[erlang-questions] node.js vs erlang
Paulo F. Oliveira
paulo.ferraz.oliveira@REDACTED
Tue Jun 17 15:07:00 CEST 2014
"Node is very popular so I'm trying to understand what it is about node
that is attractive."
Having recently moved from Node.js (JavaScript really) to Erlang, a few
things come to mind:
1. a lot of browser frontend (i.e. JavaScript) developers almost don't have
to learn anything new to develop server-side code using Node.js
2. npm (for sure) is one of the best package management systems I've
used... really simple (oh, and the fact that you can use specific versions
of deps in your app and not be restricted by a previous choice, sure helps
a lot)
3. npmjs.org :D
4. the debugger (node-inspector): I miss this :(
5. you can share server-side and browser-side code
On the other hand, for high concurrency, I wouldn't recommend it (it's
heavy when you have to spawn a few thousand processes to do _parallel_ and
then the OS can't easily cope with this), as it's single threaded (ok,
there's Cluster, but...). And also, the fact that tail recursion is
non-existing...
At the moment, though, I enjoy prototyping with Node.js and implementing
with Erlang. :)
- Paulo F. Oliveira
On 17 June 2014 13:41, Joe Armstrong <erlang@REDACTED> wrote:
>
> On Tue, Jun 17, 2014 at 2:05 PM, Darach Ennis <darach@REDACTED> wrote:
>
>> Hi all,
>>
>> For this to be comparable both Erlang and Node.js need to be running
>> similarly. I don't see how a concurrent Erlang runtime with multiple
>> schedulers
>> can be compared with a single-threaded Node.js implementation objectively
>> or
>> fairly...
>>
>>
> It's actually the programming models I want to compare and not the
> performance - what worries me about node is the run-to-completion
> semantics of event callbacks - namely that a long-running event will block
> the server preventing short computations from being performed. The
> short jobs which could be done immediately have to wait until the long jobs
> have finished - this should reflect in the average latencies of a request.
>
> I made a little experiment (a fibonacci server in erlang and node) and
> fired off
> 1000 parallel requests to compute fib(N) with N a random number from
> 10..40.
>
> As I suspected many of the fib(10) events are blocked by ongoing
> computation of
> fib(40) - this reflect in the latencies.
>
> Node is about 1.6 times faster than Erlang - but the latencies for small
> computations
> are terrible - Erlang never blocks so the response times are more
> predictable.
>
> And yes I know that fib can be offloaded to a background processor or
> parallelised
> in JS with a bit of black magic - but manually converting a long lived
> computation into
> a re-entrant non-blocking version is very difficult.
>
> The node books say something like "make sure that callbacks
> run-to-completion quickly"
> I would say that complying with this advice is extremely difficult. It's
> very difficult to guess
> which computations will take a long time, and even if you know it's
> difficult to break them into
> small re-entrant chunks.
>
> Node is very popular so I'm trying to understand what it is about node
> that is attractive.
> npm for example, looks well engineered and something we could learn from.
> The node
> web servers are easy to setup and run, so I'd like to see if we could make
> equally
> easy to use Erlang servers.
>
> Performance is not a primary concern - easy of programming and correctness
> are.
>
> Cheers
>
> /Joe
>
>
>
>
>
>
>
>> Using node cluster with the same number of cluster instances as erlang
>> schedulers might be a fairer environment for comparison. However, as
>> numeric computations are fairly efficient in Node.js and inefficient in
>> Erlang
>> relative to Java or C it may take a few iterations to get a fair
>> comparison
>> in place. Node cluster is a standard part of node.js:
>>
>> http://nodejs.org/api/cluster.html
>>
>> There are various attempts at implementing fibers and lightweight threads
>> in Node.js (eg: https://github.com/laverdet/node-fibers/) but there is
>> nothing
>> common here. This would approximate an erlang runtime more closely at
>> the cost of deviating a little from a commonly found node runtime... Ho
>> hum.
>>
>> As javascript runtimes start to adopt vectorized instructions and other
>> optimisations their speed relative to a C baseline has and will continue
>> to
>> steadily improve and has been for a number of years, especially with V8.
>>
>> Good luck with the benchmarking!
>>
>> Cheers,
>>
>> Darach.
>>
>>
>> On Tue, Jun 17, 2014 at 12:48 PM, Joe Armstrong <erlang@REDACTED> wrote:
>>
>>>
>>>
>>>
>>> On Tue, Jun 17, 2014 at 1:00 PM, Greg Young <gregoryyoung1@REDACTED>
>>> wrote:
>>>
>>>> Are you testing against single threaded node or one of the clustered
>>>> versions or multiple processes or?
>>>>
>>>>
>>>>
>>> Single threaded
>>>
>>> /Joe
>>>
>>>
>>>> On Tue, Jun 17, 2014 at 1:19 PM, Joe Armstrong <erlang@REDACTED>
>>>> wrote:
>>>>
>>>>>
>>>>>
>>>>> On Tue, Jun 17, 2014 at 12:10 PM, Greg Young <gregoryyoung1@REDACTED>
>>>>> wrote:
>>>>>
>>>>>> Can you really compare the two? :)
>>>>>>
>>>>>
>>>>> Yes - there are many things we can measure. Performance, Latency,
>>>>> memory usage and so on.
>>>>>
>>>>> Right now I'm measuring latency -
>>>>>
>>>>> I set up a few thousand parallel processes which request fib(N) and
>>>>> measure the latency of the responses.
>>>>>
>>>>> the results will be published when I understand them :-)
>>>>>
>>>>> /Joe
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>>
>>>>>>
>>>>>> On Mon, Jun 16, 2014 at 5:55 PM, Juan Facorro <juan.facorro@REDACTED
>>>>>> > wrote:
>>>>>>
>>>>>>> Hi Joe,
>>>>>>>
>>>>>>> There's a semicolon missing after the declaration of fib(), which
>>>>>>> for some reason, causes the stack overflow. After adding it the error went
>>>>>>> away.
>>>>>>>
>>>>>>> HTH,
>>>>>>>
>>>>>>> J
>>>>>>>
>>>>>>> On Monday, June 16, 2014 11:22:23 AM UTC-3, Joe Armstrong wrote:
>>>>>>>>
>>>>>>>> I'm trying to compare node.js with erlang. I'm a total node.js
>>>>>>>> novice BTW - but I've written some JS.
>>>>>>>>
>>>>>>>> Program 1 is just fibonacci - I want a web server to compute fib(N)
>>>>>>>>
>>>>>>>> So requesting http://127.0.0.1:8124/fib?n=2 should compute and
>>>>>>>> return fib(2)
>>>>>>>>
>>>>>>>> My node.js attempt crashes
>>>>>>>> Here's the code in fib.js
>>>>>>>>
>>>>>>>> --- fib.js
>>>>>>>>
>>>>>>>> var http = require('http');
>>>>>>>> var url = require('url');
>>>>>>>>
>>>>>>>> function fib(n) {
>>>>>>>> if (n < 2) {
>>>>>>>> return 1;
>>>>>>>> } else {
>>>>>>>> return fib(n - 2) + fib(n - 1);
>>>>>>>> }
>>>>>>>> }
>>>>>>>>
>>>>>>>> http.createServer(function (req, res) {
>>>>>>>> var q = url.parse(req.url, true).query;
>>>>>>>> var n = q.n;
>>>>>>>> var result = fib(n);
>>>>>>>> console.log('fib('+ n + ')= '+result);
>>>>>>>> res.writeHead(200, {'Content-Type': 'text/plain'});
>>>>>>>> res.end(result.toString());
>>>>>>>> }).listen(8124, "127.0.0.1");
>>>>>>>>
>>>>>>>> console.log('Server running at http://127.0.0.1:8124/');
>>>>>>>>
>>>>>>>> -- end
>>>>>>>>
>>>>>>>> -- now we run it
>>>>>>>>
>>>>>>>> $ node fib.js
>>>>>>>> Server running at http://127.0.0.1:8124/
>>>>>>>> fib(2)= 2
>>>>>>>>
>>>>>>>> /home/ejoearm/Dropbox/experiments/hello_world/fib.js:5
>>>>>>>> function fib(n) {
>>>>>>>> ^
>>>>>>>> RangeError: Maximum call stack size exceeded
>>>>>>>>
>>>>>>>> fib(2) has run out of stack space????
>>>>>>>>
>>>>>>>> $ node --version
>>>>>>>> v0.8.21
>>>>>>>>
>>>>>>>> Any ideas what I'm doing wrong
>>>>>>>>
>>>>>>>> Cheers
>>>>>>>>
>>>>>>>> /Joe
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> --
>>>>>>> Remember to send a copy to erlang (dot) questions (at) erlang (dot)
>>>>>>> org when posting.
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>>>>>>
>>>>>>
>>>>>>
>>>>>> --
>>>>>> Studying for the Turing test
>>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>> --
>>>> Studying for the Turing test
>>>>
>>>
>>>
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