Catalog Templates

Note: catalog templates are ALPHA functionality and may adopt breaking changes

Concept and Design

File-Based Catalogs (FBC) are a major improvement to the imperative update graph approaches of previous versions. FBCs give operator authors a declarative and deterministic approach to defining their update graph. However, FBCs can get complex, especially as the number of releases and dependencies scale. We introduce the concept of a catalog template (referred to as template going forward) as an approach to simplifying interacting with FBCs.

In this context, there are two components to every template:

1. An arbitrary API
2. An executable which processes #1 and produces a valid FBC.

The templates supported by opm are:

• the basic template, which provides a simplified abstraction of an FBC
• the semver template, which provides the capability to generate an entire upgrade graph

Basic Template

The basic template is an input schema which eliminates FBC information that can be retrieved from existing registries when we process it. Within the schema, users can add entries composed of any valid FBC schema components, but supply only the bundle image reference for any olm.bundle objects. This results in a greatly simplified, smaller document. This approach may be attractive to operator authors who maintain existing catalogs and just want to simplify the format, or for operator authors who need to retain an update graph which cannot be based on semver.

Usage

opm alpha render-template basic [flags] <filename>

--skip-tls-verify and --use-http are mutually exclusive flags.

Example

In a very simple example, we define an olm.package and an olm.channel composed of two olm.bundle objects that have an image name attribute but no other attributes/properties.

schema: olm.template.basic
entries:
  - schema: olm.package
    name: example-operator
    defaultChannel: stable
  - schema: olm.channel
    package: example-operator
    name: stable
    entries:
      - name: example-operator.v0.1.0
      - name: example-operator.v0.2.0
        replaces: example-operator.v0.1.0
  - schema: olm.bundle
    image: docker.io/example/example-operator-bundle:0.1.0
  - schema: olm.bundle
    image: docker.io/example/example-operator-bundle:0.2.0

Using the opm alpha render-template basic command on this input generates the full FBC (skipping large bundle metadata objects):

---
defaultChannel: stable
name: example-operator
schema: olm.package
---
entries:
- name: example-operator.v0.1.0
- name: example-operator.v0.2.0
  replaces: example-operator.v0.1.0
name: stable
package: example-operator
schema: olm.channel
---
image: docker.io/example/example-operator-bundle:0.1.0
name: example-operator.v0.1.0
package: example-operator
properties:
- type: olm.gvk
  value:
    group: example.com
    kind: App
    version: v1
- type: olm.package
  value:
    packageName: example-operator
    version: 0.1.0
relatedImages:
- image: gcr.io/kubebuilder/kube-rbac-proxy:v0.8.0
  name: ""
- image: docker.io/example/example-operator-bundle:0.1.0
  name: ""
- image: docker.io/example/example-operator:0.1.0
  name: ""
schema: olm.bundle
---
image: docker.io/example/example-operator-bundle:0.2.0
name: example-operator.v0.2.0
package: example-operator
properties:
- type: olm.gvk
  value:
    group: example.com
    kind: App
    version: v1
- type: olm.package
  value:
    packageName: example-operator
    version: 0.2.0
relatedImages:
- image: gcr.io/kubebuilder/kube-rbac-proxy:v0.8.0
  name: ""
- image: docker.io/example/example-operator-bundle:0.2.0
  name: ""
- image: docker.io/example/example-operator:0.2.0
  name: ""
schema: olm.bundle

Converting from FBC to Basic Template

The opm tool provides the capability to render existing File-Based Catalogs to basic catalog templates in JSON or YAML formats.

Usage

opm alpha convert-template basic [flags] <filename>

--skip-tls-verify and --use-http are mutually exclusive flags.

Example template in JSON format after the conversion:

{
  "schema": "olm.template.basic",
  "entries": [
    {
      "schema": "olm.package",
      "name": "hello-kubernetes",
      "defaultChannel": "alpha",
      "description": "hello-kubernetes"
    },
    {
      "schema": "olm.channel",
      "name": "alpha",
      "package": "hello-kubernetes",
      "entries": [
        {
          "name": "hello-kubernetes.v0.0.1"
        }
      ]
    },
    {
      "schema": "olm.bundle",
      "image": "docker.io/test/hello-kubernetes-operator-bundle:v0.0.1"
    }
  ]
}

Semver Template

Since a catalog template is identified as an input schema which is processed to generate a valid FBC, we can define a semver template as a schema which uses channel conventions to facilitate the auto-generation of channels adhering to Semantic Versioning (semver) guidelines and consistent with best practices on channel naming. This approach may be attractive to operator authors who are defining a new upgrade graph, or are already close enough to this template’s conventions to be able to adopt it.

DISCLAIMER: since version build metadata MUST be ignored when determining version precedence (see spec #10) when using semver, if any bundles differ only by build metadata the render attempt will generate a fatal error.

This alpha version of the semver template has the following goals:

• terse grammar to minimize creation/maintenance effort
• idempotent output
• simple channel promotion
• demonstration of a common type of channel maturity model
• minor-version (Y-stream) and major-version (X-stream) versioning capabilities
• clear mapping between input schema and output FBC attributes

Note: The semver template depends on the optional csv.spec.version field. If you want to use the semver catalog template, you must specify a version in your extension’s CSV.

Specification

Like best practices recommended channel naming, this template supports channel names Candidate, Fast, and Stable, in order of increasing channel stability. We leverage this relationship when calculating the default channel for the package.

GenerateMajorChannels and GenerateMinorChannels dictate whether this template will generate X-stream or Y-stream channels (attributes can be set independently). If omitted, only minor (Y-stream) channels will be generated.

Under each channel are a list of bundle image references which contribute to that channel. At least one channel must have bundle images.

The olm.semver cue schema is:

#Package: {
  schema: "olm.semver"

  // optional flag to control generating minor-version channels, defaults to _true_ if unspecified
  GenerateMinorChannels?: bool

  // optional flag to control generating major-version channels, defaults to _false_ if unspecified
  GenerateMajorChannels?: bool

  // optional preference for major- or minor-version channels, when both are generated and identical in stability and version
  DefaultChannelTypePreference?: string

  // optional candidate channel
  Candidate?: {
    Bundles: [...#ImageEntry]
  }

  // optional fast channel
  Fast?: {
    Bundles: [...#ImageEntry]
  }

  // optional stable channel
  Stable?: {
    Bundles: [...#ImageEntry]
  }

  #ImageEntry: {
    Image: string
  }
}

Usage

opm alpha render-template semver [flags] <filename>

--skip-tls-verify and --use-http are mutually exclusive flags.

Examples

With the following (hypothetical) example we define a mock bundle which has 11 versions, represented across each of the channel types:

Schema: olm.semver
GenerateMajorChannels: true
GenerateMinorChannels: true
Candidate:
  Bundles:
  - Image: quay.io/foo/olm:testoperator.v0.1.0
  - Image: quay.io/foo/olm:testoperator.v0.1.1
  - Image: quay.io/foo/olm:testoperator.v0.1.2
  - Image: quay.io/foo/olm:testoperator.v0.1.3
  - Image: quay.io/foo/olm:testoperator.v0.2.0
  - Image: quay.io/foo/olm:testoperator.v0.2.1
  - Image: quay.io/foo/olm:testoperator.v0.2.2
  - Image: quay.io/foo/olm:testoperator.v0.3.0
  - Image: quay.io/foo/olm:testoperator.v1.0.0
  - Image: quay.io/foo/olm:testoperator.v1.0.1
  - Image: quay.io/foo/olm:testoperator.v1.1.0
Fast:
  Bundles:
  - Image: quay.io/foo/olm:testoperator.v0.2.1
  - Image: quay.io/foo/olm:testoperator.v0.2.2
  - Image: quay.io/foo/olm:testoperator.v0.3.0
  - Image: quay.io/foo/olm:testoperator.v1.0.1
  - Image: quay.io/foo/olm:testoperator.v1.1.0
Stable:
  Bundles:
  - Image: quay.io/foo/olm:testoperator.v1.0.1

In this example, Candidate has the entire version range of bundles, Fast has a mix of older and more-recent versions, and Stable channel only has a single published entry.

Generating major-version channels

If we set the template attributes

GenerateMajorChannels: true
GenerateMinorChannels: false

we generate the following major channels (filtering out large bundle metadata):

---
defaultChannel: stable-v1
name: testoperator
schema: olm.package
---
entries:
- name: testoperator.v0.1.0
- name: testoperator.v0.1.1
- name: testoperator.v0.1.2
- name: testoperator.v0.1.3
  skips:
  - testoperator.v0.1.0
  - testoperator.v0.1.1
  - testoperator.v0.1.2
- name: testoperator.v0.2.0
- name: testoperator.v0.2.1
- name: testoperator.v0.2.2
  replaces: testoperator.v0.1.3
  skips:
  - testoperator.v0.2.0
  - testoperator.v0.2.1
- name: testoperator.v0.3.0
  replaces: testoperator.v0.2.2
name: candidate-v0
package: testoperator
schema: olm.channel
---
entries:
- name: testoperator.v1.0.0
- name: testoperator.v1.0.1
  skips:
  - testoperator.v1.0.0
- name: testoperator.v1.1.0
  replaces: testoperator.v1.0.1
name: candidate-v1
package: testoperator
schema: olm.channel
---
entries:
- name: testoperator.v0.2.1
- name: testoperator.v0.2.2
  skips:
  - testoperator.v0.2.1
- name: testoperator.v0.3.0
  replaces: testoperator.v0.2.2
name: fast-v0
package: testoperator
schema: olm.channel
---
entries:
- name: testoperator.v1.0.1
- name: testoperator.v1.1.0
  replaces: testoperator.v1.0.1
name: fast-v1
package: testoperator
schema: olm.channel
---
entries:
- name: testoperator.v1.0.1
name: stable-v1
package: testoperator
schema: olm.channel

We generated a channel for each template channel entity corresponding to each of the 0.#.#, 1.#.# major version ranges with skips to the head of the highest semver in a channel. We also generated a replaces edge to traverse across minor version transitions within each major channel. Finally, we generated an olm.package object, setting as default the most-stable channel head we created. This process will prefer Stable channel over Fast, over Candidate and then a higher bundle version over a lower version.
(Please note that the naming of the generated channels indicates the digits of significance for that channel. For example, fast-v1 is a decomposed channel of the fast type which contains only major versions of contributing bundles matching v1.)

Generating minor-version channels

For contrast, if we set the template attributes

GenerateMinorChannels: true
GenerateMajorChannels: false

we generate the following minor channels (again filtering out large bundle metadata):

---
defaultChannel: stable-v1.0
name: testoperator
schema: olm.package
---
entries:
  - name: testoperator.v0.1.0
  - name: testoperator.v0.1.1
  - name: testoperator.v0.1.2
  - name: testoperator.v0.1.3
    skips:
      - testoperator.v0.1.0
      - testoperator.v0.1.1
      - testoperator.v0.1.2
name: candidate-v0.1
package: testoperator
schema: olm.channel
---
entries:
  - name: testoperator.v0.2.0
  - name: testoperator.v0.2.1
  - name: testoperator.v0.2.2
    replaces: testoperator.v0.1.3
    skips:
      - testoperator.v0.2.0
      - testoperator.v0.2.1
name: candidate-v0.2
package: testoperator
schema: olm.channel
---
entries:
  - name: testoperator.v0.3.0
    replaces: testoperator.v0.2.2
name: candidate-v0.3
package: testoperator
schema: olm.channel
---
entries:
  - name: testoperator.v1.0.0
  - name: testoperator.v1.0.1
    skips:
      - testoperator.v1.0.0
name: candidate-v1.0
package: testoperator
schema: olm.channel
---
entries:
  - name: testoperator.v1.1.0
    replaces: testoperator.v1.0.1
name: candidate-v1.1
package: testoperator
schema: olm.channel
---
entries:
  - name: testoperator.v0.2.1
  - name: testoperator.v0.2.2
    skips:
      - testoperator.v0.2.1
name: fast-v0.2
package: testoperator
schema: olm.channel
---
entries:
  - name: testoperator.v0.3.0
    replaces: testoperator.v0.2.2
name: fast-v0.3
package: testoperator
schema: olm.channel
---
entries:
  - name: testoperator.v1.0.1
name: fast-v1.0
package: testoperator
schema: olm.channel
---
entries:
  - name: testoperator.v1.1.0
    replaces: testoperator.v1.0.1
name: fast-v1.1
package: testoperator
schema: olm.channel
---
entries:
  - name: testoperator.v1.0.1
name: stable-v1.0
package: testoperator
schema: olm.channel

Here, a channel is generated for each template channel which differs by minor version, and each channel has a replaces edge from the predecessor channel to the next-lesser minor bundle version. Please note that at no time do we transgress across major-version boundaries with the channels, to be consistent with the semver convention for major versions, where the purpose is to make incompatible API changes.

Generating both channel types, and disambiguating default channel selection

In the case that we generate both major-version and minor-version channels:

GenerateMinorChannels: true
GenerateMajorChannels: true

we can easily end up in a situation where our results yield indifferentiable results, for e.g.:

---
entries:
- name: testoperator.v1.0.1
name: stable-v1
package: testoperator
schema: olm.channel
---
entries:
- name: testoperator.v1.0.1
name: stable-v1.0
package: testoperator
schema: olm.channel

In this situation, both channels have matching channel archetypes and the channel heads have the same versions. The DefaultChannelTypePreference attribute allows us to deterministically select a single channel in this case. This attribute defaults to prefer minor-version channels (DefaultChannelTypePreference: minor), but can be overridden in the schema if the author wishes to prefer major-version channels instead (DefaultChannelTypePreference: major).

With DefaultChannelTypePreference set to major, our most-stable channels and package output would look like

---
defaultChannel: stable-v1
name: testoperator
schema: olm.package
---
entries:
- name: testoperator.v1.0.1
name: stable-v1
package: testoperator
schema: olm.channel
---
entries:
- name: testoperator.v1.0.1
name: stable-v1.0
package: testoperator
schema: olm.channel