The Upstream service sends a 406 status code but it is required to respond to the client with a 404 status code. How can the status code be changed?
Changing the response status code sent to the client with a post-function plugin
Uses:
Kong Gateway
TL;DR
How can the response status code be changed?
Add a post-function plugin running in the header_filter phase that checks kong.service.response.get_status() and, when it matches the unwanted upstream status code, calls kong.response.exit() with the desired status code and body before the response reaches the client.
Steps
You can use a post-function serverless plugin to change the response details. For example, create a Kong Service that points to https://httpbin.org (note: httpbin.org is a public demo service outside Kong’s control and may be temporarily unavailable; substitute any reachable upstream that lets you request a specific status code);
curl -X POST 'https://api.kong.lan:8444/default/services' \
-H 'Content-Type: application/json' \
--data-raw '{
"host": "httpbin.org",
"protocol": "https",
"name": "remote-httpbin",
"port": 443,
"retries": 0
}'and a corresponding Route for the Service;
curl -X POST 'https://api.kong.lan:8444/default/services/remote-httpbin/routes' \
-H 'Content-Type: application/json' \
--data-raw '{
"name": "remote-httpbin",
"paths": [
"/remote-httpbin"
]
}'Test the Kong API with the /status endpoint from httpbin.org (note the 406 response code);
curl -s https://proxy.kong.lan/remote-httpbin/status/406 -w "%{http_code}"
{"message": "Client did not request a supported media type.", "accept": ["image/webp", "image/svg+xml", "image/jpeg", "image/png", "image/*"]}406Create a serverless.lua file containing code like this;
if (kong.service.response.get_status() == 406) then
return kong.response.exit(404, {message="no Route matched with those values"})
endAdd the plugin to a Route;
curl -s -X POST 'https://api.kong.lan:8444/default/routes/remote-httpbin/plugins' \
-F 'name="post-function"' \
-F 'config.header_filter=@"./serverless.lua"'Test the Kong API again, with the same /status endpoint from httpbin.org. Note the 404 response code from the plugin;
curl -s https://proxy.kong.lan/remote-httpbin/status/406 -w "%{http_code}"
{"message":"no Route matched with those values"}404Test the Kong API again, with the same /status endpoint from httpbin.org. Note the 200 response code from the Upstream is unchanged by the plugin.
curl -s https://proxy.kong.lan/remote-httpbin/status/200 -w "%{http_code}"
200