Building better Node.js applications on MariaDB

Node.js Connector
Diego DUPIN
MariaDB Connector Engineer
MariaDB Corporation

PROGRAM
- Getting started
- Best practice
- Advanced topic
- ORM

NODE.JS CONNECTORS
Existing community connectors
● mysqljs/mysql (npm mysql)
(+ Promise-mysql to have promise)
● sidorares/node-mysql2 (npm mysql2)
● mscdex/node-mariasql (npm mariasql)
New connector
● MariaDB/mariadb-connector-nodejs (npm
mariadb)

WHY A NEW CONNECTOR
● New functionalities
● Better performance
Benchmark : “SELECT * FROM mysql.user LIMIT 1” on local DB

QUICK START - INSTALLATION
through npm.
$ npm install mariadb
To use the Connector, you need to import the package into your application code.
const mariadb = require('mariadb'); //promise implementation
or
const mariadb = require('mariadb/callback'); //callback implementation

QUICK START - CONNECTION
Promise
const mariadb = require("mariadb");
mariadb.createConnection({
user: "root",
database: "db",
host: "localhost",
port: 3306
})
.then(conn => {
console.log("Connected successful");
conn.end();
})
.catch(err => {
console.log("Error: " + err.message);
});
const mariadb = require("mariadb/callback");
const conn = mariadb.createConnection({
user: "root",
database: "db",
host: "localhost",
port: 3306
});
conn.connect(err => {
if (err) {
console.log("Error: " + err.message);
} else {
console.log("Connected successful");
conn.end();
}
});
Callback

QUICK START - INSERT
conn.query(
"CREATE TEMPORARY TABLE myTable " +
"(id int NOT NULL AUTO_INCREMENT, firstName varchar(256), lastName varchar(256), " +
" PRIMARY KEY (id))"
)
.then(() => {
return conn.query("INSERT INTO myTable(firstName, lastName) VALUES (?, ?)", [
"john",
"smith"
]);
})
.then(res => {
console.log(res); //{ affectedRows: 1, insertId: 1, warningStatus: 0 }
conn.end();
})
.catch(err => { });

QUICK START - SELECT
conn.query(
"SELECT ID,COLLATION_NAME FROM INFORMATION_SCHEMA.COLLATIONS " +
"WHERE CHARACTER_SET_NAME = ? LIMIT 2",
["utf8mb4"]
)
.then(res => {
console.log(res);
/* resultset is an array of rows, represented by JSON object
[
{ ID: 45, COLLATION_NAME: 'utf8mb4_general_ci' },
{ ID: 46, COLLATION_NAME: 'utf8mb4_bin' }
]
*/
conn.end();
})
.catch(err => { … });

CONNECTION ESSENTIAL API
● connection.query(sql[, values]) → Promise: Executes a query.
● connection.queryStream(sql[, values]) → Emitter: Executes a query, streaming results.
● connection.batch(sql, values) → Promise: fast batch processing.
● connection.beginTransaction() → Promise: Begins a transaction.
● connection.commit() → Promise: Commits the current transaction, if any.
● connection.rollback() → Promise: Rolls back the current transaction, if any.
● connection.ping() → Promise: Sends a 1 byte packet to the database to validate the connection.
● connection.end() → Promise: Gracefully close the connection.

SSL
One-Way SSL Authentication or Two-Way SSL Authentication
const fs = require("fs");
const mariadb = require('mariadb');
//reading certificates from file
const serverCert = [fs.readFileSync("server.pem", "utf8")];
//connecting
mariadb
.createConnection({
user: "myUser",
host: "myHost.com",
ssl: {
ca: serverCert
}
}).then(conn => {})

POOLING
Basically a database connection cache implementation
Connections are expensive. On local DB:
● 2.4ms for a basic connection
● 0.05ms for a simple query
Problem : correctness and reliability

POOLING
Event implementation
- Pool handle new connection creation one by one
- New connection are added to idle connection queue
On connection failure:
- Pool revalidate all other connections
- Continue creating new connections creation one by one
Connection request are queued separately
Idle
Connections

POOLING
Connection request
Idle
ConnectionsConnection request
Connection request
Request
queue

POOLING
- Implementation to handle query pikes
Example with a pool that is configured to have a maximum of 50 connections. actual
connection number is 5.
With a basis of a connection creation taking 2.4ms, and query taking 0.05ms (example
on a local server).
Everything is quiet, and then ... Boom! ... 100 queries on the pool at once, wanting a
connection.

POOLING
Connection pools SIZING error
Example 10 000 user simultaneously, 20 000 transaction per second.
What value to connectionLimit (max connection number in pool) ?
100 ? 500 ? 1000 ?

POOLING - CONFIGURATION
acquireTimeout
t
acquireTimeout Timeout to get a new connection from pool.
Maximum number of connection in pool.
Delay to avoid connection validation
Disabling connection control
connectionLimit
minDelayValidation
noControlAfterUse

POOL API
● pool.getConnection() → Promise : Creates a new connection.
● pool.query(sql[, values]) → Promise: Executes a query.
● pool.batch(sql, values) → Promise: Executes a batch
Stats
● pool.activeConnections() → Number: Gets current active connection number.
● pool.totalConnections() → Number: Gets current total connection number.
● pool.idleConnections() → Number: Gets current idle connection number.
● pool.taskQueueSize() → Number: Gets current stacked request.

POOLING - CONFIGURATION
const pool = mariadb.createPool({ user: "root", database: "testn", host: "localhost", port: 3306,
sessionVariables: { wait_timeout: 31536000 },
acquireTimeout: 5000, connectionLimit: 8,
});
pool
.getConnection()
.then(conn => {
console.log("Connected successfully to server");
conn.release();
})
.catch(err => {
console.log("Error during connection: " + err.message);
});
Server expect connection to be used (@wait_timeout)

MULTI-HOST - ESSENTIAL API
“Cluster” offer handle multiple pools permitting load balancing and high availability
const mariadb = require("mariadb");
const cluster = mariadb.createPoolCluster();
cluster.add("master", { host: "mydb1.com", ... });
cluster.add("slave1", { host: "mydb2.com", ... });
cluster
.getConnection("slave*", "RR") //RR: ROUND-ROBIN
.then(conn => { })
.catch(err => { });

client
Master
Slave B
Slave A
Cluster.getConnection("slave*", "RR")

MULTI-HOST
SELECTORS
● RR (round-robin)
● RANDOM
● ORDER

● poolCluster.add(id, config) : add a pool to cluster.
● poolCluster.remove(pattern) : remove and end pool according to pattern.
● poolCluster.end() → Promise : end cluster.
● poolCluster.getConnection(pattern, selector) → Promise : return a connection from
cluster.
● poolCluster.of(pattern, selector) → FilteredPoolCluster : return a subset of cluster.

poolCluster.of(pattern, selector) → FilteredPoolCluster : return a subset of cluster.
const cluster = mariadb.createPoolCluster();
cluster.add("master", { host: "mydb1.com", ... });
const slaves = cluster.of(/^slave?/, 'RANDOM');
slaves.getConnection().then( ... );
slaves.query(sql, values).then( ... );
slaves.batch(sql, values).then( ... );

PIPELINING
Pipelining is a technique in which
multiple requests are sent on a single
TCP connection without waiting for the
corresponding responses.
This saves round trip time.

PIPELINING - without
const uuid = uuidv1(); //generate new UUID
conn
.beginTransaction()
.then(() => {
return conn.query("INSERT INTO basket(basketId) values (?)", uuid);
})
.then(() => {
return conn.query(
"INSERT INTO basket_item(basketId, itemId) VALUES (?, ?)",
[ uuid, 100 ]);
})
.then(() => {
return conn.query(
[ uuid, 101 ]);
})
.then(() => { conn.commit(); })
.catch(err => { conn.rollback(); });

PIPELINING - with
const uuid = uuidv1(); //generate new UUID
conn
.beginTransaction()
.then(() => {
return Promise.all([
conn.query("INSERT INTO basket(basketId) values (?)", uuid),
conn.query(
[uuid, 100]),
conn.query(
[uuid, 101])
]);
})
.then(() => { conn.commit(); })
.catch(err => { conn.rollback(); });

PIPELINING
Local DB:
abuse : socket buffering

Streaming
Goal : Avoid loading all in memory
● Streaming resultset -> avoiding loading large resultset totally into memory
○ By event
○ With pipe
● Streaming sent -> sending buffer by chunk

Streaming resultset
BY EVENT :
Limitations :
● Server net_write_timeout.
○ For a command: SET STATEMENT net_write_timeout=10000 FOR XXX
○ For a connection: sessionVariables: { net_write_timeout: 31536000 }
connection
.queryStream("SELECT * FROM mysql.user")
.on("error", err => {})
.on("fields", meta => {})
.on("data", row => {})
.on("end", () => {});

Streaming resultset
USING PIPE : const someWriterStream = fs.createWriteStream("./jsonUsers.txt");
const transformStream = new stream.Transform({
objectMode: true,
transform: function transformer(chunk, encoding, callback) {
callback(null, JSON.stringify(chunk));
}
});
const queryStream = connection.queryStream("SELECT * FROM mysql.user");
stream.pipeline(queryStream, transformStream, someWriterStream);

Streaming - sending
const https = require("https");
https.get(
"https://node.green/#ES2018-features-Promise-prototype-finally-basic-support", //3Mb page
readableStream => {
connection
.query("INSERT INTO StreamingContent (b) VALUE (?)", [readableStream])
.then(res => {})
.catch(err => {});
});
Limitations :
● Server net_read_timeout : SET STATEMENT net_read_timeout=10000 FOR XXX
○ For a connection: sessionVariables: { net_read_timeout: 10000 }
● max_allowed_packet

BATCH INSERT
conn.batch("INSERT INTO myTable(firstName, lastName) VALUES (?, ?)", [
["john", "smith"],
["jack", "brown"]
]);
})
.then(res => { })
.catch(err => { });
Benchmark : 100 * insert 100 characters on local DB

ORM
$ npm install --save express body-parser sequelize@5.0.0-beta.16 mariadb
const Sequelize = require('sequelize');
const sequelize = new Sequelize('testn', 'root', null, {
host: 'localhost',
dialect: 'mariadb',
pool: {
max: 5,
min: 5,
acquire: 30000,
idle: 10000
}
});

ORM
const User = sequelize.define('myUser', {
id: { type: Sequelize.INTEGER, primaryKey: true, autoIncrement: true },
firstName: { type: Sequelize.STRING },
lastName: { type: Sequelize.STRING }
});
User.sync({ force: true })
.then(() => {
return User.create({ firstName: 'John', lastName: 'Hancock' });
});

ORM
const express = require('express');
const bodyParser = require('body-parser');
const app = express();
app.use(bodyParser.json());
const port = 3000;
app.listen(port, () => { console.log(`Running on http://localhost:${port}`) });
// get all users
app.get('/api/users', (req, res) => {
User.findAll().then(users => res.json(users))
});

DEBUGGING
Connection options ‘trace’ default to false, nice to have in development mode.
{ Error: (conn=149, no: 1146, SQLState: 42S02) Table 'testn.unknownTable' doesn't exist
sql: SELECT * FROM unknownTable - parameters:[]
at Object.module.exports.createError (/home/diego/IdeaProjects/test_node/node_modules/mariadb/lib/misc/errors.js:55:10)
at Packet.readError (/home/diego/IdeaProjects/test_node/node_modules/mariadb/lib/io/packet.js:506:19)
at Query.readResponsePacket (/home/diego/IdeaProjects/test_node/node_modules/mariadb/lib/cmd/resultset.js:47:28)
at PacketInputStream.receivePacket (/home/diego/IdeaProjects/test_node/node_modules/mariadb/lib/io/packet-input-stream.js:73:9)
at PacketInputStream.onData (/home/diego/IdeaProjects/test_node/node_modules/mariadb/lib/io/packet-input-stream.js:129:20)
at Socket.emit (events.js:197:13)
at addChunk (_stream_readable.js:288:12)
at readableAddChunk (_stream_readable.js:269:11)
at Socket.Readable.push (_stream_readable.js:224:10)
at TCP.onStreamRead [as onread] (internal/stream_base_commons.js:145:17)
fatal: false,
errno: 1146,
sqlState: '42S02',
code: 'ER_NO_SUCH_TABLE' }

DEBUGGING
With trace
{ Error: (conn=150, no: 1146, SQLState: 42S02) Table 'testn.unknownTable' doesn't exist
sql: SELECT * FROM unknownTable - parameters:[]
at Object.module.exports.createError (/home/diego/IdeaProjects/test_node/node_modules/mariadb/lib/misc/errors.js:55:10)
...
at TCP.onStreamRead [as onread] (internal/stream_base_commons.js:145:17)
From event:
at /home/diego/IdeaProjects/test_node/node_modules/mariadb/lib/connection.js:166:29
at new Promise (<anonymous>)
at Connection.query (/home/diego/IdeaProjects/test_node/node_modules/mariadb/lib/connection.js:164:12)
at mariadb.createConnection.then.conn (/home/diego/IdeaProjects/test_node/lib/promise/trace.js:13:8)
at processTicksAndRejections (internal/process/next_tick.js:81:5)
fatal: false,
errno: 1146,
sqlState: '42S02',
code: 'ER_NO_SUCH_TABLE' }

AVOID TCP-IP layer for local connection
Connection options ‘socketPath‘ for local server
- UNIX domain
- Windows named pipe
const mariadb = require('mariadb');
mariadb.createConnection({ socketPath: '/tmp/mysql.sock', user: 'root' })
.then(conn => { ... })
.catch(err => { ... });

METADATA
● Select query = row datas + metadata
Metadata = datatype, format, and lots of additional infos: schema, table name,
table alias, column name, column alias, … Not always needed
conn.query("select * from mysql.user u LIMIT 1")
.then(rows => {
console.log(rows);
// [
// { Host: 'localhost', User: 'root', … }
// ]
});
conn .query({
sql: "select * from mysql.user u LIMIT 1",
rowsAsArray: true
})
.then(rows => {
console.log(rows);
// [
// [ 'localhost', 'root', …]
// ]
});

What next ?
Authentication plugins (Kerberos, ed25519)
Performance improvement
Failover enhancement
Pools improvement

Building better Node.js applications on MariaDB

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