Make healthcheck backends protocol configurable

[Miouge1]

New feature

What did you do?

[backends]
  [backends.backend1]
    [backends.backend1.healthcheck]
    path = "/health"
    interval = "10s"
    port = 8081

What did you expect to see?

[backends]
  [backends.backend1]
    [backends.backend1.healthcheck]
    path = "/health"
    interval = "10s"
    port = 8081
    proto = "http" # or "https"

What did you see instead?

So such option available.

Output of traefik version:

Version:      v1.4.2
Codename:     roquefort
Go version:   go1.9.2
Built:        2017-11-02_01:47:46PM
OS/Arch:      linux/amd64

What is your environment & configuration (arguments, toml, provider, platform, ...)?

Application is running over HTTPS but the monitoring port is HTTP only.

[emilevauge]

@Miouge1 we don't see any use case for this. Why do you need to run the heakthcheck on another port ?

[softkot]

Here is my usercase for another port: I am running Java GRPC service on port 8443 and it can't be used for healthcheck thus java GRPC does not handle HTTP proto either. The only case for me it to create simple HTTP service within same process and handle healtcheck there.

P.S. Docs says it has port option but it does not works. I have look into the sources and it seems to be true.

P.P.S. There was the pull request that try to match docs with actual behaviour.

[Miouge1]

My use case is similar to @softkot's: the application runs on HTTPS (:443) but the health probe in HTTP only (on :8080). That way, :443 is exposed externally by Traefik but :8080 is internal only.

To be noted that the doc says:

For example:

[backends]
  [backends.backend1]
    [backends.backend1.healthcheck]
    path = "/health"
    interval = "10s"

To use a different port for the healthcheck:

[backends]
  [backends.backend1]
    [backends.backend1.healthcheck]
    path = "/health"
    interval = "10s"
    port = 8080

but there is no guarantee that the other port number is running the same protocol (HTTP or HTTPS).

[softkot]

This issue is somehow related to #1967 when KV storage is used there is no way to use port either.

I think it will be right to set both the protocol, path and port for any case. And have protocol to support native HTTP2 (grpc) checks and set path for some GRPC healthcheck method.