typeorm/docs/connection.md

Working with Connection

• What is Connection
• Creating a new connection
• Creating a new connection from the configuration file
  • Loading from ormconfig.json
  • Loading from ormconfig.js
  • Loading from ormconfig.env or from environment variables
  • Loading from ormconfig.yml
  • Loading from ormconfig.xml
• Using ConnectionManager
• Working with connection
• Replication
• API
  • Main API
  • Connection API
  • ConnectionManager API

What is Connection

Connection setups a real connection with your database. Depend on database type it may also setup a connection pool. Connection (or connection pool) setup is made when connect method is called. Disconnection (or closing all connections in the pool) is made when close method is called. Generally, you must create connection only once in your application bootstrap, and close it after you completely finished working with database.

Creating a new connection

There are several ways how connection can be created. The most simple and common way is to use createConnection and createConnections methods.

• createConnection creates a single connection:

import {createConnection, Connection} from "typeorm";

const connection: Connection = await createConnection({
    type: "mysql",
    host: "localhost",
    port: 3306,
    username: "test",
    password: "test",
    database: "test"
});

• createConnections creates multiple connections:

import {createConnections, Connection} from "typeorm";

const connections: Connection[] = await createConnections([{
    name: "default",
    type: "mysql",
    host: "localhost",
    port: 3306,
    username: "test",
    password: "test",
    database: "test"
}, {
    name: "test2-connection",
    type: "mysql",
    host: "localhost",
    port: 3306,
    username: "test",
    password: "test",
    database: "test2"
}]);

Both these methods automatically call Connection#connect method.

Both these methods automatically load configuration from ormconfig file if connection options not specified. For example:

import {createConnection, Connection} from "typeorm";

// here createConnection will load connection options from
// ormconfig.json / ormconfig.js / ormconfig.yml / ormconfig.env / ormconfig.xml
// files, or from special environment variables
// if ormconfig contains multiple connections then it will load connection named "default" 
// or connection without name at all (which means it will be named "default" by default)
const connection: Connection = await createConnection();

// if createConnections is called instead of createConnection then 
// it will initialize and return all connections defined in ormconfig file

Different connections must have different names. By default, if connection name is not specified it's equal to default. Usually you use multiple connections when you have multiple databases or multiple connection configurations.

Once you create a connection you can obtain it anywhere from your app, using getConnection method:

import {getConnection} from "typeorm";

// can be used once createConnection is called and is resolved
const connection = getConnection();

// if you have multiple connections you can get connection by name:
const secondConnection = getConnection("test2-connection");

Avoid creating extra classes / services to store and manager your connections. This functionality is already embed into TypeORM - you don't need to overengineer and create useless abstractions.

Creating a new connection from the configuration file

Most of the times you want to store your connection options in a separate configuration file. It makes it convenient and easy to manage. TypeORM supports multiple configuration sources for this purpose. You'll only need to create ormconfig.[format] file in root directory of your application (near package.json), put your configuration there and in app call createConnection() without any configuration passed:

import {createConnection, Connection} from "typeorm";

// createConnection method will automatically read connection options from your ormconfig file
const connection: Connection = await createConnection();

Loading from ormconfig.json

Create ormconfig.json file in project root (near package.json). It should have following content:

{
   "type": "mysql",
   "host": "localhost",
   "port": 3306,
   "username": "test",
   "password": "test",
   "database": "test"
}

You can specify any other options from ConnectionOptions. For more information about connection options see ConnectionOptions documentation.

If you want to create multiple connections then simply create multiple connections in a single array:

[{
   "name": "default",
   "type": "mysql",
   "host": "localhost",
   "port": 3306,
   "username": "test",
   "password": "test",
   "database": "test"
}, {
   "name": "second-connection",
   "type": "mysql",
   "host": "localhost",
   "port": 3306,
   "username": "test",
   "password": "test",
   "database": "test"
}]

Loading from ormconfig.js

Create ormconfig.js file in project root (near package.json). It should have following content:

module.exports = {
   "type": "mysql",
   "host": "localhost",
   "port": 3306,
   "username": "test",
   "password": "test",
   "database": "test"
}

You can specify any other options from ConnectionOptions. If you want to create multiple connections then simply create multiple connections in a single array and return it.

Loading from ormconfig.env or from environment variables

Create ormconfig.env file in project root (near package.json). It should have following content:

TYPEORM_CONNECTION = mysql
TYPEORM_HOST = localhost
TYPEORM_USERNAME = root
TYPEORM_PASSWORD = admin
TYPEORM_PORT = 3000
TYPEORM_SYNCHRONIZE = true
TYPEORM_LOGGING = true
TYPEORM_ENTITIES = entity/.*js,modules/**/entity/.*js

List of available env variables you can set:

• TYPEORM_CONNECTION
• TYPEORM_HOST
• TYPEORM_USERNAME
• TYPEORM_PASSWORD
• TYPEORM_PORT
• TYPEORM_URL
• TYPEORM_SID
• TYPEORM_SCHEMA
• TYPEORM_SYNCHRONIZE
• TYPEORM_MIGRATIONS_RUN
• TYPEORM_ENTITIES
• TYPEORM_MIGRATIONS
• TYPEORM_SUBSCRIBERS
• TYPEORM_ENTITY_SCHEMAS
• TYPEORM_LOGGING
• TYPEORM_LOGGER
• TYPEORM_ENTITY_PREFIX
• TYPEORM_MAX_QUERY_EXECUTION_TIME
• TYPEORM_ENTITIES_DIR
• TYPEORM_MIGRATIONS_DIR
• TYPEORM_SUBSCRIBERS_DIR
• TYPEORM_DRIVER_EXTRA

ormconfig.env should be used only during development. On production you can set all these values in real ENVIRONMENT VARIABLES.

You cannot define multiple connections using env file or environment variables. If your app has multiple connections then use alternative configuration storage format.

Loading from ormconfig.yml

Create ormconfig.yml file in project root (near package.json). It should have following content:

default: # default connection
    host: "localhost"
    port: 3306
    username: "test"
    password: "test"
    database: "test"
    
second-connection: # other connection
    host: "localhost"
    port: 3306
    username: "test"
    password: "test"
    database: "test2"

You can use any connection options available.

Loading from ormconfig.xml

Create ormconfig.xml file in project root (near package.json). It should have following content:

<connections>
    <connection type="mysql" name="default">
        <host>localhost</host>
        <username>root</username>
        <password>admin</password>
        <database>test</database>
        <port>3000</port>
        <logging>true</logging>
    </connection>
    <connection type="mysql" name="second-connection">
        <host>localhost</host>
        <username>root</username>
        <password>admin</password>
        <database>test2</database>
        <port>3000</port>
        <logging>true</logging>
    </connection>
</connections>

You can use any connection options available.

Using ConnectionManager

You can create connection using ConnectionManager class. For example:

import {getConnectionManager, ConnectionManager, Connection} from "typeorm";

const connectionManager: ConnectionManager = getConnectionManager(); // or you can initialize your own connection manager like this: new ConnectionManager()
const connection: Connection = connectionManager.create({
    type: "mysql",
    host: "localhost",
    port: 3306,
    username: "test",
    password: "test",
    database: "test",
});
await connection.connect(); // performs connection

This is not general way of creating connection, but it may be useful for some users. For example users who want to create connection and store its instance, but have a control when actual "connection" will be established. Also you can create and maintain your own ConnectionManager:

import {getConnectionManager, ConnectionManager, Connection} from "typeorm";

const connectionManager = new ConnectionManager(); // or you can initialize your own connection manager like this: new ConnectionManager()
const connection: Connection = connectionManager.create({
    type: "mysql",
    host: "localhost",
    port: 3306,
    username: "test",
    password: "test",
    database: "test",
});
await connection.connect(); // performs connection

But note, this way you won't be able to use getConnection() method anymore - you'll need to store your connection manager instance and use connectionManager.get method to get a connection you need.

Generally avoid this method and avoid unnecessary complications in your application, use ConnectionManager only if you really think you need it.

Working with connection

Once you setup connection you can use it anywhere in your app using getConnection method. For example:

import {getConnection} from "typeorm";
import {User} from "../entity/User";

export class UserController {
    
    @Get("/users")
    getAll() {
        return getConnection().manager.find(User);
    }
    
}

You can also use ConnectionManager#get method to get a connection, but using getConnection() method is enough in most cases.

Using connection you work with your entities, particularly using EntityManager and Repository. For more information about them see Entity Manager and Repository documentation.

But generally, you don't use Connection so much. Most of the times you only create a connection. There are getRepository() and getManager() functions you can access your connection's manager and repositories without directly using connection object. For example:

import {getManager, getRepository} from "typeorm";
import {User} from "../entity/User";

export class UserController {
    
    @Get("/users")
    getAll() {
        return getManager().find(User);
    }
    
    @Get("/users/:id")
    getAll(@Param("id") userId: number) {
        return getRepository(User).findOneById(User);
    }
    
}

Replication

You can setup read/write replication using TypeORM. Example of replication connection settings:

{
  type: "mysql",
  logging: true,
  replication: {
    master: {
      host: "server1",
      port: 3306,
      username: "test",
      password: "test",
      database: "test"
    },
    slaves: [{
      host: "server2",
      port: 3306,
      username: "test",
      password: "test",
      database: "test"
    }, {
      host: "server3",
      port: 3306,
      username: "test",
      password: "test",
      database: "test"
    }]
  }
}

All schema update and write operations are performed using master server. All simple queries performed by using find methods or select query builder are using random slave instance.

If you want explicitly use master in SELECT created by query builder, you can use following code:

const postsFromMaster = await connection.createQueryBuilder(Post, "post")
    .setQueryRunner(connection.createQueryRunner("master"))
    .getMany();

Replication is supported by mysql, postgres and sql server databases.

Mysql supports deep configuration:

{
  replication: {
    master: {
      host: "server1",
      port: 3306,
      username: "test",
      password: "test",
      database: "test"
    },
    slaves: [{
      host: "server2",
      port: 3306,
      username: "test",
      password: "test",
      database: "test"
    }, {
      host: "server3",
      port: 3306,
      username: "test",
      password: "test",
      database: "test"
    }],
    
    /**
    * If true, PoolCluster will attempt to reconnect when connection fails. (Default: true)
    */
    canRetry: true,

    /**
     * If connection fails, node's errorCount increases.
     * When errorCount is greater than removeNodeErrorCount, remove a node in the PoolCluster. (Default: 5)
     */
    removeNodeErrorCount: 5,

    /**
     * If connection fails, specifies the number of milliseconds before another connection attempt will be made.
     * If set to 0, then node will be removed instead and never re-used. (Default: 0)
     */
     restoreNodeTimeout: 0,

    /**
     * Determines how slaves are selected:
     * RR: Select one alternately (Round-Robin).
     * RANDOM: Select the node by random function.
     * ORDER: Select the first node available unconditionally.
     */
    selector: "RR"
  }
}

API

Main API

• createConnection() - Creates a new connection and registers it in global connection manager. If connection options parameter is omitted then connection options are read from ormconfig file or environment variables.

import {createConnection} from "typeorm";

const connection = await createConnection({
    type: "mysql",
    host: "localhost",
    port: 3306,
    username: "test",
    password: "test",
    database: "test"
});

• createConnections() - Creates multiple connections and registers them in global connection manager. If connection options parameter is omitted then connection options are read from ormconfig file or environment variables.

import {createConnections} from "typeorm";

const connection = await createConnections([{
    name: "connection1",
    type: "mysql",
    host: "localhost",
    port: 3306,
    username: "test",
    password: "test",
    database: "test"
}, {
    name: "connection2",
    type: "mysql",
    host: "localhost",
    port: 3306,
    username: "test",
    password: "test",
    database: "test"
}]);

• getConnectionManager() - Gets connection manager which stores all created (using createConnection method) connections.

import {getConnectionManager} from "typeorm";

const defaultConnection = getConnectionManager().get("default");
const secondaryConnection = getConnectionManager().get("secondary");

• getConnection() - Gets connection which was created by using createConnection method.

import {getConnection} from "typeorm";

const connection = getConnection();
// if you have named connection you can specify its name:
const secondaryConnection = getConnection("secondary-connection");

• getEntityManager() - Gets EntityManager from connection. Connection name can be specified to indicate what connection's entity manager should be taken.

import {getEntityManager} from "typeorm";

const manager = getEntityManager();
// you can use manager methods now

const secondaryManager = getEntityManager("secondary-connection");
// you can use secondary connection manager methods

• getRepository() - Gets some entity's Repository from connection. Connection name can be specified to indicate what connection's entity manager should be taken.

import {getRepository} from "typeorm";

const userRepository = getRepository(User);
// you can use repository methods now

const blogRepository = getRepository(Blog, "secondary-connection");
// you can use secondary connection repository methods

• getTreeRepository() - Gets some entity's TreeRepository from connection. Connection name can be specified to indicate what connection's entity manager should be taken.

import {getTreeRepository} from "typeorm";

const userRepository = getTreeRepository(User);
// you can use repository methods now

const blogRepository = getTreeRepository(Blog, "secondary-connection");
// you can use secondary connection repository methods

• getMongoRepository() - Gets some entity's MongoRepository from connection. Connection name can be specified to indicate what connection's entity manager should be taken.

import {getMongoRepository} from "typeorm";

const userRepository = getMongoRepository(User);
// you can use repository methods now

const blogRepository = getMongoRepository(Blog, "secondary-connection");
// you can use secondary connection repository methods

Connection API

• name - Connection name. If you created nameless connection then its equal to "default". You use this name when you work with multiple connections and call getConnection(connectionName: string)

const connectionName: string = connection.name;

• options - Connection options used to create this connection. For more information about connection options see Connection Options documentation.

const connectionOptions: ConnectionOptions = connection.options;
// you can cast connectionOptions to MysqlConnectionOptions or any other xxxConnectionOptions depend on database driver you use

• isConnected - Indicates if real connection to the database is established.

const isConnected: boolean = connection.isConnected;

• driver - Underlying database driver used in this connection.

const driver: Driver = connection.driver;
// you can cast connectionOptions to MysqlDriver or any other xxxDriver depend on database driver you use

• manager - EntityManager used to work with connection entities. For more information about EntityManager see Entity Manager and Repository documentation.

const manager: EntityManager = connection.manager;
// you can call manager methods, for example find:
const user = await manager.findOneById(1);

• mongoManager - MongoEntityManager used to work with connection entities in mongodb connections. For more information about MongoEntityManager see MongoDB documentation.

const manager: MongoEntityManager = connection.mongoManager;
// you can call manager or mongodb-manager specific methods, for example find:
const user = await manager.findOneById(1);

• connect - Performs connection to the database. When you use createConnection method it automatically calls this method and you usually don't need to call it by yourself.

await connection.connect();

• close - Closes connection with the database. Usually you call this method when your application is shutdown.

await connection.close();

• synchronize - Synchronizes database schema. When synchronize: true is set in connection options it calls exactly this method. Usually you call this method when your application is shutdown.

await connection.synchronize();

• dropDatabase - Drops the database and all its data. Be careful with this method on production since this method will erase all your database tables and their data. Can be used only after connection to the database is established.

await connection.dropDatabase();

• runMigrations - Runs all pending migrations.

await connection.runMigrations();

• undoLastMigration - Reverts last executed migration.

await connection.undoLastMigration();

• hasMetadata - Checks if metadata for a given entity is registered. Learn more about metadata in Entity Metadata documentation.

if (connection.hasMetadata(User))
    const userMetadata = connection.getMetadata(User);

• getMetadata - Gets EntityMetadata of the given entity. You can also specify a table name and if entity metadata with such table name is found it will be returned. Learn more about metadata in Entity Metadata documentation.

const userMetadata = connection.getMetadata(User);
// now you can get any information about User entity

• getRepository - Gets Repository of the given entity. You can also specify a table name and if repository for given table is found it will be returned. Learn more about repositories in Repository documentation.

const repository = connection.getRepository(User);
// now you can call repository methods, for example find:
const users = await repository.findOneById(1);

• getTreeRepository - Gets TreeRepository of the given entity. You can also specify a table name and if repository for given table is found it will be returned. Learn more about repositories in Repository documentation.

const repository = connection.getTreeRepository(Category);
// now you can call tree repository methods, for example findTrees:
const categories = await repository.findTrees();

• getMongoRepository - Gets getMongoRepository of the given entity. This repository is used for entities in MongoDB connection. Learn more about mongodb support refer to MongoDB documentation.

const repository = connection.getMongoRepository(User);
// now you can call mongodb-specific repository methods, for example createEntityCursor:
const categoryCursor = repository.createEntityCursor();
const category1 = await categoryCursor.next();
const category2 = await categoryCursor.next();

• getCustomRepository - Gets customly defined repository. Learn more about custom repositories in Repository documentation.

const userRepository = connection.getCustomRepository(UserRepository);
// now you can call methods inside your custom repository - UserRepository class
const crazyUsers = await userRepository.findCrazyUsers();

• transaction - Provides a single transaction where multiple database requests will be executed in a single database transaction. Learn more about transactions in Transactions documentation.

await connection.transaction(async manager => {
    // NOTE: you must perform all database operations using given manager instance
    // its a special instance of EntityManager working with this transaction
    // and don't forget to await things here
});

• query - Executes a raw SQL query.

const rawData = await connection.query(`SELECT * FROM USERS`);

• createQueryBuilder - Creates a query builder use to build SQL queries. Learn more about query builder in QueryBuilder documentation.

const users = await connection.createQueryBuilder()
    .select()
    .from(User, "user")
    .where("user.name = :name", { name: "John" })
    .getMany();

• createQueryRunner - Creates a query runner used to work with a single real database connection, manage it and work with it. Learn more about query runners in QueryRunner documentation.

const queryRunner = connection.createQueryRunner();

// you can use it methods only after you call connect method
// which performs real database connection
await queryRunner.connect();

// .. now you can work with query runner and call its methods

// very important - don't forget to release query runner once you finished working with it
await queryRunner.release();

ConnectionManager API

• create - Creates a new connection and register it in the manager.

const connection = connectionManager.create({
    type: "mysql",
    host: "localhost",
    port: 3306,
    username: "test",
    password: "test",
    database: "test"
});

• get - Gets already created connection stored in the manager by its name.

const defaultConnection = connectionManager.get("default");
const secondaryConnection = connectionManager.get("secondary");

• has - Checks if connection is registered in the given connection manager.

if (connectionManager.has("default")) {
    // ...
}