Multiple sources for Argo CD applications

Before the multiple sources feature was introduced in Argo CD 2.6, Argo CD was limited to managing applications from a single Git or Helm repository. Users had to manage every application as an individual entity in Argo CD, even if the resources were stored across multiple repositories.

With the multiple sources feature, you can now create an Argo CD application specifying resources stored in multiple repositories. This means you can manage resources separately in different repositories and combine them into a single entity for deployment and management.

Note: The feature is still marked as a Beta feature for Argo CD. The user interface (UI) and command-line interface (CLI) are not supported for multiple sources; they respond as if only the first source is specified.

Use cases

Examples of the use of multiple sources feature include:

• Combining resources from different repositories for microservice-based applications.
• Managing shared libraries or common resources across multiple teams or repositories.
• Combining resources from different branches of a Git repository for testing or experimentation.
• Managing resources for different environments (e.g., development, staging, production) in separate Git repositories.
• Specifying Helm value files from an external Git repository.

In all of these scenarios, the multiple sources feature lets you combine resources from different Git repositories to create an application entity. This helps organizations manage the resources separately and share them across multiple applications.

Examples of multiple sources applications

Suppose you have two Git repositories, each containing a Helm chart for a different application component. With the multiple sources feature, you can combine these two Helm charts into a single application in Argo CD. Let's see an example of how the Argo CD application specification YAML file with multiple sources might look like:

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: my-app
spec:
  project: my-project
  sources:
    - repoURL: https://github.com/my-org/chart-repo-1
      targetRevision: HEAD
    - repoURL: https://github.com/my-org/chart-repo-2
      path: charts/chart-2
  destination:
    server: https://kubernetes.default.svc
    namespace: my-namespace
  syncPolicy:
    automated:
      prune: true

In this example, the application my-app is pulling resources from two Git repositories:

• https://github.com/my-org/chart-repo-1
• https://github.com/my-org/chart-repo-2

The first repository is synced to the root directory, while the second is synced to the charts/chart-2 directory. The combined resources from these two repositories will be deployed to the my-namespace namespace in the Kubernetes cluster. With this configuration, Argo CD can manage both Helm charts as a single application, making it easier to deploy and maintain the components of your application.

The multiple sources feature also allows users to specify value files from different Git repositories to a Helm chart stored in either a Helm repository or Git repository. Let's consider the following example to understand the use case:

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: my-app
spec:
  project: my-project
 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.gom/org/value-files.git'
    targetRevision: dev
    ref: values
  destination:
    server: https://kubernetes.default.svc
    namespace: my-namespace
  syncPolicy:
    automated:
      prune: true

In the preceding example with multiple sources and external value files for the Helm source, the Prometheus chart uses the value file stored in the repository git.example.gom/org/value-files.git. The tag $values resolves to the root of the value-files repository referenced by the ref key in the list of sources. The $values variable can be specified only at the beginning of the value file path. Taking the value files from an external Helm source is not currently supported. So, you would want to avoid setting the Chart field for the source used for referencing value files.

If the path field is set in the source with a ref key set (in the last example, the source with key ref: values), Argo CD will attempt to generate resources from the git repository at that URL. If the path field is not set, Argo CD will use the repository solely as a source of value files.

Conclusion

The multiple sources feature in Argo CD 2.6 provides control and flexibility for managing resources spanning multiple repositories for a single application, making it easier to manage these resources. You can find more details about the feature in the documentation. The feature will be available in Red Hat OpenShift GitOps 1.8.