separating v4 router instrumentation to its own addhook

Author: crysmags

packages/datadog-instrumentations/src/express.js

@@ -60,16 +60,23 @@ function wrapResponseRender (render) {
 addHook({ name: 'express', versions: ['>=4'] }, express => {
   shimmer.wrap(express.application, 'handle', wrapHandle)
 
-  shimmer.wrap(express.Router, 'use', wrapRouterMethod)
-  shimmer.wrap(express.Router, 'route', wrapRouterMethod)
-
   shimmer.wrap(express.response, 'json', wrapResponseJson)
   shimmer.wrap(express.response, 'jsonp', wrapResponseJson)
   shimmer.wrap(express.response, 'render', wrapResponseRender)
 
   return express
 })
 
+// Express 5 does not rely on router in the same way as v4 and should not be instrumented anymore.
+// It would otherwise produce spans for router and express, and so duplicating them.
+// We now fall back to router instrumentation
+addHook({ name: 'express', versions: ['4'] }, express => {
+  shimmer.wrap(express.Router, 'use', wrapRouterMethod)
+  shimmer.wrap(express.Router, 'route', wrapRouterMethod)
+
+  return express
+})
+
 const queryParserReadCh = channel('datadog:query:read:finish')
 
 function publishQueryParsedAndNext (req, res, next) {