Meadow Connection Dgraph

A Dgraph database connection provider for the Meadow ORM. Wraps dgraph-js-http as a Fable service, providing HTTP client management with optional auth token support and schema generation from Meadow table schemas.

Features

• Dgraph HTTP Client -- Managed connection to Dgraph Alpha via dgraph-js-http
• Fable Service Provider -- Registers with a Fable instance for dependency injection, logging, and configuration
• Schema-Driven DDL -- Generates Dgraph predicate declarations and type definitions from Meadow table schemas with automatic index directives
• Auth Token Support -- Optional Alpha auth token for secured Dgraph clusters
• Connection Safety -- Guards against double-connect with descriptive logging
• Direct Client Access -- Exposes the underlying Dgraph client and stub via pool and stub getters
• Graph-Native Types -- Maps Meadow types to Dgraph scalar types with appropriate index strategies (exact, term, fulltext, int, float, hour)

Installation

npm install meadow-connection-dgraph

Quick Start

const libFable = require('fable');
const MeadowConnectionDGraph = require('meadow-connection-dgraph');

let fable = new libFable(
{
	DGraph:
	{
		Server: 'localhost',
		Port: 8080
	}
});

fable.serviceManager.addServiceType('MeadowDGraphProvider', MeadowConnectionDGraph);
fable.serviceManager.instantiateServiceProvider('MeadowDGraphProvider');

fable.MeadowDGraphProvider.connectAsync(
	(pError, pClient) =>
	{
		if (pError)
		{
			console.error('Connection failed:', pError);
			return;
		}

		// Use the Dgraph client for transactions
		let tmpTxn = pClient.newTxn();
		tmpTxn.query('{ animals(func: type(Animal)) { uid Name Age } }')
			.then((pResult) =>
			{
				console.log(pResult.data);
			});
	});

Configuration

Dgraph settings are provided through the Fable settings DGraph object or constructor options:

let fable = new libFable(
{
	DGraph:
	{
		Server: 'localhost',
		Port: 8080,
		AuthToken: ''
	}
});

Configuration Options

| Setting | Type | Default | Description | |---------|------|---------|-------------| | Server / host | String | 'localhost' | Dgraph Alpha hostname or IP | | Port / port | Number | 8080 | Dgraph Alpha HTTP port | | AuthToken / authToken | String | '' | Optional Alpha auth token | | MeadowConnectionDGraphAutoConnect | Boolean | false | Auto-connect on instantiation |

API

connectAsync(fCallback)

Open the Dgraph HTTP client connection. This is the recommended connection method.

| Parameter | Type | Description | |-----------|------|-------------| | fCallback | Function | Callback receiving (error, client) |

connect()

Synchronous connection method. Creates the client stub and client instance.

pool (getter)

Returns the underlying DgraphClient instance for direct query and mutation access.

stub (getter)

Returns the raw DgraphClientStub for low-level HTTP operations.

connected (property)

Boolean indicating whether the Dgraph client has been established.

generateCreateTableStatement(pMeadowTableSchema)

Generate Dgraph predicate declarations and a type definition from a Meadow table schema.

createTable(pMeadowTableSchema, fCallback)

Generate and apply a schema to the connected Dgraph instance via client.alter().

createTables(pMeadowSchema, fCallback)

Create all schemas defined in a Meadow schema object (iterates pMeadowSchema.Tables sequentially).

generateDropTableStatement(pTableName)

Generate a drop type descriptor for the given type name.

Predicate Type Mapping

| Meadow Type | Dgraph Type | Index Directive | |-------------|-------------|-----------------| | ID | int | @index(int) | | GUID | string | @index(exact) | | ForeignKey | int | @index(int) | | Numeric | int | @index(int) | | Decimal | float | @index(float) | | String | string | @index(exact, term) | | Text | string | @index(fulltext) | | DateTime | datetime | @index(hour) | | Boolean | int | @index(int) |

Part of the Retold Framework

Meadow Connection Dgraph is a database connector for the Meadow data access layer:

• meadow -- ORM and data access framework
• foxhound -- Query DSL used by Meadow
• stricture -- Schema definition tool
• meadow-endpoints -- RESTful endpoint generation
• fable -- Application services framework

Testing

Run the test suite:

npm test

Run with coverage:

npm run coverage

Related Packages

• meadow -- Data access and ORM
• meadow-connection-mysql -- MySQL connection provider
• meadow-connection-mssql -- MSSQL connection provider
• meadow-connection-sqlite -- SQLite connection provider
• fable -- Application services framework

License

MIT

Contributing

Pull requests are welcome. For details on our code of conduct, contribution process, and testing requirements, see the Retold Contributing Guide.