Lapis/Openresty where do the superpowers they come from?

martin.felis · 2014-03-04T02:19:54+00:00

Hello! On Fri, Feb 28, 2014 at 8:30 PM, ming zhang wrote: > I would like to pass configurations as a big complex table in a separate > .lua file. the...

Lapis/Openresty where do the superpowers they come from?

martin.felis

Hi there!

I have been looking at the Lapis framework over the weekend and it felt pretty good. On it's webpage it states:

"... With the power of Lua coroutines code is written synchronously but runs asynchronously, without all that callback spaghetti seen in other asynchronous platforms..."

Now I was wondering where exactly the magic is happening. I do know a bit about Lua's coroutines, especially their use in http://www.lua.org/pil/9.4.html. Now I was wondering where do they happen in Lapis or Openresty in general. After some searching I am guessing it is due to the cosockets in the HttpLuaModule. Furthermore the modules listed in http://wiki.nginx.org/HttpLuaModule#Description make use of the HttpLuaModule. So when using them it internally uses Lua's coroutines and as a user of the listed modules one does not have to worry about manually handling the coroutines.

Is this correct or am I confusing things here?

Thanks for all the work and keep it up!

Cheers,
Martin

leafot

Lapis doesn't use cosockets in its implementation currently. (Although I'd like to make the switch in the future.) All asynchronous actions (queries, http requests) are triggered through ngx.location.capture: http://wiki.nginx.org/HttpLuaModule#ngx.location.capture

On Mon, Mar 3, 2014 at 10:19 AM, Martin Felis <marti...@gmail.com> wrote:

Hi there!

I have been looking at the Lapis framework over the weekend and it felt pretty good. On it's webpage it states:

"... With the power of Lua coroutines code is written synchronously but runs asynchronously, without all that callback spaghetti seen in other asynchronous platforms..."

Now I was wondering where exactly the magic is happening. I do know a bit about Lua's coroutines, especially their use in http://www.lua.org/pil/9.4.html. Now I was wondering where do they happen in Lapis or Openresty in general. After some searching I am guessing it is due to the cosockets in the HttpLuaModule. Furthermore the modules listed in http://wiki.nginx.org/HttpLuaModule#Description make use of the HttpLuaModule. So when using them it internally uses Lua's coroutines and as a user of the listed modules one does not have to worry about manually handling the coroutines.

Is this correct or am I confusing things here?

Thanks for all the work and keep it up!

Cheers,
Martin

.

agentzh

Hello!

On Mon, Mar 3, 2014 at 10:19 AM, Martin Felis wrote:
> Now I was wondering where exactly the magic is happening. I do know a bit
> about Lua's coroutines, especially their use in
> http://www.lua.org/pil/9.4.html.

The magic happens under the hood, automatically, everytime you call a
IO-like ngx_lua primitives, like the cosocket API,
ngx.location.capture*() API, ngx.sleep(), ngx.flush(true), and etc.
Basically, if the call finds it impossible to complete the request
immediately, then it automatically *yields* the current Lua "light
thread" (implemented upon Lua coroutines), and later *resumes* the
thread later upon the corresponding events. The user Lua code that is
able to run the nonblocking IO primitives is always run inside a
"light thread" implemented atop Lua coroutines, like the Lua code
specified by content_by_lua and access_by_lua directives.

Regards,
-agentzh