graphql-schema-registry

Graphql schema storage as dockerized on-premise service for federated graphql gateway server (based on apollo server) as alternative to Apollo studio

Features

• Stores versioned schema for graphql-federated services
• Serves schema for graphql gateway based on provided services & their versions
• Validates new schema to be compatible with other running services
• Provides UI for developers to see stored schema & its history diff
• Stores & shows in UI persisted queries passed by the gateway for debugging

Roadmap

• client tracking (for breaking changes)
• schema usage tracking (for breaking changes)
• separate APQs (use cache only) from backend-registered persisted queries (use DB only)

Installation

Assuming you have nvm & docker installed:

nvm use
npm install
npm run build
docker-compose up --build

Open http://localhost:6001

Configuration

We rely on docker network and uses hostnames from docker-compose.yml. Check app/config.js to see credentials that node service uses to connect to mysql & redis and change it if you install it with own setup. If you use dynamic service discovery (consul/etcd), edit diplomat.js

The following are the different environment variables that are looked up that allow configuring the schema registry in different ways.

Variable Name	Description	Default
DB_HOST	Host name of the MySQL server	gql-schema-registry-db
DB_USERNAME	Username to connect to MySQL	root
DB_SECRET	Password used to connect to MySQL	root
DB_PORT	Port used when connecting to MySQL	3306
DB_NAME	Name of the MySQL database to connect to	schema-registry
DB_EXECUTE_MIGRATIONS	Controls whether DB migrations are executed upon registry startup or not	true
REDIS_HOST	Host name of the Redis server	gql-schema-registry-redis
REDIS_PORT	Port used when connecting to Redis	6379
REDIS_SECRET	Password used to connect to MySQL	Empty
ASSETS_URL	Controls the url that web assets are served from	localhost:6001

Use cases

Validating schema on deploy

On pre-commit / deploy make a POST /schema/validate to see if its compatible with current schema.

Schema registration

On service start-up (runtime), make POST to /schema/push to register schema (see API reference for details). Make sure to handle failure.

Architecture

Tech stack

Frontend (/client folder)	Backend (/app folder)
react	nodejs 14
apollo client	express, hapi/joi
styled-components	apollo-server-express, dataloader
	redis 6
	knex
	mysql 8

Components

graphql-schema-registry service is one of the components for graphql federation, but it needs tight integration with gateway. Check out examples folder on how to implement it. Note however, that gateway is very simplified and does not have proper error handling, cost limits or fail-safe mechanisms.

DB structure

Migrations are done using knex

Development

DB migrations

To create new DB migration, use:

npm install knex -g
knex migrate:make my_migration_name_here --migrations-directory migrations

If not using the default configuration of executing DB migrations on service startup, you can run the following npm command prior to starting the registry:

npm run migrate-db

The command can be prefixed with any environment variable necessary to configure DB connection (in case you ALTER DB with another user), such as:

DB_HOST=my-db-host DB_PORT=6000 npm run migrate-db

Contribution

• Before making PR, make sure to run npm run version & fill CHANGELOG

Honorable mentions

Original internal mission that resulted in this project consisted of (in alphabetical order):

• aleksandergasna
• ErikSchults
• LexSwed
• tot-ra

Rest API documentation

GET /schema/latest

Simplified version of /schema/compose where latest versions from different services is composed. Needed mostly for debugging

POST /schema/compose

Lists schema based on passed services & their versions. Used by graphql gateway to fetch schema based on current containers

Request params (optional, raw body)

{
  "services": [
    {"name": "service_a", "version": "ke9j34fuuei"},
    {"name": "service_b", "version": "e302fj38fj3"},
  ]
}

Response example

• ✅ 200

{
    "success": true,
    "data": [
        {
            "id": 2,
            "service_id": 3,
            "version": "ke9j34fuuei",
            "name": "service_a",
            "added_time": "2020-12-11T11:59:40.000Z",
            "type_defs": "\n\ttype Query {\n\t\thello: String\n\t}\n",
            "is_active": 1
        },
        {
            "id": 3,
            "service_id": 4,
            "version": "v1",
            "name": "service_b",
            "added_time": "2020-12-14T18:51:04.000Z",
            "type_defs": "type Query {\n  world: String\n}\n",
            "is_active": 1
        }
    ]
}

• ❌ 400 "services[0].version" must be a string
• ❌ 500 Internal error (DB is down)

Request params

• services{ name, version}

If services is not passed, schema-registry tries to find most recent versions. Logic behind the scenes is that schema with highest added_time OR updated_time is picked as latest. If time is the same, schema.id is used.

POST /schema/push

Validates and registers new schema for a service.

Request params (optional, raw body)

{
  "name": "service_a",
  "version": "ke9j34fuuei",
  "type_defs": "\n\ttype Query {\n\t\thello: String\n\t}\n"
}

POST /schema/validate

Validates schema, without adding to DB

Request params (raw body)

• name
• version
• type_defs

POST /schema/diff

Compares schemas and finds breaking or dangerous changes between provided and latest schemas.

• name
• version
• type_defs

DELETE /schema/delete/:schemaId

Deletes specified schema

Request params

Property	Type	Comments
schemaId	number	ID of sechema

GET /persisted_query

Looks up persisted query from DB & caches it in redis if its found

Request params (query)

Property	Type	Comments
key	string	hash of APQ (with apq: prefix)

POST /persisted_query

Adds persisted query to DB & redis cache

Request params (raw body)

Property	Type	Comments
key	string	hash of APQ (with apq: prefix)
value	string	Graphql query