andref5 / midnight

Kong Golang plugin lab

midnight

Golang middleware Kong plugin for study purposes only.

Build

go build -buildmode plugin midnight.go

Test

In sample/change-pokemon-type.yml has the configuration for the kong service / route and plugin that makes the transformation in the api https://docs.pokemontcg.io/#api_v1cards_get. With the following flow:

• Change service path [:id] v1/cards/:id with path request [.+] /change/.+
• Make request to api
• To each response "card.types" random new type
• Build result on "message"
• Return to client

cd sample
docker-compose up

curl -v localhost:8000/change/xy7-54

# {"message":"Change types for pokemon Gardevoir[xy7-54] from [Fairy] to [Darkness]"}

How it works

• Configure Kong Service with upstream URL. You can add named parameter on path with ":" + parameter name.

  EX.
  https://api.pokemontcg.io/v1/cards/:id
  

• Configure Kong Route

• Add plugin midnight with following config:

  • [uri] - key (parameter name) value (index on request path) pair where to get named parameters

    EX.
    # config
    {"id":1}
    # request path
    /change/xy7-54
    # kong service path
    /v1/cards/:id
    # become
    /v1/cards/xy7-54
    

  • [in/out] - golang template to build with request params ([in]) to change request body to upstream and response params ([out]) to change resposen body to client. Midnigth add useful template sprig functions http://masterminds.github.io/sprig/

    EX.
    # response body
    {"card":{"name": "Pikachu"}}
    # config [out] template
    {{ {"pokemon": "{{ .card.name }}"} }}
    # become
    {"pokemon": "Pikachu"}
    

Etc

• Kong plugin has some limitations.There are no header_filter or body_filter phases.

• Length must be at least 1 on kong plugin configs. Add an empty space in the unused configuration.