strictEqual(
+        acc['_maxSize'],
+        ExponentialHistogramAccumulation.MIN_MAX_SIZE
+      );
+    });
+  });
 });
 
 describe('ExponentialHistogramAggregation', () => {