feat: Add prometheus exporter (#483)

* fix(http-plugin): move node-sdk to dev deps

* feat: update dependencies

* feat: server implementation and tests

* fix: remove console logger

* fix: add types

* feat(prometheus-exporter): counter and gauge

* feat(prometheus-exporter): implement counter and gauge

* feat(prometheus-exporter): export configuration interface

* fix: linting

* fix: typo

Co-Authored-By: Mayur Kale <mayurkale@google.com>

* chore: document ExporterConfig

* fix: dependencies

* fix: typo

Co-Authored-By: Mayur Kale <mayurkale@google.com>

* chore: document sanitize method and make behavior more strict

* chore: do not use global prom-client registry

* chore: add defaults to description and metric endpoint

* test: export couter, gauge, multiple, and none

* test: sanitize prom metric names

* fix: typo

Co-Authored-By: Mayur Kale <mayurkale@google.com>

* chore: make _server read only

* test: add tests for prom export configuration

* style: make comments descriptive

* test: update tests for label sets

* fix: lint

packages/opentelemetry-exporter-prometheus/package.json

@@ -1,7 +1,6 @@
 {
   "name": "@opentelemetry/exporter-prometheus",
   "version": "0.2.0",
-  "private": true,
   "description": "OpenTelemetry Exporter Prometheus provides a metrics endpoint for Prometheus",
   "main": "build/src/index.js",
   "types": "build/src/index.d.ts",
@@ -43,16 +42,20 @@
     "@types/node": "^12.6.9",
     "codecov": "^3.5.0",
     "gts": "^1.1.0",
-    "mocha": "^6.2.0",
+    "mocha": "^6.2.2",
     "nyc": "^14.1.1",
     "rimraf": "^3.0.0",
     "ts-mocha": "^6.0.0",
     "ts-node": "^8.3.0",
+    "tslint-consistent-codestyle": "^1.16.0",
     "tslint-microsoft-contrib": "^6.2.0",
     "typescript": "3.7.2"
   },
   "dependencies": {
+    "@opentelemetry/base": "^0.2.0",
     "@opentelemetry/core": "^0.2.0",
-    "@opentelemetry/types": "^0.2.0"
+    "@opentelemetry/metrics": "^0.2.0",
+    "@opentelemetry/types": "^0.2.0",
+    "prom-client": "^11.5.3"
   }
 }

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

@@ -0,0 +1,53 @@
+/*!
+ * Copyright 2019, OpenTelemetry Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import * as types from '@opentelemetry/types';
+
+/**
+ * Configuration interface for prometheus exporter
+ */
+export interface ExporterConfig {
+  /**
+   * App prefix for metrics, if needed
+   *
+   * @default ''
+   * */
+  prefix?: string;
+
+  /**
+   * Endpoint the metrics should be exposed at with preceeding slash
+   * @default '/metrics'
+   */
+  endpoint?: string;
+
+  /**
+   * Port number for Prometheus exporter server
+   *
+   * Default registered port is 9464:
+   * https://github.com/prometheus/prometheus/wiki/Default-port-allocations
+   * @default 9464
+   */
+  port?: number;
+
+  /**
+   * Define if the Prometheus exporter server will be started
+   * @default false
+   */
+  startServer?: boolean;
+
+  /** Standard logging interface */
+  logger?: types.Logger;
+}

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

@@ -14,4 +14,5 @@
  * limitations under the License.
  */
 
-//
+export * from './prometheus';
+export * from './export/types';