Referencing a loop object

Question

i am currently checking out tanka + jsonnet. But evertime i think i understand it... sth. new irritates me. Can somebody help me understand how to do a loop-reference? (Or general better solution?)

Trying to create multiple deployments with a corresponding configmapVolumeMount and i am not sure how to reference to the according configmap object here? (using a configVolumeMount it works since it refers to the name, not the object).

deployment: [
  deploy.new(
    name='demo-' + instance.name,
    ],
  )
  + deploy.configMapVolumeMount('config-' + instance.name, '/config.yml', k.core.v1.volumeMount.withSubPath('config.yml'))
  for instance in $._config.demo.instances
],

configMap: [
  configMap.new('config-' + instance.name, {
   'config.yml': (importstr 'files/config.yml') % {
      name: instance.name,
      ....
    },
  }),
  for instance in $._config.demo.instances
]

regards

Answer 1

Great to read that you're making progress with tanka, it's an awesome tool (once you learned how to ride it heh).

Find below a possible answer, see inline comments in the code, in particular how we ab-use tanka layout flexibility, to "populate" deploys: [...] array with jsonnet objects containing each paired deploy+configMap.

config.jsonnet

{
  demo: {
    instances: ['foo', 'bar'],
    image: 'nginx',  // just as example
  },
}

main.jsonnet

local config = import 'config.jsonnet';
local k = import 'github.com/grafana/jsonnet-libs/ksonnet-util/kausal.libsonnet';

{
  local deployment = k.apps.v1.deployment,
  local configMap = k.core.v1.configMap,
  _config:: import 'config.jsonnet',

  // my_deploy(name) will return name-d deploy+configMap object
  my_deploy(name):: {
    local this = self,
    deployment:
      deployment.new(
        name='deploy-%s' % name,
        replicas=1,
        containers=[
          k.core.v1.container.new('demo-%s' % name, $._config.demo.image),
        ],
      )
      + deployment.configMapVolumeMount(
        this.configMap,
        '/config.yml',
        k.core.v1.volumeMount.withSubPath('config.yml')
      ),
    configMap:
      configMap.new('config-%s' % name)
      + configMap.withData({
        // NB: replacing `importstr 'files/config.yml';` by
        //     a simple YAML multi-line string, just for the sake of having
        //     a simple yet complete/usable example.
        'config.yml': |||
          name: %(name)s
          other: value
        ||| % { name: name },  //
      }),
  },

  // Tanka is pretty flexible with the "layout" of the Kubernetes objects
  // in the Environment (can be arrays, objects, etc), below using an array
  // for simplicity (built via a loop/comprehension)
  deploys: [$.my_deploy(name) for name in $._config.demo.instances],
}

output

$ tk init
[...]

## NOTE: using https://kind.sigs.k8s.io/ local Kubernetes cluster
$ tk env set --server-from-context kind-kind environments/default
[... save main.jsonnet, config.jsonnet to ./environments/default/]

$ tk apply --dry-run=server environments/default
[...]
configmap/config-bar created (server dry run)
configmap/config-foo created (server dry run)
deployment.apps/deploy-bar created (server dry run)
deployment.apps/deploy-foo created (server dry run)