Inject extra fields to API backend

nginx.conf

upstream threescale_admin_api {
  # 3scale adminstration API
  server MYCOMPANY-admin.3scale.net:443 max_fails=5 fail_timeout=30;
}

location = /threescale_appfind {
  internal;
  set $provider_key "PROVIDERKEY";

  proxy_pass "https://threescale_admin_api/admin/api/applications/find.xml?provider_key=$provider_key&app_id=$app_id";
  proxy_set_header  Host  "MYCOMPANY-admin.3scale.net";
}

location / {
  # below the other variable initializations
  set $app_id null;
  set $organizationId null;
  set $brandId null;
  
  ## add these lines below the other "proxy_set_header" lines
  proxy_set_header X-Org-Id $organizationId;
  proxy_set_header X-Brand-Id $brandId;
  ##
}

nginx.lua

function set_app_info(app_id)
  local metadata = ngx.shared.metadata
  local app_data = metadata:get(app_id)
  local brandId, organizationId

  if app_data then
    local idx = app_data:find(":")
    if idx then
      brandId = app_data:sub(1, idx-1)
      organizationId = app_data:sub(idx+1)
    end
  else
    local res = ngx.location.capture("/threescale_appfind", { share_all_vars = true })
    local m1, err1 = ngx.re.match(res.body, [[<brandId>(\S+)<\/brandId>]])
    local m2, err2 = ngx.re.match(res.body, [[<organizationId>(\S+)<\/organizationId>]])
    if m1 then brandId        = m1[1] end
    if m2 then organizationId = m2[1] end
    brandId        = brandId        or "none"
    organizationId = organizationId or "none"
    -- the last parameter is the expiration time in seconds (0=no expiration)
    -- it is recommended to set an expiration time to sync any metadata changes
    metadata:set(app_id, brandId .. ":" .. organizationId, 0)
  end

  ngx.var.brandId = brandId
  ngx.var.organizationId = organizationId
end

-- call set_app_info(ngx.var.app_id) at the end of the file