✨ Add metrics endpoint (#1515)

This commit adds the new package prom-client in order to expose metrics
to prometheus as well as the endpoint and the configuration to do so.

packages/cli/config/index.ts

@@ -446,6 +446,20 @@ const config = convict({
 	},
 
 	endpoints: {
+		metrics: {
+			enable: {
+				format: 'Boolean',
+				default: false,
+				env: 'N8N_ENABLE_METRICS',
+				doc: 'Enable metrics endpoint',
+			},
+			prefix: {
+				format: String,
+				default: 'n8n_',
+				env: 'N8N_METRICS_PREFIX',
+				doc: 'An optional prefix for metric names. Default: n8n_',
+			},
+		},
 		rest: {
 			format: String,
 			default: 'rest',
@@ -471,7 +485,7 @@ const config = convict({
 			doc: 'Disable production webhooks from main process. This helps ensures no http traffic load to main process when using webhook-specific processes.',
 		},
 		skipWebhoooksDeregistrationOnShutdown: {
-			/** 
+			/**
 			 * Longer explanation: n8n deregisters webhooks on shutdown / deactivation
 			 * and registers on startup / activation. If we skip
 			 * deactivation on shutdown, webhooks will remain active on 3rd party services.

packages/cli/package.json

@@ -111,6 +111,7 @@
         "oauth-1.0a": "^2.2.6",
         "open": "^7.0.0",
         "pg": "^8.3.0",
+        "prom-client": "^13.1.0",
         "request-promise-native": "^1.0.7",
         "sqlite3": "^5.0.1",
         "sse-channel": "^3.1.1",

packages/cli/src/Server.ts

@@ -23,6 +23,7 @@ import * as csrf from 'csrf';
 import * as requestPromise from 'request-promise-native';
 import { createHmac } from 'crypto';
 import { compare } from 'bcryptjs';
+import * as promClient from 'prom-client';
 
 import {
 	ActiveExecutions,
@@ -108,6 +109,7 @@ import * as parseUrl from 'parseurl';
 import * as querystring from 'querystring';
 import * as Queue from '../src/Queue';
 import { OptionsWithUrl } from 'request-promise-native';
+import { Registry } from 'prom-client';
 
 class App {
 
@@ -197,6 +199,16 @@ class App {
 
 	async config(): Promise<void> {
 
+		const enableMetrics = config.get('endpoints.metrics.enable') as boolean;
+		let register: Registry;
+
+		if (enableMetrics === true) {
+			const prefix = config.get('endpoints.metrics.prefix') as string;
+			register = new promClient.Registry();
+			register.setDefaultLabels({ prefix });
+			promClient.collectDefaultMetrics({ register });
+		}
+
 		this.versions = await GenericHelpers.getVersions();
 		this.frontendSettings.versionCli = this.versions.cli;
 
@@ -204,7 +216,7 @@ class App {
 
 		const excludeEndpoints = config.get('security.excludeEndpoints') as string;
 
-		const ignoredEndpoints = ['healthz', this.endpointWebhook, this.endpointWebhookTest, this.endpointPresetCredentials];
+		const ignoredEndpoints = ['healthz', 'metrics', this.endpointWebhook, this.endpointWebhookTest, this.endpointPresetCredentials];
 		ignoredEndpoints.push.apply(ignoredEndpoints, excludeEndpoints.split(':'));
 
 		const authIgnoreRegex = new RegExp(`^\/(${_(ignoredEndpoints).compact().join('|')})\/?.*$`);
@@ -386,7 +398,7 @@ class App {
 		this.app.use(history({
 			rewrites: [
 				{
-					from: new RegExp(`^\/(${this.restEndpoint}|healthz|css|js|${this.endpointWebhook}|${this.endpointWebhookTest})\/?.*$`),
+					from: new RegExp(`^\/(${this.restEndpoint}|healthz|metrics|css|js|${this.endpointWebhook}|${this.endpointWebhookTest})\/?.*$`),
 					to: (context) => {
 						return context.parsedUrl!.pathname!.toString();
 					},
@@ -454,7 +466,16 @@ class App {
 			ResponseHelper.sendSuccessResponse(res, responseData, true, 200);
 		});
 
-
+		// ----------------------------------------
+		// Metrics
+		// ----------------------------------------
+		if (enableMetrics === true) {
+			this.app.get('/metrics', async (req: express.Request, res: express.Response) => {
+				const response = await register.metrics();
+				res.setHeader('Content-Type', register.contentType);
+				ResponseHelper.sendSuccessResponse(res, response, true, 200);
+			});
+		}
 
 		// ----------------------------------------
 		// Workflow
@@ -1728,7 +1749,7 @@ class App {
 						stoppedAt: result.stoppedAt ?  new Date(result.stoppedAt) : undefined,
 						finished: result.finished,
 					};
-	
+
 					return returnData;
 				}