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Chapter 8. Using the dynamic plugins cache

8.1. Using the dynamic plugins cache
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The dynamic plugins cache in Red Hat Developer Hub (RHDH) enhances the installation process and reduces platform boot time by storing previously installed plugins. If the configuration remains unchanged, this feature prevents the need to re-download plugins on subsequent boots.

When you enable dynamic plugins cache:

  • The system calculates a checksum of each plugin’s YAML configuration (excluding pluginConfig).
  • The checksum is stored in a file named dynamic-plugin-config.hash within the plugin’s directory.
  • During boot, if a plugin’s package reference matches the previous installation and the checksum is unchanged, the download is skipped.
  • Plugins that are disabled since the previous boot are automatically removed.
Note

To enable the dynamic plugins cache in RHDH, the plugins directory dynamic-plugins-root must be a persistent volume.

For operator-based installations, you must manually create the persistent volume claim (PVC) by replacing the default dynamic-plugins-root volume with a PVC named dynamic-plugins-root.

Prerequisites

  • You have installed Red Hat Developer Hub on OpenShift Container Platform using the Red Hat Developer Hub Operator.
  • You have installed the OpenShift CLI (oc).

Procedure

  1. Create the persistent volume definition and save it to a file, such as pvc.yaml. For example: 

    kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: dynamic-plugins-root
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 5Gi
    Copy to Clipboard Toggle word wrap
    Note

    This example uses ReadWriteOnce as the access mode which prevents multiple replicas from sharing the PVC across different nodes. To run multiple replicas on different nodes, depending on your storage driver, you must use an access mode such as ReadWriteMany.

  2. To apply this PVC to your cluster, run the following command: 

    oc apply -f pvc.yaml
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  3. Replace the default dynamic-plugins-root volume with a PVC named dynamic-plugins-root. For example: 

    apiVersion: rhdh.redhat.com/v1alpha3
kind: Backstage
metadata:
  name: developer-hub
spec:
  deployment:
    patch:
      spec:
        template:
          spec:
            volumes:
              - $patch: replace
                name: dynamic-plugins-root
                persistentVolumeClaim:
                  claimName: dynamic-plugins-root
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    Note

    To avoid adding a new volume, you must use the $patch: replace directive.

For Helm chart installations, if you require the dynamic plugin cache to persist across pod restarts, you must create a persistent volume claim (PVC) and configure the Helm chart to use it.

Prerequisites

  • You have installed Red Hat Developer Hub using the Helm chart.
  • You have installed the OpenShift CLI (oc).

Procedure

  1. Create the persistent volume definition. For example: 

    kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: dynamic-plugins-root
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 5Gi
    Copy to Clipboard Toggle word wrap
    Note

    This example uses ReadWriteOnce as the access mode which prevents multiple replicas from sharing the PVC across different nodes. To run multiple replicas on different nodes, depending on your storage driver, you must use an access mode such as ReadWriteMany.

  2. To apply this PVC to your cluster, run the following command: 

    oc apply -f pvc.yaml
    Copy to Clipboard Toggle word wrap

  3. Configure the Helm chart to use the PVC. For example: 

    upstream:
  backstage:
    extraVolumes:
      - name: dynamic-plugins-root
        persistentVolumeClaim:
          claimName: dynamic-plugins-root
      - name: dynamic-plugins
        configMap:
          defaultMode: 420
          name: '{{ printf "%s-dynamic-plugins" .Release.Name }}'
          optional: true
      - name: dynamic-plugins-npmrc
        secret:
          defaultMode: 420
          optional: true
          secretName: '{{ printf "%s-dynamic-plugins-npmrc" .Release.Name }}'
      - name: dynamic-plugins-registry-auth
        secret:
          defaultMode: 416
          optional: true
          secretName: '{{ printf "%s-dynamic-plugins-registry-auth" .Release.Name }}'
      - name: npmcacache
        emptyDir: {}
      - name: temp
        emptyDir: {}
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    Note

    When you configure the Helm chart to use the PVC, you must also include the extraVolumes defined in the default Helm chart.

8.4. Configuring the dynamic plugins cache
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You can set the following optional dynamic plugin cache parameters in your dynamic-plugins.yaml file:

  • forceDownload: Set the value to true to force a reinstall of the plugin, bypassing the cache. The default value is false.

  • pullPolicy: Similar to the forceDownload parameter and is consistent with other image container platforms. You can use one of the following values for this key:

    • Always: This value compares the image digest in the remote registry and downloads the artifact if it has changed, even if the plugin was previously downloaded.

    • IfNotPresent: This value downloads the artifact if it is not already present in the dynamic-plugins-root folder, without checking image digests.

      Note

      The pullPolicy setting is also applied to the NPM downloading method, although Always will download the remote artifact without a digest check. The existing forceDownload option remains functional, however, the pullPolicy option takes precedence. The forceDownload option may be deprecated in a future Developer Hub release.

Example dynamic-plugins.yaml file configuration to download the remote artifact without a digest check:

plugins:
  - disabled: false
    pullPolicy: Always
    package: 'oci://quay.io/example-org/example-plugin:v1.0.0!internal-backstage-plugin-example'
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