Refactor VPN proxy client implementation

src/server/prometheusMetrics.ts

@@ -0,0 +1,177 @@
+import type { ServerResponse } from 'node:http';
+
+const COUNTER_PATTERN = /^\d+$/;
+
+const labelValue = (value: unknown) => String(value ?? '')
+  .replaceAll('\\', '\\\\')
+  .replaceAll('\n', '\\n')
+  .replaceAll('"', '\\"');
+
+const labels = (values: Record<string, unknown>) => Object.entries(values)
+  .map(([key, value]) => `${key}="${labelValue(value)}"`)
+  .join(',');
+
+function record(value: unknown): Record<string, unknown> {
+  return value && typeof value === 'object' && !Array.isArray(value)
+    ? value as Record<string, unknown>
+    : {};
+}
+
+function counter(value: unknown) {
+  const decimal = String(value ?? '');
+  if (!COUNTER_PATTERN.test(decimal)) throw new Error(`Invalid Prometheus counter: ${decimal}`);
+  return decimal;
+}
+
+function timestamp(value: unknown) {
+  const milliseconds = Date.parse(String(value ?? ''));
+  return Number.isFinite(milliseconds) ? String(milliseconds / 1000) : null;
+}
+
+function metric(
+  lines: string[],
+  name: string,
+  metricLabels: Record<string, unknown>,
+  value: unknown,
+) {
+  lines.push(`${name}{${labels(metricLabels)}} ${value}`);
+}
+
+export function renderPrometheusMetrics(value: unknown) {
+  const snapshot = record(value);
+  const traffic = record(snapshot.traffic);
+  const lines = [
+    '# HELP harbor_traffic_bytes_total Total traffic accounted by Harbor.',
+    '# TYPE harbor_traffic_bytes_total counter',
+  ];
+  metric(lines, 'harbor_traffic_bytes_total', { source: 'gateway' }, counter(traffic.gatewayBytes));
+  metric(lines, 'harbor_traffic_bytes_total', { source: 'proxy' }, counter(traffic.proxyBytes));
+
+  const globalFreshness = [
+    ['gateway', traffic.gatewayObservedAt],
+    ['proxy', traffic.proxyObservedAt],
+  ].map(([source, observedAt]) => [source, timestamp(observedAt)] as const).filter(([, observedAt]) => observedAt);
+  if (globalFreshness.length) {
+    lines.push(
+      '# HELP harbor_traffic_last_observed_timestamp_seconds Unix timestamp of the last successful Harbor traffic observation.',
+      '# TYPE harbor_traffic_last_observed_timestamp_seconds gauge',
+    );
+    for (const [source, observedAt] of globalFreshness) {
+      metric(lines, 'harbor_traffic_last_observed_timestamp_seconds', { source }, observedAt);
+    }
+  }
+
+  const devices = Array.isArray(snapshot.devices) ? snapshot.devices.map(record) : [];
+  if (devices.length) {
+    lines.push(
+      '# HELP harbor_device_info Current Harbor device identity metadata.',
+      '# TYPE harbor_device_info gauge',
+    );
+    for (const device of devices) {
+      metric(lines, 'harbor_device_info', {
+        device_id: device.id,
+        name: device.alias || device.hostname || device.ip || device.id,
+        ip: device.ip || '',
+      }, '1');
+    }
+  }
+
+  const deviceTraffic = devices.flatMap((device) => [
+    timestamp(device.trafficObservedAt)
+      ? { device, source: 'gateway', observedAt: timestamp(device.trafficObservedAt), uploadBytes: device.uploadBytes, downloadBytes: device.downloadBytes }
+      : null,
+    timestamp(device.proxyTrafficObservedAt)
+      ? { device, source: 'proxy', observedAt: timestamp(device.proxyTrafficObservedAt), uploadBytes: device.proxyUploadBytes, downloadBytes: device.proxyDownloadBytes }
+      : null,
+  ].filter((entry): entry is NonNullable<typeof entry> => entry !== null));
+  if (deviceTraffic.length) {
+    lines.push(
+      '# HELP harbor_device_traffic_bytes_total Total traffic accounted by Harbor for a device.',
+      '# TYPE harbor_device_traffic_bytes_total counter',
+    );
+    for (const { device, source, uploadBytes, downloadBytes } of deviceTraffic) {
+      metric(lines, 'harbor_device_traffic_bytes_total', {
+        device_id: device.id,
+        source,
+        direction: 'download',
+      }, counter(downloadBytes));
+      metric(lines, 'harbor_device_traffic_bytes_total', {
+        device_id: device.id,
+        source,
+        direction: 'upload',
+      }, counter(uploadBytes));
+    }
+
+    lines.push(
+      '# HELP harbor_device_traffic_last_observed_timestamp_seconds Unix timestamp of the last successful device traffic observation.',
+      '# TYPE harbor_device_traffic_last_observed_timestamp_seconds gauge',
+    );
+    for (const { device, source, observedAt } of deviceTraffic) {
+      metric(lines, 'harbor_device_traffic_last_observed_timestamp_seconds', {
+        device_id: device.id,
+        source,
+      }, observedAt);
+    }
+  }
+
+  const domainTraffic = record(snapshot.domainTraffic);
+  const domainSeries = Array.isArray(domainTraffic.series) ? domainTraffic.series.map(record) : [];
+  if (domainSeries.length) {
+    lines.push(
+      '# HELP harbor_device_domain_traffic_bytes_total Traffic observed by sing-box for a device and domain.',
+      '# TYPE harbor_device_domain_traffic_bytes_total counter',
+    );
+    for (const series of domainSeries) {
+      for (const [direction, value] of [
+        ['download', series.downloadBytes],
+        ['upload', series.uploadBytes],
+      ]) {
+        metric(lines, 'harbor_device_domain_traffic_bytes_total', {
+          device_id: series.deviceId,
+          domain: series.domain,
+          service: series.service,
+          source: series.source,
+          direction,
+        }, counter(value));
+      }
+    }
+  }
+  const domainObservedAt = timestamp(domainTraffic.observedAt);
+  if (domainObservedAt) {
+    lines.push(
+      '# HELP harbor_domain_traffic_last_observed_timestamp_seconds Unix timestamp of the last successful sing-box connection observation.',
+      '# TYPE harbor_domain_traffic_last_observed_timestamp_seconds gauge',
+    );
+    lines.push(`harbor_domain_traffic_last_observed_timestamp_seconds ${domainObservedAt}`);
+  }
+  if (domainTraffic.overflowConnections != null) {
+    lines.push(
+      '# HELP harbor_domain_traffic_overflow_connections_total Connections aggregated after the domain series limit was reached.',
+      '# TYPE harbor_domain_traffic_overflow_connections_total counter',
+    );
+    lines.push(`harbor_domain_traffic_overflow_connections_total ${counter(domainTraffic.overflowConnections)}`);
+  }
+  const attributionEvents = record(domainTraffic.attributionEvents);
+  if (domainTraffic.attributionEvents) {
+    lines.push(
+      '# HELP harbor_domain_traffic_attribution_events_total Connections with incomplete Harbor domain attribution.',
+      '# TYPE harbor_domain_traffic_attribution_events_total counter',
+    );
+    for (const outcome of ['unresolved_host', 'unknown_device', 'unsupported_source']) {
+      metric(
+        lines,
+        'harbor_domain_traffic_attribution_events_total',
+        { outcome },
+        counter(attributionEvents[outcome]),
+      );
+    }
+  }
+
+  return `${lines.join('\n')}\n`;
+}
+
+export function sendPrometheusMetrics(res: ServerResponse, snapshot: unknown) {
+  const body = renderPrometheusMetrics(snapshot);
+  res.writeHead(200, { 'content-type': 'text/plain; version=0.0.4; charset=utf-8' });
+  res.end(body);
+}