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
• Stores service urls emulating managed federation: you no longer need to hardcode the services in your gateway's constructor, or rely on an additonal service (etcd, consul) for service discovery
• Async schema registration of new schema with events to avoid polling (schema-registry -> kafka -> gateway)

Roadmap

(Pull requests are encouraged on these topics)

• client tracking (for breaking changes)
• schema usage tracking (for breaking changes)
• separate ephemeral automatic PQs, registered by frontend (use cache only with TTL) from true PQs backend-registered persisted queries (use DB only)
• integrate inspector

Configuration

We use environment variables for configuration. You can:

• pass them directly
• add .env file and dotenv will pick them up
• add them to docker-compose.yml or Dockerfile

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 Redis	Empty
ASSETS_URL	Controls the url that web assets are served from	localhost:6001
NODE_ENV	Specifies the environment. Use production to load js/css from dist/assets	Empty
ASYNC_SCHEMA_UPDATES	Specifies if async achema updates is enabled	false
KAFKA_BROKER_HOST	Host name of the Kafka broker, used if ASYNC_SCHEMA_UPDATES = true	gql-schema-registry-kafka
KAFKA_BROKER_PORT	Port used when connecting to Kafka, used if ASYNC_SCHEMA_UPDATES = true	9092

For development we rely on docker network and use hostnames from docker-compose.yml. Node service uses to connect to mysql & redis and change it if you install it with own setup. For dynamic service discovery (if you need multiple hosts for scaling), override app/config.js and diplomat.js

Installation

With default settings, UI should be accessible at http://localhost:6001

On bare host

git clone https://github.com/pipedrive/graphql-schema-registry.git && cd graphql-schema-registry
cp example.env .env && nano .env
node schema-registry.js

Docker image

We have docker image published for main node service.

docker run -e DB_HOST=localhost -e DB_USERNAME=root pipedrive/graphql-schema-registry

Docker-compose

git clone https://github.com/pipedrive/graphql-schema-registry.git && cd graphql-schema-registry
docker-compose up

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.

See example for nodejs/ESM.

Schema migration

If service A contains schema that needs to be migrated to service B, we need to orchestrate schema & traffic change. Instead of juggling with schema status flags, we suggest the following scenario:

• service B gets deployed with new schema which includes cycle of attempts to register new schema (for example every 5 sec).
• schema-registry responds with validation errors
• service A without conflicting schema gets deployed & updates schema-registry
• service B manages to register new schema & stops the cycle

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.

In gateway, you may also find useful our graphql-query-cost library too. Check it out

DB structure

Migrations are done using knex

Development

Dockerized mode

nvm use
npm install
npm run build
docker-compose -f docker-compose.dev.yml up

Running in light mode

To have fast iteration of working on UI changes, you can avoid running node service in docker, and run only mysql & redis

docker-compose -f docker-compose.light.yml up
DB_HOST=localhost DB_PORT=6000 REDIS_HOST=localhost REDIS_PORT=6004 PORT=6001 node schema-registry.js

DB migrations

To create new DB migration, use:

npm run new-db-migration

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

• Commit often (instead of making huge commits)
• Add verb at the beginning of commit message
• Add why you're doing something in commit message
• Reference issues
• When making a pull request, be sure to follow the format of what is the problem you're fixing, what was changed & how to test it. Screenshots/videos are a welcome
• Fill CHANGELOG

Authors and acknowledgment

Current maintainer - @tot-ra. Mention in PR, if it is stuck

Original internal mission that resulted in this project going live:

• aleksandergasna
• ErikSchults
• LexSwed

See main blog post

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",
      "url": "http://localhost:6111",
      "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",
      "url": "http://localhost:6112",
      "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"
}

URL is optional if you use urls from schema-registry as service discovery

{
  "name": "service_b",
  "version": "jiaj51fu91k",
  "type_defs": "\n\ttype Query {\n\t\tworld: String\n\t}\n",
  "url": "http://service-b.develop.svc.cluster.local"
}

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/:schemaId

Deletes specified schema

Request params

Property	Type	Comments
schemaId	number	ID of sechema

DELETE /service/:name

Deletes specified service including all schemas registered for that service

Request params

Property	Type	Comments
name	string	name of service

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