url_a --> kong-plugin-url-regex-rewriter --> url_b --> upstream
eg.
source: /a/resource
target: /b/resource
in plugin setting page:
set regex = /a/(.*)$
set replace = /b/$1
refer to :
ngx.re.sub(subject, regex, replace, options?)
the arg url_a pass to sub function as subject, regex and replace are the same as setting page.