Introduction

I’m newbie in krakend, i have two backend that accessed sequential, first access host let’s say a.com to get an id from there, then the second backend have dynamic host depends on the id from a.com response if the id is 1 then the host for the second backend is b if the id is 2 then the host for the second backend is c

Question

How to deliver the response from a.com to next backend request

{
  "$schema": "https://www.krakend.io/schema/krakend.json",
  "version": 3,
  "name": "Test Proxying & Microservices",
  "timeout": "3000ms",
  "cache_ttl": "300s",
  "endpoints": [
    {
      "endpoint": "/protected/{path}",
      "extra_config": {
        "proxy": {
          "sequential": true
        }
      },
      "backend": [
        {
          "encoding": "no-op",
          "@comment": "Authentication Service",
          "url_pattern": "/api/v1/allocations",
          "method": "GET",
          "host": ["https://a.com"],
          "disable_host_sanitize": false,
          "extra_config": {
            "modifier/lua-backend": {
              "sources": ["authz.lua"],
              "allow_open_libs": true,
              "post": "print('Auth Response'); local r = response.load(); r:headers('Accept','*/*'); print(r);authz_proxy_decorator(r)"
            }
          }
        },
        {
          "@comment": "Genesist Base",
          "encoding": "no-op",
          "url_pattern": "/{path}",
          "host": ["https://{dynamic_host_from_resp0_next_host}.com"],
          "extra_config": {
            "modifier/lua-backend": {
              "sources": ["authz.lua"],
              "pre": "print('Backend response, pre-logic:'); local r = request.load(); print(r:headers('Accept')); get_previous_code(r);"
            }
          }
        }
      ]
    }
  ]
}

I expect if a.com response {“host”: c} then the next backend will be c.com