timeToFirstByte: fix #298

* move to a separate core module

core/modules/requestsMonitor/requestsMonitor.js

@@ -18,8 +18,6 @@ exports.module = function(phantomas) {
 	phantomas.setMetric('postRequests');          // @desc number of POST requests
 	phantomas.setMetric('httpsRequests');         // @desc number of HTTPS requests
 	phantomas.setMetric('notFound');              // @desc number of HTTP 404 responses
-	phantomas.setMetric('timeToFirstByte');       // @desc time it took to receive the first byte of the first response (that was not a redirect)
-	phantomas.setMetric('timeToLastByte');        // @desc time it took to receive the last byte of the first response (that was not a redirect)
 	phantomas.setMetric('bodySize');              // @desc size of the uncompressed content of all responses @unreliable
 	phantomas.setMetric('contentLength');         // @desc size of the content of all responses (based on Content-Length header) @unreliable
 	phantomas.setMetric('httpTrafficCompleted');  // @desc time it took to receive the last byte of the last HTTP response
@@ -48,12 +46,6 @@ exports.module = function(phantomas) {
 		}
 	}
 
-	// when the monitoring started?
-	var loadStartedTime;
-	phantomas.on('loadStarted', function(res) {
-		loadStartedTime = Date.now();
-	});
-
 	phantomas.on('onResourceRequested', function(res, request) {
 		// store current request data
 		var entry = requests[res.id] = {
@@ -300,22 +292,14 @@ exports.module = function(phantomas) {
 		}
 	});
 
-	// TTFB / TTLB metrics
-	var ttfbMeasured = false;
-
-	phantomas.on('recv', function(entry, res) {
-		// check the first response which is not a redirect (issue #74)
-		if (!ttfbMeasured && !entry.isRedirect) {
-			phantomas.setMetric('timeToFirstByte', entry.timeToFirstByte, true);
-			phantomas.setMetric('timeToLastByte', entry.timeToLastByte, true);
-
-			ttfbMeasured = true;
-
-			phantomas.log('Time to first byte: set to %d ms for <%s> (HTTP %d)', entry.timeToFirstByte, entry.url, entry.status);
-			phantomas.emit('responseEnd', entry, res); // @desc the first response (that was not a redirect) fully received
-		}
+	// completion of the last HTTP request
+	var loadStartedTime;
+	phantomas.on('loadStarted', function(res) {
+		// when the monitoring started?
+		loadStartedTime = Date.now();
+	});
 
-		// completion of the last HTTP request
+        phantomas.on('recv', function(entry, res) {
 		phantomas.setMetric('httpTrafficCompleted', entry.recvEndTime - loadStartedTime);
 	});
 };

core/modules/timeToFirstByte/timeToFirstByte.js

@@ -0,0 +1,42 @@
+/**
+ * TTFB / TTLB metrics
+ */
+'use strict';
+
+exports.version = '1.1';
+
+exports.module = function(phantomas) {
+	var measured = false,
+		reqId = 1; // request ID to consider when calculating TTFB / TTLB
+
+	phantomas.setMetric('timeToFirstByte'); // @desc time it took to receive the first byte of the first response (that was not a redirect)
+	phantomas.setMetric('timeToLastByte'); // @desc time it took to receive the last byte of the first response (that was not a redirect)
+
+	phantomas.on('recv', function(entry, res) {
+		// metrics already calculated
+		if (measured) {
+			return;
+		}
+
+		if (entry.isRedirect) {
+			// wait for the next request
+			reqId = entry.id + 1;
+
+			phantomas.log('Time to first byte: response #%d <%s> is a redirect (waiting for response #%d)', entry.id, entry.url, reqId);
+			return;
+		}
+
+		// check the first response which is not a redirect (issue #74)
+		if (entry.id === reqId) {
+			phantomas.setMetric('timeToFirstByte', entry.timeToFirstByte, true);
+			phantomas.setMetric('timeToLastByte', entry.timeToLastByte, true);
+
+			measured = true;
+
+			phantomas.log('Time to first byte: set to %d ms for #%d request to <%s> (HTTP %d)', entry.timeToFirstByte, entry.id, entry.url, entry.status);
+			phantomas.log('Time to last byte: set to %d ms', entry.timeToLastByte);
+
+			phantomas.emit('responseEnd', entry, res); // @desc the first response (that was not a redirect) fully received
+		}
+	});
+};