Luvit – Asynchronous I/O for Lua

http://luvit.io/

by metacontent • 13 years ago

104 36 13 years ago

luvit.io

halayli3• 13 years ago

For those interested, lthread now supports AIO.

It's still in dev branch, but I'll be merging it soon:

http://webmon.com/blog/2013/02/19/lthread-now-supports-userl...

https://github.com/halayli/lthread/blob/dev/src/lthread_io.c

FooBarWidget2• 13 years ago

lthread is very interesting. Thanks for the links!

vier3• 13 years ago

digressing from luvit...

how does the stack copying technique (as used in lthread) compare to segmented stacks (as used in go)? The swap technique is very simple but I would assume that the stack copy shows up in profiles and is significantly slower than the segmented stack technique... Are there any benchmarks?

FooBarWidget2• 13 years ago

Hm, that's unfortunately to hear. Ruby 1.8 implemented green threads by using stack copying. It was discovered that this resulted in significant performance hits: http://timetobleed.com/fixing-threads-in-ruby-18-a-2-10x-per...

halayli3• 13 years ago

Segmented stacks will take much more space. One of the reasons I went with stack copy is because it allows me to create a million lthreads if I wanted without worrying about memory.

Lthread is in C, an environment where you control/manage your memory. Using slab allocators and high performance malloc like jemalloc, you can avoid allocating a lot of your variables on the stack and the stack copy will become minimal. In most of the production code I have running using lthread, stack copying is on the average of 300 bytes.

tracker1• 13 years ago

Not sure exactly how duped this is for HN... For those that don't know.. Lua is a scripting language, perhaps a bit more structured than it's more popular counterparts (JavaScript and Python), having very good performance characteristics. It's very popular in terms of Game development.

Luvit is essentially a lua interpreter with bindings to libuv (the same core IO library used in NodeJS). And could mainly be considered an alternative to NodeJS, which it most closely resembles.

Some, who don't like JS syntax may wish to consider Luvit, as it will perform close to, and sometimes better than NodeJS, with some similar gotchas.

wereHamster2• 13 years ago

> Lua is a scripting language, perhaps a bit more structured than it's more popular counterparts (JavaScript and Python)

I wouldn't say it has more structure than Python or JavaScript. Lua has only these types: number, string, boolean, table, function, nil, userdata and thread. Table acts as a hybrid between list and map, just like Array/Object in JavaScript. And users rarely are exposed directly to userdata/thread, that's more something you'd use when you write a library (use userdata to emulate classes etc). The Lua VM is also much simpler than the other two, it's a simple stack machine. There are no tuples like in python, no first-class support for classes.

s_baby2• 13 years ago

I thought Lua used a register based VM.

dottrap• 13 years ago

Lua IS a register based machine. The white paper done by the Lua authors is the reason most of the industry has moved to register based machines. (Apple SquirrelFish for Safari was the first to read it and implement it and everybody followed suit to compete.) http://www.lua.org/doc/jucs05.pdf

Lua has true multiple return value support. The overall usefulness of tuples in light of this feature is not clear.

Lua has first class support for functions and actually supports functional programming unlike Python which cripples many techniques and where Javascript has broken lexical scoping. Lua uses metamethod programming to allow you to build functionality like classes; Javascript has prototype inheritance which is different than Python's classical inheritance. Each is just different; not necessarily more or less structured.

Also, never confuse simple for being primitive. Lua IS incredibly simple and elegant. But all the simple things in the language work together elegantly to allow for amazingly sophisticated things.

eric_bullington• 13 years ago

Lua has a register-based VM. You're probably thinking of Lua's C API, which is stack-based.

EDIT: Also, I just remembered that Lua started as a stack-based VM, but moved to register-based at around version 5. So you could be thinking of the old Lua, too.

matt_m2• 13 years ago

I've been using this lately on a personal project.

For those who don't know, this is basically a clone of the Node.js API in the Lua language (using the LuaJIT compiler). This is interesting because:

- LuaJIT is often faster than V8 and uses less memory

- LuaJIT has a built in C FFI and supports C datatypes for working with low level libraries (or even writing low level code in Lua)

- Lua has coroutines

I think this is already being used in production at Rackspace, mainly because of the lower memory usage.

s_baby2• 13 years ago

I think Rackspace is using openresty.

http://openresty.org/

pquerna• 13 years ago

Rackspace use hundreds of open source projects.

Luvit.io is specifically being used in our Host Monitoring Agent, which is open source and you can find here:

https://github.com/racker/virgo

This is used to collect all kinds of host metrics (CPU, disk, ram, custom scripts, mysql, etc) for the Cloud Monitoring Product.

graue4• 13 years ago

Link to the project? I always like to see examples.

Blogging about your experience using it would probably get you some decent traffic, too.

russell_h2• 13 years ago

I suspect the project he's referring to is our monitoring agent: https://github.com/racker/virgo

We're working on splitting this out into a reusable platform for writing lightweight host-based agents. Luvit works out fairly well for this - our monitoring agent runs in around 5mb resident memory, works on Windows (although we haven't released that yet) and is relatively easy to code on.

Shameless plug: if this sort of stuff interests you, hit me up, my email is in my profile.

matt_m2• 13 years ago

I haven't released it yet, maybe I'll do a Show HN in the future!

pooriaazimi• 13 years ago

also:

- Lua (as a language) is for the most part better designed than JavaScript

limmeau• 13 years ago

For a while, I thought that luvit is completely undocumented. But then, I found out that one just goes to nodejs.org ...

So far, I mostly like it. Recently, I used it to build a PoC for an in-house testing tool for embedded devices and decided to slap a web interface onto it for fun (just like Twisted provokes you to add an NNTP and an SSH interface just for fun).

What I'm a bit unhappy with is the decision to be incompatible with the rest of the Lua world. From what I read in the mailing list, it's not just "sorry, that rock uses blocking file IO" but rather "Lua is Lua, and luvit is luvit".

vier3• 13 years ago

The luvit page notably lacks a link to libuv - the I/O engine behind it.

https://github.com/joyent/libuv

thomasfl• 13 years ago

+1 for the lovable name.

TheZenPsycho3• 13 years ago

I saw this and for a while I thought "Oh yeah, that's pretty cool, but why isn't the lua community into it?" Then I really looked into luasocket[1], which uses a this api called ltn12, based around dataflow programming concepts. In most respects this is a much much more elegant way of doing network programming than the node.js way. This is the sort of thing you would want to implement on top of node.js to make the callback hell easier to deal with- and compared to luasocket, luvit is a step backward. But this is the standard way of doing networking in lua.

[1] http://w3.impa.br/~diego/software/luasocket/

graue4• 13 years ago

Any good open-source (or closed) examples of web apps built on this?

The idea sounds neat, but I'm wary of concepts that aren't seeing real-world use. Node.js has momentum, Luvit has a little bit of momentum, this? In the web development community, I've never heard of the approach, which suggests using it might be more DIY than I'd like. Also the copyright date is 2004-2007. Abandoned?

TheZenPsycho3• 13 years ago

Forgive me for being a bit ignorant about this, since I'm quite a bit outside the lua community myself. (and didn't quite expect to get voted to the top here) I've done some googling around, and It's hard to say if luasocket is abandoned as such- but there are several forks of it. Regardless, it's the standard library that pretty much anyone and everyone uses for networking. There are a number of forks on github of luasocket- maintained presumably to add features needed for specific projects.

There is the Kepler project http://www.keplerproject.org/ , which appears to be much like the commonJS project for javascript- with luasocket at its core. Kepler project lists http://slimfastclinic.com/ and http://www.bestjuicer.biz/ as websites that were built with lua. (though they may be out of date since the slimfastclinic.com says it's wordpress)

It might also be worth pointing out, just as a side note, that mod_lua for apache has existed for a while https://httpd.apache.org/docs/trunk/mod/mod_lua.html

jamesbritt• 13 years ago

Previous discussion:

https://news.ycombinator.com/item?id=4767401

kostja• 13 years ago

Tarantool/Box I/O gives you luasocket-style API[1] in cooperative multitasking environment + database backend (if necessary).

[1] http://tarantool.org/dist/master/tarantool_user_guide.html#s...

Luvit – Asynchronous I/O for Lua

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