unify name prefix of metrics exposed using promclient

Change the prefix to reflect the "new" name of the service. May be this even should be configurable at some point.

This is a breaking change.

src/createApp.js

@@ -26,7 +26,7 @@ import { viteManifestToDeps } from './util.js'
 const swaggerDocument = yaml.load(fs.readFileSync('./src/swagger.yaml', 'utf8'))
 
 const startUpTimeGauge = new promClient.Gauge({
-  name: 'manifest_service_startup_time',
+  name: 'core_ui_middleware_startup_time',
   help: 'Time to warm up cache'
 })
 

src/files.js

@@ -24,13 +24,24 @@ async function fetchData (path, baseUrl, appendix) {
 }
 
 const fileCounter = new promClient.Counter({
-  name: 'manifest_service_file_cache_fetches',
+  name: 'core_ui_middleware_file_cache_fetches',
   help: 'Number of fetched files'
 })
 const fileErrorCounter = new promClient.Counter({
-  name: 'manifest_service_file_cache_fetch_errors',
+  name: 'core_ui_middleware_file_cache_fetch_errors',
   help: 'Number of errors while fetching files'
 })
+
+const pullThroughRequestCounter = new promClient.Counter({
+  name: 'core_ui_middleware_file_cache_pull_through_request_count',
+  help: 'Number of files requested after warmup (not referenced in manifest)'
+})
+
+const pullThroughCacheCounter = new promClient.Counter({
+  name: 'core_ui_middleware_file_cache_pull_through_cache_size',
+  help: 'Number of files added after warmup (not referenced in manifest)'
+})
+
 class FileCache {
   constructor () {
     this._cache = {}
@@ -47,6 +58,8 @@ class FileCache {
     this._isCaching = true
 
     logger.debug('beginning to warm up cache')
+    pullThroughCacheCounter.reset()
+    pullThroughRequestCounter.reset()
     const cache = Object.fromEntries(await (async function () {
       const files = Object.keys(deps)
       const chunkSize = 50
@@ -91,10 +104,12 @@ class FileCache {
 
   async fetchAndStore (path) {
     if (config.urls.length === 0) await config.load()
+    pullThroughRequestCounter.inc()
     const [[key, value]] =
       (await Promise.allSettled(config.urls.map(baseUrl => fetchData(path, baseUrl))))
         .filter(r => r.status === 'fulfilled').map(r => r.value)
     this._cache[key.slice(1)] = value
+    pullThroughCacheCounter.inc()
     return value
   }