ocm_toi-bootstrapping.md

ocm toi-bootstrapping — Tiny OCM Installer Based On Component Versions

Description

TOI is a small toolset on top of the Open Component Model. It provides a possibility to run images taken from a component version with user configuration and feed them with the content of this component version. It is some basic mechanism, which can be used to execute simple installation steps based on content described by the Open Component Model (see ocm bootstrap package).

Therefore, a dedicated resource type toiPackage is defined, which describes an installation package to be handled by TOI. When calling the ocm bootstrap package command it is selected by a resource identity pattern. The first resource in given component version matching the pattern is used. A possible use case could be to provide different packages for different environments. The resource can use an identity attribute platform=<value>. By specifying just the platform attribute, the appropriate package will be chosen.

The bootstrap command uses this package resource to determine a TOI executor together with executor configuration and additional client specific settings to describe a dedicated installation.

To do this the package describes dedicated actions that can be executed by the bootstrap command. Every action (for example install) refers to an executor, which is executed to perform the action.

An executor is basically an image following the TOI specification for passing information into the image execution and receiving results from the execution. An executor specification can be described in two ways:

• it either directly describes a resource of type ociImage or
• it describes a resource of type toiExecutor, which defines the image to use and some default settings. It furthermore describes the features and requirements of the executor image.

The package describes configuration values for every configured executor as well as general credentials requirements and required user configuration which must be passed along with the bootstrap command. The executor specification may then optionally map this package global settings into executor specific views.

After validation of the input and its mapping to an executor specific format, finally, a container with the selected executor image is created, that contains the content of the initial component version in form of a Common Transport Archive and all the specified configuration data.

The execution of the container may do the needful to achieve the goal of the requested action and provide some labeled output files, which will be passed to the caller.

The toiPackage Resource

This resource describes an installable software package, whose content is contained in the component version, which contains the package resource.

It is a plain yaml resource with the media types media type application/x-yaml, text/yaml or

application/vnd.toi.ocm.software.package.v1+yaml) containing information required to control the instantiation of an executor.

It has the following format:

• description (optional) string

  A short description of the installation package and some configuration hints.

• executors []ExecutorSpecification

• configTemplate (optional) yaml

  This is a spiff template used to generate The user config that is finally passed to the executor. If no template is specified the user parameter input will be processed directly without template.

• configScheme (optional) yaml

  This is a JSONSCHEMA used to validate the user input prior to merging with the template

• templateLibraries (optional) []ResourceReference

  This is a list of resources whose content is used as additional stubs for the template processing.

• credentials (optional) map[string]CredentialRequest

  Here the package may request the provisioning of some credentials with a dedicated name/purpose and structure. If specified the bootstrap command requites the specification of a credentials file providing the information how to satisfy those credential requests.

• additionalResources (optional) map[string]AdditionalResource)

  A set of additional resources specified by an OCM resource reference or direct data as byte, string or yaml. The key describes the meaning of the resource. The following keys have a special meaning:

  • configFile: an example template for a parameter file
  • credentialsFile: an example template for a credentials file

  Those templates can be downloaded with ocm bootstrap config.

ExecutorSpecification

The executor specification describes the available actions and their mapping to executors. It uses the following fields:

• actions []string

  The list of actions this executor can be used for. If nothings is specified the executor will be used for all actions. The first matching executor entry will be used to execute an action by the bootstrap command

• resourceRef []ResourceReference

  An OCM resource reference describing a component version resource relative to the component version containing the package resource.

• config (optional) yaml

  This is optional static executor config passed to the executor as is. It is to describe the set of elements on which the actual execution of the executor should work on.

• parameterMapping (optional) spiff yaml

  This is an optional spiff template used to process the actual package parameter set passed by the caller to transform it to the requirements of the actual executor.

  A package has a global parameter setting, but possibly multiple different executors for different actions. They might have different requirements/formats concerning the parameter input. Therefore, the executor specification allows to map the provided user input, accordingly.

• credentialMapping (optional) map[string]string

  This is an optional mapping to map credential names used by the package to the needs of dedicated executors.

  A package has global parameter setting, but possibly multiple different executors for different action. They might have different requirements/formats concerning the parameter input. There the executor specification allows to map the provided user input, accordingly

• image (development) object

  Instead of a resourceRef it is possible to directly specify an absolute image.

  ATTENTION: this is intended for development purposes, ONLY. Do not use it for final component versions.

  It has the field ref and the optional field digest.

• outputs (optional) map[string]string

  This field can be used to map the names of outputs provided by a dedicated executor outputs to package outputs.

ResourceReference

An OCM resource reference describes a resource of a component version. It is always evaluated relative to the component version providing the resource that contains the resource reference. It uses the following fields:

• resourcePath (optional) []Identity

  This is sequence of reference identities used to follow a chain of component version references starting with the actual component version. If not specified the specified resource will be taken from the actual component version.

• resource Identity

  This is the identity of the resource in the selected component version.

AdditionalResource

This field has either the fields of a ResourceReference to refer to the content of an OCM resource or the field:

• content string|[]byte|YAML

  Either a resource reference or the field content must be given. The content field may contain a string or an inline YAML document. For larger content the resource reference form should be preferred.

Identity

An identity specification is a map[string]string. It describes the identity attributes of a desired resource in a component version. It always has at least one identity attribute name, which is the resource name field of the desired resource. If this resource defines additional identity attributes, the complete set must be specified.

Input Mapping for Executors

An optional parameterMapping in the executor section can be used to process the global package user-specified parameters to provide specifc values expected by the executor.

This is done by a spiff template. Here special functions are provided to access specific content:

• hasCredentials(string[,string]) bool

  This function can be used to check whether dedicated credentials are effectively provided for the actual installation.

  The name is the name of the credentials as described in the credentials request section optionally mapped to the name used for the executor (field credentialMapping).

  If the second argument is given, it checks for the named property in the credential set.

• getCredentials(string[,string]) map[string]string | string

  This functions provides the property set of the provided credentials.

  If the second argument is given, it returns the named property in the selected credential set.

  If the property name is an asterisks (*) a single property is expected, whose value is returned.

User Config vs Executor Config

An executor is typically able to handle a complete class of installations. It describes a dedicated installation mechanism, but not a dedicated installation source. Although, there might be specialized images for dedicated installation sources, in general the idea is to provide more general executors, for example an helmexecutor, which is able to handle any helm chart, not just a dedicated helm deployment.

Because of this, there is a clear separation between an installation specific configuration, which is provided by the user calling the TOI commands, and the parameterization of the executor, which is completely specified in the package.

The task of the package is to represent a dedicated deployment source. As such it has to provide information to tell the executor what to install, while the user configuration is used to describe the instance specific settings.

Back to the example of a helminstaller executor, the executor config contained in the package resource describes the helm chart, which should be installed and the way how the user input is mapped to chart values. Here, also the localizations are described in an executor specific way.

Therefore, an executor expects a dedicated configuration format, which can be specified in the executor resource in form of a JSON scheme.

The package then may provide a package specific scheme for the instance configuration. This value-set is dependent on the installation source (the helm chart in this example).

For further details you have to refer to the dedicated executor and package definitions.

The toiExecutor Resource

Instead of directly describing an image resource in the package file, it is possible to refer to a resource of type toiExecutor. This is a yaml file with the media type application/x-yaml, text/yaml or application/vnd.toi.ocm.software.package.v1+yaml) containing common information about the executor. If this flavor is used by the package, this information is used to validate settings in the package specification.

It has the following format:

• imageRef ResourceReference

  This field reference the image resource relative to the component version providing the executor resource

• configTemplate (optional) yaml

  This a spiff template used to generate The executor config from the package specification that is finally passed to the executor. If no template is specified the executor config specified in the package will be processed directly without template.

• configScheme (optional) yaml

  This is a JSONSCHEMA used to validate the executor config from the package prior to merging with the template

• templateLibraries (optional) []ResourceReference

  This is a list of resources whose content is used as additional stubs for the template processing.

• credentials (optional) map[string]CredentialRequest

  Here the executor may request the provisioning of some credentials with a dedicated name/purpose and structure. If specified it will be propagated to a using package. It this uses an own credentials section, this one will be filtered and checked for the actual executor.

• outputs (optional) map[string]OutputSpecification

  This field can be used to describe the provided outputs of this executor. The OutputSpecification contains only the field description, so far. It is intended to be extended to contain further information to more formally describe the type of output.

• image (development) object

  Instead of an imageRef it is possible to directly specify an absolute image.

  ATTENTION: this is intended for development purposes, ONLY. Do not use it for final component versions.

  It has the field ref and the optional field digest.

Client Parameters

Common to all executors a parameter file can be provided by the caller. The package specification may provide a spiff template for this parameter file. It can be used, for example to provide useful defaults. The actually provided content is merged with this template.

To validate user configuration a JSON scheme can be provided. The user input is validated first against this scheme before the actual merge is done.

Credentials

Additionally credentials can be requested to be provided by a client. This is done with the credentials field. It is a map of credentials names and their meaning and/or handling.

It uses the following fields:

• description string

  This field should describe the purpose of the credential.

• properties map[string]string

  This field should describe the used credential fields

• consumerId map[string]

  This field can be used to optionally define a consumer id that should be set in the OCM support library, if used by the executor. At least the field type and one additional field must be set.

Credentials are provided in an ocm config file (see ocm configfile). It uses a memory credential repository with the name default to store the credentials under the given name. Additionally appropriate consumer ids will be propagated, if requested in the credentials request config.

Executor Image Contract

The executor image is called with the action as additional argument. It is expected that is defines a default entry point and a potentially empty list of standard arguments.

It is called with two arguments:

• name of the action to execute

• identity of the component version containing the package the executor is executed for.

  This can be used to access the component descriptor to get access to further described resources in the executor config

The container used to execute the executor image gets prepared a standard filesystem structure used to provide all the executor inputs before the execution and reading provided executor outputs after the execution.

/
└── toi
    ├── inputs
    │   ├── config      configuration from package specification
    │   ├── ocmrepo     OCM filesystem repository containing the complete
    │   │               component version of the package
    │   └── parameters  merged complete parameter file
    ├── outputs
    │   ├── <out>       any number of arbitrary output data provided
    │   │               by executor
    │   └── ...
    └── run             good practice: typical location for the executed command

After processing it is possible to return named outputs. The name of an output must be a filename. The executor section in the package specification maps those files to logical outputs in the outputs section.

<file name by executor> -> <logical output name>

Basically the output may contain any data, but is strongly recommended to use yaml or json files, only. This enables further formal processing by the TOI toolset.

Examples

description: |
  This package is just an example.
executors:
  - actions:
    - install
    resourceRef:
      resource:
        name: installerimage
    config:
      level: info
#   parameterMapping:  # optional spiff mapping of Package configuration to
#      ....            # executor parameters
    outputs:
       test: bla
credentials:
  target:
    description: kubeconfig for target kubernetes cluster
    consumerId:
      type: Kubernetes
      purpose: target
configTemplate:
  parameters:
    username: admin
    password: (( &merge ))
configScheme:
  type: object
  required:
    - parameters
  additionalProperties: false
  properties:
    parameters:
      type: object
      required:
      - password
      additionalProperties: false
      properties:
        username:
          type: string
        password:
          type: string
additionalResources:
  configFile:
    resource:
      name: config-file

SEE ALSO

Parents

• ocm — Open Component Model command line client

Additional Links

• ocm bootstrap package — bootstrap component version
• ocm bootstrap package — bootstrap component version
• ocm bootstrap config
• ocm configfile — configuration file