HCP Packer Support

Note: HCP Packer is under active development, and we suggest plugin maintainers to keep up with the SDK changes for more on HCP Packer support.

This page explains how to update a custom plugin so that it can publish image metadata to the HCP Packer registry. Refer to Custom Builders and Custom Post-Processors for details about creating an external Packer plugin.

Before pushing metadata to the HCP Packer registry, Packer uses the par.artifact.metadata key to query a builder artifact for the image metadata that a particular component would like to have stored in the registry.

For details and examples of how to manage image metadata, refer to the HCP Packer GitHub documentation.

Builder Artifact

To support HCP Packer, changes must be made to the plugin's build artifact. The artifact should keep the appropriate Image metadata in state under the key par.artifact.metadata. The expected key is provided by the image.ArtifactStateURI constant.

To make HCP Packer support easier, we ship an Image package with the packer-plugin-sdk. We provide the FromArtifact function to easily create an Image with the basic information contained in the Artifact. If customization is necessary, the FromArtifact accepts override functions as the second argument, and that can be used to set different values for the metadata.

The Image metadata must contain every metadata HCP Packer should store about this component. The structure is:

// Image represents the metadata for some Artifact in the HCP Packer Registry.
type Image struct {
    // ImageID is a unique reference identifier stored on the HCP Packer registry
    // that can be used to get back the built artifact of a builder or post-processor.
    ImageID string
    // ProviderName represents the name of the top level cloud or service where the built artifact resides.
    // For example "aws, azure, docker, gcp, and vsphere".
    ProviderName string
    // ProviderRegion represents the location of the built artifact.
    // For cloud providers region usually maps to a cloud region or zone, but for things like the file builder,
    // S3 bucket or vsphere cluster region can represent a path on the upstream datastore, or cluster.
    ProviderRegion string
    // Labels represents additional details about an image that a builder or post-processor may with to provide for a given build.
    // Any additional metadata will be made available as build labels within a HCP Packer registry iteration.
    Labels map[string]string
    // SourceImageID is the cloud image ID of the image that was used as the
    // source for this image. If set, the HCP Packer registry will be able
    // link the parent and child images for ancestry visualizations and
    // dependency tracking.
    SourceImageID string
}

Where ImageID, ProviderName, and SourceImageID are mandatory fields.

Examples using the FromArtifact method:

Simple form:

func (a *Artifact) State(name string) interface{} {
    if name == registryimage.ArtifactStateURI {
        img, err := registryimage.FromArtifact(a)
        if err != nil {
            log.Printf("[DEBUG] error encountered when creating a registry image %v", err)
            return nil
        }
      return img
    }
    return a.StateData[name]
}

Using overrides:

func (a *Artifact) State(name string) interface{} {
    if name == registryimage.ArtifactStateURI {
        img, err := registryimage.FromArtifact(a,
                registryimage.WithID(a.Name),
                registryimage.WithRegion(a.Region.Name()),
                registryimage.WithProvider("happy-cloud"),
                registryimage.WithSourceID(a.SourceID),
                registryimage.SetLabels(a.Labels),
              )
        if err != nil {
            log.Printf("[DEBUG] error encountered when creating a registry image %v", err)
            return nil
        }
      return img
    }
    return a.StateData[name]
}

See packer-plugin-sdk/packer/registry/image for additional examples.

SDK Version

The HCP Packer support is available from packer-plugin-sdk >= v0.2.7

Plugins Example

The following plugins currently support HCP Packer and are great references for development:

HCP Packer

To get to know HCP Packer, visit the HCP Packer documentation or try the Get Started with HCP Packer tutorials.