fix(*): don't invoke region detection code on the module toplevel and…

… advise against trying to (#81)

README.md

@@ -50,17 +50,20 @@ read that setting, hence you have to set it manually, see [the docs](https://tie
 ### Global settings
 
 This library depends on global settings. Especially the core services for authentication
-and metadata. Many of those can (also) be specified as environment variables.
+and metadata. Many of those can (also) be specified as environment variables.  Environment
+variables can only be accessed during the OpenResty `init` phase.  Thus, to ensure correct
+configuration from environment variables, the `resty.aws.config` module must be required on
+the top-level of the module using this library:
 
-Hence it is recommended to populate the global configuration object at application start
-in the OpenResty `init` phase. Simply add the following line;
-
-```
-        local _ = require("resty.aws.config").global
+```Lua
+local aws_config = require("resty.aws.config")
 ```
 
-This ensures the environment variables can still be read (in the `init` phase). And
-the auto-detection of the AWS region will execute.
+The `.global` property of the `aws_config` variable can then be used as the global
+configuration.  Note that when `.global` is first accessed, automatic region detection
+through the AWS metadata service is performed.  Thus, it is not advisable to access
+it on the module level unless to avoid startup delays in non-AWS environment, caused by
+the requests to the metadata service timing out.
 
 ---
 
@@ -166,6 +169,11 @@ Release process:
 1. upload using: `VERSION=x.y.z APIKEY=abc... make upload`
 1. test installing the rock from LuaRocks
 
+### 1.3.3 (13-Sep-2023)
+
+- fix: don't invoke region detection code on the module toplevel and advise against trying to.
+  [81](https://github.com/Kong/lua-resty-aws/pull/81)
+
 ### 1.3.2 (13-Sep-2023)
 
 - fix: unsigned request should support network related config option

src/resty/aws/utils.lua

@@ -5,14 +5,8 @@
 local semaphore = require "ngx.semaphore"
 local http = require "resty.luasocket.http"
 local json = require "cjson"
-local global_config = require("resty.aws.config").global
-
--- get the Env vars here, they have been stored in the config module
-local AWS_REGION = global_config.AWS_REGION
-local AWS_DEFAULT_REGION = global_config.AWS_DEFAULT_REGION
-local AWS_EC2_METADATA_DISABLED = global_config.AWS_EC2_METADATA_DISABLED
-local ECS_CONTAINER_METADATA_URI_V4 = global_config.ECS_CONTAINER_METADATA_URI_V4
-local ECS_CONTAINER_METADATA_URI_V3 = global_config.ECS_CONTAINER_METADATA_URI
+local aws_config = require("resty.aws.config")
+
 local ECS_CONTAINER_METADATA_URI_V2 = "http://169.254.170.2/v2/"
 local IDMS_URI = "http://169.254.169.254"
 local METADATA_TIMEOUTS = 5000  -- in milliseconds
@@ -112,12 +106,12 @@ function Utils.getECSTaskMetadata(subpath, version)
   local url
   local version = version and version:upper() or "V4"
   if version == "V4" then
-    url = ECS_CONTAINER_METADATA_URI_V4
+    url = aws_config.global.ECS_CONTAINER_METADATA_URI_V4
     if not url then
       return nil, "ECS metadata url V4 not found in env var ECS_CONTAINER_METADATA_URI_V4"
     end
   elseif version == "V3" then
-    url = ECS_CONTAINER_METADATA_URI_V3
+    url = aws_config.global.ECS_CONTAINER_METADATA_URI_V3
     if not url then
       return nil, "ECS metadata url V3 not found in env var ECS_CONTAINER_METADATA_URI"
     end
@@ -172,23 +166,23 @@ do  -- getCurrentRegion
   end
 
   local function detect_region()
-    if AWS_REGION then
+    if aws_config.global.AWS_REGION then
       ngx.log(ngx.DEBUG, "detecting AWS region from AWS_REGION env variable")
-      set_region(AWS_REGION)
+      set_region(aws_config.global.AWS_REGION)
       return true
     else
       ngx.log(ngx.DEBUG, "no AWS_REGION env variable")
     end
 
-    if AWS_DEFAULT_REGION then
+    if aws_config.global.AWS_DEFAULT_REGION then
       ngx.log(ngx.DEBUG, "detecting AWS region from AWS_DEFAULT_REGION env variable")
-      set_region(AWS_DEFAULT_REGION)
+      set_region(aws_config.global.AWS_DEFAULT_REGION)
       return true
     else
       ngx.log(ngx.DEBUG, "no AWS_DEFAULT_REGION env variable")
     end
 
-    if ECS_CONTAINER_METADATA_URI_V4 then
+    if aws_config.global.ECS_CONTAINER_METADATA_URI_V4 then
       ngx.log(ngx.DEBUG, "detecting AWS region from ECS_CONTAINER_METADATA_URI_V4 env variable")
       local metadata, err = Utils.getECSTaskMetadata("/task", "V4")
       if not metadata then
@@ -201,7 +195,7 @@ do  -- getCurrentRegion
       ngx.log(ngx.DEBUG, "no ECS_CONTAINER_METADATA_URI_V4 env variable")
     end
 
-    if ECS_CONTAINER_METADATA_URI_V3 then
+    if aws_config.global.ECS_CONTAINER_METADATA_URI_V3 then
       ngx.log(ngx.DEBUG, "detecting AWS region from ECS_CONTAINER_METADATA_URI env variable")
       local metadata, err = Utils.getECSTaskMetadata("/task", "V3")
       if not metadata then
@@ -214,7 +208,7 @@ do  -- getCurrentRegion
       ngx.log(ngx.DEBUG, "no ECS_CONTAINER_METADATA_URI env variable")
     end
 
-    if AWS_EC2_METADATA_DISABLED then
+    if aws_config.global.AWS_EC2_METADATA_DISABLED then
       ngx.log(ngx.DEBUG, "AWS_EC2_METADATA_DISABLED is set, skipping region detection from IDMSv2 metadata")
     else
       ngx.log(ngx.DEBUG, "detecting AWS region from IDMSv2 metadata")