Why does node.js scale? Libuv & epoll & fcntl 

Thanks so much! will keep them coming, hope you like them!

Thanks man, appreciate it a lot! When you’re just starting a channel this kind of support really helps you persevere.

Hey Muhammad, thank you so much for the kind words, if you can help me spreading this video with your friends I’ll be sure to make a follow up. I’m glad this was helpful

Argentinian living close to the border with Brazil

I like it, will curate a list of good videos about them and link them. Thanks for the input, that’s a great addition I can make.

Hey Gabriel, is there a continuation for this video?

I don't have them anywhere other than my notes. I'll get around to publishing them somewhere

If enough people want it I'll work on a part 2 for this video.

@@Gabzim I would be definitely interested in part 2 video :)

Absolutely! it's The Linux Programming Interface. www.amazon.com/Linux-Programming-Interface-System-Handbook/dp/1593272200

Hey @dan nahari, I need to revisit this since it's been a while since I last went through the source code, allow me some time to walk through it and I'll get back to you.

@@Gabzim Thank you, I appreciate it 🙂

@@Gabzim Hi, Did you have the chance to check it?

I will. I was thinking about using some examples to illustrate this video

I’m not sure I understand 100% what you’re struggling to see, if I understand correctly, the thread does block waiting for io when polling for new available data from network. However, it calculates how long to block for depending on other things it has to do. If there’s no data from the network and you have absolutely nothing else to do except a timer in 5ms, it’ll block for AT MOST 5 ms (the network could come before)

Blocking is a good compromise if you don’t have other code that’s ready to run, you get to minimize syscalls to read data and your program is activated instantly when data is ready to be read while you’re blocked, however you don’t want to block for too long for obvious reasons.

@@Gabzim I thought this was the traditional (poll) approach - checking from time to time to see what happened to the event. This looks like that, when I would expect epoll to actually signal to the calling thread when the event is done, so it doesn't have to block. I am probably missing the bigger picture here, will go over the video again some time in the future.

I can make a video about epoll. So to answer your main question, you can add file descriptors to epoll and then ask the OS: *"is anything ready for me to read from?"* and in that same call you say *"I'd like to wait for x amount of milliseconds if nothing is"*. If anything *IS* ready for you to operate on, then you don't block at all, because epoll will return immediately, however *IF nothing is ready*, epoll will block for the given timeout you passed. So the 2 cases are: 1. Something is ready: you don't block at all. 2. Nothing is ready: you block for as long as you want. Obviously if you pass in a huge timeout then you WILL block the main thread for that huge timeout (or if you pass in -1, which means block until something is ready). So what libuv will do is: do I have anything left to do? pass in *0* so we don't block at all. If I don't, wait for a little bit (how that little bit is calculated is beyond this comment). So you DO block the main thread when you don't have any pending work, but you block for a bit so that it doesn't impact your application.

Nonblocking IO in linux is useful on sockets, not really to do nonblocking io on files... why? because files are always considered ready to read/write from, but the operations themselves are blocking (I don't want to go too in depth in a comment). As for your question: *How can a single threaded program have a function execute, that will take 2 minutes as an example, and not block the main thread?* If you are executing synchronous code (computing some value etc), for the whole 2 minutes, then you WILL block the main thread for 2 mins. Epoll helps you to do nonblocking IO, but if you're not doing IO, you will block.

Hehe yes I am, it’s my Argentinian accent coming through 😅 and the fact that English is my second language. Hehe nice catch.

Noted, will continue to include these kinds of details then!