feat(api): add prometheus metrics

Currently we support metrics for the Node.js runtime and HTTP endpoints.

README.md

@@ -48,6 +48,14 @@ You can use Sentry to automatically detect and report any exceptions thrown.
 - `SENTRY_ENABLED`: **false**, Set to `true` to enable Sentry.
 - `SENTRY_DSN`: _Required_, but only if `SENTRY_ENABLED` is `true`. The [DSN](https://docs.sentry.io/product/sentry-basics/dsn-explainer/) for your Sentry project.
 
+#### Prometheus
+
+You can use Prometheus to track various metrics about your Listory deployment.
+
+The metrics will be exposed on the `/api/metrics` endpoint. Make sure that this endpoint is not publicly available in your deployment.
+
+- `PROMETHEUS_ENABLED`: **false**, Set to `true` to enable Prometheus Metrics.
+
 ## Development
 
 ### Configure Spotify API Access

package-lock.json

@@ -833,6 +833,17 @@
         "minimist": "^1.2.0"
       }
     },
+    "@digikare/nestjs-prom": {
+      "version": "1.0.0",
+      "resolved": "https://registry.npmjs.org/@digikare/nestjs-prom/-/nestjs-prom-1.0.0.tgz",
+      "integrity": "sha512-iuIdnZlwZ5EVHfcqXRveB+7J/xlv1LAvroW2qxmH9G+NjAHNTaouheDwivyKUfZHaXP9Q3Zp1pN24l3rvZi6+A==",
+      "requires": {
+        "@nestjs/testing": "^7.3.2",
+        "prom-client": "^12.0.0",
+        "response-time": "^2.3.2",
+        "url-value-parser": "^2.0.1"
+      }
+    },
     "@dsherret/to-absolute-glob": {
       "version": "2.0.2",
       "resolved": "https://registry.npmjs.org/@dsherret/to-absolute-glob/-/to-absolute-glob-2.0.2.tgz",
@@ -2198,7 +2209,6 @@
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       "resolved": "https://registry.npmjs.org/@nestjs/testing/-/testing-7.5.2.tgz",
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-      "dev": true,
       "requires": {
         "optional": "0.1.4",
         "tslib": "2.0.3"
@@ -2207,8 +2217,7 @@
         "tslib": {
           "version": "2.0.3",
           "resolved": "https://registry.npmjs.org/tslib/-/tslib-2.0.3.tgz",
-          "integrity": "sha512-uZtkfKblCEQtZKBF6EBXVZeQNl82yqtDQdv+eck8u7tdPxjLu2/lp5/uPW+um2tpuxINHWy3GhiccY7QgEaVHQ==",
-          "dev": true
+          "integrity": "sha512-uZtkfKblCEQtZKBF6EBXVZeQNl82yqtDQdv+eck8u7tdPxjLu2/lp5/uPW+um2tpuxINHWy3GhiccY7QgEaVHQ=="
         }
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@@ -4135,6 +4144,11 @@
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       "integrity": "sha512-1Yj8h9Q+QDF5FzhMs/c9+6UntbD5MkRfRwac8DoEm9ZfUBZ7tZ55YcGVAzEe4bXsdQHEk+s9S5wsOKVdZrw0tQ=="
     },
+    "bintrees": {
+      "version": "1.0.1",
+      "resolved": "https://registry.npmjs.org/bintrees/-/bintrees-1.0.1.tgz",
+      "integrity": "sha1-DmVcm5wkNeqraL9AJyJtK1WjRSQ="
+    },
     "body-parser": {
       "version": "1.19.0",
       "resolved": "https://registry.npmjs.org/body-parser/-/body-parser-1.19.0.tgz",
@@ -10524,6 +10538,11 @@
         "ee-first": "1.1.1"
       }
     },
+    "on-headers": {
+      "version": "1.0.2",
+      "resolved": "https://registry.npmjs.org/on-headers/-/on-headers-1.0.2.tgz",
+      "integrity": "sha512-pZAE+FJLoyITytdqK0U5s+FIpjN0JP3OzFi/u8Rx+EV5/W+JTWGXG8xFzevE7AjBfDqHv/8vL8qQsIhHnqRkrA=="
+    },
     "once": {
       "version": "1.4.0",
       "resolved": "https://registry.npmjs.org/once/-/once-1.4.0.tgz",
@@ -10544,8 +10563,7 @@
     "optional": {
       "version": "0.1.4",
       "resolved": "https://registry.npmjs.org/optional/-/optional-0.1.4.tgz",
-      "integrity": "sha512-gtvrrCfkE08wKcgXaVwQVgwEQ8vel2dc5DDBn9RLQZ3YtmtkBss6A2HY6BnJH4N/4Ku97Ri/SF8sNWE2225WJw==",
-      "dev": true
+      "integrity": "sha512-gtvrrCfkE08wKcgXaVwQVgwEQ8vel2dc5DDBn9RLQZ3YtmtkBss6A2HY6BnJH4N/4Ku97Ri/SF8sNWE2225WJw=="
     },
     "optionator": {
       "version": "0.8.3",
@@ -11087,6 +11105,14 @@
       "resolved": "https://registry.npmjs.org/process-nextick-args/-/process-nextick-args-2.0.1.tgz",
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     },
+    "prom-client": {
+      "version": "12.0.0",
+      "resolved": "https://registry.npmjs.org/prom-client/-/prom-client-12.0.0.tgz",
+      "integrity": "sha512-JbzzHnw0VDwCvoqf8y1WDtq4wSBAbthMB1pcVI/0lzdqHGJI3KBJDXle70XK+c7Iv93Gihqo0a5LlOn+g8+DrQ==",
+      "requires": {
+        "tdigest": "^0.1.1"
+      }
+    },
     "promise-inflight": {
       "version": "1.0.1",
       "resolved": "https://registry.npmjs.org/promise-inflight/-/promise-inflight-1.0.1.tgz",
@@ -11465,6 +11491,15 @@
       "integrity": "sha1-LGN/53yJOv0qZj/iGqkIAGjiBSo=",
       "dev": true
     },
+    "response-time": {
+      "version": "2.3.2",
+      "resolved": "https://registry.npmjs.org/response-time/-/response-time-2.3.2.tgz",
+      "integrity": "sha1-/6cbq5UtYvfB1Jt0NDVfvGjf/Fo=",
+      "requires": {
+        "depd": "~1.1.0",
+        "on-headers": "~1.0.1"
+      }
+    },
     "restore-cursor": {
       "version": "3.1.0",
       "resolved": "https://registry.npmjs.org/restore-cursor/-/restore-cursor-3.1.0.tgz",
@@ -12483,6 +12518,14 @@
         }
       }
     },
+    "tdigest": {
+      "version": "0.1.1",
+      "resolved": "https://registry.npmjs.org/tdigest/-/tdigest-0.1.1.tgz",
+      "integrity": "sha1-Ljyyw56kSeVdHmzZEReszKRYgCE=",
+      "requires": {
+        "bintrees": "1.0.1"
+      }
+    },
     "terminal-link": {
       "version": "2.1.1",
       "resolved": "https://registry.npmjs.org/terminal-link/-/terminal-link-2.1.1.tgz",
@@ -13312,6 +13355,11 @@
       "integrity": "sha1-2pN/emLiH+wf0Y1Js1wpNQZ6bHI=",
       "dev": true
     },
+    "url-value-parser": {
+      "version": "2.0.1",
+      "resolved": "https://registry.npmjs.org/url-value-parser/-/url-value-parser-2.0.1.tgz",
+      "integrity": "sha512-bexECeREBIueboLGM3Y1WaAzQkIn+Tca/Xjmjmfd0S/hFHSCEoFkNh0/D0l9G4K74MkEP/lLFRlYnxX3d68Qgw=="
+    },
     "use": {
       "version": "3.1.1",
       "resolved": "https://registry.npmjs.org/use/-/use-3.1.1.tgz",

package.json

@@ -23,6 +23,7 @@
     "test:e2e": "jest --config ./apps/listory/test/jest-e2e.json"
   },
   "dependencies": {
+    "@digikare/nestjs-prom": "^1.0.0",
     "@hapi/joi": "17.1.1",
     "@nestjs/common": "7.5.2",
     "@nestjs/config": "0.5.0",

src/app.module.ts

@@ -9,6 +9,7 @@ import { DatabaseModule } from "./database/database.module";
 import { HealthCheckModule } from "./health-check/health-check.module";
 import { ListensModule } from "./listens/listens.module";
 import { LoggerModule } from "./logger/logger.module";
+import { MetricsModule } from "./metrics/metrics.module";
 import { MusicLibraryModule } from "./music-library/music-library.module";
 import { ReportsModule } from "./reports/reports.module";
 import { SourcesModule } from "./sources/sources.module";
@@ -25,6 +26,7 @@ import { UsersModule } from "./users/users.module";
       exclude: ["/api*"],
     }),
     RavenModule,
+    MetricsModule.forRoot(),
     AuthModule,
     UsersModule,
     SourcesModule,

src/config/config.module.ts

@@ -42,6 +42,9 @@ import { ConfigModule as NestConfigModule } from "@nestjs/config";
           is: Joi.valid(true),
           then: Joi.required(),
         }),
+
+        // Prometheus for Metrics (Optional)
+        PROMETHEUS_ENABLED: Joi.boolean().default(false),
       }),
     }),
   ],

src/metrics/metrics.module.ts

@@ -0,0 +1,51 @@
+import { InboundMiddleware, PromModule } from "@digikare/nestjs-prom";
+import { DEFAULT_PROM_OPTIONS } from "@digikare/nestjs-prom/dist/prom.constants";
+import {
+  DynamicModule,
+  MiddlewareConsumer,
+  Module,
+  NestModule,
+} from "@nestjs/common";
+
+// Dirty hack because we can not conditionally import modules based on
+// injected services and upstream module does not support dynamic configuration
+//
+// https://github.com/digikare/nestjs-prom/issues/27
+const promEnabled = process.env.PROMETHEUS_ENABLED === "true";
+
+@Module({})
+export class MetricsModule implements NestModule {
+  static forRoot(): DynamicModule {
+    const module = {
+      imports: [],
+      providers: [],
+    };
+    if (promEnabled) {
+      const promOptions = {
+        metricPath: "/api/metrics",
+        withDefaultsMetrics: true,
+        withDefaultController: true,
+      };
+
+      module.imports.push(PromModule.forRoot(promOptions));
+
+      module.providers.push({
+        provide: DEFAULT_PROM_OPTIONS,
+        useValue: promOptions,
+      });
+    }
+
+    return {
+      module: MetricsModule,
+      ...module,
+    };
+  }
+
+  configure(consumer: MiddlewareConsumer) {
+    if (promEnabled) {
+      // We register the Middleware ourselves to avoid tracking
+      // latency for static files served for the frontend.
+      consumer.apply(InboundMiddleware).forRoutes("/api");
+    }
+  }
+}