Support setting HTTP trigger listen address in env var

[kate-goldenring]

Enables setting the shim's HTTP trigger listen address in SPIN_HTTP_LISTEN_ADDR (same naming scheme as Spin CLI). This can now be set in a container spec, which follows the approach of configuring the Spin runtime via container environment variables that is laid out in this draft SKIP.

closes #52
related #128

[jsturtevant]

LGTM

[rajatjindal]

LGTM :)

[kate-goldenring]

@radu-matei @jsturtevant @Mossaka @devigned it would be great to get this merged before the next release if possible. There are two commented LGTMs but a review would be appreciated

[devigned]

+1 lgtm.

One thing to consider for future, but might be hard to change at this point, is that the default port is 80. Perhaps, we may want to consider a higher port range default.

Also, it might be nice to represent the informational container spec field of ports.containerPorts with the value of the SPIN_HTTP_LISTEN_ADDR_ENV via the Spin operator when creating the SpinApp, so it's more clear to folks.

[kate-goldenring]

Also, it might be nice to represent the informational container spec field of ports.containerPorts with the value of the SPIN_HTTP_LISTEN_ADDR_ENV via the Spin operator when creating the SpinApp, so it's more clear to folks.

@devigned, to clarify, are you suggesting adding a ports.containerPorts field to the SpinApp CRD? I agree that we need a clean way to set this in the SpinApp

[devigned]

@kate-goldenring hmm... not necessarily adding ports.containerPorts to the SpinApp since it is an array and it would probably better represented in a more Spin domain specific singular value field. I was suggesting that when the SpinApp is processed by the operator that the end product, the resulting pod / container spec would have that informational field. For example:

apiVersion: ...
kind: SpinApp
metadata:
  name: my-app
spec:
  httpListeningPort: 3000 # this drives configuration of the pod / container spec and informs the pod.spec.ports.containerPort
  otherStuff: ...
---
apiVersion: v1
kind: Pod
metadata:
  name: my-app
spec:
  containers:
  - name: spin-app
    ports:
      - containerPort: 3000 # this is only for information