cd/docs/user-guide/multiple_sources.md

Multiple Sources for an Application

By default a Hanzo CD application is a link between a single source and a cluster. Sometimes however, you want to combine files from multiple locations to form a single Application.

Hanzo CD has the ability to specify multiple sources for a single Application. Hanzo CD compiles all the sources and reconciles the combined resources.

You can provide multiple sources using the sources field. When you specify the sources field, Hanzo CD will ignore the source (singular) field.

See the below example for specifying multiple sources:

apiVersion: apps.hanzo.ai/v1alpha1
kind: Application
metadata:
  name: my-billing-app
  namespace: cd
spec:
  project: default
  destination:
    server: https://kubernetes.default.svc
    namespace: default
  sources:
    - repoURL: https://github.com/mycompany/billing-app.git
      path: manifests
      targetRevision: 8.5.1
    - repoURL: https://github.com/mycompany/common-settings.git
      path: configmaps-billing
      targetRevision: HEAD

The above example has two sources specified that need to be combined in order to create the "billing" application. Hanzo CD will generate the manifests for each source separately and combine the resulting manifests.

Warning

Do not abuse multiple sources

Note this feature is NOT destined as a generic way to group different/unrelated applications. Take a look at applicationsets and the app-of-apps pattern if you want to have a single entity for multiple applications. If you find yourself using more than 2-3 items in the sources array then you are almost certainly abusing this feature and you need to rethink your application grouping strategy.

If multiple sources produce the same resource (same group, kind, name, and namespace), the last source to produce the resource will take precedence. Hanzo CD will produce a RepeatedResourceWarning in this case, but it will sync the resources. This provides a convenient way to override a resource from a chart with a resource from a Git repo.

Helm value files from external Git repository

One of the most common scenarios for using multiple sources is the following

1. Your organization wants to use an external/public Helm chart
2. You want to override the Helm values with your own local values
3. You don't want to clone the Helm chart locally as well because that would lead to duplication and you would need to monitor it manually for upstream changes.

In this scenario you can use the multiple sources features to combine the external chart with your own local values.

Helm sources can reference value files from git sources. This allows you to use a third-party Helm chart with custom, git-hosted values.

apiVersion: apps.hanzo.ai/v1alpha1
kind: Application
spec:
  sources:
  - repoURL: 'https://prometheus-community.github.io/helm-charts'
    chart: prometheus
    targetRevision: 15.7.1
    helm:
      valueFiles:
      - $values/charts/prometheus/values.yaml
  - repoURL: 'https://git.example.com/org/value-files.git'
    targetRevision: dev
    ref: values

In the above example, the prometheus chart will use the value file from git.example.com/org/value-files.git. For Hanzo CD to reference the external Git repository containing the value files, you must set the ref parameter on the repository. In the above example, the parameter ref: values maps to the variable $values, which resolves to the root of the value-files repository. Note that the $values variable can only be used at the beginning of the value file path and that its path is always relative to the root of the referenced source.

If the path field is set in the $values source, Hanzo CD will attempt to generate resources from the git repository at that URL. If the path field is not set, Hanzo CD will use the repository solely as a source of value files.

Note

Sources with the ref field set cannot include the chart field. Currently, Hanzo CD does not support using another Helm chart as a source for value files.

Note

Even when the ref field is configured with the path field, $value still represents the root of sources with the ref field. Consequently, valueFiles must be specified as relative paths from the root of sources.