Working with policy sequence

A policy sequence organizes multiple policies and applies them in a specified order to enforce consistent API behavior.

The following specifications are a part of the file structure of a policy sequence:

kind. The value of the kind field specifies the type of policy sequence. The exact value depends on the gateway:
- webMethods API Gateway uses StagedPolicySequence, where policies are defined in predefined, sequential stages with a fixed execution order.
- DataPower Gateway uses DataPowerAssembly, where policies are defined as ordered processing actions within an assembly, and executed in the sequence in which they are defined.
- DataPower Nano Gateway uses FreeFlowPolicySequence, where policies are defined without predefined stages, allowing flexible arrangement of policy execution.
apiVersion. Defines the API schema version.
metadata. The metadata section contains identifying attributes of the policy sequence. It can include details such as:
- name. Unique identifier of the policy sequence.
- namespace. Logical grouping or scope where the policy sequence is defined.
- version. Version number of the policy sequence.
- tags. Keywords used for categorization.
- labels. Labels categorize a policy sequence for identification, filtering, and management. You can define labels with any user-defined values. For example:
```
labels:
    gatewayTypes:
      - webMethods
```
  In this example, the gatewayTypes label uses a gateway name as a sample value. This example only shows one possible use. Labels can represent any classification that makes sense.
spec. Lists referenced policies under appropriate categories.

Referencing policies

A policy is referenced in a policy sequence file using the $ref parameter in the format:

$ref: namespace:name:version

The components of this reference include:

name. This is the label/identifier for the policy.
namespace. This is the group label/identifier used to organize related policies. Namespaces are used to group related assets under a common category in order to organize the policies.
version. This is a user-defined value that indicates the version of the policy. It helps track changes and manage updates over time.

You can link the policy sequence to an API or a Global policy by using the policy-sequence parameter, following the same $ref format.

A sample for policy sequence is as follows:

kind: StagedPolicySequence
metadata:
  name: policy_sequence
  version: 1.0
  namespace: sample
  tags:
    - dev_policies
spec: #Lists all the stages with policies in each of them
    
    transport: 
      - $ref: sample:transport_protocol:1
    
    security:  
      - $ref: sample:identify_and_authorize:1.0
    
    monitoring: 
      - $ref: sample:log_invocation:1.0
      - $ref: sample:rate-limiter:1.0
      - $ref: sample:service_cache:1.0
      - $ref: sample:monitor:1.0

This policy sequence file references multiple policies, ensuring they are applied in a structured manner. The transport section links to the Transport_policy, while the routing section links to Routing_policy, both under the default namespace.