Experimenting with Node.js

http://jeffkreeftmeijer.com/2010/experimenting-with-node-js/

by jkreeftmeijer • 16 years ago

171 84 16 years ago

CitizenKane2• 16 years ago

Extremely cool demo. It would be interesting to see this applied to analytics, so you could see exactly what people are doing on your site in real time. Although that would also be a bit creepy.

riklomas• 16 years ago

There's already something called Hummingbird that does that: http://mnutt.github.com/hummingbird/

CitizenKane2• 16 years ago

Hummingbird shows traffic in real time. It doesn't show mouse movement or user activity in real time.

JakeSc2• 16 years ago

I am thoroughly impressed, and excited for the prospect of unimaginably awesome web applications. I do have a few thoughts:

- How easy would this be to implement in another event-driven server, such as Tornado?

- I have an identifiable "mouse ID" in this app. Is this secure? Surely the security aspects of web sockets have been key in their design, but I am left with a bit of uneasiness with my browser opening a TCP connection to another server. I believe WebSockets will pave the way for a whole new class of web-based attacks, and possibly even highly mobile worms.

Joeboy• 16 years ago

Please could you move your cursors out of the way? I'm trying to read the text.

Edit: This lame comment is the highest rated here? You disappoint me.

jkreeftmeijer3• 16 years ago

There's a "disable" button in the yellow box. That'll make them go away completely. :)

ppplll• 16 years ago

It would be interesting to hear from the author how the server is handling HackerNews traffic

jkreeftmeijer3• 16 years ago

Hi, author here. While building this thing, the Node server had the tendency to drop out. I'm monitoring it with God (http://god.rubyforge.org/) now, so it restarts whenever anything goes wrong.

I'm genuinely impressed by how it's holding out now. :)

mishmash• 16 years ago

What kind of traffic have you gotten in the last hour?

jokull• 16 years ago

Could you elaborate on this at all? What kind of traffic are you getting (max concurrent requests handled perhaps)? Any idea why Node dropped out?

MisterWebz• 16 years ago

I'm wondering if Javascript will start being heavily used server-side? Would it be wise to start learning JS and how to use Node.js or is it absolutely not suitable for production use?

Charuru• 16 years ago

You should absolutely start learning it. node.js already has a large amount of traction and is being used in production in numerous places:

http://wiki.github.com/ry/node/

_urga6• 16 years ago

Regardless of the popularity of Javascript on the server-side, if you're writing a web-based application, then your architecture will benefit from:

1. Shared code between client and server.

2. Specialization in one language.

V8 and Node are at least a very good combination for server-side Javascript.

Re: "is it absolutely not suitable for production use?"

Node in alpha state is already more production ready than many "production ready" tools.

kylemathews• 16 years ago

The cursors looked disturbingly like flies. Pretty insane demo.

Kilimanjaro• 16 years ago

Make it funnier, show us a maze and people trying to solve it in real time. Replace the mouse pointer with a colored token and constrain its movement to the walls of the maze.

axod2• 16 years ago

This was a startup idea I had when I started Mibbit (I decided on balance webchat had more potential than multiplayer web games).

The idea was 'mouse games'. I had a similar setup where you could see everyones mouse cursor. I planned a whole load of multiplayer games where you could chase each other, complete puzzles, click on other people to kill them, draw circles round other players to trap them, etc etc. You could have messages show up like "First to draw a square gets a point". "Move to the left get a point". "Move as far away from everyone else as you can. Most isolated player gets a point". You could have objects being thrown at cursors, and you have to dodge them. Tons of potential to be a fun way for people to waste time :)

I'm sure it would have been great fun to make :)

icey3• 16 years ago

It still sounds like a pretty cool idea to me - I'd certainly check it out if something like that existed.

nhnifong2• 16 years ago

It a strange mix of disappointment and excitement to find out someone has just released a better finished version of what you were working on. Oh well, I guess I'll finish it anyways.

jkreeftmeijer3• 16 years ago

Please let me know when you finish it. I would love to see your code. :)

nhnifong2• 16 years ago

It has mutated quite a lot since I started... I'm taking the positions of everyone's mouse and feeding them to Fortune's sweep line algorithm to make Voronoi diagrams. I've made it look like you are a cell squeezing through layers of tissue. http://uncc.ath.cx/applets/Voronoi_Standalone/

drats• 16 years ago

amusing: http://i.imgur.com/qHWYm.jpg

weixiyen3• 16 years ago

I made this RPG node demo a while back: http://sleeperbot.com

I'm not using any server monitoring so it can crash at any moment.

Would love to get more than 15 users on here moving around and see what happens.

code: http://github.com/weixiyen/avatar

someone_here• 16 years ago

Your comment is less than a minute old and it's already giving a 502 Bad Gateway error :(

weixiyen3• 16 years ago

sorry was messing with nginx config. it's up now

JakeSc2• 16 years ago

I would highly recommend sanitizing chat input. As a quick demo, type '<script>alert("a")</script>' or something.

Very cool concept though.

weixiyen3• 16 years ago

thanks, i put that in.

the blinky body toggle was pretty cool to see though :)

reeses• 16 years ago

Why is it that within ten seconds, I felt compelled to "hump" other arrows with my own?

It was also interested to see if I could get other people to form lines and other constructs, without any communication other than my own cursor.

WilliamLP• 16 years ago

I'm with you that I found the social implications of this many times more interesting than the technical ones!

jamwt4• 16 years ago

While I think it's great that more and more developers are being exposed to building network applications using async I/O (which I guess is "evented" now) via Node.js, I think it's worthwhile to point out that the state of the art has moved well beyond these kind of callback frameworks. The reason is simple: it sucks programming in callback patterns on serious, large projects. You end up with lots of routines that are 6 or 7 callback chained together--and don't forget to attach error callbacks as well at each point.

In the Python world, for example, eventlet, gevent, and diesel (disclosure: my project) all use coroutines to achieve very high performance asynchronous I/O that's still written in a "synchronous" style. And before that, CCP games has been using stackless python to do coroutine-based networking for the servers behind the very popular MMORPG eve online (http://www.tentonhammer.com/node/10044).

Even slicker, in languages like Erlang and Haskell (via forkIO + the select/epoll I/O manager), support for asynchronous networking using "blocking-style" code is a fundamental language/compiler/vm feature. When you write any code in these languages, you're transparently taking advantage of the same scaling characteristics node.js and its ilk provide.

So, I'd humbly suggest to anyone getting serious about doing this kind of programming that they investigate some of these systems (which are usually built by weary callback-style async I/O veterans) and leapfrog the rest of their peers. Consider Node.js a gateway drug.

Linkage:

http://eventlet.net/ http://github.org/jamwt/diesel http://en.wikipedia.org/wiki/Asynchronous_I/O#Light-weight_p... http://www.galois.com/~dons/slides/a-scalable-io-manager-for...

icey3• 16 years ago

I think developers get attracted to frameworks because of fun examples like the one linked in the posting. Until there are multitudes of interesting examples using other tech, I think it's going to be an uphill battle to attract significant numbers of developers to them.

Since many of the Node.js demos like this one are open-source it's much easier for developers to download working code and make modifications to see how everything works.

The technically superior solutions often get overlooked for the most accessible ones.

_urga6• 16 years ago

Re: "The technically superior solutions often get overlooked for the most accessible ones."

Are there any server-side Javascript environments being overlooked? And would it be fair to say that these are technically superior to V8 + Node?

dylanz• 16 years ago

I definitely agree when it comes to the code scalability of something like Node.js (although, I haven't built gargantuan javascript applications before, but am going to assume that it's not necessarily a pleasant experience).

Diesel looks great. When looking into alternatives in Erlang/Haskell/Scala, or XMPP/BOSH, either it's not easy to find quick how-to examples, or I'm looking in the wrong places. Any fingers in the right direction would be welcome.

tibbe• 16 years ago

The Glasgow Haskell Compiler (GHC) uses async I/O to implement all I/O actions (e.g. printing to stdout, opening a socket) and it's completely invisible to the programmer. Bryan O'Sullivan and I have rewritten the implementation used in GHC and GHC 6.14 will offer much better scalability (using epoll/kqueue) than previous version.

Just fork of a thread per connection (using forkIO) and just call normal I/O actions. The implementation will multiplex those forkIO threads onto a single OS thread that calls epoll/kqueue.

tdmackey• 16 years ago

Coroutines bring their own headaches and baggage. To say that callbacks are behind "state of the art" is a little misplaced,; its just a different way of doing things. With coroutines you have to worry about IO all over the place and have to make your functions coroutine safe and Ryan Dahl, the node.js creator, will argue with you all day long about coroutines vs callbacks.

I do agree, though, that developers should not ignore other ways of doing things, just don't discredit the callback way of doing things as it can be useful.

jerf2• 16 years ago

"With coroutines you have to worry about IO all over the place and have to make your functions coroutine safe and Ryan Dahl,"

No, no, a thousand times no. Node.js partisans really need to start actually using Erlang or Haskell for a little while before spouting this canned line off. You do not have to jump through enormous hoops to deal with IO in Haskell or Erlang, it just works.

Callbacks are behind the state of the art. Coroutines or generators or any other cooperative-multitasking primitives in languages that didn't support them from day one and have enormous sets of libraries not "cooperative-aware" are behind the state of the art, too.

This is all just "cooperative multithreading" again and I am yet to see anyone explain why this time is going to turn out any different than last time we tried cooperative multithreading.

spc4762• 16 years ago

Really? I recently wrote a framework to do networking with Lua. The network code itself is event based, but each TCP connection is handled by a Lua coroutine which makes it easy to write straightforward code such as:

  function main(socket)
   io.stdout:write("connection from " .. tostring(socket))
   while(true)
     local cmd = string.upper(socket:read())
     if cmd == "SHOW" then
       socket:write("show me some stuff\n")
     elseif cmd == "PING" then
       for i = 1 , 15 do
         socket:write(".")
         socket:sleep(1)
       end
       socket:write("\n")
     elseif cmd == "QUIT" then
       socket:write("Good bye\n");
       return
     elseif cmd == nil then
       return
     end
   end
  end

Makes writing simple servers nice and easy.

creationix3• 16 years ago

Whether you like the model or not, the fact is that JavaScript with it's callback/event based model is what browsers understand. And the internet isn't going anywhere anytime soon.

Node is an attempt at using this successful model on the server too where is can solve massive scalability issues using the exact paradigm front-end devs already know.

Also while there are many technical ways to make code look blocking, but really be running other events under the hood, it's this exact implicit running of "other stuff" that makes writing threaded code so hard. You have to assume that things can change between every function call because you don't know if somewhere down the chain it's doing pseudo-blocking.

JavaScript's model is simple, you provide callbacks and you know exactly at what boundaries things can happen asynchronously.

In summary, node is one way of doing it. We think it's a better model and it's proven itself in the browser. If you think another model is better, than by all means go for it!

Let the leapfrogging begin ;)

_delirium• 16 years ago

I agree this is currently the best way of using similar models on both the client and server side. It'll be interesting to see if anything changes, on either side or both, when webworkers (browser threads) get more widespread support. At least it's likely that more direct comparisons of the programming models will be possible in the future.

jamwt4• 16 years ago

I think javascript is a fine little language.

But: I don't make my server-side language decisions based on what happens to be in the browser. To think that a language required for use in such a constrained environment is just _coincidentally_ also the best language to use server-side where people have been doing event-based programming for decades seems... unlikely. It would be as ridiculous as asserting that we should all use postscript in the browser because that's the standard we've been using in printers for the last 20 years.

I suppose if you make the argument that browsers dictate that developers _must_ learn javascript, and therefore, with Node.js they can also program server-side without ever needing to learn a second language, that is a sound argument. I don't, however, know many good programmer that spend a career knowing exactly one language.

folletto• 16 years ago

Programmer-mentality is somewhat different from other mentalities, but it's still bound to simplicity laws.

The technologies you are describing were already there, but it's not just a problem of technology, feature set or execution power. It's also a matter of simplicity.

Node.js is working because it gives so much power with a very simple approach. And by approach I mean also how much is simple to understand it and start producing something useful.

That's exactly the reason why we use more abstract languages, and that's the reason why Node.js is getting a lot of attention recently. If you don't know any language, do you think it's simpler to start with Erlang or Haskell, or with JavaScript? I don't have any proof, but my bet is surely on JavaScript. :)

And even the most obvious things are important. Because maybe a uber-developer can ignore the small details, but most of the programmers aren't uber, they just want to develop easily and happily. Every little detail matters. Just see how many steps you need to install Erlang on your machine, and how many steps you need to do the same with node. It seems stupid, I know. But when you sum every detail... it matters. :)

At the same time, this gives power to the uber-programmers out there to bring on more cutting-edge solutions when they need them, and feed the "simple" level with their discoveries and experience, making the language and frameworks evolve.

If you're right, one day we are going to have simple coroutines - in the complex, environmental and social sense expressed above. Maybe even in Node.js, because in the end JavaScript 1.7 afaik supports yield and V8 could implement it in the future. ;)

gcampbell• 16 years ago

How many steps you need to install Erlang on your machine: "sudo apt-get install erlang"?

Andi• 16 years ago

Use Step, man: http://github.com/creationix/step

creationix3• 16 years ago

I have written extensively on this topic, here are a few articles. Here is the progression leading up to the development of Step.

http://howtonode.org/control-flow http://howtonode.org/control-flow-part-ii http://howtonode.org/control-flow-part-iii http://howtonode.org/do-it-fast http://howtonode.org/step-of-conductor

IsaacSchlueter2• 16 years ago

I've heard this before. "Oh, callbacks are fine for little things like this hello world demo, but for Big Programs, you need (threads/coroutines/etc.) because they're Serious Business."

That might be true. Maybe for Big Programs, something else is better. But I think the problem is that setting out to build a Big Program for Serious Business is Doing It Wrong.

The best frameworks (or, at least, my favorite frameworks) are collections of small tools with consistent interfaces and interchangeable parts.

If you can manage callbacks for a 100-200 LOC program, then you can build a Big Program out of such modules with a little bit of forethought. Instead of setting out to write a Big Program, why not try to figure out how to express your Big Problem in terms of a bunch of Little Problems, and then come up with a way to have Little Programs assemble.

Then, assemble the Little Programs to solve the Little Problems. There is no solveable Big Problem which cannot be broken down into some finite set of Little Problems.

Callbacks make it natural to solve problems in this manner.

I actively develop a several thousand line NodeJS project. It's quite nice, actually.

jamwt4• 16 years ago

I don't know how to completely address your post b/c it responds to assertions I didn't make. I said nothing about "Serious Business"--and bundling threads and coroutines together is like bundling horseshoes and bicycles. I made no defense of threads.

Callback style, within an I/O handler, is (almost always) a concession to the event loop. When I'm writing a program, I write:

  routine():
    result = do_one_thing()
    do_next_thing(result)
    do_whatever()

With callback based I/O, you need the routine to end so the "reactor" up the call stack can get control again to do I/O on your behalf:

  routine_1():
    return make_some_io_request(callback=routine_2)

  routine_2():
    return make_another_io_request(callback=routine_3)

  routine_3():
    return send_response_to_original_socket()

Now, if you were desperate, you could just call over to the reactor like this:

  routine():
    resp = do_io_for_me()
    next_resp = do_more_io_for_me(resp)
    return transform(next_resp)

.. but, there are (at least) two problems with this:

1. You're making the stack deeper every time you "call over" to the reactor... you will stack overflow eventually

2. In most languages, the reactor doesn't have a way to "call back into" your stack frame and resume it.

Coroutines are a way to "call over" to the reactor, have your stack state frozen (in heap space, without going deeper in the call stack), and then "unfreeze it" later on, when the reactor has completed the IO.

The greenlet package provides this for Python; Haskell and Erlang have native support for this. And, this is ultimately how you want to program. A(); B(); C(). Sure, there are exceptions for UI driven callbacks, and callback patterns aren't all bad, but typically in network IO cases, the callbacks are explicitly a concession to the I/O loop's need to be scheduled, made necessary by a missing language or vm feature.

And: cleaner code benefits 200 LOC apps as much as it does 200k LOC apps. A good design is a good design at any scale.

sh1mmer• 16 years ago

I plan to prove this point with code. Please stand by.

mikealrogers• 16 years ago

I've said it before and I'll say it again: if callbacks are so hard how come all these liberal arts majors write a shit load of working jQuery code?

I think the real problem is that callbacks are too simple for people that want to obsess about engineering new primitives and programming styles.

_urga6• 16 years ago

I agree with you that a synchronous programming interface is easier than an asynchronous programming interface.

However, none of the systems you suggest make it possible to write code that can be run by both the server and the browser.

If you were writing web applications, which represent the typical use-case for Node, then this would be a prerequisite.

allertonm2• 16 years ago

It can hardly be a "prerequisite" given that most web applications built to date have managed to do without it.

It's a convenience, at least intuitively, but in practice one has to wonder what parts of your code run in both browser and server and do async I/O.

aslakhellesoy2• 16 years ago

Web sockets are great, but almost all of the demos I see use a separate port (i.e. not port 80), making the app useless in practice.

Come on guys - it's _Web_ sockets, not intranet sockets.

lftl• 16 years ago

Could you elaborate on why a nonstandard port makes these apps useless?

user242• 16 years ago

corporate firewalls blocking nonstandard ports, you running other apps on those ports, your firewall throwing a wobbly, general nonstandardness.

if 80 is impractical, many people suggest running off 443 as that (the https port) is unlikely to be filtered.

maushu2• 16 years ago

The problem here is that to bind the websocket to the port 80 they would need to code their whole sites in node.js (with no reverse proxying from nginx and the likes) or at least make a reverse proxy in node.js and use it as front-end.

olalonde2• 16 years ago

Is the server down? I cannot see any arrow even when I open multiple windows (Chrome 5).

maushu2• 16 years ago

Check your firewall, the websocket doesn't use the port 80.

igrigorik• 16 years ago

Great stuff.

Just for sake of completeness, you can basically copy-paste that code into Ruby as well via em-websocket: http://github.com/igrigorik/em-websocket

Also, to avoid some of the callback muck that a few have brought up: http://github.com/igrigorik/em-synchrony

(same idea, closures + coroutines to abstract the callbacks).

olalonde2• 16 years ago

For some reason, the background picture is distorted when remote mouses hover it (Chrome 5). Anyone has an explanation?

DaemonXI• 16 years ago

http://i.imgur.com/OCaBf.jpg

I feel OK about doing this.

einaros• 16 years ago

I feel conflicted about doing this: http://www.youtube.com/watch?v=jULOA7mSOac&fmt=22

Experimenting with Node.js

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