bug: Lru Cache Problem in traffic-split

[Marco-Zheng]

Issue description

When i set cache in _M.init() by using timer , it was successfuly, but get nil in _M.access() function, see details as below Steps

Environment

• apisix version (cmd: apisix version): 2.6

Steps to reproduce

Here is my extension code to timely fetch some data from etcd in traffic-split plugin

OIDC_CACHE_TTL
local version_control_lrucache = lru_new(1024 * 4)


local function traffic_info_fetch_per_env(profile_active)
    local key = "/version_control/"..profile_active
    local res, err = core.etcd.get(key)
    if not res or res.status ~= 200 then
        --core.log.error("failed to get global rule[", key, "]: ", err)
        return
    end
    local version_control = res.body.node.value
    version_control_lrucache:set("version_control:"..profile_active, version_control, OIDC_CACHE_TTL)
    core.log.error("push complte")
end

local function traffic_info_fetch()
    core.log.error("start traffic info pull")
    local profile_actives = {"dev", "uat", "pre", "prod"}
    for _, profile_active in ipairs(profile_actives) do
        traffic_info_fetch_per_env(profile_active)
    end
end

function _M.init()
    timers.register_timer("plugin#traffic-split", traffic_info_fetch, true)
end

function _M.destroy()
    timers.unregister_timer("plugin#traffic-split", true)
end

Then i add below code in _M.acccess() function in order to get the data from cache

local version_control = version_control_lrucache:get("version_control:uat")

But the weird thing is that my cache settings are successful , when I fetch data from cache, it was nil
My lua_code_cache is open

Actual result

cache get is nil

Error log

No error log

Expected result

get the cache what i set in

[Marco-Zheng]

It seems that the memory is not shared between different processes caused, if apisix has something memory shared cache utils(like lua_shared_dict)

[tzssangglass]

yes, lrucache is shared in worker. and lua_shared_dict is shared by differents workers.

[Marco-Zheng]

seems using lua_shared_dict can resolve this problem

[tzssangglass]

I'm turning this issue into a discussion because it's not the code for the project.