Kong custom plugin

This repo contains plugins to enhance the experience of using GraphQL API with Kong API Gateway, including:

Proxy cache plugin

Used to cached GraphQL query response. The plugin support most of the features provided by Kong Enterprise GraphQL Proxy Caching Advanced plugin along with additional features:

Cached request is stored in redis
Integrate with Loki & Prometheus

Recognize mutilple requests are the same and returned the cached result already created when making the first request instead of making query to upstream service again. Support cases:

Ex1: All requests contain the same fields but the order are not identical:

# 1st query
query Country {
  country(code: "VN") {
      emoji,    
      name,
      native,
      capital
    }
}
    
# 2nd query: field order are changed, contain comment
query Country {
  country(code: "VN") {
      emoji, name,
      capital, # graphql cmt
      native
  }
}

# 3rd query: operation name, type are omitted
{
    country(code: "VN") {
        native, emoji, name, capital
    } 
}

Ex2: All requests use the same variables but in declare, use in different order

# 1st query
query Repository($name: String!, $owner: String!, $followRenames: Boolean) {
  repository(name: $name, owner: $owner, followRenames: $followRenames) {
    allowUpdateBranch
    autoMergeAllowed
    id
    createdAt
    owner {
      avatarUrl
      id
      login
      url
    }
    isPrivate
  }
}

# variables
{
  "name": "kong-custom-plugin",
  "owner": "BuiChiTrung",
  "followRenames": true
}

# 2nd query
query Repository($followRenames: Boolean, $owner: String!, $name: String!) {
  repository(name: $name, owner: $owner, followRenames: $followRenames) {
    owner {
      avatarUrl
      id
      login
      url
    }
    allowUpdateBranch
    autoMergeAllowed
    createdAt
    id
    isPrivate
  }
}

# variables
{
  "name": "kong-custom-plugin",
  "followRenames": true,
  "owner": "BuiChiTrung"
}

Cache key

MD5(requestHeader | graphQLAST | graphQL Variable)

requestHeader: the content of headers specified in plugin config
graphQLAST: the AST of graphQL query

Plugin config

TTLseconds: the expired time of request.
ErrTTLSeconds: the expired time of error request with 4xx status (default = TTLSeconds)
Headers: the list of header used to create cache key.
LogFileSizeMaxMB: the max size of a log file.
LogAgeMaxDays: expire date of log file.
RedisHealthCheckIntervalSecond: the time a job is executed to check redis health periodically

Plugin APIs

Written using Fiber framework: ./fiber-app. Cache key used for these APIs can be retrieved in the X-Cache-Key in response.

GET cache entity:

curl --location 'http://localhost:9080/proxy-cache/<cache_key>' \

UPSERT cache entity:

curl --location 'http://localhost:9080/proxy-cache' \
--data '{
    "cacheKey": "<cache-key>",
    "value": "<new-cache-value>"
}'

DELETE cache entity:

curl --location --request DELETE 'http://localhost:9080/proxy-cache/<cache-key>'

PURGE cache entity: remove all cache keys

curl --location --request DELETE 'http://localhost:9080/proxy-cache'

GraphQL portal

This plugin is intergated with several popular libraries for GraphQL to use for all GraphQL services registered in Kong (these services must have graphql tag) including:

graphiql: GraphQL IDE provide playground to test your GraphQL APIs.
graphql-voyager: Represent any GraphQL API as an interactive graph.
graphql-query-generator: Used to generate GraphQL query randomly from a given schema.

Installation

Setup kong and the plugin

The docker-compose file follows Kong installation document via Docker.
Start docker containers
```
make up
```
Note: At the second time of running these containers you should comment out the kong-gateway-db-bootstrap service in docker-compose.yaml as it only used as the first time you run these container to migration Kong initial db to the psql volumn: ./db/psql.

Enable the plugin

Globally

curl --location 'http://localhost:8001/plugins' \
--data '{
    "name": "proxy-cache-graphql",
    "config": {
        "ttlseconds":  5
    }
}'

For a single service

curl --location 'http://localhost:8001/services/SERVICE_NAME|SERVICE_ID/plugins' \
--data '{
    "name": "proxy-cache-graphql",
    "config": {}
}'

For a single route

curl --location 'http://localhost:8001/routes/ROUTE_NAME|ROUTE_ID/plugins' \
--data '{
    "name": "proxy-cache-graphql",
    "config": {}
}'

Other commands

Stop docker containers
```
make down
```
Update the plugin source code & rerun containers
```
make restart
```
Run fiber app separately
```
make run fiber 
```

Folder structure

bin: binary built Go file.
fiber-app: an application server written using fiber framework which provide API to all plugins.
kong/plugins: plugin source code
- go-wait: test plugin written in Go.
- hello-world: test plugin written in Lua.
- proxy-cache-graphql: proxy-cache-graphql plugin.

# README