[OpenWrt-Devel] LuaJIT Vs Lua and other questions

[Anton D. Kachalov]

Hello, Jo.

30.06.2016, 01:15, "Jo-Philipp Wich" <jo at mein.io>:
> Hi Anton,
>
>>  First I've tried to name package as "luajit" and add CONFLICTS:=lua
>>  (version should be provided to conflict with) and PROVIDES:=lua
>>  variables like for RPM to make a replacement package, but I get a
>>  dependency loop. Therefore, I name produceable packages "lua" and
>>  "liblua". The problem is that I unable to override default "lua"
>>  package from openwrt tree (it is not possible to "uninstall", no
>>  effect of scripts/feeds uninstall ...). Only one possible way is to
>>  remove "lua" directory from "package" dir and install own luajit pack
>>  via "scripts/feeds install -p ... luajit". Does mainstream package
>>  directory has a feed name while it is not separate from build tree
>>  like an extra openwrt/packages repo and other 3rd party repos? It
>>  could be fair to have an ability to override core packages with
>>  "scripts/feeds install".
>
> Overwriting existing packages with other packages having the same name
> from external feeds is messy and will always lead to undefined behavior,
> don't do that. What would probably work is packaging luajit separately
> and replace the existing /usr/bin/lua with a program like:
>
> -- 8< --
> #!/bin/sh
>
> if [ -x "/usr/bin/luajit" ]; then
>   exec /usr/bin/luajit "$@"
> else
>   exec /usr/bin/lua.bin "$@"
> fi
> -- >8 --

This variant do not solve packages' dependencies problem. And I still need to somehow recompile (and disable mainstream "lua" first) packages with LuaJIT libs. Brute replacement works better in such case. I don't want to waste space for two Lua version in the system.
Just a generic question – what is the obstacles to move from Lua interpreter to LuaJIT? There are minor changes in regexp's quotes. Other things seems to work. I've completely recompile stuff with LuaJIT.


>>  I'm going to use LuaJIT on our BMCs (ARM Aspeed SoC) as a HTTP API
>>  backend. Nginx compiled with LuaJIT takes about 220 RPS on dynamic
>>  content (reading one value from i2c bus at each call). With auth
>>  checking (and caching result of auth via ubus for 1min at Nginx site
>>  via shared dict) I've got 200 RPS (9% drop). For reference, static
>>  pages serves by Nginx at 330 RPS. Simple micropython http server
>>  takes 40 RPS. LUCI + uhttpd is dramatically slow (2-4 RPS) even with
>>  LuaJIT cause at each request there are a lot and a lot of file
>>  access.
>
> Did you try uhttpd-mod-lua to avoid bootstrapping with each request? Its
> likely still way slower but should offer better performance compared to
> execute Lua as CGI.

Yeap, I switched to it later. It doesn't speed up a lot, but much better.

>>  Current LuCI modules are not compatible with Nginx (there are
>>  a lot of global vars read & write). So, as a replacement for IPMI
>>  proto calls we would prefer to use RPC calls (REST-like) made
>>  separately from LUCI eco system. We leave LUCI for Web configuration
>>  staff only.
>>
>>  Also I found a little complicated to add more authentication methods
>>  (like AD, LD, Radius, O-Auth and so on).
>
> You mean PAM? Or authentication for LuCI?

This is a good question. With simple configuration I have only file-based auth, no PAM. I would like to have one authenticator for system-wide services such as ssh and LuCI with it's RPC. I didn't see any evidence of PAM support in LuCI. But I might not look well through the code.

>>  It's a little tricky, but
>>  possible. I made O-Auth like http requester to our auth center. For
>>  HTTP-RPC module it should be done as duplicate code.
>
> You mean the UBUS HTTP RPC?

Right.

>
>>  Another problem that I've faced is an access from Nginx to ubus
>>  (nginx runs under "nobody"). I'm able to send requests, but get an
>>  empty response. Only Nginx running under root lead to receive a
>>  proper answers. Socket file has enough permissions. What is the
>>  proper way to configure ubus to allow nginx process to make requests
>>  to ubus?
>
> You can ship a /usr/share/acl.d/*.json file along with your application
> to whitelist certain ubus namespaces/procedures for a given unix user
> context, see
> https://github.com/openwrt/luci/commit/81e80c4b876e8e68bb8b022c39d0941e2c1ccb56
> for example.

Thanks, I'll try.

-- 
Anton D. Kachalov
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