Environment variables do not take effect in the default configuration file.

[flearc]

Apisix supports the utilization of environment variables (${{VAR}}) within its configuration file. However, I have observed that these variables do not appear to take effect when defined in the default configuration file (config-default.yaml) and a custom configuration file is used through APISIX_PROFILE. The relevant code that governs this behavior is located here:

apisix/apisix/cli/file.lua

Line 235 in 6278ae0

function _M.read_yaml_conf(apisix_home)

. It seems that Apisix first reads the default YAML file and then the customized YAML file. However, the resolve_conf_var() function is only executed for the customized YAML file.

I am unsure whether this behavior is intentional, particularly whether Apisix is intentionally designed not to read variables from the default YAML file. If this is indeed the case, I believe it would be valuable for Apisix to offer explanatory documentation clarifying the usage of variables. I have identified two places where environment variables are employed:

1. Here:

   apisix/conf/config.yaml

   Line 28 in 6278ae0

   # To configure via environment variables, you can use `${{VAR}}` syntax. For instance:

2. And here:

   apisix/docs/zh/latest/admin-api.md

   Line 70 in 6278ae0

   要通过环境变量进行配置，可以使用 `${{VAR}}` 语法。例如：

   .

If this behavior is not intentional, I would recommend extending the functionality to the default YAML file as well. Otherwise, it might appear peculiar that environment variables can only be employed in customized configuration files and not in the default configuration file.

[flearc]

See #11340