adding documentation under #2

# CRIDGE: A Service to manage Custom Resources in a Kubernetes Cluster

## Intended Audience: OSL developers

 >  Kubernetes is an orchestration system for automating software deployment, scaling, and management. One can interact though the Kubernetes API and it has a set of objects ready for use out of the box. Custom Resource Definitions (CRDs) is a way that allows to manage things other than Kubernetes itself and allows to create our own objects The use of CRDs makes the possibilities of Kubernetes management almost limitless. You can extend the base Kubernetes API with any object you like using CRDs.

- Watchers are created for this namespace for e.g. new secrets, config maps etc , so that they can be available back as resources to the Inventory of OSL (Note only Secrets for now are watched)

# Expose CRD based service specs for users in catalog 

- A CRD is exposed as a Resource Specification

	- Many attributes of the CRD are translated into characteristics

	- The following specific characteristics are added:

		- _CR_SPEC: Used for providing the json Custom Resource description to apply

		- _CR_CHECK_FIELD: Used for providing the field that need to be checked for the resource status

		- _CR_CHECKVAL_STANDBY: Used for providing the equivalent value from resource to signal the standby status

		- _CR_CHECKVAL_ALARM: Used for providing the equivalent value from resource to signal the alarm status

		- _CR_CHECKVAL_AVAILABLE: Used for providing the equivalent value from resource to signal the available status

		- _CR_CHECKVAL_RESERVED: Used for providing the equivalent value from resource to signal the reserved status

		- _CR_CHECKVAL_UNKNOWN: Used for providing the equivalent value from resource to signal the unknown status

		- _CR_CHECKVAL_SUSPENDED: Used for providing the equivalent value from resource to signal the suspended status

- Create a new Service Specification and use this Resource Specification in Resource Specification Relationships

	- Then the Service Specification is saved as ResourceFacingServiceSpecification

- We can give at this stage values to the characteristics:

		- _CR_SPEC, _CR_CHECK_FIELD, _CR_CHECKVAL_STANDBY, _CR_CHECKVAL_ALARM, _CR_CHECKVAL_AVAILABLE, _CR_CHECKVAL_RESERVED, _CR_CHECKVAL_UNKNOWN, _CR_CHECKVAL_SUSPENDED

- We can create LCM rules

- Create a new Service Specification and use the Resource Facing Service Specification in Service Specification Relationships

	- Then the Service Specification is saved as CustomerFacingServiceSpecification

- We can give at this stage values to the characteristics: 

	- _CR_SPEC, _CR_CHECK_FIELD, _CR_CHECKVAL_STANDBY, _CR_CHECKVAL_ALARM, _CR_CHECKVAL_AVAILABLE, _CR_CHECKVAL_RESERVED, _CR_CHECKVAL_UNKNOWN, _CR_CHECKVAL_SUSPENDED

- We can create LCM rules for this new Service Specification

- Expose configurable values for users to configure during service order

<img src="img06.png" width=1024px>

# Expose CRDs as Service Specifications in OpenSlice catalogs 

See [ExposingKubernetesResources](ExposingKubernetesResources.md)

# Service Orchestration and CRDs/CRs

- Assume the following simple CRD of a calculator model accepting two params (spec section) and an action and returning a result (status section)

- The controller (the calculato code) is implemented in any language and is installed in a Kubernetes cluster

```

apiVersion: apiextensions.k8s.io/v1

```

=======

> LCM rules can be used to change attributes of this yaml/json file, before sending this before the orchestration

However, the following issue needs to be solved: ** How to map the CR lifecycle that is defined in the CRD with the TMF resource Lifecycle? **

- It sends to the message bus the current resource for creation or update to the TMF service inventory

---

# Example CRD and its controller

To illustrate the powerful concept of Kubernetes operators and how they can be utilized to offer a service through OpenSlice, 

let's provide an example of a "Calculator as a Service." 

This example will demonstrate the flexibility and capabilities of Kubernetes operators in managing custom resources 

and automating operational tasks.

---

## Offering "Calculator as a Service" through OpenSlice

- We have a service that can accept two integers and an action (SUM, SUB, etc) and returns a result

- We would like to offer it as a Service through OpenSlice

- So when a user orders it with some initial parameters, OpenSlice will create it and return the result

- Also while the service is active, we can do further calculations, until we destroy it.

- Assume the following simple CRD of a calculator model accepting two params (spec section) and an action and returning a result (status section)

- The controller (the calculato code) is implemented in any language and is installed in a Kubernetes cluster

```

apiVersion: apiextensions.k8s.io/v1

kind: CustomResourceDefinition

metadata:

  name: mycalculators.examples.osl.etsi.org

spec:

  group: examples.osl.etsi.org

  names:

    kind: MyCalculator

    plural: mycalculators

    singular: mycalculator

  scope: Namespaced

  versions:

  - name: v1alpha1

    schema:

      openAPIV3Schema:

        properties:

          spec:

            properties:

              parama:

                type: integer

              paramb:

                type: integer

              action:

                type: string

            type: object

          status:

            properties:

              result:

                type: integer

              status:

                type: string

            type: object

        type: object

    served: true

    storage: true

    subresources:

      status: {}

```

Request to the cluster (through e.g. kubectl apply)

```

apiVersion: examples.osl.etsi.org/v1alpha1

kind: MyCalculator

metadata:

  name: mycalculator.examples.osl.etsi.org

spec:

  parama: 170

  paramb: 180

  action: 'SUM'

```

Response

```

apiVersion: examples.osl.etsi.org/v1alpha1

kind: MyCalculator

metadata:

  creationTimestamp: '2023-12-05T12:26:07Z’

<snip>

status:

  result: 350

  status: CALCULATED

spec:

  action: SUM

  parama: 170

  paramb: 180

```

To perform this through OpenSlice as a Service Specification ready to be ordered we need to do the following:

---

### CRD is saved automatically as Resource Specification

As soon as the CRD is deployed in the cluster (e.g. by your admin via kubctl or via any installation through the internet) it is automatically transformed and is available in OpenSlice catalogs as a Resource Specification.

- See also the fully qualified name of the resource specification.

- The resource specification name is quite unique, so you can install the CRD in many clusters around the internet. Each CRD on each cluster will appear here

<img src="img07.png" >

<img src="img08.png" width=1024px>

---

### Create a ResourceFacingServiceSpecification

<img src="img09.png" width=1024px>

<img src="img10.png" width=1024px>

### Creation of CRD-related characteristics

- We need now to adjust some characteristics of this CRD as Resoruce Specification.

- OpenSlice transalted automatically the CRD spec in a flat list of characteristics.So the "spec" section from the original yaml for example, is now unfold into: spec, spec.parama, spec.paramb, etc. the same for "status" object

- We need to make OpenSlice aware of when the service will be active. 

	- So we go to characteristic _CR_CHECK_FIELD and we define that the field that shows the status of the service is the characteristic "status.status" (is a text field) 

	- Then we go to _CR_CHECKVAL_AVAILABLE and we define the value CALCULATED, which signals the following: When the characteristic "status.status" has the value "CALCULATED" then OpenSlice will mark the underlying service as "ACTIVE"

	- We need also to define the yaml file that OpenSLice will use to create the new resource in the kubernetes cluster

	- We insert the YAML in the characteristic _CR_SPEC

	the _CR_SPEC is: ```

apiVersion: examples.osl.etsi.org/v1alpha1

kind: MyCalculator

metadata:

  name: mycalculator.examples.osl.etsi.org

spec:

  parama: 170

  paramb: 180

  action: 'SUM'

```

<img src="img11.png" width=1024px>

> However the values are fixed. How do we allow a user to pass parameters through OpenSlice

### Pass parameters through OpenSlice

We need to Create LCM rules in ResourceFacingServiceSpecification

- The goal of the rules is to allow the user to pass parameters to the actual resource towards the cluster.

- we will create one rule that will pass the parameters just before creating the service (PRE_PROVISION phase)

- we will create one rule that will pass the parameters while the service is active (SUPERVISION phase)

- The rules will be the same

<img src="img12.png" width=1024px>

If we see one rule it will look like the following:

<img src="img13.png" width=1024px>

- We need to change the _CR_SPEC characteristic

- We use a block that changes a String according to variables

- See that we have as Input string the YAML string lines

	- see that parama, paramb has a %d (they accept integers), action is %s (accepts a string)

	- See that the variables tha will replace the %d, %d and %s are an list

		- the first %d will be replaced with the value from characteristic spec.parama

		- the second %d will be replaced with the value from characteristic spec.paramb

		- the %s will be replaced with the value from characteristic spec.action

### Create a CustomerFacingServiceSpecification

We will now expose it to our users by creating a CustomerFacingServiceSpecification

<img src="img14.png" width=1024px>

Expose it then to a catalogue for orders through the Service Categories and Service Catalogs

<img src="img15.png">

### Order the Service

When a user orders the service, it will look like this:

<img src="img16.png" width=1024px>

- After the Service Order we have 2 services in service inventory on CFS and on RFS. Both have references to values

- CRIDGE updates the Resource in Resource Inventory and OSOM updated the Services in Service Inventory

- The Actual resources are running in the Kubernetes cluster managed by OpenSlice

- The result is in the characteristic status.result

<img src="img17.png" width=800px>

<img src="img18.png" width=1024px>

## What's next?

 ### Modify the running service

 -  See examples of exposing operators via OpenSlice:

 	- [Exposing Kubernetes Operators as a Service : Offering "Calculator as a Service" through OpenSlice](ExposingCRDs_aaS_Example_Calculator.md)

 The use can modify the service

<img src="img19.png" width=1024px>

- After a while the update is applied to the cluster, the controller will pick up the resource update and patch the resource

- CRIDGE updates the Resource in Resource Inventory and OSOM updates the Services in Service Inventory

<img src="img20.png" width=1024px>

# Exposing Kubernetes Operators as a Service : Offering "Calculator as a Service" through OpenSlice

## Intended Audience: Service Designers

To illustrate the powerful concept of Kubernetes operators and how they can be utilized to offer a service through OpenSlice, 

let's provide an example of a "Calculator as a Service." 

This example will demonstrate the flexibility and capabilities of Kubernetes operators in managing custom resources 

and automating operational tasks.

---

## Offering "Calculator as a Service" through OpenSlice

- We have a service that can accept two integers and an action (SUM, SUB, etc) and returns a result

- We would like to offer it as a Service through OpenSlice

- So when a user orders it with some initial parameters, OpenSlice will create it and return the result

- Also while the service is active, we can do further calculations, until we destroy it.

- Assume the following simple CRD of a calculator model accepting two params (spec section) and an action and returning a result (status section)

- The controller (the calculato code) is implemented in any language and is installed in a Kubernetes cluster

```

apiVersion: apiextensions.k8s.io/v1

kind: CustomResourceDefinition

metadata:

  name: mycalculators.examples.osl.etsi.org

spec:

  group: examples.osl.etsi.org

  names:

    kind: MyCalculator

    plural: mycalculators

    singular: mycalculator

  scope: Namespaced

  versions:

  - name: v1alpha1

    schema:

      openAPIV3Schema:

        properties:

          spec:

            properties:

              parama:

                type: integer

              paramb:

                type: integer

              action:

                type: string

            type: object

          status:

            properties:

              result:

                type: integer

              status:

                type: string

            type: object

        type: object

    served: true

    storage: true

    subresources:

      status: {}

```

Request to the cluster (through e.g. kubectl apply)

```

apiVersion: examples.osl.etsi.org/v1alpha1

kind: MyCalculator

metadata:

  name: mycalculator.examples.osl.etsi.org

spec:

  parama: 170

  paramb: 180

  action: 'SUM'

```

Response

```

apiVersion: examples.osl.etsi.org/v1alpha1

kind: MyCalculator

metadata:

  creationTimestamp: '2023-12-05T12:26:07Z’

<snip>

status:

  result: 350

  status: CALCULATED

spec:

  action: SUM

  parama: 170

  paramb: 180

```

To perform this through OpenSlice as a Service Specification ready to be ordered we need to do the following:

---

### CRD is saved automatically as Resource Specification

As soon as the CRD is deployed in the cluster (e.g. by your admin via kubctl or via any installation through the internet) it is automatically transformed and is available in OpenSlice catalogs as a Resource Specification.

- See also the fully qualified name of the resource specification.

- The resource specification name is quite unique, so you can install the CRD in many clusters around the internet. Each CRD on each cluster will appear here

<img src="img07.png" >

<img src="img08.png" width=1024px>

---

### Create a ResourceFacingServiceSpecification

<img src="img09.png" width=1024px>

<img src="img10.png" width=1024px>

### Creation of CRD-related characteristics

- We need now to adjust some characteristics of this CRD as Resoruce Specification.

- OpenSlice transalted automatically the CRD spec in a flat list of characteristics.So the "spec" section from the original yaml for example, is now unfold into: spec, spec.parama, spec.paramb, etc. the same for "status" object

- We need to make OpenSlice aware of when the service will be active. 

	- So we go to characteristic _CR_CHECK_FIELD and we define that the field that shows the status of the service is the characteristic "status.status" (is a text field) 

	- Then we go to _CR_CHECKVAL_AVAILABLE and we define the value CALCULATED, which signals the following: When the characteristic "status.status" has the value "CALCULATED" then OpenSlice will mark the underlying service as "ACTIVE"

	- We need also to define the yaml file that OpenSLice will use to create the new resource in the kubernetes cluster

	- We insert the YAML in the characteristic _CR_SPEC

	the _CR_SPEC is: ```

apiVersion: examples.osl.etsi.org/v1alpha1

kind: MyCalculator

metadata:

  name: mycalculator.examples.osl.etsi.org

spec:

  parama: 170

  paramb: 180

  action: 'SUM'

```

<img src="img11.png" width=1024px>

> However the values are fixed. How do we allow a user to pass parameters through OpenSlice

### Pass parameters through OpenSlice

We need to Create LCM rules in ResourceFacingServiceSpecification

- The goal of the rules is to allow the user to pass parameters to the actual resource towards the cluster.

- we will create one rule that will pass the parameters just before creating the service (PRE_PROVISION phase)

- we will create one rule that will pass the parameters while the service is active (SUPERVISION phase)

- The rules will be the same

<img src="img12.png" width=1024px>

If we see one rule it will look like the following:

<img src="img13.png" width=1024px>

- We need to change the _CR_SPEC characteristic

- We use a block that changes a String according to variables

- See that we have as Input string the YAML string lines

	- see that parama, paramb has a %d (they accept integers), action is %s (accepts a string)

	- See that the variables tha will replace the %d, %d and %s are an list

		- the first %d will be replaced with the value from characteristic spec.parama

		- the second %d will be replaced with the value from characteristic spec.paramb

		- the %s will be replaced with the value from characteristic spec.action

### Create a CustomerFacingServiceSpecification

We will now expose it to our users by creating a CustomerFacingServiceSpecification

<img src="img14.png" width=1024px>

Expose it then to a catalogue for orders through the Service Categories and Service Catalogs

<img src="img15.png">

### Order the Service

When a user orders the service, it will look like this:

<img src="img16.png" width=1024px>

- After the Service Order we have 2 services in service inventory on CFS and on RFS. Both have references to values

- CRIDGE updates the Resource in Resource Inventory and OSOM updated the Services in Service Inventory

- The Actual resources are running in the Kubernetes cluster managed by OpenSlice

- The result is in the characteristic status.result

<img src="img17.png" width=800px>

<img src="img18.png" width=1024px>

 ### Modify the running service

 The use can modify the service

<img src="img19.png" width=1024px>

- After a while the update is applied to the cluster, the controller will pick up the resource update and patch the resource

- CRIDGE updates the Resource in Resource Inventory and OSOM updates the Services in Service Inventory

<img src="img20.png" width=1024px>

 No newline at end of file