@ajd I would disagree with this statement very easily and very confidently.
> really
yes
> multi-threading and non blocking io are two separate tools
asio is a way of minimizing the number of threads in a system and extracting maximum performance.
> i don't think anyone's asserting that
It follows by logical deduction. There are only 3 possible criticisms of node.js 1. I need shared memory 2. I dislike Javascript 3. I dislike asio
Given that the cancer post doesn't make a big deal of 1 and 2. you are left with 3. And if you read his follow up post he is again complaining about "event-loop" programming. Yes he is indeed complaining about asio. asio necessarily introduces event loops.
There is only one reason to use multiple threads over multiple pre-started processes. You need the shared memory. You should still be able to pull off shared memory in node but it can be cumbersome. I am yet to see anyone complain about needing shared memory and hence disliking nodejs. Its either
1. "threads are robust for cpu bound workloads"
- which can be solved by simply launching as many nodejs processes as Python processes, though you only need to launch as many nodejs instances as cores if you are not interested in winning this argument.
2. "Don't force this programming model on me"
It is not forcing any programming model on you except that shared memory is harder. And yes you cannot acquire a lock and go off and do io. If you want to do that then you can, by piling up pending events in a queue, but the ugliness of the code will stick out easily. You might as well switch to Python/Java threads or whatsoever.
> of course, you can spawn 40 other process - but i don't like a model where that's your /only/ option
Can you describe the other options you want to try?
Check this out http://teddziuba.com/2011/10/straight-talk-on-event-loops.ht... He has broken down his own defense with his fancifully named "Theorem 2". If you do more IO than CPU then "use more threads". Except he doesn't give you the number of threads because he doesn't know how many. In fact, he cannot know. And this is why asio is a win.
Fact is on an n-core system if you launch n nodejs processes you are guaranteed one of the 4 hold true 1. You service all requests thrown at the system 2. You maximize the CPU utilization 3. You maximize I/O utilization 4. You maximize RAM utilization - "4. is some what pedantic"
i.e. it will extract the maximum possible performance from the hardware you throw at it. It is just a consequence of making sure all io is non blocking. With a threaded solution you will never get the number of threads right and you will end up with a server that cannot serve all requests even when it has spare CPU, spare I/O capacity and spare RAM. Maximizing CPU utilization implicitly assumes the absence of locks. If you use asio as well as locks CPU utilization will not be maximized. This is something that most of the "nodejs" critics don't understand or fail to appreciate.
Yes shared memory is harder to do in node, but erlang doesn't do shared memory, Python cannot do threads sensibly, Java cannot do coroutines, why dump hate on nodejs because it isn't an ideal environment for a solution that requires shared memory? Sure there are many problems that require shared memory. However 95% of webservers don't fall into this category.
Lastly ted's inexperience really shows here, he is only 27 years old and has a lot left to learn. To start with he can stop trying to school Ryan Dahl, who is someone who certainly knows his Computer Science and is making a valuable contribution to the community.
Lastly as a practical exercise, try to build (at least as a thought experiment) some web service that outperforms node using respected platforms such as Python and Ruby. asio is a technique for IO bound loads but node will do better than Ruby/Python even on CPU bound loads thanks to V8. An order of magnitude faster. I have said that you need to have n processes for n cores, but in practice it seems just one process turns out to be enough as loads tend to be io bound and V8 is typically 10 times faster than Ruby. And if you have coroutines event based programming is not hard at all. So yes people have discovered that one nodejs process has replaced their two dozen Ruby processes and is serving out twice as many requests from the same box and they are impressed. And they don't care about what Ted thinks.
As a footnote, of course, you can do shared memory within a single nodejs process(trivially true), but for pure CPU workloads Java/C++ would probably be a better option.
