Overview

This interface layer handles the communication with MySQL via the mysql interface protocol.

Usage

Requires

The interface layer will set the following states, as appropriate:

• {endpoint_name}.connected The relation is established, but MySQL has not provided the information to use the database

• {endpoint_name}.available MySQL is ready for use. You can get the connection information via the following methods:

  • host()
  • port()
  • database() (the database name)
  • user()
  • password()

• {endpoint_name}.changed The connection info is all available and has changed. You should clear this flag in your charm once you have dealt with the change.

An example charm using this might look like:

from charmhelpers.core import hookenv
from charms.reactive import when_all, when_any
from charms.reactive import set_flag
from charms.reactive import clear_flag
from charms.reactive import endpoint_from_name
from charms.reactive import data_changed

@when_all('db.available',
          'config.set.admin-pass')
@when_any('db.changed',
          'config.changed.admin-pass')
def render_config():
    mysql = endpoint_from_flag('db.available')
    render_template('app-config.j2', '/etc/app.conf', {
        'admin_pass': hookenv.config('admin-pass'),
        'db_conn': mysql.connection_string(),
    })
    set_flag('charm.needs-restart')
    clear_flag('db.changed')
    clear_flag('config.changed.admin-pass')

@when('charm.needs-restart')
def restart_service():
    hookenv.service_restart('myapp')
    clear_flag('charm.needs-restart')