How to register and use custom variable?

[loseself]

Description

Referenced document: https://apisix.apache.org/zh/docs/apisix/plugin-develop/#%E6%B3%A8%E5%86%8C%E8%87%AA%E5%AE%9A%E4%B9%89%E5%8F%98%E9%87%8F

How do I use it?, "register custom variable"
Can you provide demo?

how to register
how to get
how to destroy
how to modify
and announcements

---

After I registered, and reload plugin, there is an error

local core = require "apisix.core"

core.ctx.register_var("a6_labels_zone2", function(ctx)
local route = ctx.matched_route and ctx.matched_route.value
if route and route.labels then
return route.labels.zone
end
return nil
end)

22826 [lua] events.lua:194: do_handlerlist(): worker-events: event callback failed; source=/apisix/admin/plugins/reload, event=PUT, pid=47 error='/usr/local/apisix/apisix/plugin.lua:113: attempt to index local 'plugin' (a number value)
stack traceback:
/usr/local/apisix/apisix/plugin.lua:113: in function 'load_plugin'
/usr/local/apisix/apisix/plugin.lua:191: in function 'load'
/usr/local/apisix/apisix/plugin.lua:300: in function 'load'
/usr/local/apisix/apisix/admin/init.lua:309: in function </usr/local/apisix/apisix/admin/init.lua:307>
[C]: in function 'xpcall'
...local/apisix//deps/share/lua/5.1/resty/worker/events.lua:185: in function 'do_handlerlist'
...local/apisix//deps/share/lua/5.1/resty/worker/events.lua:219: in function 'do_event_json'
...local/apisix//deps/share/lua/5.1/resty/worker/events.lua:361: in function 'poll'
...local/apisix//deps/share/lua/5.1/resty/worker/events.lua:380: in function <...local/apisix//deps/share/lua/5.1/resty/worker/events.lua:375>', data=1648092700, context: ngx.timer

Environment

• APISIX version (run apisix version): 2.12.1
• Operating system (run uname -a): Darwin Kernel Version 21.1.0: Wed Oct 13 17:33:23 PDT 2021; root:xnu-8019.41.5~1/RELEASE_X86_64 x86_64
• OpenResty / Nginx version (run openresty -V or nginx -V): nginx version: openresty/1.19.9.1
• etcd version, if relevant (run curl http://127.0.0.1:9090/v1/server_info): version: 3.4.15, API version: 3.4
• APISIX Dashboard version, if relevant:
• Plugin runner version, for issues related to plugin runners:
• LuaRocks version, for installation issues (run luarocks --version): 3.8.0

[liangliang4ward]

like this:

apisix/apisix/stream/plugins/mqtt-proxy.lua

Lines 26 to 28 in d1d8a8e

	core.ctx.register_var("mqtt_client_id", function(ctx)
	return ctx.mqtt_client_id
	end)

[loseself]

thanks

[loseself]

How to destroy

[tzssangglass]

see: #6656 (comment)

[shuaijinchao]

How to destroy

you can use core.ctx.register_var("xxxx", function(ctx) return nil end) destroy.

[amrellafy]

Loading the lua file is enough to register the custom variable or it must be a part of a custom plugin?

[tokers]

Loading the lua file is enough to register the custom variable or it must be a part of a custom plugin?

It doesn't have to be a plugin, you can even modify the core codebase of APISIX and register some custom variables. But please make sure that you know what you're doing, or something might be broken.

[amrellafy]

@tokers so loading the lua file is enough?
Then It might be there is no need to modify the codebase?

[github-actions]

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[github-actions]

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