Add a workaround to avoid conflicts with NewRelic

lib/server-app.js

@@ -161,7 +161,15 @@ proto.middleware = function(name, paths, handler) {
 
   this._skipLayerSorting = true;
   this.use(paths, handler);
-  this._router.stack[this._router.stack.length - 1].phase = fullPhaseName;
+
+  var layer = this._findLayerByHandler(handler);
+  if (layer) {
+    // Set the phase name for sorting
+    layer.phase = fullPhaseName;
+  } else {
+    debug('No matching layer is found for %s %s', fullPhaseName, handlerName);
+  }
+
   this._skipLayerSorting = false;
 
   this._sortLayersByPhase();
@@ -169,6 +177,35 @@ proto.middleware = function(name, paths, handler) {
   return this;
 };
 
+/*
+ * Find the corresponding express layer by handler
+ *
+ * This is needed because monitoring agents such as NewRelic can add handlers
+ * to the stack. For example, NewRelic adds sentinel handler. We need to search
+ * the stackto find the correct layer.
+ */
+proto._findLayerByHandler = function(handler) {
+  // Other handlers can be added to the stack, for example,
+  // NewRelic adds sentinel handler. We need to search the stack
+  for (var k = this._router.stack.length - 1; k >= 0; k--) {
+    if (this._router.stack[k].handle === handler ||
+      // NewRelic replaces the handle and keeps it as __NR_original
+      this._router.stack[k].handle['__NR_original'] === handler
+      ) {
+      return this._router.stack[k];
+    } else {
+      // Aggressively check if the original handler has been wrapped
+      // into a new function with a property pointing to the original handler
+      for (var p in this._router.stack[k].handle) {
+        if (this._router.stack[k].handle[p] === handler) {
+          return this._router.stack[k];
+        }
+      }
+    }
+  }
+  return null;
+};
+
 // Install our custom PhaseList-based handler into the app
 proto.lazyrouter = function() {
   var self = this;

test/app.test.js

@@ -65,6 +65,62 @@ describe('app', function() {
       });
     });
 
+    it('allows extra handlers on express stack during app.use', function(done) {
+      function handlerThatAddsHandler(name) {
+        app.use(namedHandler('extra-handler'));
+        return namedHandler(name);
+      }
+
+      var myHandler;
+      app.middleware('routes:before',
+        myHandler = handlerThatAddsHandler('my-handler'));
+      var found = app._findLayerByHandler(myHandler);
+      expect(found).to.be.object;
+      expect(myHandler).to.equal(found.handle);
+      expect(found).have.property('phase', 'routes:before');
+      executeMiddlewareHandlers(app, function(err) {
+        if (err) return done(err);
+        expect(steps).to.eql(['my-handler', 'extra-handler']);
+        done();
+      });
+    });
+
+    it('allows handlers to be wrapped as __NR_handler on express stack',
+      function(done) {
+        var myHandler = namedHandler('my-handler');
+        var wrappedHandler = function(req, res, next) {
+          myHandler(req, res, next);
+        };
+        wrappedHandler['__NR_handler'] = myHandler;
+        app.middleware('routes:before', wrappedHandler);
+        var found = app._findLayerByHandler(myHandler);
+        expect(found).to.be.object;
+        expect(found).have.property('phase', 'routes:before');
+        executeMiddlewareHandlers(app, function(err) {
+          if (err) return done(err);
+          expect(steps).to.eql(['my-handler']);
+          done();
+        });
+      });
+
+    it('allows handlers to be wrapped as a property on express stack',
+      function(done) {
+        var myHandler = namedHandler('my-handler');
+        var wrappedHandler = function(req, res, next) {
+          myHandler(req, res, next);
+        };
+        wrappedHandler['__handler'] = myHandler;
+        app.middleware('routes:before', wrappedHandler);
+        var found = app._findLayerByHandler(myHandler);
+        expect(found).to.be.object;
+        expect(found).have.property('phase', 'routes:before');
+        executeMiddlewareHandlers(app, function(err) {
+          if (err) return done(err);
+          expect(steps).to.eql(['my-handler']);
+          done();
+        });
+      });
+
     it('injects error from previous phases into the router', function(done) {
       var expectedError = new Error('expected error');