Emit heap/RSS gauges on every healthcheck hit (#60227)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: heiskr

src/frame/middleware/healthcheck.ts

@@ -1,5 +1,6 @@
 import express from 'express'
 import { noCacheControl } from './cache-control'
+import statsd from '@/observability/lib/statsd'
 
 const router = express.Router()
 
@@ -12,6 +13,12 @@ const router = express.Router()
 router.get('/', function healthcheck(req, res) {
   noCacheControl(res)
 
+  const mem = process.memoryUsage()
+  statsd.gauge('memory_heap_used', mem.heapUsed, ['event:healthcheck'])
+  statsd.gauge('memory_heap_total', mem.heapTotal, ['event:healthcheck'])
+  statsd.gauge('memory_rss', mem.rss, ['event:healthcheck'])
+  statsd.gauge('memory_external', mem.external, ['event:healthcheck'])
+
   res.sendStatus(200)
 })