Merge pull request #266 from DanCunnington/express_probe

Fix for express probe

Author: tobespc

README.md

@@ -17,7 +17,7 @@ Node Application Metrics provides the following built-in data collection sources
  Memory             | Process and system memory usage
  GC                 | Node/V8 garbage collection statistics
  Event Loop         | Event loop latency information
- Express            | Express Web Framework application request monitoring
+ Express            | Express 4.x Web Framework application request monitoring
  Loop               | Event loop timing metrics
  Function profiling | Node/V8 function profiling (disabled by default)
  HTTP               | HTTP request calls made of the application
@@ -397,7 +397,7 @@ Emitted when a PostgreSQL query is made to the `pg` module.
     * `duration` (Number) the time taken for the PostgreSQL query to be responded to in ms.
 
 ### Event: 'express'
-Emitted when an express request finishes its response.
+Emitted when an express request finishes its response. Note. appmetrics has only been tested with express 4.x, support is not guaranteed for lower versions.
 * `data` (Object) the data from the Express request/response.
     * `method` (String) The HTTP method for this request.
     * `url` (String) The target URL for this request.

probes/express-probe.js

@@ -41,26 +41,28 @@ ExpressProbe.prototype.attach = function(name, target) {
   var newTarget = aspect.afterConstructor(target, {});
 
   // Map the application object to the newTarget
-  newTarget = newTarget.application;
+  if (newTarget.application) {
+    newTarget = newTarget.application;
+    
+    // Ensure we are only attaching the probe to this target once
+    if (!newTarget.__ddProbeAttached__) {
+      newTarget.__ddProbeAttached__ = true;
 
-  // Ensure we are only attaching the probe to this target once
-  if (!newTarget.__ddProbeAttached__) {
-    newTarget.__ddProbeAttached__ = true;
+      // Before we make the call to an applicaton method
+      aspect.before(newTarget, applicationMethods, function(target, methodName, methodArgs, probeData) {
+        
+        // Patch the callback - i.e. the user's function when someone vists an application URL
+        aspect.aroundCallback(methodArgs, probeData, function(target, args, probeData) {
+          that.metricsProbeStart(probeData, methodName, methodArgs);
+          that.requestProbeStart(probeData, methodName, methodArgs);
 
-    // Before we make the call to an applicaton method
-    aspect.before(newTarget, applicationMethods, function(target, methodName, methodArgs, probeData) {
-      
-      // Patch the callback - i.e. the user's function when someone vists an application URL
-      aspect.aroundCallback(methodArgs, probeData, function(target, args, probeData) {
-        that.metricsProbeStart(probeData, methodName, methodArgs);
-        that.requestProbeStart(probeData, methodName, methodArgs);
-
-      }, function(target, args, probeData, ret) {
-          methodArgs.statusCode = args[1].statusCode;
-          that.metricsProbeEnd(probeData, methodName, methodArgs);
-          that.requestProbeEnd(probeData, methodName, methodArgs);
+        }, function(target, args, probeData, ret) {
+            methodArgs.statusCode = args[1].statusCode;
+            that.metricsProbeEnd(probeData, methodName, methodArgs);
+            that.requestProbeEnd(probeData, methodName, methodArgs);
+        });
       });
-    });
+    }
   }
   return target;
 }