Update react-server to write server side timings/logs to the response

document.

See: redfin#272

packages/react-server/core/logging/response.js

@@ -0,0 +1,79 @@
+var common      		= require('./common')
+,	SuperLogger 		= process.env.IS_SERVER ? require('winston').Transport : class {}
+,	RLS = require('../util/RequestLocalStorage').getNamespace();
+
+// A subset of stats that are logged are not associated with requests
+// or occur before the request context is initialized. Simply ignore
+// those logs here.
+var queue = () => {
+	if(RLS.isActive()) {
+		return RLS().queue || (RLS().queue = []);
+	}
+	else {
+		return [];
+	}
+}
+
+class ResponseLogger extends SuperLogger {
+	constructor(options) {
+		super();
+		this.name = 'ResponseLogger';
+		this.level = options.level || 'debug';
+		this.module = options.name;
+		this.lastModuleToken  = options.name.split('.').pop();
+	}
+
+	log(level, msg, meta, callback) {
+		var tuple = [
+			this.module,
+			msg,
+			meta[this.key],
+			this.lastModuleToken,
+		];
+
+		queue().push(tuple);
+		// Yield to the next log transport.
+		callback(null, true);
+	}
+
+	flushToResponse(res) {
+		if(queue().length > 0) {
+			res.write("<script>");
+			res.write("window.serverLogs = window.serverLogs || {};");
+			res.write(`window.serverLogs.${this.name}Logs = ${JSON.stringify(queue())};\n`);
+			res.write("</script>");
+		}
+	}
+}
+
+class TimeResponseLogger extends ResponseLogger {
+	constructor(options){
+		super(options);
+		this.name = 'TimeResponseLogger';
+		this.level = 'fast';
+		this.key   = 'ms';
+	}
+}
+
+class GaugeResponseLogger extends ResponseLogger {
+	constructor(options){
+		super(options);
+		this.name = 'GaugeResponseLogger';
+		this.level = 'ok';
+		this.key   = 'val';
+	}
+}
+
+var getTransportForGroup = function(group, opts) {
+	if(group == "time") {
+		return new TimeResponseLogger(opts);
+	}
+	else if(group == "gauge") {
+		return new GaugeResponseLogger(opts);
+	}
+	else {
+		return new ResponseLogger(opts);
+	}
+}
+
+module.exports = {getTransportForGroup, TimeResponseLogger, TimeResponseLogger, ResponseLogger};

packages/react-server/core/logging/server.js

@@ -7,11 +7,11 @@ var winston = require('winston')
 	isEmpty       : require("lodash/isEmpty"),
 	trimStart     : require("lodash/trimStart"),
 	truncate      : require("lodash/truncate"),
-};
+}
+,   responseTransport = require('./response');
 
 var makeLogger = function(group, opts){
 	var config = common.config[group];
-
 	var fileTransport = new (winston.transports.File)({
 		name      : 'file',
 		level     : config.baseLevel,
@@ -23,6 +23,7 @@ var makeLogger = function(group, opts){
 	var logger = new (winston.Logger)({
 		transports: [
 			fileTransport,
+			responseTransport.getTransportForGroup(group, opts),
 		],
 	});
 

packages/react-server/core/renderMiddleware.js

@@ -751,6 +751,15 @@ function writeBody(req, res, context, start, page) {
 	// Don't leave dead timers hanging around.
 	retval.promise.then(() => clearTimeout(timeout));
 
+	// Flush timing/log data to the response document
+	retval.promise.then(() => {
+		if (req.query._debug_output_logs) {
+			logger.transports.ResponseLogger.flushToResponse(res);
+			logger.timeLogger.transports.TimeResponseLogger.flushToResponse(res);
+			logger.gaugeLogger.transports.GaugeResponseLogger.flushToResponse(res);
+		}
+	});
+
 	return retval.promise;
 }