# Group Parameterized Endpoints
In most cases, the endpoint should be detected automatically through the language agents, service mesh observability solution,
or configuration of meter system.

There are some special cases, especially when people use REST style URI, the application codes put the parameter in the endpoint name,
such as putting order id in the URI, like `/prod/ORDER123` and `/prod/ORDER123`. But logically, people expect they could
have an endpoint name like `prod/{order-id}`. This is the feature of parameterized endpoint grouping designed for.

If the incoming endpoint name hit the rules, SkyWalking will grouping the endpoint by rules.

SkyWalking provides 2 ways to support endpoint grouping:
1. Endpoint name grouping by OpenAPI definitions.
2. Endpoint name grouping by custom configuration.

The 2 grouping features can work together in sequence.
## Endpoint name grouping by OpenAPI definitions
The OpenAPI definitions are the documents based on The [OpenAPI Specification (OAS)](https://www.openapis.org/) which used to define a standard, language-agnostic interface for HTTP APIs.
SkyWalking now support `OAS v2.0+`, could parse the documents `(yaml)` and build the grouping rules from them automatically.


### How to use
1. Add some `Specification Extensions` for SkyWalking config in the OpenAPI definition documents, otherwise, all configs are default:<br />
   `${METHOD}` is a reserved placeholder which represents the HTTP method eg. `POST/GET...` <br />
   `${PATH}` is a reserved placeholder which represents the path eg. `/products/{id}`.

   | Extension Name | Required | Description | Default Value |
   |-----|-----|-----|-----|
   | x-sw-service-name | false | The service name which these endpoints belong to | The directory name which the OpenAPI definition documents belong to |
   | x-sw-endpoint-name-match-rule | false | The rule used to match the endpoint.| `${METHOD}:${PATH}` |
   | x-sw-endpoint-name-format | false | The endpoint name after grouping.| `${METHOD}:${PATH}` |

   These extensions are under `OpenAPI Object`. For example, the document below has a full custom config:

``` yaml
openapi: 3.0.0
x-sw-service-name: serviceB
x-sw-endpoint-name-match-rule: "${METHOD}:${PATH}"
x-sw-endpoint-name-format: "${METHOD}:${PATH}"

info:
  description: OpenAPI definition for SkyWalking test.
  version: v2
  title: Product API
  ...
```

   We highly recommend using the default config, the custom config (`x-sw-endpoint-name-match-rule/x-sw-endpoint-name-format`) would be considered as part of the match rules (regex pattern).
   We provide some cases in `org.apache.skywalking.oap.server.core.config.group.openapi.EndpointGroupingRuleReader4OpenapiTest`, you could validate your custom config as well.

2. All OpenAPI definition documents should be located in the `openapi-definitions` directory, with at most two levels directories. Recommend using the service name as the subDirectory name then you are not required to set `x-sw-service-name`. For example:
  ```
├── openapi-definitions
│   ├── serviceA
│   │   ├── customerAPI-v1.yaml
│   │   └── productAPI-v1.yaml
│   └── serviceB
│       └── productAPI-v2.yaml
```
3. The feature is enabled by default, you can disable it by setting the `Core Module` configuration `${SW_CORE_ENABLE_ENDPOINT_NAME_GROUPING_BY_OPAENAPI:false}`

### Rules match priority 
We recommend designing the API path as clear as possible. If the API path is fuzzy and an endpoint name might match multiple paths, SkyWalking would follow the match priority to select one as below orders:
1. The exact path matched first. 
   Eg. `/products or /products/inventory`
2. The path which has the less variables.
   Eg. `/products/{var1}/{var2} and /products/{var1}/abc`, endpoint name `/products/123/abc` will match the second one.
3. If the paths have the same number of variables, match the longest path, and the vars are considered to be `1`.
   Eg. `/products/abc/{var1} and products/{var12345}/ef`, endpoint name `/products/abc/ef` will match the first one, because `length("abc") = 3` is larger than `length("ef") = 2`.
### Examples
If we have an OpenAPI definition doc `productAPI-v2.yaml` in directory `serviceB` like this:
```yaml

openapi: 3.0.0

info:
  description: OpenAPI definition for SkyWalking test.
  version: v2
  title: Product API

tags:
  - name: product
    description: product
  - name: relatedProducts
    description: Related Products

paths:
  /products:
    get:
      tags:
        - product
      summary: Get all products list
      description: Get all products list.
      operationId: getProducts
      responses:
        "200":
          description: Success
          content:
            application/json:
              schema:
                type: array
                items:
                  $ref: "#/components/schemas/Product"
  /products/{region}/{country}:
    get:
      tags:
        - product
      summary: Get products regional
      description: Get products regional with the given id.
      operationId: getProductRegional
      parameters:
        - name: region
          in: path
          description: Products region
          required: true
          schema:
            type: string
        - name: country
          in: path
          description: Products country
          required: true
          schema:
            type: string
      responses:
        "200":
          description: successful operation
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/Product"
        "400":
          description: Invalid parameters supplied
  /products/{id}:
    get:
      tags:
        - product
      summary: Get product details
      description: Get product details with the given id.
      operationId: getProduct
      parameters:
        - name: id
          in: path
          description: Product id
          required: true
          schema:
            type: integer
            format: int64
      responses:
        "200":
          description: successful operation
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/ProductDetails"
        "400":
          description: Invalid product id
    post:
      tags:
        - product
      summary: Update product details
      description: Update product details with the given id.
      operationId: updateProduct
      parameters:
        - name: id
          in: path
          description: Product id
          required: true
          schema:
            type: integer
            format: int64
        - name: name
          in: query
          description: Product name
          required: true
          schema:
            type: string
      responses:
        "200":
          description: successful operation
    delete:
      tags:
        - product
      summary: Delete product details
      description: Delete product details with the given id.
      operationId: deleteProduct
      parameters:
        - name: id
          in: path
          description: Product id
          required: true
          schema:
            type: integer
            format: int64
      responses:
        "200":
          description: successful operation
  /products/{id}/relatedProducts:
    get:
      tags:
        - relatedProducts
      summary: Get related products
      description: Get related products with the given product id.
      operationId: getRelatedProducts
      parameters:
        - name: id
          in: path
          description: Product id
          required: true
          schema:
            type: integer
            format: int64
      responses:
        "200":
          description: successful operation
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/RelatedProducts"
        "400":
          description: Invalid product id

components:
  schemas:
    Product:
      type: object
      description: Product id and name
      properties:
        id:
          type: integer
          format: int64
          description: Product id
        name:
          type: string
          description: Product name
      required:
        - id
        - name
    ProductDetails:
      type: object
      description: Product details
      properties:
        id:
          type: integer
          format: int64
          description: Product id
        name:
          type: string
          description: Product name
        description:
          type: string
          description: Product description
      required:
        - id
        - name
    RelatedProducts:
      type: object
      description: Related Products
      properties:
        id:
          type: integer
          format: int32
          description: Product id
        relatedProducts:
          type: array
          description: List of related products
          items:
            $ref: "#/components/schemas/Product"


```

Here are some cases:

   | Incoming Endpiont | Incoming Service | x-sw-service-name | x-sw-endpoint-name-match-rule | x-sw-endpoint-name-format | Matched | Grouping Result |
   |-----|-----|-----|-----|-----|-----|-----|
   | `GET:/products` | serviceB | default | default | default | true | `GET:/products` |
   | `GET:/products/123` | serviceB | default | default | default |  true | `GET:/products{id}` |
   | `GET:/products/asia/cn` | serviceB | default | default | default | true | `GET:/products/{region}/{country}` |
   | `GET:/products/123/abc/efg` | serviceB | default | default | default |  false | `GET:/products/123/abc/efg` | 
   | `<GET>:/products/123` | serviceB | default | default | default | false | `<GET>:/products/123`|
   | `GET:/products/123` | serviceC | default | default | default | false | `GET:/products/123` |
   | `GET:/products/123` | serviceC | serviceC | default | default | true | `GET:/products/123` |
   | `<GET>:/products/123` | serviceB | default | `<${METHOD}>:${PATH}` | `<${METHOD}>:${PATH}` | true | `<GET>:/products/{id}` |
   | `GET:/products/123` | serviceB | default | default | `${PATH}:<${METHOD}>` | true | `/products/{id}:<GET>` |
   | `/products/123:<GET>` | serviceB | default | `${PATH}:<${METHOD}>` | default | true | `GET:/products/{id}` |


## Endpoint name grouping by custom configuration
Current, user could set up grouping rules through the static YAML file, named `endpoint-name-grouping.yml`,
or use [Dynamic Configuration](dynamic-config.md) to initial and update the endpoint grouping rule.

### Configuration Format
No matter in static local file or dynamic configuration value, they are sharing the same YAML format.

```yaml
grouping:
  # Endpoint of the service would follow the following rules
  - service-name: serviceA
    rules:
      # Logic name when the regex expression matched.
      - endpoint-name: /prod/{id}
        regex: \/prod\/.+
```