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Connecting applications to Compose for MySQL - Old

This page describes how to connect to Compose for MySQL using your deployment's connection string, so that you can start connecting to MySQL immediately. This quick connection guide covers connection drivers and gives code samples for JavaScript, Go, Python, Java, and Ruby.

If you don't have a Compose for MySQL deployment yet, see the Connecting to Compose for MySQL guide, which will help you to set one up.

The Connection String

The connection string is the first point of reference to extract nearly all the information you need to connect to a database. You can find the connection string in the deployment’s Connection Info panel.

The connection string is formatted as a URI that can be used where drivers and applications understand the standardized format. Other applications can extract the essential details from the connection string URI.

An example connection string might look like this:

An example connection string from the Compose UI.

An example connection string from the Compose UI.

To use it you need to enter the username and password into the [username] and [password] positions respectively. If you want to use the 'admin' user's password, you can find it by revealing the password in the Credentials panel:

Credentials in the Connection info panel.

Credentials in the Connection info panel.

The [username] and [password] are then automatically replaced with your credentials in the displayed connection string.

Note: The examples in this guide connect with the admin user account. The admin user is a fully privileged user who has administrative access to all our databases. However, for security reasons, the admin account should only be used to create users and grant them privileges, and not to connect to applications.

Other drivers use component parts of the connection URI – the host name and port – for their connection parameters. The host name is found after the @ symbol and the port number is after the :. They are marked in the following screenshot:

An example connection string.

An example connection string.

Every Compose deployment automatically has a database with the name "compose" created in it to ensure at least one database exists and can be connected to with the default connection string.

If you don't designate a database to connect to, you need the USE my_database command to select a database; a MySQL connection doesn't have to specify a database to connect.


All MySQL deployments have SSL enabled by default; however, the way MySQL does SSL means it will also accept non-SSL connections. This means that, when configuring your application's MySQL driver, you need to ensure that it creates a secure connection. With the MySQL command line, you can do this by adding --ssl-mode=REQUIRED to the connection command. For application drivers, the settings are specific to the driver. In the examples we will show commands that should always and only connect with SSL enabled.

Using the Self-Signed Certificate

Compose deployments offer a self-signed certificate, which can be used to validate the host being talked to.

To use the self-signed certificate, copy it to a file. The certificate is found on the Deployment Overview page:

How to show the certificate.

How to show the certificate.

Click the Show certificate button. Then enter your Compose account password to view the certificate:

An example SSL certificate.

An example SSL certificate.

Copy and paste the text from -----BEGIN CERTIFICATE----- to -----END CERTIFICATE----- into a file with the extension .cert or .pem, depending on which the connection driver requires. Save the file to a location that you can access because we'll need the certificate's path later.

Connecting with JavaScript and Node.js

The leading driver for MySQL for Node.js is the node-mysql driver. We'll walk through setting up a simple Node.js/MySQL connection here. If you want to follow along, make sure that Node.js and npm are installed on your system.

After initializing a new project using npm init, install the driver package in the project’s folder:

npm install mysql --save

The driver and its dependencies are installed in the node_modules folder, and the driver will appear under dependencies in the package.json file.

You can use the following code to connect to MySQL.

const mysql = require('mysql');  
const fs = require('fs');

const connection = mysql.createConnection(  
        host: '',
        port: 15942,
        user: 'admin',
        password: 'mypass',
        ssl: {
            ca: fs.readFileSync(__dirname + '/cert.crt')

connection.query('SHOW DATABASES', (err, rows) => {  
    if (err) throw err;
    for (let i = 0, len = rows.length; i < len; i++) {


  • SHOW DATABASES is a MySQL command that lists the databases that a user has privileges for.
  • All the databases in the deployment are displayed because the script uses the admin user.
  • The results of the query are returned as an array of objects.

Connecting with Go

Go has a generic interface for SQL databases and using it with the go-sql-driver will provide us with several options to connect to MySQL. The problem with the driver is that we cannot verify the self-signed certificate. The only TLS/SSL option we have with self-signed certificates is skip-verify, which is less than optimal.

To connect to MySQL using Go, first install the go-sql-driver package to your $GOPATH:

go get

You can use the following code to connect to MySQL.

package main

import (  
    _ ""

func main() {  
    db, err := sql.Open("mysql", "admin:mypass@tcp(")
	if err != nil {
    defer db.Close()
	rows, err := db.Query("SHOW DATABASES")
    if err != nil {

	var dbNames string
    for rows.Next() {
    	err := rows.Scan(&dbNames)
    	if err != nil {

Connecting with Python

You can connect to MySQL with Python using MySQL's official Python connector.

First, install the connector package. After installing the package, you can connect to our database using the following code:

import mysql.connector

config = {  
    'user': 'admin',
    'password': 'mypass',
    'host': '',
    'port': 15942,
    'database': 'compose',

    # Create SSL connection with the self-signed certificate
    'ssl_verify_cert': True,
    'ssl_ca': 'cert.pem'

connect = mysql.connector.connect(**config)  
cur = connect.cursor()  
cur.execute("SHOW DATABASES")

for row in cur:  



  • The example imports the MySQL connector and adds any connection parameters within a config dictionary. A secure connection is initialized using the deployment's self-signed certificate in the connection dictionary.
  • ssl_verify_cert requires the ssl_ca option. Using the configuration option 'ssl_verify_cert': True, ensures that the server's certificate and the certificate stored in cert.pem are the same. If there's a certificate error, a ValueError is returned, indicating that the certificates don't match.
  • A useful list of the available connection arguments can be found here.
  • The MySQL Python connector requires that a cursor object be instantiated in order to execute SQL queries. In this code sample, the cursor method of the connection object here is assigned the variable cur, and the variable query is assigned to the SQL command, which tells MySQL to show all of the deployment's databases.
  • The execute method executes database operations that convert Python objects to MySQL commands over a secure connection. In this example, the execution method tells MySQL to show all the databases, iterating over them, before logging the output to the console and closing the connection.

Connecting with Java

To connect with Java, first download and install MySQL's Connector/J JDBC driver.

You can then connect to a deployment using the following code:

import java.sql.*;

public class Main {

    public static void main(String[] args) {


       String user = "admin";
       String password = "mypass";
       String URL = "jdbc:mysql://" +

                "&useSSL=true" +
        try {

            Connection conn = DriverManager.getConnection(URL, user, password);

            Statement st = conn.createStatement();
            ResultSet rs = st.executeQuery("SHOW DATABASES");

            while ( {
                String dbname = rs.getString("Database");
                System.out.format("%s\n", dbname);


        } catch (Exception ex) {


  • The basic information to set up a connection is within the connection string. We use that with the JDBC API and store that string in the variable URL:
  • The username and password for the deployment are stored in separate variables, which are used to establish a connection with the JDBC DriverManager.getConnection() method.
  • The connection string includes the host name, port, and database; the SSL options are appended to the connection string.
  • The sample establishes an SSL connection, which is verified using the self-signed certificate. You can connect to the server without these options, but the connection would be insecure and would result in a warning from MySQL:
"Establishing SSL connection without server's identity verification is not recommended. According to MySQL 5.5.45+, 5.6.26+ and 5.7.6+ requirements SSL connection must be established by default..."
  • To allow the driver to process the certificate, the credentials are saved in a file called cert.pem. The certificate cannot be used directly. Instead, create a trust store to hold the certificate's credentials using keytool, The following command imports the cert.pem file, assigns it the alias composeCert, and defines the output file as a keystore called truststore. It uses the password henrythedog to unlock the keystore.
keytool -import --alias composeCert -file ./cert.pem -keystore ./truststore -storepass henrythedog
  • The setProperty method on and uses the information from the keystore. The system properties should be set towards the top of the program to run early at runtime; preferably before the Connection variable is set, so that they're locked in before starting an SSL connection.
  • After creating the connection, a Statement object is returned and the query is executed against the object. This returns a ResultSet which is used to iterate through and print the database names.

Connecting with Ruby

There are a number of MySQL drivers for Ruby. The sample connection code uses MySQL2.

You can connect to MySQL by installing MySQL2 according to the instructions in the driver's Github repository and using the following code:

require "mysql2"  
config = {  
    "hostname": "",
    "port": 15942,
    "database": "compose",
    "username": "admin",
    "password": "mypass",
    "sslCA": "cert.pem",
    "sslverify": true
conn =  
results = conn.query("SHOW DATABASES")  
results.each {|row| puts row["Database"]}  


  • The config hash contains all of the connection configuration, including setting up an SSL connection. For details of all the configuration options, see the MySQL2 readme.
  • To set up a secure connection using the self-signed certificate, sslCA and sslverify are set. sslCA is the path of the .pem or .cert file containing the certificate, and sslverify is set to true in order to check for a valid certificate.
  • The constructor initializes a new connection variable, using the connection configuration in config.
  • results contains an array of hashes, which are iterated through and printed to the console.

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Connecting applications to Compose for MySQL - Old