From 0c92cdeed2ef080eec547a6be80e5b9c7dbc3d42 Mon Sep 17 00:00:00 2001
From: Tiger He <tigerhe7@gmail.com>
Date: Tue, 1 Sep 2020 12:25:20 -0400
Subject: [PATCH] feat: add support for Distributions (#125)

* initial update

* Update after api testing

* Adding optional param to Distribution type

* fix lint attempt

* fix lint and tests

* fix lint

* fix tests

* throw error for incompatible distributionValue aggregated

* update test

* fix lint

* fix lint

* update comment
---
 .../src/transform.ts                          | 17 ++++++--
 .../src/types.ts                              |  2 +-
 .../test/transform.test.ts                    | 43 +++++++++++--------
 3 files changed, 39 insertions(+), 23 deletions(-)

diff --git a/packages/opentelemetry-cloud-monitoring-exporter/src/transform.ts b/packages/opentelemetry-cloud-monitoring-exporter/src/transform.ts
index 89132464..b3d5c76f 100644
--- a/packages/opentelemetry-cloud-monitoring-exporter/src/transform.ts
+++ b/packages/opentelemetry-cloud-monitoring-exporter/src/transform.ts
@@ -237,12 +237,21 @@ function transformValue(
   value: number | OTDistribution | OTHistogram
 ) {
   if (isDistributionValue(value)) {
-    // TODO: Add support for Distribution
-    throw new Error('Distributions are not yet supported');
+    throw Error('unsupported distribution value type');
+    // no buckets aggregated, which is a required param in `distributionValue` for Cloud Monitoring v3
   }
   if (isHistogramValue(value)) {
-    // TODO: Add support for Histogram
-    throw new Error('Histograms are not yet supported');
+    return {
+      distributionValue: {
+        // sumOfSquaredDeviation param not aggregated
+        count: value.count,
+        mean: value.sum / value.count,
+        bucketOptions: {
+          explicitBuckets: { bounds: value.buckets.boundaries },
+        },
+        bucketCounts: value.buckets.counts,
+      },
+    };
   }
 
   if (valueType === OTValueType.INT) {
diff --git a/packages/opentelemetry-cloud-monitoring-exporter/src/types.ts b/packages/opentelemetry-cloud-monitoring-exporter/src/types.ts
index 38b21e6f..1ddeba53 100644
--- a/packages/opentelemetry-cloud-monitoring-exporter/src/types.ts
+++ b/packages/opentelemetry-cloud-monitoring-exporter/src/types.ts
@@ -88,7 +88,7 @@ export interface Point {
 export interface Distribution {
   count: number;
   mean: number;
-  sumOfSquaredDeviation: number;
+  sumOfSquaredDeviation?: number;
   bucketOptions: { explicitBuckets: { bounds: Bucket[] } };
   bucketCounts: number[];
   exemplars?: Exemplar[];
diff --git a/packages/opentelemetry-cloud-monitoring-exporter/test/transform.test.ts b/packages/opentelemetry-cloud-monitoring-exporter/test/transform.test.ts
index 7d178f01..e6d851a7 100644
--- a/packages/opentelemetry-cloud-monitoring-exporter/test/transform.test.ts
+++ b/packages/opentelemetry-cloud-monitoring-exporter/test/transform.test.ts
@@ -341,7 +341,7 @@ describe('transform', () => {
       assert(!result.interval.startTime);
     });
 
-    it('should throw an error when given a distribution value', () => {
+    it('should export a distribution value', () => {
       const metricDescriptor: OTMetricDescriptor = {
         name: METRIC_NAME,
         description: METRIC_DESCRIPTION,
@@ -359,19 +359,16 @@ describe('transform', () => {
         timestamp: process.hrtime(),
       };
 
-      try {
-        TEST_ONLY.transformPoint(
+      assert.throws(() => {
+        return TEST_ONLY.transformPoint(
           point,
           metricDescriptor,
           new Date().toISOString()
         );
-        assert.fail('should have thrown an error');
-      } catch (err) {
-        assert(err.message.toLowerCase().includes('distributions'));
-      }
+      }, /unsupported distribution value type/);
     });
 
-    it('should thrown an error when given a histogram value', () => {
+    it('should export a histogram value', () => {
       const metricDescriptor: OTMetricDescriptor = {
         name: METRIC_NAME,
         description: METRIC_DESCRIPTION,
@@ -391,16 +388,26 @@ describe('transform', () => {
         timestamp: process.hrtime(),
       };
 
-      try {
-        TEST_ONLY.transformPoint(
-          point,
-          metricDescriptor,
-          new Date().toISOString()
-        );
-        assert.fail('should have thrown an error');
-      } catch (err) {
-        assert(err.message.toLowerCase().includes('histograms'));
-      }
+      const result = TEST_ONLY.transformPoint(
+        point,
+        metricDescriptor,
+        new Date().toISOString()
+      );
+
+      assert.deepStrictEqual(result.value, {
+        distributionValue: {
+          bucketCounts: [1, 2],
+          bucketOptions: {
+            explicitBuckets: {
+              bounds: [10, 30],
+            },
+          },
+          count: 3,
+          mean: 23.333333333333332,
+        },
+      });
+      assert(result.interval.endTime);
+      assert(result.interval.startTime);
     });
   });
 });