Proposal: support advanced matching based on POST form

[bzp2010]

Proposal

Background

Currently, advanced matching only uses URL query data when matching on request content, and does not support advanced matching with fields in POST form as conditions.

Objectives

Support for POST form as matching conditions by adding new matching key.

Solutions

Determine the added matching key prefix

I think we can add a new post_arg_ prefix as a POST form data prefix, this is similar to the arg_ used in the query parameter currently provided by openresty.

Modify the mt metatable in ctx.lua and add a new key processor

The main purpose of the current modification is to handle POST form submissions with Content-Type x-www-form-urlencoded.

Use ngx.req.read_body() and fetch data from ngx.req.get_post_args() according to read requirements in the metatable to achieve complete on-demand inert loading with the help of the metatable feature. The currently used lua-resty-expr can automatically get the target value and compare it with the meta table based on the expression.

current arg_:

apisix/apisix/core/ctx.lua

Lines 167 to 176 in 042ce5c

	elseif core_str.has_prefix(key, "arg_") then
	local arg_key = sub_str(key, 5)
	local args = request.get_uri_args()[arg_key]
	if args then
	if type(args) == "table" then
	val = args[1]
	else
	val = args
	end
	end

demo:

if core_str.has_prefix(key,"post_arg_") then
  ngx.req.read_body()
  local args, err = ngx.req.get_post_args()
  loacl post_arg_key = sub_str(key, 10)
  val = args[post_arg_key]

Pre-fetching modifications

1. apisix/core/ctx.lua: Add new key processor
2. t/*: Add test case
3. Add documents for new function
4. Optional: Add support for its configuration to the Dashboard

Other

What are your ideas?

[tokers]

+1, Proposal LGTM.

[tzssangglass]

+1, useful

[jagerzhang]

请教下，这个新增特性是否支持content-type=application/json的POST请求中的body过滤?
目前我们是通过 serverless-pre来实现的，如果这个特性能支持，那就更优雅了。

[tzssangglass]

not support yet, here:

apisix/apisix/core/ctx.lua

Line 186 in cc43b9f

if request.header(nil, "Content-Type") == "application/x-www-form-urlencoded" then

json is nested and complicated.

[jagerzhang]

@tzssangglass 那还是只能用serverless解决body字段路由的问题了~ 希望可以支持下。。。

[tzssangglass]

@tzssangglass 那还是只能用serverless解决body字段路由的问题了~ 希望可以支持下。。。

can you submit a new issue about support this?