Digital Ocean将一个Droplet连接到另一个Droplet的MySQL DB

Question

I have 2 droplets, both with a LAMP stack (Ubuntu 16.04). Both also have PHPMyAdmin installed, run a PHP application, and have a self-signed SSH certificate that auto redirects to https.

What I would like to do is connect to the MySQL database that's on Droplet 1 from the app on Droplet 2. I know you can do this by running a MySQL server on Droplet 1, but both need to run a full PHP app in this case.

Here is what I've already done and tried:

• Enabled private networking on both droplets (see this tutorial )
• On Droplet 1 I've added port 3306 to the firewall with sudo ufw allow 3306/tcp and sudo service ufw restart
• Both have the same firewall settings applied that are configured in the DO interface. I've added 'All TCP', 'All ports' from source 'Droplet 2'
• Outbound rules on the firewall settings are 'ICMP', 'All TCP' and 'All UDP' from 'All ports' and 'All IPv4' and 'All IPv6'
• I've created a MySQL user through PMA on Droplet 1 with hostname %

My PHP app connection settings (CodeIgniter 3.1.7)

$db['remotedb'] = array(
'dsn' => '',
'hostname' => 'PRIVATE IP OF DROPLET HERE', // in the format xx.xx.xx.xx so without https:// in front of it 
'port' => 3306,
'username' => 'user',
'password' => 'password',
'database' => 'database',
'dbdriver' => 'mysqli',
'dbprefix' => '',
'pconnect' => FALSE,
'dbdebug' => FALSE,
'cacheon' => FALSE,
'cachedir' => '',
'charset' => 'utf8',
'dbcollat' => 'utf8generalci',
'swappre' => '',
'encrypt' => FALSE,
'compress' => FALSE,
'stricton' => FALSE,
'failover' => array(),
'savequeries' => TRUE
);

Currently the app on Droplet 2 can not connect to the database that runs on Droplet 1. What am I missing?

A few questions:

• When installing both droplets I've ran mysql_secure_installation . If I remember correctly that disables remote access to the mysql databases, but not sure. I also don't know how to enable it again (if needed).
• Do I need to do anything in the /etc/mysql/my.cnf file with bind-address?
• When creating the user on Droplet 1 through PMA, did I use the right settings?
• Any other setting that I'm missing?

EDIT Running netstat -nltp gives

Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      -               
tcp        0      0 0.0.0.0:25              0.0.0.0:*               LISTEN      -               
tcp        0      0 127.0.0.1:3306          0.0.0.0:*               LISTEN      -               
tcp6       0      0 :::22                   :::*                    LISTEN      -               
tcp6       0      0 :::25                   :::*                    LISTEN      -               
tcp6       0      0 :::443                  :::*                    LISTEN      -               
tcp6       0      0 :::80                   :::*                    LISTEN      -     

Answer 1

Make sure you have the correct bind address in your my.cnf file.

bind-address                   = << private IP here >>

Heads up, MySQL only supports binding to 0, 1 or all IP addresses on your server so if you don't want to listen on the private and public IP then you'll have to use the private IP and the settings of your PHP app on Droplet to connect to that instead of 127.0.0.1 .