Add Kompose support

Kompose is an awesome conversion tool which creates Kubernetes descriptor objects from Docker compose files.

The idea is to extend the fabric8:resource goal to support Docker compose files via an external CLI call to kompose. This should be possible to be switched on either explicitly by a configuration option <composeFile> in the XML configuration or maybe even implicitly by monitoring a directory src/main/fabric8-kompose for the content of some docker-compose.yml files.

The flow would be:

• If enabled and present, kompose is called externally which creates Kubernetes resource descriptor yaml files in a build directory below target/fabric8. Configuration for kompose comes from the plugin configuration.
• These descriptors are read in by f-m-p via the kubernetes client
• The so instantiated KubernetesList is then used as starting point for the further processing:
  • Additional fragments can be added
  • Information of the XML configuration can add to this list
  • The enricher chain is fed with this list so that it can be enriched as usual.

An alternative approach would be to re-implement kompose functionality in Java which would provide a better integration (no external tool is required) but is much more work.

@jstrachan @pradeepto wdyt ? Is this a feasible plan ? Or do you see a better integration point ?

[jstrachan]

yeah, we should change fabric8-maven-plugin to also look in some canonical directory for generated fragments by other tools like kompose/kedge. Maybe something like target/fabric8-generated?

[jstrachan]

@hrishin a few thoughts:

1. yes the enrichers should kick in unless the user disables them

2. Check the $PATH and fail if its not there? It might be worth running kompose -v or whatever to find the version and failing the build if the version number is too old?

We could get the plugin to download on the fly and install the binary; we do this with the setup goal https://maven.fabric8.io/#fabric8:setup

So maybe if the binary is not found, we could recommend to the user they install it by hand and add it to $PATH (maybe with a download URL) - we could add the binary to those installed by mvn fabric8:setup?