Bringing chaos to order in your Node.js app

Talk given at Node.js Dublin meetup - talks about using the cls node module

Transcript

1. BRINGING CHAOS TO ORDER IN YOUR NODE.JS APP DAN JENKINS NIMBLE APE https://nimblea.pe
2. WHO AM I?
3. WHO AM I? DAN JENKINS NODE.JS DEVELOPER / ARCHITECT GOOGLE DEVELOPER EXPERT IN WEBRTC LOVE LEGO & TECHNIC GENERAL GEEK FOUNDER OF NIMBLE APE LTD ❤ OPEN SOURCE 3
4. 4 /danjenkins
5. 5 @dan_jenkins
6. 6 nimblea.pe | @nimbleapeltd
8. NODE.JS & I STARTED WITH NODE.JS WHEN IT WAS A BABY - 0.4 BUILT MANY, MANY MICROSERVICES AND REST APIS WITH NODE SPENT THE PAST YEAR WORKING ON A PLATFORM CALLED RESPOKE - WEBRTC 8
9. FUNNY STORY… 9 H E L L O my name is Dan G O O G L E I / O
10. WARNING… SOME BAD PRACTICES ARE USED IN SOME OF THE EXAMPLES. I KNOW YOU SHOULDN’T DO THESE THINGS. BUT, ITS THE EASIEST WAY TO SHOW THE POINT IN THE SMALL CONFINES OF A SLIDE DECK. I PROMISE I KNOW WHAT I’M DOING… 10
11. NODE.JS APPS CAN GET IN A REAL MESS…
12. WHO’S WRITTEN CODE LIKE THIS ? 12 createAdministrator: function (req, res) { Administrators.create({some: data}, function cb(error, admin) { if (error) { console.error('Error creating Admin'); res.send(500) return; } res.admin = admin; doAnotherCall(res, function cb2(err2){ res.send(200, res.admin); }); }); }
13. OR LIKE THIS 13 var http = require('http'); var uuid = require('uuid'); function respond(res) { console.log('Got request with ID', res.id); res.end('Response'); } var server = http.createServer(function handleRequest(req, res){ res.id = uuid(); respond(res) }); server.listen(8080, function(){ console.log("Server listening on: http://localhost:8080"); });
14. OR LIKE THIS 14 var http = require('http'); var uuid = require('uuid'); function doSomething(res, id) { console.log('Do something with request with ID', id); respond(res, id); } function respond(res, id) { console.log('Responding to request with ID', id); res.end('Response'); } var server = http.createServer(function handleRequest(req, res){ var id = uuid(); doSomething(res, id); }); server.listen(8080, function(){ console.log("Server listening on: http://localhost:8080"); });
15. EVERYONE HAS AT SOME POINT…
16. DON’T TRY AND DENY IT…
17. WHAT PROBLEM ARE WE TRYING TO SOLVE?
18. PASSING DATA AROUND TO OTHER FUNCTIONS FOR USE LATER
19. 19 req.id = ‘foo’; console.log(req.id);
20. FOR EXAMPLE, SERVICE BASED LOGGING
21. 21 ASSIGN A REQUEST ID HERE AND HAVE IT SENT ON TO ALL OTHER SERVICES WHICH MEANS ALL YOUR LOGS FROM ALL YOUR SERVICES ALL TIE TOGETHER
22. WHAT’S THE ANSWER?
23. 23 OBVIOUSLY…
24. CLS NODE-CONTINUATION-LOCAL-STORAGE USERLAND MODULE UTILISES ASYNC-LISTENER 24 /othiym23/node-continuation-local-storage / continuation-local-storage /package/async-listener
25. IT HAS NOTHING TO DO WITH LOCAL-STORAGE IN THE BROWSER
26. “Continuation-local storage works like thread-local storage in threaded programming, but is based on chains of Node-style callbacks instead of threads.” 26
27. IT MEANS YOU CAN STOP DOING THIS… 27 var http = require('http'); var uuid = require('uuid'); function respond(res) { console.log('Got request with ID', res.id); res.end('Response'); } var server = http.createServer(function handleRequest(req, res){ res.id = uuid(); respond(res); }); server.listen(8080, function(){ console.log("Server listening on: http://localhost:8080"); });
28. AND START DOING THIS… 28 var http = require('http'); var uuid = require('uuid'); var createNamespace = require('continuation-local-storage').createNamespace; var namespace = createNamespace('request-life'); function respond(res) { console.log('Got request with ID', namespace.get('requestId')); res.end('Response'); } var server = http.createServer(function handleRequest(req, res){ namespace.set('requestId', uuid()); respond(res); }); server.listen(8080, function(){ console.log('Server listening on: http://localhost:8080'); });
29. IT’S MORE IMPRESSIVE THAN IT LOOKS IN THIS SIMPLE EXAMPLE I PROMISE
30. THAT’S AWESOME! WHAT DO I NEED TO DO?
31. 1 31 var createNamespace = require('continuation-local-storage').createNamespace; var session = createNamespace('my session'); var db = require('./lib/db.js'); function start(options, next) { db.fetchUserById(options.id, function (error, user) { if (error) return next(error); session.set('user', user); next(); }); }
32. 2 32 var getNamespace = require('continuation-local-storage').getNamespace; var session = getNamespace('my session'); var render = require('./lib/render.js') function finish(response) { var user = session.get('user'); render({user: user}).pipe(response); }
33. SO IT JUST WORKS? I DON’T HAVE TO DO ANYTHING FUNKY?
34. KINDA…
35. BEWARE NATIVE INTERACTIONS
36. ANYTHING THAT TOUCHES NATIVE CODE; YOU’LL NEED TO SHIM
37. SHIM ALL THE THINGS
38. /package/shimmer /othiym23/shimmer
39. 39 var http = require('http'); var shimmer = require('shimmer'); shimmer.wrap(http, 'request', function (original) { return function () { console.log("Starting request!"); var returned = original.apply(this, arguments) console.log("Done setting up request -- OH YEAH!"); return returned; }; });
40. OR USE AN EXISTING ONE
41. 41 require('cls-mysql')(ns); require('cls-redis')(ns); require('cls-q')(ns); require('cls-bluebird')(ns); require('cls-es6-promise')(ns); require('cls-bcrypt')(ns);
43. YOU NEED TO BE WARY!
44. 44 // Copyright (c) 2015. David M. Lee, II 'use strict'; var shimmer = require('shimmer'); // require mysql first; otherwise you can get some bizarre // "object is not a function" errors if cls-mysql is loaded first. require('mysql'); var Protocol = require('mysql/lib/protocol/Protocol'); var Pool = require('mysql/lib/Pool'); module.exports = function(ns) { shimmer.wrap(Protocol.prototype, '_enqueue', function(enqueue) { return function(sequence) { sequence._callback = ns.bind(sequence._callback); return enqueue.call(this, sequence); }; }); shimmer.wrap(Pool.prototype, 'getConnection', function(getConnection) { return function(cb) { return getConnection.call(this, ns.bind(cb)); }; }); };
45. YOU HAVE TO KNOW WHAT TO SHIM!
46. AND BEWARE THE INTERNALS OF THE MODULE CHANGING
47. AN INTERNAL MODULE CHANGE !== A PUBLIC API CHANGE
48. WHICH MEANS YOU COULD BE HIT BY A MINOR VERSION BUMP
49. WHICH COULD RESULT IN A FAILING APPLICATION
50. IT ALSO HAS A PERFORMANCE COST THE MORE YOU HAVE, THE MORE YOU’LL IMPACT YOUR PERFORMANCE COST IS AGAINST A NAMESPACE, NOT DATA IN THE NAMESPACE KEEP THINGS TO A MINIMUM 50
51. SO WHY USE IT?
52. IF YOU’RE DOING IT RIGHT… YOU SHOULD BE USING SHRINKWRAP ANYWAY (OR ANOTHER TECHNIQUE TO LOCK DEPENDENCIES) SO BREAKAGES SHOULD BE LIMITED TO YOUR DEVELOPMENT ENVIRONMENT WHICH MEANS MOAR BONUS FOR LITTLE TO NO RISK VERY LOW PERFORMANCE COST 52
53. THANKS! DAN JENKINS @dan_jenkins
54. MOST EXAMPLES WERE TAKEN FROM https://github.com/othiym23/node-continuation-local-storage https://github.com/othiym23/shimmer https://github.com/building5/cls-mysql 54