"attempt to yield across C-call boundary" occur while connect()

[bigplum]

I package redis functions into a module testdb.lua, and include it in another module testm.lua.

testm.lua is required in test.lua, which is running by ngx_lua:

content_by_lua_file luas/test.lua;

Finally, the error occur:

2012/04/07 22:10:32 [error] 24794#0: *185113 1, client: 127.0.0.1, server: localhost, request: "GET /test HTTP/1.1"
2012/04/07 22:10:32 [error] 24794#0: *185113 lua handler aborted: runtime error: attempt to yield across C-call boundary, client: 127.0.0.1, server: localhost, request: "GET /test HTTP/1.1"

The first ngx.log() is excuted, but second not. So is there anything wrong in redis:connect()?

All the files could be found in: https://gist.github.com/2329313

thanks.

[bigplum]

If we put get_rtdb() into a function, it works well.

https://gist.github.com/raw/2329313/691fac7cbfac56ea331c1866e0c32400d271942d/testm1.lua

curl localhost/test
ok testm
ok test

[agentzh]

It seems that the require function is implemented as a C function, which cannot be yielded in the middle of the require call. The LuaJIT implementation does not support yielding across the C function call boundary, just like the standard Lua 5.1 interpreter. Your work-around indeed eliminated this and hence worked.

[bigplum]

It looks like you said.

[yangm97]

Sorry if I’m stealing this issue, but I still don’t get how to work around this. Here’s my situation:

database.lua

local config = require 'config'

local red

if ngx then
	local redis = require 'resty.http'
	red = redis:new()
	red:connect(config.redis.host, config.redis.port)
else
	local redis = require 'redis'
	red = redis.connect(config.redis.host, config.redis.port)
end

red:select(config.redis.db)

return red

main.lua and many other “plugins”:

local db = require ‘database’
…
db:hset('bot:usernames', '@'..msg.from.username:lower(), msg.from.id)
...

So I have this wrapper mainly because my application can run either with or without openresty and because I wanted to avoid copy-pasting (the somewhat big) database connection code.

The error message is the same (lua entry thread aborted: runtime error: attempt to yield across C-call boundary).

[agentzh]

@yangm97 Your usage is wrong. Please read the documentation more carefully:

https://github.com/openresty/lua-resty-redis/#limitations

[agentzh]

@yangm97 Also, read the discussion above.

[yangm97]

I read both. Also I kind see where it’s failing and why (“The resty.redis object instance cannot be stored in a Lua variable at the Lua module level”) but I really don’t see a solution other than copy-pasting 13 lines of code across ~30 files to work around this.

[seven1240]

seems set on ngx.ctx works for me

local resty_redis = require "resty.redis"
local redis = resty_redis:new()

redis:set_timeout(1000) -- 1 sec
ngx.ctx.redis = redis

[cleverpig]

seems set on ngx.ctx works for me

local resty_redis = require "resty.redis"
local redis = resty_redis:new()

redis:set_timeout(1000) -- 1 sec
ngx.ctx.redis = redis

But it is a short lifetime(request) by using ngx.ctx