redirecting Haproxy HTTP-requests in mode tcp

Question

I would like to return a http-response status 200 to http-requests which are send on port 8883. The port is used for mqtt but we would like to catch http-requests on it.

The configuration I have now is (Haproxy 2.2):

frontend smqtt
    bind :8883
    mode tcp
    use_backend port_check if HTTP
    default_backend smqtt-broker

backend smqtt-broker
    mode tcp
    server A-SMQTT <ip>:<port> check
    server B-SMQTT <ip>:<port> check

backend port_check
    mode http
    http-response return status 200 content-type "text/plain" lf-string "Port Check Success"

The MQTT backend (default_backend) is working but the 'catching' of HTTP-requests is not. How can I detect (and change the backend) if a HTTP-request is coming in mode tcp?

Answer 1

You will need to give HAProxy some time to inspect the package.

I suggest to add this line tcp-request inspect-delay 5s into frontend

frontend smqtt
  bind :8883
  mode tcp
  
  tcp-request inspect-delay 5s

  use_backend port_check if HTTP
  default_backend smqtt-broker

Answer 2

The working configuration is:

frontend smqtt
    bind :8883
    mode tcp
    tcp-request inspect-delay 5s
    tcp-request content capture req.proto_http len 1
    use_backend port_check if HTTP
    default_backend smqtt_broker

backend smqtt_broker
    mode tcp
    server A-SMQTT <ip>:<port> check
    server B-SMQTT <ip>:<port> check

backend port_check
    mode http
    http-request return content-type "text/plain" string "Port Check Succes"

Have to capture req.proto_http and http-request instead of http-response.