Instrument the subfunctions of warmServer with datadog (#16854)

Co-authored-by: James M. Greene <JamesMGreene@github.com>

lib/warm-server.js

@@ -4,6 +4,16 @@ const loadRedirects = require('./redirects/precompile')
 const loadSiteData = require('./site-data')
 const loadSiteTree = require('./site-tree')
 
+// Instrument these functions so that
+// it's wrapped in a timer that reports to Datadog
+const dog = {
+  loadPages: statsd.asyncTimer(loadPages, 'load_pages'),
+  loadPageMap: statsd.asyncTimer(loadPageMap, 'load_page_map'),
+  loadRedirects: statsd.asyncTimer(loadRedirects, 'load_redirects'),
+  loadSiteData: statsd.asyncTimer(loadSiteData, 'load_site_data'),
+  loadSiteTree: statsd.asyncTimer(loadSiteTree, 'load_site_tree')
+}
+
 // For local caching
 let pageList, pageMap, site, redirects, siteTree
 
@@ -32,21 +42,21 @@ async function warmServer () {
   if (!pageList || !site) {
     // Promise.all is used to load multiple things in parallel
     [pageList, site] = await Promise.all([
-      pageList || loadPages(),
-      site || loadSiteData()
+      pageList || dog.loadPages(),
+      site || dog.loadSiteData()
     ])
   }
 
   if (!pageMap) {
-    pageMap = await loadPageMap(pageList)
+    pageMap = await dog.loadPageMap(pageList)
   }
 
   if (!redirects) {
-    redirects = await loadRedirects(pageList, pageMap)
+    redirects = await dog.loadRedirects(pageList, pageMap)
   }
 
   if (!siteTree) {
-    siteTree = await loadSiteTree(pageMap, site, redirects)
+    siteTree = await dog.loadSiteTree(pageMap, site, redirects)
   }
 
   if (process.env.NODE_ENV !== 'test') {
@@ -58,7 +68,7 @@ async function warmServer () {
 
 // Instrument the `warmServer` function so that
 // it's wrapped in a timer that reports to Datadog
-const instrumentedWarmServer = statsd.asyncTimer(warmServer, 'warm_server')
+dog.warmServer = statsd.asyncTimer(warmServer, 'warm_server')
 
 // We only want statistics if the priming needs to occur, so let's wrap the
 // real method and return early [without statistics] whenever possible
@@ -68,5 +78,5 @@ module.exports = async function warmServerWrapper () {
     return getWarmedCache()
   }
 
-  return instrumentedWarmServer()
+  return dog.warmServer()
 }