Add Express Trace Plugin (#363)

PR-URL: #363

config.js

@@ -42,6 +42,7 @@ module.exports = {
     // This field is experimental.
     plugins: {
       'connect': path.join(__dirname, 'src/plugins/plugin-connect.js'),
+      'express': path.join(__dirname, 'src/plugins/plugin-express.js'),
       'grpc': path.join(__dirname, 'src/plugins/plugin-grpc.js'),
       'hapi': path.join(__dirname, 'src/plugins/plugin-hapi.js'),
       'http': path.join(__dirname, 'src/plugins/plugin-http.js'),

src/hooks/index.js

@@ -36,10 +36,7 @@ var fs = require('fs');
 // will result in the module itself being patched.
 // Note: the order in which filenames are defined in the hooks determines the
 // order in which they are loaded.
-var toInstrument = Object.create(null, {
-  'express': { enumerable: true, value: { file: './userspace/hook-express.js',
-      patches: {} } }
-});
+var toInstrument = Object.create(null);
 
 var logger;
 

src/plugins/plugin-express.js

@@ -0,0 +1,93 @@
+/**
+ * Copyright 2017 Google Inc. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+'use strict';
+var shimmer = require('shimmer');
+var methods = require('methods').concat('use', 'route', 'param', 'all');
+
+var SUPPORTED_VERSIONS = '4.x';
+
+function patchModuleRoot(express, api) {
+  var labels = api.labels;
+  function applicationActionWrap(method) {
+    return function expressActionTrace() {
+      if (!this._google_trace_patched && !this._router) {
+        this._google_trace_patched = true;
+        this.use(middleware);
+      }
+      return method.apply(this, arguments);
+    };
+  }
+
+  function middleware(req, res, next) {
+    var options = {
+      name: req.path,
+      traceContext: req.get(api.constants.TRACE_CONTEXT_HEADER_NAME),
+      url: req.originalUrl,
+      skipFrames: 3
+    };
+    api.runInRootSpan(options, function(rootSpan) {
+      if (!rootSpan) {
+        next();
+        return;
+      }
+
+      // Set outgoing trace context.
+      res.set(api.constants.TRACE_CONTEXT_HEADER_NAME,
+        rootSpan.getTraceContext());
+
+      api.wrapEmitter(req);
+      api.wrapEmitter(res);
+
+      var url = req.protocol + '://' + req.hostname + req.originalUrl;
+      rootSpan.addLabel(labels.HTTP_METHOD_LABEL_KEY, req.method);
+      rootSpan.addLabel(labels.HTTP_URL_LABEL_KEY, url);
+      rootSpan.addLabel(labels.HTTP_SOURCE_IP, req.connection.remoteAddress);
+
+      // wrap end
+      var originalEnd = res.end;
+      res.end = function(chunk, encoding) {
+        res.end = originalEnd;
+        var returned = res.end(chunk, encoding);
+
+        if (req.route && req.route.path) {
+          rootSpan.addLabel('express/request.route.path', req.route.path);
+        }
+        rootSpan.addLabel(labels.HTTP_RESPONSE_CODE_LABEL_KEY, res.statusCode);
+        rootSpan.endSpan();
+        return returned;
+      };
+
+      next();
+    });
+  }
+
+  methods.forEach(function(method) {
+    shimmer.wrap(express.application, method, applicationActionWrap);
+  });
+}
+
+function unpatchModuleRoot(express) {
+  methods.forEach(function(method) {
+    shimmer.unwrap(express.application, method);
+  });
+}
+
+module.exports = [{
+    versions: SUPPORTED_VERSIONS,
+    patch: patchModuleRoot,
+    unpatch: unpatchModuleRoot
+}];