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File-based catalogs

Operator Lifecycle Manager (OLM) v1 is a Technology Preview feature only. Technology Preview features are not supported with Red Hat production service level agreements (SLAs) and might not be functionally complete. Red Hat does not recommend using them in production. These features provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process.

For more information about the support scope of Red Hat Technology Preview features, see Technology Preview Features Support Scope.

Operator Lifecycle Manager (OLM) v1 in OKD supports file-based catalogs for discovering and sourcing cluster extensions, including Operators, on a cluster.

Highlights

File-based catalogs are the latest iteration of the catalog format in Operator Lifecycle Manager (OLM). It is a plain text-based (JSON or YAML) and declarative config evolution of the earlier SQLite database format, and it is fully backwards compatible. The goal of this format is to enable Operator catalog editing, composability, and extensibility.

Editing

With file-based catalogs, users interacting with the contents of a catalog are able to make direct changes to the format and verify that their changes are valid. Because this format is plain text JSON or YAML, catalog maintainers can easily manipulate catalog metadata by hand or with widely known and supported JSON or YAML tooling, such as the jq CLI.

This editability enables the following features and user-defined extensions:

  • Promoting an existing bundle to a new channel

  • Changing the default channel of a package

  • Custom algorithms for adding, updating, and removing upgrade edges

Composability

File-based catalogs are stored in an arbitrary directory hierarchy, which enables catalog composition. For example, consider two separate file-based catalog directories: catalogA and catalogB. A catalog maintainer can create a new combined catalog by making a new directory catalogC and copying catalogA and catalogB into it.

This composability enables decentralized catalogs. The format permits Operator authors to maintain Operator-specific catalogs, and it permits maintainers to trivially build a catalog composed of individual Operator catalogs. File-based catalogs can be composed by combining multiple other catalogs, by extracting subsets of one catalog, or a combination of both of these.

Duplicate packages and duplicate bundles within a package are not permitted. The opm validate command returns an error if any duplicates are found.

Because Operator authors are most familiar with their Operator, its dependencies, and its upgrade compatibility, they are able to maintain their own Operator-specific catalog and have direct control over its contents. With file-based catalogs, Operator authors own the task of building and maintaining their packages in a catalog. Composite catalog maintainers, however, only own the task of curating the packages in their catalog and publishing the catalog to users.

Extensibility

The file-based catalog specification is a low-level representation of a catalog. While it can be maintained directly in its low-level form, catalog maintainers can build interesting extensions on top that can be used by their own custom tooling to make any number of mutations.

For example, a tool could translate a high-level API, such as (mode=semver), down to the low-level, file-based catalog format for upgrade edges. Or a catalog maintainer might need to customize all of the bundle metadata by adding a new property to bundles that meet a certain criteria.

While this extensibility allows for additional official tooling to be developed on top of the low-level APIs for future OKD releases, the major benefit is that catalog maintainers have this capability as well.

Directory structure

File-based catalogs can be stored and loaded from directory-based file systems. The opm CLI loads the catalog by walking the root directory and recursing into subdirectories. The CLI attempts to load every file it finds and fails if any errors occur.

Non-catalog files can be ignored using .indexignore files, which have the same rules for patterns and precedence as .gitignore files.

Example .indexignore file
# Ignore everything except non-object .json and .yaml files
**/*
!*.json
!*.yaml
**/objects/*.json
**/objects/*.yaml

Catalog maintainers have the flexibility to choose their desired layout, but it is recommended to store each package’s file-based catalog blobs in separate subdirectories. Each individual file can be either JSON or YAML; it is not necessary for every file in a catalog to use the same format.

Basic recommended structure
catalog
├── packageA
│   └── index.yaml
├── packageB
│   ├── .indexignore
│   ├── index.yaml
│   └── objects
│       └── packageB.v0.1.0.clusterserviceversion.yaml
└── packageC
    └── index.json
    └── deprecations.yaml

This recommended structure has the property that each subdirectory in the directory hierarchy is a self-contained catalog, which makes catalog composition, discovery, and navigation trivial file system operations. The catalog can also be included in a parent catalog by copying it into the parent catalog’s root directory.

Schemas

File-based catalogs use a format, based on the CUE language specification, that can be extended with arbitrary schemas. The following _Meta CUE schema defines the format that all file-based catalog blobs must adhere to:

_Meta schema
_Meta: {
  // schema is required and must be a non-empty string
  schema: string & !=""

  // package is optional, but if it's defined, it must be a non-empty string
  package?: string & !=""

  // properties is optional, but if it's defined, it must be a list of 0 or more properties
  properties?: [... #Property]
}

#Property: {
  // type is required
  type: string & !=""

  // value is required, and it must not be null
  value: !=null
}

No CUE schemas listed in this specification should be considered exhaustive. The opm validate command has additional validations that are difficult or impossible to express concisely in CUE.

An Operator Lifecycle Manager (OLM) catalog currently uses three schemas (olm.package, olm.channel, and olm.bundle), which correspond to OLM’s existing package and bundle concepts.

Each Operator package in a catalog requires exactly one olm.package blob, at least one olm.channel blob, and one or more olm.bundle blobs.

All olm.* schemas are reserved for OLM-defined schemas. Custom schemas must use a unique prefix, such as a domain that you own.

olm.package schema

The olm.package schema defines package-level metadata for an Operator. This includes its name, description, default channel, and icon.

olm.package schema 
#Package: {
  schema: "olm.package"

  // Package name
  name: string & !=""

  // A description of the package
  description?: string

  // The package's default channel
  defaultChannel: string & !=""

  // An optional icon
  icon?: {
    base64data: string
    mediatype:  string
  }
}

olm.channel schema

The olm.channel schema defines a channel within a package, the bundle entries that are members of the channel, and the upgrade edges for those bundles.

If a bundle entry represents an edge in multiple olm.channel blobs, it can only appear once per channel.

It is valid for an entry’s replaces value to reference another bundle name that cannot be found in this catalog or another catalog. However, all other channel invariants must hold true, such as a channel not having multiple heads.

olm.channel schema 
#Channel: {
  schema: "olm.channel"
  package: string & !=""
  name: string & !=""
  entries: [...#ChannelEntry]
}

#ChannelEntry: {
  // name is required. It is the name of an `olm.bundle` that
  // is present in the channel.
  name: string & !=""

  // replaces is optional. It is the name of bundle that is replaced
  // by this entry. It does not have to be present in the entry list.
  replaces?: string & !=""

  // skips is optional. It is a list of bundle names that are skipped by
  // this entry. The skipped bundles do not have to be present in the
  // entry list.
  skips?: [...string & !=""]

  // skipRange is optional. It is the semver range of bundle versions
  // that are skipped by this entry.
  skipRange?: string & !=""
}

When using the skipRange field, the skipped Operator versions are pruned from the update graph and are longer installable by users with the spec.startingCSV property of Subscription objects.

You can update an Operator incrementally while keeping previously installed versions available to users for future installation by using both the skipRange and replaces field. Ensure that the replaces field points to the immediate previous version of the Operator version in question.

olm.bundle schema

olm.bundle schema 
#Bundle: {
  schema: "olm.bundle"
  package: string & !=""
  name: string & !=""
  image: string & !=""
  properties: [...#Property]
  relatedImages?: [...#RelatedImage]
}

#Property: {
  // type is required
  type: string & !=""

  // value is required, and it must not be null
  value: !=null
}

#RelatedImage: {
  // image is the image reference
  image: string & !=""

  // name is an optional descriptive name for an image that
  // helps identify its purpose in the context of the bundle
  name?: string & !=""
}

olm.deprecations schema

The optional olm.deprecations schema defines deprecation information for packages, bundles, and channels in a catalog. Operator authors can use this schema to provide relevant messages about their Operators, such as support status and recommended upgrade paths, to users running those Operators from a catalog.

An olm.deprecations schema entry contains one or more of the following reference types, which indicates the deprecation scope. After the Operator is installed, any specified messages can be viewed as status conditions on the related Subscription object.

Table 1. Deprecation reference types
Type Scope Status condition

olm.package

Represents the entire package

PackageDeprecated

olm.channel

Represents one channel

ChannelDeprecated

olm.bundle

Represents one bundle version

BundleDeprecated

Each reference type has their own requirements, as detailed in the following example.

Example olm.deprecations schema with each reference type 
schema: olm.deprecations
package: my-operator (1)
entries:
  - reference:
      schema: olm.package (2)
    message: | (3)
    The 'my-operator' package is end of life. Please use the
    'my-operator-new' package for support.
  - reference:
      schema: olm.channel
      name: alpha (4)
    message: |
    The 'alpha' channel is no longer supported. Please switch to the
    'stable' channel.
  - reference:
      schema: olm.bundle
      name: my-operator.v1.68.0 (5)
    message: |
    my-operator.v1.68.0 is deprecated. Uninstall my-operator.v1.68.0 and
    install my-operator.v1.72.0 for support.
1 Each deprecation schema must have a package value, and that package reference must be unique across the catalog. There must not be an associated name field.
2 The olm.package schema must not include a name field, because it is determined by the package field defined earlier in the schema.
3 All message fields, for any reference type, must be a non-zero length and represented as an opaque text blob.
4 The name field for the olm.channel schema is required.
5 The name field for the olm.bundle schema is required.

The deprecation feature does not consider overlapping deprecation, for example package versus channel versus bundle.

Operator authors can save olm.deprecations schema entries as a deprecations.yaml file in the same directory as the package’s index.yaml file:

Example directory structure for a catalog with deprecations
my-catalog
└── my-operator
    ├── index.yaml
    └── deprecations.yaml
Additional resources

Properties

Properties are arbitrary pieces of metadata that can be attached to file-based catalog schemas. The type field is a string that effectively specifies the semantic and syntactic meaning of the value field. The value can be any arbitrary JSON or YAML.

OLM defines a handful of property types, again using the reserved olm.* prefix.

olm.package property

The olm.package property defines the package name and version. This is a required property on bundles, and there must be exactly one of these properties. The packageName field must match the bundle’s first-class package field, and the version field must be a valid semantic version.

olm.package property 
#PropertyPackage: {
  type: "olm.package"
  value: {
    packageName: string & !=""
    version: string & !=""
  }
}

olm.gvk property

The olm.gvk property defines the group/version/kind (GVK) of a Kubernetes API that is provided by this bundle. This property is used by OLM to resolve a bundle with this property as a dependency for other bundles that list the same GVK as a required API. The GVK must adhere to Kubernetes GVK validations.

olm.gvk property 
#PropertyGVK: {
  type: "olm.gvk"
  value: {
    group: string & !=""
    version: string & !=""
    kind: string & !=""
  }
}

olm.package.required

The olm.package.required property defines the package name and version range of another package that this bundle requires. For every required package property a bundle lists, OLM ensures there is an Operator installed on the cluster for the listed package and in the required version range. The versionRange field must be a valid semantic version (semver) range.

olm.package.required property 
#PropertyPackageRequired: {
  type: "olm.package.required"
  value: {
    packageName: string & !=""
    versionRange: string & !=""
  }
}

olm.gvk.required

The olm.gvk.required property defines the group/version/kind (GVK) of a Kubernetes API that this bundle requires. For every required GVK property a bundle lists, OLM ensures there is an Operator installed on the cluster that provides it. The GVK must adhere to Kubernetes GVK validations.

olm.gvk.required property 
#PropertyGVKRequired: {
  type: "olm.gvk.required"
  value: {
    group: string & !=""
    version: string & !=""
    kind: string & !=""
  }
}

Example catalog

With file-based catalogs, catalog maintainers can focus on Operator curation and compatibility. Because Operator authors have already produced Operator-specific catalogs for their Operators, catalog maintainers can build their catalog by rendering each Operator catalog into a subdirectory of the catalog’s root directory.

There are many possible ways to build a file-based catalog; the following steps outline a simple approach:

  1. Maintain a single configuration file for the catalog, containing image references for each Operator in the catalog:

    Example catalog configuration file
    name: community-operators
repo: quay.io/community-operators/catalog
tag: latest
references:
- name: etcd-operator
  image: quay.io/etcd-operator/index@sha256:5891b5b522d5df086d0ff0b110fbd9d21bb4fc7163af34d08286a2e846f6be03
- name: prometheus-operator
  image: quay.io/prometheus-operator/index@sha256:e258d248fda94c63753607f7c4494ee0fcbe92f1a76bfdac795c9d84101eb317

  2. Run a script that parses the configuration file and creates a new catalog from its references:

    Example script
    name=$(yq eval '.name' catalog.yaml)
mkdir "$name"
yq eval '.name + "/" + .references[].name' catalog.yaml | xargs mkdir
for l in $(yq e '.name as $catalog | .references[] | .image + "|" + $catalog + "/" + .name + "/index.yaml"' catalog.yaml); do
  image=$(echo $l | cut -d'|' -f1)
  file=$(echo $l | cut -d'|' -f2)
  opm render "$image" > "$file"
done
opm generate dockerfile "$name"
indexImage=$(yq eval '.repo + ":" + .tag' catalog.yaml)
docker build -t "$indexImage" -f "$name.Dockerfile" .
docker push "$indexImage"

Guidelines

Consider the following guidelines when maintaining file-based catalogs.

Immutable bundles

The general advice with Operator Lifecycle Manager (OLM) is that bundle images and their metadata should be treated as immutable.

If a broken bundle has been pushed to a catalog, you must assume that at least one of your users has upgraded to that bundle. Based on that assumption, you must release another bundle with an upgrade edge from the broken bundle to ensure users with the broken bundle installed receive an upgrade. OLM will not reinstall an installed bundle if the contents of that bundle are updated in the catalog.

However, there are some cases where a change in the catalog metadata is preferred:

  • Channel promotion: If you already released a bundle and later decide that you would like to add it to another channel, you can add an entry for your bundle in another olm.channel blob.

  • New upgrade edges: If you release a new 1.2.z bundle version, for example 1.2.4, but 1.3.0 is already released, you can update the catalog metadata for 1.3.0 to skip 1.2.4.

Source control

Catalog metadata should be stored in source control and treated as the source of truth. Updates to catalog images should include the following steps:

  1. Update the source-controlled catalog directory with a new commit.

  2. Build and push the catalog image. Use a consistent tagging taxonomy, such as :latest or :<target_cluster_version>, so that users can receive updates to a catalog as they become available.

CLI usage

For instructions about creating file-based catalogs by using the opm CLI, see Managing custom catalogs.

For reference documentation about the opm CLI commands related to managing file-based catalogs, see CLI tools.

Automation

Operator authors and catalog maintainers are encouraged to automate their catalog maintenance with CI/CD workflows. Catalog maintainers can further improve on this by building GitOps automation to accomplish the following tasks:

  • Check that pull request (PR) authors are permitted to make the requested changes, for example by updating their package’s image reference.

  • Check that the catalog updates pass the opm validate command.

  • Check that the updated bundle or catalog image references exist, the catalog images run successfully in a cluster, and Operators from that package can be successfully installed.

  • Automatically merge PRs that pass the previous checks.

  • Automatically rebuild and republish the catalog image.