fix(admin): use local config to fetch global rules in standalone mode

[janiussyafiq]

Description

In standalone mode (config_provider: yaml), the get_global_rules() function in apisix/admin/global_rules.lua unconditionally calls core.etcd.get("/global_rules") to check for duplicate plugin conflicts whenever a global rule is validated. This is triggered on every PUT /apisix/admin/configs request from the ingress-controller that contains a global_rules entry, causing repeated etcd connection errors in the logs even though etcd is not used in standalone mode.

Root cause: check_conf calls get_global_rules() which has no awareness of the current config provider, so it always attempts an etcd read regardless of deployment mode.

Fix: guard get_global_rules() to return nil immediately when local_conf.deployment.config_provider == "yaml", skipping the etcd call entirely. This is safe because returning nil causes check_conf to skip the conflict loop (already guarded by if global_rules then), and in standalone mode the ingress-controller is responsible for sending a consistent config atomically.

Which issue(s) this PR fixes:

Fixes #12989

Checklist

• I have explained the need for this PR and the problem it solves
• I have explained the changes or the new features added to this PR
• I have added tests corresponding to this change
• I have updated the documentation to reflect this change
• I have verified that this change is backward compatible (If not, please discuss on the APISIX mailing list first)

[shreemaan-abhishek]

get_global_rules is used to check if the incoming global rule conflicts with existing global rules, skipping the check entirely doesn't seem correct.

[janiussyafiq]

that is right, good catch! should still get the global rules for standalone mode cases to prevent warning log from checking etcd. will do the fix

[nic-6443]

The judgment of deployment.config_provider == "yaml" is not comprehensive, as its value can also be json. We can encapsulate a function to determine whether the current config_provider is local.

[janiussyafiq]

fixed