k8s-libsonnet

Helpers for creating k8s resources without abuse of constructor functions.

Features

• exposes k8s "named arrays" as objects that can be more easily overriden (env_+:{BAR: {value:'override'}})
• allows to apply overrides on all objects of a given type, e.g. all Objects (e.g. namespace), all PodSpecs (e.g. labels)

Example:

(import '../k8s.libsonnet').RootComponent {
  configmap: $.k8s.v1.ConfigMap {
    metadata+: { name: 'foo' },
    data: { bar: 'baz' },
  },

  deployment: $.k8s.apps.v1.Deployment {
    metadata+: { name: 'nginx' },
    spec+: {
      replicas: 2,
      selector+: { matchLabels: { app: 'nginx' } },
      template+: {
        metadata+: { labels: { app: 'nginx' } },
        spec+: {
          containers_+: {
            nginx: {
              image: 'nginx:1.14.2',
              env_+: {
                BAR: { valueFrom: { configMapKeyRef: {
                  name: $.configmap.metadata.name,
                  key: 'bar',
                } } },
              },
              ports_+: {
                http: { containerPort: 80 },
              },
            },
          },
        },
      },
    },
  },

  service: $.k8s.v1.Service {
    metadata+: { name: 'nginx' },
    spec+: {
      selector+: $.deployment.spec.selector.matchLabels,
      ports_+: {
        http: { port: 80, targetPort: 'http' },
      },
    },
  },

}

Example: define namespace for all objects

(import 'simple.jsonnet') {
  k8s+: {
    ObjectMeta+: {
      namespace: 'my-ns',
    },
  },
}

Example: add annotations to all resources including pods

Everything you add under ObjectMeta will be inherited by all objects you define in your templates.

A Deployment or a StatefulSet object will thus include the provided metadata in its own resource metadata. When the Deployment or StatefulSet (or Job, CronJob, ...) create pods they do so using a template defined in their spec. That template can contain a metadata object that will govern which metadata the "pod" resource will have.

If you want to add a metadata field that will appear in all resources, including those generated at runtime by resources such as Deployment or StatefulSet, you can override the ObjectTemplateMeta field:

(import 'simple.jsonnet') {
  k8s+: {
    ObjectTemplateMeta+: {
      annotations+: {
        'app.kubernetes.io/name': 'foo',
      }
    }
  }
}

Example: add annotations to a specific kind

(import 'simple.jsonnet') {
  k8s+: {
    v1+: {
      Service+: {
        annotations+: {
          'traefik.ingress.kubernetes.io/service.sticky.cookie.name': 'foobar',
        }
      }
    }
  }
}

Example: overlay any pod template

There are many resource types that can create Pod (Deployment, StatefulSet, Job, ...). All of them have a common way to express pod parameters, called a PodTemplateSpec.

All the resource type templates defined in k8s-libsonnet that include a PodTemplateSpec share the same k8s.PodTemplateSpec template. This means you can just extend that template and include overlays which will be shared by all pods.

A common use case are node selectors and tolerations:

(import 'complex-app.jsonnet') {
  k8s+: {
    v1+: {
      PodTemplateSpec+: {
        metadata+: {
          annotations+: {
            'cluster-autoscaler.kubernetes.io/safe-to-evict': 'true'
          }
        },
        spec+: {
          nodeSelector+: {
            'kubernetes.io/os': 'linux',
          }
        }
      }
    }
  }
}

Note that with PodTemplateSpec you can add annotations that will only appear in pod template specs and not in the resource metadata on the root. If you define metadata fields in the ObjectTemplateMeta, they will appear both here and in the root resource metadata.