From fc28665d090f4426ece597ea44546dbc1d95d665 Mon Sep 17 00:00:00 2001
From: Jamie Danielson <jamieedanielson@gmail.com>
Date: Mon, 10 Jul 2023 11:31:57 -0400
Subject: [PATCH] docs(sdk-metrics): add example of exponential histogram
 metric (#3855)

Co-authored-by: Chengzhong Wu <legendecas@gmail.com>
Co-authored-by: Marc Pichler <marc.pichler@dynatrace.com>
---
 doc/metrics.md                         |  8 ++---
 examples/otlp-exporter-node/metrics.js | 44 ++++++++++++++++++++++----
 experimental/CHANGELOG.md              |  4 +++
 3 files changed, 45 insertions(+), 11 deletions(-)

diff --git a/doc/metrics.md b/doc/metrics.md
index 7162f43638..e2f2b5a147 100644
--- a/doc/metrics.md
+++ b/doc/metrics.md
@@ -20,7 +20,7 @@ _Metrics API Reference: <https://open-telemetry.github.io/opentelemetry-js/class
   - [Customizing the metric attributes of instrument](#customizing-the-metric-attributes-of-instrument)
 - [Exporting measurements](#exporting-measurements)
   - [Exporting measurements to Prometheus](#exporting-measurements-to-prometheus)
-  - [Exporting measurements to Opentelemetry Protocol](#exporting-measurements-to-opentelemetry-protocol)
+  - [Exporting measurements to OpenTelemetry Protocol](#exporting-measurements-to-opentelemetry-protocol)
 
 ## Getting Started
 
@@ -266,7 +266,7 @@ Most of the time, instruments will be used to measure operations in your applica
 
 ```typescript
 async function myTask() {
-  const histogram = meter.createHistogram("taks.duration");
+  const histogram = meter.createHistogram("task.duration");
   const startTime = new Date().getTime()
   try {
     // Wait for five seconds before continuing code execution
@@ -479,7 +479,7 @@ new View({
 
 After you have instrumented your application with metrics, you also need to make
 sure that the metrics get collected by your metrics backend. The most common formats
-that are used are Prometheus and OLTP.
+that are used are Prometheus and OTLP.
 
 The latter is the [OpenTelemetry protocol format](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/protocol/otlp.md)
 which is supported by the OpenTelemetry Collector. The former is based on the [OpenMetrics
@@ -528,7 +528,7 @@ at: <https://github.com/open-telemetry/opentelemetry-js/tree/main/experimental/e
 ## Exporting measurements to OpenTelemetry Protocol
 
 OpenTelemetry JavaScript comes with three different kinds of exporters that export
-the OTLP protocol, a) [over HTTP](https://github.com/open-telemetry/opentelemetry-js/tree/main/experimental/packages/opentelemetry-exporter-metrics-otlp-http), b) [over GRPC](https://www.npmjs.com/package/@opentelemetry/exporter-metrics-otlp-grpc), c) [over Protofbuf](https://www.npmjs.com/package/@opentelemetry/exporter-metrics-otlp-proto).
+the OTLP protocol, a) [over HTTP](https://github.com/open-telemetry/opentelemetry-js/tree/main/experimental/packages/opentelemetry-exporter-metrics-otlp-http), b) [over GRPC](https://www.npmjs.com/package/@opentelemetry/exporter-metrics-otlp-grpc), c) [over Protobuf](https://www.npmjs.com/package/@opentelemetry/exporter-metrics-otlp-proto).
 
 The example below shows how you can configure OpenTelemetry JavaScript to use
 the OTLP exporter using http/protobuf.
diff --git a/examples/otlp-exporter-node/metrics.js b/examples/otlp-exporter-node/metrics.js
index f6c3efa55b..0594ba42e3 100644
--- a/examples/otlp-exporter-node/metrics.js
+++ b/examples/otlp-exporter-node/metrics.js
@@ -4,25 +4,50 @@ const { DiagConsoleLogger, DiagLogLevel, diag } = require('@opentelemetry/api');
 const { OTLPMetricExporter } = require('@opentelemetry/exporter-metrics-otlp-http');
 // const { OTLPMetricExporter } = require('@opentelemetry/exporter-metrics-otlp-grpc');
 // const { OTLPMetricExporter } = require('@opentelemetry/exporter-metrics-otlp-proto');
-const { MeterProvider, PeriodicExportingMetricReader } = require('@opentelemetry/sdk-metrics');
+// const { ConsoleMetricExporter } = require('@opentelemetry/sdk-metrics');
+const {
+  ExponentialHistogramAggregation,
+  MeterProvider,
+  PeriodicExportingMetricReader,
+  View,
+} = require('@opentelemetry/sdk-metrics');
 const { Resource } = require('@opentelemetry/resources');
-const { SemanticResourceAttributes } = require('@opentelemetry/semantic-conventions');
+const {
+  SemanticResourceAttributes,
+} = require('@opentelemetry/semantic-conventions');
 
 // Optional and only needed to see the internal diagnostic logging (during development)
 diag.setLogger(new DiagConsoleLogger(), DiagLogLevel.DEBUG);
 
-const metricExporter = new OTLPMetricExporter({});
+const metricExporter = new OTLPMetricExporter({
+  // headers: {
+  //   foo: 'bar'
+  // },
+});
+
+// Define view for the exponential histogram metric
+const expHistogramView = new View({
+  aggregation: new ExponentialHistogramAggregation(),
+  // Note, the instrumentName is the same as the name that has been passed for
+  // the Meter#createHistogram function for exponentialHistogram.
+  instrumentName: 'test_exponential_histogram',
+});
 
+// Create an instance of the metric provider
 const meterProvider = new MeterProvider({
   resource: new Resource({
     [SemanticResourceAttributes.SERVICE_NAME]: 'basic-metric-service',
   }),
+  views: [expHistogramView],
 });
 
-meterProvider.addMetricReader(new PeriodicExportingMetricReader({
-  exporter: metricExporter,
-  exportIntervalMillis: 1000,
-}));
+meterProvider.addMetricReader(
+  new PeriodicExportingMetricReader({
+    exporter: metricExporter,
+    // exporter: new ConsoleMetricExporter(),
+    exportIntervalMillis: 1000,
+  })
+);
 
 const meter = meterProvider.getMeter('example-exporter-collector');
 
@@ -38,10 +63,15 @@ const histogram = meter.createHistogram('test_histogram', {
   description: 'Example of a Histogram',
 });
 
+const exponentialHistogram = meter.createHistogram('test_exponential_histogram', {
+  description: 'Example of an ExponentialHistogram',
+});
+
 const attributes = { pid: process.pid, environment: 'staging' };
 
 setInterval(() => {
   requestCounter.add(1, attributes);
   upDownCounter.add(Math.random() > 0.5 ? 1 : -1, attributes);
   histogram.record(Math.random(), attributes);
+  exponentialHistogram.record(Math.random(), attributes);
 }, 1000);
diff --git a/experimental/CHANGELOG.md b/experimental/CHANGELOG.md
index 7d22becab6..762a2b9aa6 100644
--- a/experimental/CHANGELOG.md
+++ b/experimental/CHANGELOG.md
@@ -4,6 +4,10 @@ All notable changes to experimental packages in this project will be documented
 
 ## Unreleased
 
+### :books: (Refine Doc)
+
+* docs(sdk-metrics): add example of exponential histogram metric [#3855](https://github.com/open-telemetry/opentelemetry-js/pull/3855) @JamieDanielson
+
 ### :boom: Breaking Change
 
 ### :rocket: (Enhancement)