From 7d89c1f910b28d0661da6f2989ddea4b9bdcc643 Mon Sep 17 00:00:00 2001
From: Ivan Santos <pragmaticivan@gmail.com>
Date: Mon, 3 Jan 2022 07:10:51 -0600
Subject: [PATCH] fix(#171): fixes missing observation callback for observable
 metrics

fixes #171
---
 src/metrics/metric-data.ts    | 11 +++++++----
 src/metrics/metric.service.ts | 28 ++++++++++++++++++++--------
 2 files changed, 27 insertions(+), 12 deletions(-)

diff --git a/src/metrics/metric-data.ts b/src/metrics/metric-data.ts
index ad3e037..f9f0ff3 100644
--- a/src/metrics/metric-data.ts
+++ b/src/metrics/metric-data.ts
@@ -1,6 +1,6 @@
 import {
   Counter, MetricOptions, metrics, UpDownCounter,
-  Histogram, ObservableGauge, ObservableCounter, ObservableUpDownCounter,
+  Histogram, ObservableGauge, ObservableCounter, ObservableUpDownCounter, ObservableResult,
 } from '@opentelemetry/api-metrics';
 import { OTEL_METER_NAME } from '../opentelemetry.constants';
 
@@ -70,6 +70,7 @@ export function getOrCreateUpDownCounter(
 export function getOrCreateObservableGauge(
   name: string,
   options: MetricOptions,
+  callback?: (observableResult: ObservableResult) => void,
 ): ObservableGauge {
   if (meterData.has(name)) {
     return meterData.get(name) as ObservableGauge;
@@ -77,7 +78,7 @@ export function getOrCreateObservableGauge(
 
   const meter = metrics.getMeterProvider().getMeter(OTEL_METER_NAME);
 
-  const observableGauge = meter.createObservableGauge(name, options);
+  const observableGauge = meter.createObservableGauge(name, options, callback);
   meterData.set(name, observableGauge);
   return observableGauge;
 }
@@ -85,6 +86,7 @@ export function getOrCreateObservableGauge(
 export function getOrCreateObservableCounter(
   name: string,
   options: MetricOptions,
+  callback?: (observableResult: ObservableResult) => void,
 ): ObservableCounter {
   if (meterData.has(name)) {
     return meterData.get(name) as ObservableCounter;
@@ -92,7 +94,7 @@ export function getOrCreateObservableCounter(
 
   const meter = metrics.getMeterProvider().getMeter(OTEL_METER_NAME);
 
-  const observableCounter = meter.createObservableCounter(name, options);
+  const observableCounter = meter.createObservableCounter(name, options, callback);
   meterData.set(name, observableCounter);
   return observableCounter;
 }
@@ -100,6 +102,7 @@ export function getOrCreateObservableCounter(
 export function getOrCreateObservableUpDownCounter(
   name: string,
   options: MetricOptions,
+  callback?: (observableResult: ObservableResult) => void,
 ): ObservableUpDownCounter {
   if (meterData.has(name)) {
     return meterData.get(name) as ObservableUpDownCounter;
@@ -107,7 +110,7 @@ export function getOrCreateObservableUpDownCounter(
 
   const meter = metrics.getMeterProvider().getMeter(OTEL_METER_NAME);
 
-  const observableCounter = meter.createObservableCounter(name, options);
+  const observableCounter = meter.createObservableCounter(name, options, callback);
   meterData.set(name, observableCounter);
   return observableCounter;
 }
diff --git a/src/metrics/metric.service.ts b/src/metrics/metric.service.ts
index 33167e6..0a0e593 100644
--- a/src/metrics/metric.service.ts
+++ b/src/metrics/metric.service.ts
@@ -1,11 +1,11 @@
 import { Injectable } from '@nestjs/common';
 import {
-  MetricOptions,
+  MetricOptions, ObservableResult,
 } from '@opentelemetry/api-metrics';
 import {
   getOrCreateCounter, getOrCreateHistogram,
   getOrCreateObservableCounter, getOrCreateObservableGauge,
-  getOrCreateObservableUpDownCounter, getOrCreateUpDownCounter, MetricType,
+  getOrCreateObservableUpDownCounter, getOrCreateUpDownCounter,
 } from './metric-data';
 
 @Injectable()
@@ -22,15 +22,27 @@ export class MetricService {
     return getOrCreateHistogram(name, options);
   }
 
-  getObservableCounter(name: string, options?: MetricOptions) {
-    return getOrCreateObservableCounter(name, options);
+  getObservableCounter(
+    name: string,
+    options?: MetricOptions,
+    callback?: (observableResult: ObservableResult) => void,
+  ) {
+    return getOrCreateObservableCounter(name, options, callback);
   }
 
-  getObservableGauge(name: string, options?: MetricOptions) {
-    return getOrCreateObservableGauge(name, options);
+  getObservableGauge(
+    name: string,
+    options?: MetricOptions,
+    callback?: (observableResult: ObservableResult) => void,
+  ) {
+    return getOrCreateObservableGauge(name, options, callback);
   }
 
-  getObservableUpDownCounter(name: string, options?: MetricOptions) {
-    return getOrCreateObservableUpDownCounter(name, options);
+  getObservableUpDownCounter(
+    name: string,
+    options?: MetricOptions,
+    callback?: (observableResult: ObservableResult) => void,
+  ) {
+    return getOrCreateObservableUpDownCounter(name, options, callback);
   }
 }