Including Optional Value Keys

This topic applies to both native Helm and Replicated Helm installations.

The Helm chart values.yaml file is not a static mapping in an application. It is possible to either remove or include values when certain conditions are met.

Remove Values

If the Helm chart values.yaml contains a static value that must be removed when deploying using the Replicated app manager, set the value to "null" (including the quotation marks) in the HelmChart custom resource manifest file.

For more information, see Deleting a Default Key in the Helm documentation.

Include Values

Some advanced use cases involve writing values to a values file only if there is a value to apply.

Helm charts such as Postgres do not treat an empty value ("") in the same way as if the key were missing from the chart. This can be necessary for applications packaged as a Helm chart that include a reference to another chart in the requirements.yaml.

For example, in the requirements.yaml of the Sentry chart, there is a reference to postgres. This is configured through the Sentry chart values.yaml:

# PostgreSQL chart configs
postgresql:
  enabled: false
  # postgresqlUsername: kong
  # postgresqlDatabase: kong
  # service:
  #   port: 5432

When the postgres chart is deployed, the existence of the database key sets the value.

The way the Sentry chart is written, it uses the value in postgresql.postgresDatabase unless it is missing. For more information, see the workers-deployment.yaml implementation.

In order to make this work reliably, we need to be able to dynamically add and remove the postgresDatabase key from the values.yaml so that it is only present if the user selects embedded_postgres.

If the user selects external postgres, we want the Sentry workers-deployment.yaml to receive the value that the user provided.

To enable this, instead of attempting to modify the render logic in the Helm chart, you can add an optionalValues section to the kind: HelmChart.

The optionalValues section includes a when condition that instructs the app manager how to determine if these keys should be merged. It also includes a recursiveMerge field that defines how to merge the dataset.

For example, using the Sentry helm chart:

apiVersion: kots.io/v1beta1
kind: HelmChart
metadata:
  name: sentry
spec:
  # chart identifies a matching chart from a .tgz
  chart:
    name: sentry
    chartVersion: 3.1.7

  # values are used in the customer environment, as a pre-render step
  # these values will be supplied to helm template
  values:
    postgresql:
      enabled: repl{{ ConfigOptionEquals `postgres_type` `embedded_postgres`}}

  optionalValues:
    - when: "repl{{ ConfigOptionEquals `postgres_type` `external_postgres`}}"
      recursiveMerge: false
      values:
        postgresql:
          postgresqlDatabase: "repl{{ ConfigOption `external_postgres_database`}}"
          postgresqlUsername: "repl{{ ConfigOption `external_postgres_username`}}"
          postgresqlHost: "repl{{ ConfigOption `external_postgres_host`}}"
          postgresqlPassword: "repl{{ ConfigOption `external_postgres_password`}}"
          postgresqlPort: "repl{{ ConfigOption `external_postgres_port`}}"

  # builder values provide a way to render the chart with all images
  # and manifests. this is used in replicated to create airgap packages
  builder:
    postgresql:
      enabled: true

The above YAML will result in the following values.yaml if the user selects external_postgres:

postgresql:
  enabled: false
  postgresqlDatabase: "repl{{ ConfigOption `external_postgres_database`}}"
  postgresqlUsername: "repl{{ ConfigOption `external_postgres_username`}}"
  postgresqlHost: "repl{{ ConfigOption `external_postgres_host`}}"
  postgresqlPassword: "repl{{ ConfigOption `external_postgres_password`}}"
  postgresqlPort: "repl{{ ConfigOption `external_postgres_port`}}"

And the following values.yaml if the user selects embedded_postgres:

postgresql:
  enabled: true

For more information about the optionalValues property, including details about the when and recursiveMerge fields, see optionalValues in HelmChart.