Warn on a potentially incorrect HTTP OTLP endpoint

examples/express/.vscode/settings.json

@@ -1,4 +1,3 @@
 {
-	"typescript.tsdk": "node_modules/typescript/lib"
+  "typescript.tsdk": "node_modules/typescript/lib"
 }
-

examples/express/src/database.ts

@@ -17,7 +17,7 @@ export const API_SLO: Objective = {
   latency: [ObjectiveLatency.Ms250, ObjectivePercentile.P99],
 };
 
-@Autometrics({objective: API_SLO})
+@Autometrics({ objective: API_SLO })
 export class DatabaseClient {
   public users: User[];
   constructor() {

examples/express/src/util.ts

@@ -1,7 +1,7 @@
 import fetch from "node-fetch";
 
 export function shouldError() {
-  if ((Math.floor(Math.random() * 100) + 1) === 1) {
+  if (Math.floor(Math.random() * 100) + 1 === 1) {
     throw new Error("Error occurred");
   }
 }

examples/fastify/.vscode/settings.json

@@ -1,4 +1,3 @@
 {
-	"typescript.tsdk": "node_modules/typescript/lib"
+  "typescript.tsdk": "node_modules/typescript/lib"
 }
-

examples/nestjs/.eslintrc.js

@@ -1,25 +1,25 @@
 module.exports = {
-  parser: '@typescript-eslint/parser',
+  parser: "@typescript-eslint/parser",
   parserOptions: {
-    project: 'tsconfig.json',
+    project: "tsconfig.json",
     tsconfigRootDir: __dirname,
-    sourceType: 'module',
+    sourceType: "module",
   },
-  plugins: ['@typescript-eslint/eslint-plugin'],
+  plugins: ["@typescript-eslint/eslint-plugin"],
   extends: [
-    'plugin:@typescript-eslint/recommended',
-    'plugin:prettier/recommended',
+    "plugin:@typescript-eslint/recommended",
+    "plugin:prettier/recommended",
   ],
   root: true,
   env: {
     node: true,
     jest: true,
   },
-  ignorePatterns: ['.eslintrc.js'],
+  ignorePatterns: [".eslintrc.js"],
   rules: {
-    '@typescript-eslint/interface-name-prefix': 'off',
-    '@typescript-eslint/explicit-function-return-type': 'off',
-    '@typescript-eslint/explicit-module-boundary-types': 'off',
-    '@typescript-eslint/no-explicit-any': 'off',
+    "@typescript-eslint/interface-name-prefix": "off",
+    "@typescript-eslint/explicit-function-return-type": "off",
+    "@typescript-eslint/explicit-module-boundary-types": "off",
+    "@typescript-eslint/no-explicit-any": "off",
   },
 };

examples/nestjs/.vscode/settings.json

@@ -1,4 +1,3 @@
 {
-	"typescript.tsdk": "node_modules/typescript/lib"
+  "typescript.tsdk": "node_modules/typescript/lib"
 }
-

examples/nestjs/src/app.controller.ts

@@ -1,5 +1,5 @@
-import { Controller, Get } from '@nestjs/common';
-import { AppService } from './app.service';
+import { Controller, Get } from "@nestjs/common";
+import { AppService } from "./app.service";
 
 @Controller()
 export class AppController {

examples/nestjs/src/app.module.ts

@@ -1,6 +1,6 @@
-import { Module } from '@nestjs/common';
-import { AppController } from './app.controller';
-import { AppService } from './app.service';
+import { Module } from "@nestjs/common";
+import { AppController } from "./app.controller";
+import { AppService } from "./app.service";
 
 @Module({
   imports: [],

examples/nestjs/src/app.service.ts

@@ -1,10 +1,10 @@
-import { Autometrics } from '@autometrics/autometrics';
-import { Injectable } from '@nestjs/common';
+import { Autometrics } from "@autometrics/autometrics";
+import { Injectable } from "@nestjs/common";
 
 @Injectable()
 @Autometrics()
 export class AppService {
   getHello(): string {
-    return 'Hello World!';
+    return "Hello World!";
   }
 }

examples/react-app-experimental/src/main.tsx

@@ -1,10 +1,10 @@
-import React from 'react'
-import ReactDOM from 'react-dom/client'
-import App from './App'
-import './index.css'
+import React from "react";
+import ReactDOM from "react-dom/client";
+import App from "./App";
+import "./index.css";
 
-ReactDOM.createRoot(document.getElementById('root') as HTMLElement).render(
+ReactDOM.createRoot(document.getElementById("root") as HTMLElement).render(
   <React.StrictMode>
     <App />
   </React.StrictMode>,
-)
+);

packages/exporter-otlp-http/src/index.ts

@@ -18,7 +18,9 @@ const MAX_SAFE_INTERVAL = 2 ** 31 - 1;
 
 export type InitOptions = {
   /**
-   * URL of the OpenTelemetry Collector to push metrics to.
+   * URL of the OpenTelemetry Collector to push metrics to. Should be a
+   * complete url with port and `/v1/metrics` endpoint:
+   * `http://localhost:4317/v1/metrics`.
    */
   url: string;
 
@@ -75,6 +77,29 @@ export function init({
   temporalityPreference = AggregationTemporalityPreference.CUMULATIVE,
   buildInfo,
 }: InitOptions) {
+  const defaultPath = "/v1/metrics" as const;
+  const defaultPort = "4317" as const;
+
+  const urlObj = new URL(url);
+
+  //`pathname` is not reliable - it will always return "/" even if no explicit
+  // path is specified (see: https://github.com/autometrics-dev/autometrics-ts/pull/126#discussion_r1335623052).
+  // If this variable is not an empty string we should only give a warning without substituting
+  const explicitPath = url.replace(urlObj.origin, "");
+
+  if (explicitPath !== "" && !explicitPath.endsWith(defaultPath)) {
+    amLogger.warn(
+      "Warning: The official OTLP/HTTP endpoint path for metrics is '/v1/metrics', your metrics data might not be submitted properly. See: https://opentelemetry.io/docs/specs/otel/protocol/exporter/#endpoint-urls-for-otlphttp",
+    );
+  }
+
+  if (explicitPath === "" && urlObj.port === defaultPort) {
+    amLogger.info(
+      "Appending default path /v1/metrics to OTLP/HTTP endpoint URL",
+    );
+    url = urlObj.origin + defaultPath;
+  }
+
   amLogger.info(`Exporter will push to the OTLP/HTTP endpoint at ${url}`);
 
   const exporter = new OTLPMetricExporter({

packages/exporter-otlp-http/tests/init.test.ts

@@ -17,7 +17,7 @@ describe("init test", () => {
     const foo = new Foo();
     foo.bar(); // one before
 
-    init({ url: "/metrics", pushInterval: 5000 });
+    init({ url: "http://localhost:4317", pushInterval: 5000 });
 
     foo.bar(); // one after
 

packages/exporter-otlp-http/tests/on-demand-push.test.ts

@@ -13,7 +13,7 @@ describe("temporality test with on-demand push", () => {
     const pushInterval = 0;
 
     init({
-      url: "/metrics",
+      url: "http://localhost:4317/",
       pushInterval,
       temporalityPreference: AggregationTemporality.DELTA,
     });

packages/exporter-otlp-http/tests/temporality.test.ts

@@ -14,7 +14,7 @@ describe("temporality test with scheduled push", () => {
     const timeout = 10; // must be smaller than `pushInterval`.
 
     init({
-      url: "/metrics",
+      url: "http://localhost:4317/",
       pushInterval,
       timeout,
       temporalityPreference: AggregationTemporality.DELTA,