feat(core): Add Prometheus metrics for n8n events and api invocations (experimental) (#5177)

* create prometheus metrics from events

* feat(core): Add more Prometheus metrics (experimental) (#5187)

* refactor(core): Add Prometheus labels to relevant metrics

* feat(core): Add more Prometheus metrics (experimental)

* add 'v' prefix to value of version label

Co-authored-by: Cornelius Suermann <cornelius@n8n.io>

packages/cli/src/eventbus/MessageEventBusDestination/Helpers.ee.ts

@@ -1,6 +1,13 @@
 /* eslint-disable import/no-cycle */
-import { MessageEventBusDestinationTypeNames } from 'n8n-workflow';
 import type { EventDestinations } from '@/databases/entities/MessageEventBusDestinationEntity';
+import { promClient } from '@/metrics';
+import {
+	EventMessageTypeNames,
+	LoggerProxy,
+	MessageEventBusDestinationTypeNames,
+} from 'n8n-workflow';
+import config from '../../config';
+import type { EventMessageTypes } from '../EventMessageClasses';
 import type { MessageEventBusDestination } from './MessageEventBusDestination.ee';
 import { MessageEventBusDestinationSentry } from './MessageEventBusDestinationSentry.ee';
 import { MessageEventBusDestinationSyslog } from './MessageEventBusDestinationSyslog.ee';
@@ -24,3 +31,85 @@ export function messageEventBusDestinationFromDb(
 	}
 	return null;
 }
+
+const prometheusCounters: Record<string, promClient.Counter<string> | null> = {};
+
+function getMetricNameForEvent(event: EventMessageTypes): string {
+	const prefix = config.getEnv('endpoints.metrics.prefix');
+	return prefix + event.eventName.replace('n8n.', '').replace(/\./g, '_') + '_total';
+}
+
+function getLabelValueForNode(nodeType: string): string {
+	return nodeType.replace('n8n-nodes-', '').replace(/\./g, '_');
+}
+
+function getLabelValueForCredential(credentialType: string): string {
+	return credentialType.replace(/\./g, '_');
+}
+
+function getLabelsForEvent(event: EventMessageTypes): Record<string, string> {
+	switch (event.__type) {
+		case EventMessageTypeNames.audit:
+			if (event.eventName.startsWith('n8n.audit.user.credentials')) {
+				return config.getEnv('endpoints.metrics.includeCredentialTypeLabel')
+					? {
+							credential_type: getLabelValueForCredential(
+								event.payload.credentialType ?? 'unknown',
+							),
+					  }
+					: {};
+			}
+
+			if (event.eventName.startsWith('n8n.audit.workflow')) {
+				return config.getEnv('endpoints.metrics.includeWorkflowIdLabel')
+					? { workflow_id: event.payload.workflowId?.toString() ?? 'unknown' }
+					: {};
+			}
+			break;
+
+		case EventMessageTypeNames.node:
+			return config.getEnv('endpoints.metrics.includeNodeTypeLabel')
+				? { node_type: getLabelValueForNode(event.payload.nodeType ?? 'unknown') }
+				: {};
+
+		case EventMessageTypeNames.workflow:
+			return config.getEnv('endpoints.metrics.includeWorkflowIdLabel')
+				? { workflow_id: event.payload.workflowId?.toString() ?? 'unknown' }
+				: {};
+	}
+
+	return {};
+}
+
+function getCounterSingletonForEvent(event: EventMessageTypes) {
+	if (!prometheusCounters[event.eventName]) {
+		const metricName = getMetricNameForEvent(event);
+
+		if (!promClient.validateMetricName(metricName)) {
+			LoggerProxy.debug(`Invalid metric name: ${metricName}. Ignoring it!`);
+			prometheusCounters[event.eventName] = null;
+			return null;
+		}
+
+		const counter = new promClient.Counter({
+			name: metricName,
+			help: `Total number of ${event.eventName} events.`,
+			labelNames: Object.keys(getLabelsForEvent(event)),
+		});
+
+		promClient.register.registerMetric(counter);
+		prometheusCounters[event.eventName] = counter;
+	}
+
+	return prometheusCounters[event.eventName];
+}
+
+export async function incrementPrometheusMetric(event: EventMessageTypes): Promise<void> {
+	const counter = getCounterSingletonForEvent(event);
+
+	if (!counter) {
+		return;
+	}
+
+	counter.inc(getLabelsForEvent(event));
+}