chore: adding timestamp for prometheus metric Counter (#947)

Co-authored-by: Daniel Dyla <[email protected]>

Author: obecny

packages/opentelemetry-exporter-prometheus/src/prometheus.ts

@@ -134,7 +134,11 @@ export class PrometheusExporter implements MetricExporter {
       // MetricRecord value is the current state, not the delta to be incremented by.
       // Currently, _registerMetric creates a new counter every time the value changes,
       // so the increment here behaves as a set value (increment from 0)
-      metric.inc(labelValues, point.value as Sum);
+      metric.inc(
+        labelValues,
+        point.value as Sum,
+        hrTimeToMilliseconds(point.timestamp)
+      );
     }
 
     if (metric instanceof Gauge) {

packages/opentelemetry-exporter-prometheus/test/prometheus.test.ts

@@ -14,18 +14,35 @@
  * limitations under the License.
  */
 
-import { ObserverResult } from '@opentelemetry/api';
+import { HrTime, ObserverResult } from '@opentelemetry/api';
 import {
   CounterMetric,
+  CounterSumAggregator,
   Meter,
   MeterProvider,
   ObserverMetric,
+  Point,
 } from '@opentelemetry/metrics';
 import * as assert from 'assert';
 import * as http from 'http';
 import { PrometheusExporter } from '../src';
 
+const mockedHrTime: HrTime = [1586347902211, 0];
+const mockedTimeMS = 1586347902211000;
+
 describe('PrometheusExporter', () => {
+  let toPoint: () => Point;
+  before(() => {
+    toPoint = CounterSumAggregator.prototype.toPoint;
+    CounterSumAggregator.prototype.toPoint = function(): Point {
+      const point = toPoint.apply(this);
+      point.timestamp = mockedHrTime;
+      return point;
+    };
+  });
+  after(() => {
+    CounterSumAggregator.prototype.toPoint = toPoint;
+  });
   describe('constructor', () => {
     it('should construct an exporter', () => {
       const exporter = new PrometheusExporter();
@@ -209,7 +226,7 @@ describe('PrometheusExporter', () => {
                 assert.deepStrictEqual(lines, [
                   '# HELP counter a test description',
                   '# TYPE counter counter',
-                  'counter{key1="labelValue1"} 20',
+                  `counter{key1="labelValue1"} 20 ${mockedTimeMS}`,
                   '',
                 ]);
 
@@ -266,7 +283,7 @@ describe('PrometheusExporter', () => {
       });
     });
 
-    it('should export multiple labelsets', done => {
+    it('should export multiple labels', done => {
       const counter = meter.createCounter('counter', {
         description: 'a test description',
         labelKeys: ['counterKey1'],
@@ -285,8 +302,8 @@ describe('PrometheusExporter', () => {
               assert.deepStrictEqual(lines, [
                 '# HELP counter a test description',
                 '# TYPE counter counter',
-                'counter{counterKey1="labelValue1"} 10',
-                'counter{counterKey1="labelValue2"} 20',
+                `counter{counterKey1="labelValue1"} 10 ${mockedTimeMS}`,
+                `counter{counterKey1="labelValue2"} 20 ${mockedTimeMS}`,
                 '',
               ]);
 
@@ -330,7 +347,7 @@ describe('PrometheusExporter', () => {
               assert.deepStrictEqual(lines, [
                 '# HELP counter description missing',
                 '# TYPE counter counter',
-                'counter 10',
+                `counter 10 ${mockedTimeMS}`,
                 '',
               ]);
 
@@ -356,7 +373,7 @@ describe('PrometheusExporter', () => {
               assert.deepStrictEqual(lines, [
                 '# HELP counter_bad_name description missing',
                 '# TYPE counter_bad_name counter',
-                'counter_bad_name 10',
+                `counter_bad_name 10 ${mockedTimeMS}`,
                 '',
               ]);
 
@@ -432,7 +449,7 @@ describe('PrometheusExporter', () => {
                 assert.deepStrictEqual(lines, [
                   '# HELP test_prefix_counter description missing',
                   '# TYPE test_prefix_counter counter',
-                  'test_prefix_counter 10',
+                  `test_prefix_counter 10 ${mockedTimeMS}`,
                   '',
                 ]);
 
@@ -461,7 +478,7 @@ describe('PrometheusExporter', () => {
                 assert.deepStrictEqual(lines, [
                   '# HELP counter description missing',
                   '# TYPE counter counter',
-                  'counter 10',
+                  `counter 10 ${mockedTimeMS}`,
                   '',
                 ]);
 
@@ -490,7 +507,7 @@ describe('PrometheusExporter', () => {
                 assert.deepStrictEqual(lines, [
                   '# HELP counter description missing',
                   '# TYPE counter counter',
-                  'counter 10',
+                  `counter 10 ${mockedTimeMS}`,
                   '',
                 ]);