bug: etcd cache

[yocaning]

Issue description

if you have own etcd cache like this：
authorizations_etcd, error = core.config.new("/authorizations", {
automatic = true,
item_schema = app_scheme
})

if the key authorizations dont have a key value （init_dir）,the etcd cache dont load when apisix restart

Environment

• apisix version (cmd: apisix version):
• OS (cmd: uname -a):
• OpenResty / Nginx version (cmd: nginx -V or openresty -V):
• etcd version, if have (cmd: run curl http://127.0.0.1:9090/v1/server_info to get the info from server-info API):
• apisix-dashboard version, if have:
• the plugin runner version, if the issue is about a plugin runner (cmd: depended on the kind of runner):
• luarocks version, if the issue is about installation (cmd: luarocks --version):

Steps to reproduce

1.authorizations_etcd, error = core.config.new("/authorizations", {
automatic = true,
item_schema = app_scheme
})
2.restart apisix
3. the authorizations_etcd dont have data

Actual result

when restart apisix. load the etcd cache data

Error log

--- dont have nodes array
{"key":"/gateway/authorizations/AKIDz8krbsJ5yKBZQpn74WFkmLPx3EXAMPLE1","createdIndex":26295,"modifiedIndex":26473,"value":{"secret":"AKIDz8krbsJ5yKBZQpn74WFkmLPx3EXAMPLE11","username":"yyy"}}

---- --other key ex:routes: (hava nodes array)
{"key":"/gateway/routes","nodes":[{"key":"/ioa-gateway/routes/00000000000000025212","createdIndex":25213,"modifiedIndex":25247,"value":{"update_time":1634119249,"methods":["GET","POST"],"id":"00000000000000025212","upstream":{"type":"roundrobin","hash_on":"vars","nodes":{"9.135:11111":1},"pass_host":"pass"},"create_time":1634118070,"status":1,"plugins":{"cors":{"allow_credential":false,"allow_origins":"","max_age":5,"expose_headers":"","allow_methods":"","allow_headers":""}}

Expected result

No response

[tzssangglass]

Is this the code you implemented yourself? If so, I'll turn this issue into a discussion and we'll discuss it in the discussion.

[yocaning]

Is this the code you implemented yourself? If so, I'll turn this issue into a discussion and we'll discuss it in the discussion.

yes

[tzssangglass]

You can look at the implementation of sync etcd data in APISIX, for example: https://github.com/apache/apisix/blob/0e7ff54e6e7ef44bee85d9f38752486d9c104921/apisix/plugin.lua# L490-L498.

In short, sync etcd data is at the init_worker_by_lua, which is not easy, but it can be done.