switch metrics to express-prom-metrics

bskylink/package.json

@@ -10,7 +10,8 @@
   "dependencies": {
     "@atproto/api": "^0.16.7",
     "@atproto/common": "^0.4.11",
-    "@haileyok/ts-util": "^1.3.4",
+    "express-prom-bundle": "^7.0.0",
+    "prom-client": "^15.1.3",
     "@types/escape-html": "^1.0.4",
     "body-parser": "^1.20.2",
     "cors": "^2.8.5",

bskylink/src/cache/safelinkClient.ts

@@ -50,12 +50,8 @@ export class SafelinkClient {
       const end = process.hrtime.bigint()
       const respTimeMs = Number(end - start) / 1_000_000 // ns to ms :3
 
-      this.ctx.metrics
+      this.ctx.safeLinkLookups.labels(status, cached ? 'yes' : 'no').inc()
-        .getCounter('safeLinkLookups')
+      this.ctx.safeLinkLookupDuration
-        .labels(status, cached ? 'yes' : 'no')
-        .inc()
-      this.ctx.metrics
-        .getHistogram('safeLinkLookupDuration')
         .labels(status, cached ? 'yes' : 'no')
         .observe(respTimeMs)
     }

bskylink/src/context.ts

@@ -1,4 +1,4 @@
-import {type MetricConfig, Metrics} from '@haileyok/ts-util'
+import {Counter, Histogram} from 'prom-client'
 
 import {SafelinkClient} from './cache/safelinkClient.js'
 import {type Config} from './config.js'
@@ -9,63 +9,39 @@ export type AppContextOptions = {
   db: Database
 }
 
-type BlinkMetricNames =
-  | 'requestDuration'
-  | 'redirects'
-  | 'shortLinkRequests'
-  | 'safeLinkLookups'
-  | 'safeLinkLookupDuration'
-
-type BlinkMetricConfig = Record<BlinkMetricNames, MetricConfig>
-
 export class AppContext {
   cfg: Config
   db: Database
-  metrics: Metrics<BlinkMetricConfig>
   safelinkClient: SafelinkClient
   abortController = new AbortController()
 
+  // Custom business metrics
+  shortLinkRequests = new Counter({
+    name: 'blink_short_link_requests_total',
+    help: 'Number of short link requests handled',
+    labelNames: ['method', 'status_code'],
+  })
+
+  redirects = new Counter({
+    name: 'blink_redirects_total',
+    help: 'Number of link redirects handled',
+    labelNames: ['safelink_rule', 'status_code'],
+  })
+
+  safeLinkLookups = new Counter({
+    name: 'blink_safe_link_lookups_total',
+    help: 'Number of safelink lookups handled',
+    labelNames: ['status', 'cached'],
+  })
+
+  safeLinkLookupDuration = new Histogram({
+    name: 'blink_safe_link_lookup_duration_milliseconds',
+    help: 'Safelink lookup duration in milliseconds',
+    labelNames: ['status', 'cached'],
+    buckets: [0.005, 0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1, 2.5, 5, 10],
+  })
+
   constructor(private opts: AppContextOptions) {
-    const metricsConfig: BlinkMetricConfig = {
-      requestDuration: {
-        type: 'histogram',
-        name: 'request_duration_millis',
-        help: 'Request duration in millis',
-        labelNames: ['path', 'method', 'code'],
-        buckets: [0.005, 0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1, 2.5, 5, 10],
-      },
-      redirects: {
-        type: 'counter',
-        name: 'redirects',
-        help: 'Number of link redirects handled',
-        labelNames: ['safelink_rule', 'code'],
-      },
-      shortLinkRequests: {
-        type: 'counter',
-        name: 'shortlink_requests',
-        help: 'Number of shortlink requests handled',
-        labelNames: ['method', 'code'],
-      },
-      safeLinkLookups: {
-        type: 'counter',
-        name: 'safelink_lookups',
-        help: 'Number of safelink lookups handled',
-        labelNames: ['status', 'cached'],
-      },
-      safeLinkLookupDuration: {
-        type: 'histogram',
-        name: 'safelink_lookup_duration_millis',
-        help: 'Request duration in millis',
-        labelNames: ['status', 'cached'],
-        buckets: [0.005, 0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1, 2.5, 5, 10],
-      },
-    }
-
-    this.metrics = new Metrics(metricsConfig, {
-      prefix: 'blink_',
-      collectDefaultMetrics: true,
-    })
-
     this.cfg = this.opts.cfg
     this.db = this.opts.db
     this.safelinkClient = new SafelinkClient(this)

bskylink/src/index.ts

@@ -3,7 +3,9 @@ import type http from 'node:http'
 
 import cors from 'cors'
 import express from 'express'
+import promBundle from 'express-prom-bundle'
 import {createHttpTerminator, type HttpTerminator} from 'http-terminator'
+import {register} from 'prom-client'
 
 import {type Config} from './config.js'
 import {AppContext} from './context.js'
@@ -31,10 +33,28 @@ export class LinkService {
     app.use(i18n.init)
 
     const ctx = await AppContext.fromConfig(cfg)
-    app = routes(ctx, app)
-    app.use(errorHandler)
 
-    ctx.metrics.registerExpressMetrics(app)
+    // Add Prometheus middleware for automatic HTTP instrumentation
+    const metricsMiddleware = promBundle({
+      includeMethod: true,
+      includePath: true,
+      includeStatusCode: true,
+      includeUp: true,
+      promClient: {
+        collectDefaultMetrics: {},
+      },
+      autoregister: false,
+      normalizePath: req => {
+        if (req.route) {
+          return req.route.path
+        }
+        return '<unmatched>'
+      },
+    })
+    app.use(metricsMiddleware)
+
+    routes(ctx, app)
+    app.use(errorHandler)
 
     return new LinkService(app, ctx)
   }
@@ -50,8 +70,8 @@ export class LinkService {
     const metricsApp = express()
     metricsApp.get('/metrics', async (_req, res) => {
       try {
-        const metrics = await this.ctx.metrics.getRegistry().metrics()
+        const metrics = await register.metrics()
-        res.set('Content-Type', this.ctx.metrics.getRegistry().contentType)
+        res.set('Content-Type', register.contentType)
         res.end(metrics)
       } catch (error) {
         res.status(500).end('Error collecting metrics')

bskylink/src/routes/createShortLink.ts

@@ -14,10 +14,7 @@ export default function (ctx: AppContext, app: Express) {
     bodyParser.json(),
     handler(async (req, res) => {
       const addMetrics = (statusCode: number) => {
-        ctx.metrics
+        ctx.shortLinkRequests.labels('POST', statusCode.toString()).inc()
-          .getCounter('shortLinkRequests')
-          .labels('POST', statusCode.toString())
-          .inc()
       }
 
       let path: string

bskylink/src/routes/redirect.ts

@@ -20,10 +20,7 @@ export default function (ctx: AppContext, app: Express) {
     '/redirect',
     handler(async (req, res) => {
       const addMetrics = (ruleStr: string, statusCode: number) => {
-        ctx.metrics
+        ctx.redirects.labels(ruleStr, statusCode.toString()).inc()
-          .getCounter('redirects')
-          .labels(ruleStr, statusCode.toString())
-          .inc()
       }
 
       let link = req.query.u

bskylink/src/routes/shortLink.ts

@@ -11,10 +11,7 @@ export default function (ctx: AppContext, app: Express) {
     '/:linkId',
     handler(async (req, res) => {
       const addMetrics = (statusCode: number) => {
-        ctx.metrics
+        ctx.shortLinkRequests.labels('GET', statusCode.toString()).inc()
-          .getCounter('shortLinkRequests')
-          .labels('GET', statusCode.toString())
-          .inc()
       }
 
       const linkId = req.params.linkId