Charm Interface - MySQL Shared
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This interface layer handles the communication with MySQL via the mysql-shared interface protocol.



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

  • {relation_name}.connected The relation is established, but MySQL has not been provided the database information.
  • {relation_name}.available MySQL is ready for use. You can get the base connection information via the following methods:
    • allowed_units()
    • database()
    • db_host()
    • hostname()
    • username()
    • password()
  • {relation_name}.available.access_network MySQL access network is ready for use. You can get this optional connection information via the following method:
    • access_network()
  • {relation_name}.available.ssl MySQL ssl data is ready for use. You can get this optional connection information via the following methods:
    • ssl_ca()
    • ssl_cert()
    • ssl_key()

For example:

from charmhelpers.core.hookenv import log, status_set, unit_get
from charms.reactive import when, when_not

def setup_database(database):
    database.configure('mydatabase', 'myusername', prefix="first")
    database.configure('mydatabase2', 'myusername2', prefix="second")

def use_database(database):
    # base data provided by our charm layer
    log("first_database=%s" % database.database("first"))
    log("first_username=%s" % database.username("first"))
    log("first_hostname=%s" % database.hostname("first"))
    log("second_database=%s" % database.database("second"))
    log("second_username=%s" % database.username("second"))
    log("second_hostname=%s" % database.hostname("second"))

    # base data provided by mysql
    log("db_host=%s" % database.db_host())
    log("first_password=%s" % database.password("first"))
    log("first_allowed_units=%s" % database.allowed_units("first"))
    log("second_password=%s" % database.password("second"))
    log("second_allowed_units=%s" % database.allowed_units("second"))

def use_database_access_network(database):
    # optional data provided by mysql
    log("access-network=%s" % database.access_network())

def use_database_ssl(database):
    # optional data provided by mysql
    log("ssl_ca=%s" % database.ssl_ca())
    log("ssl_cert=%s" % database.ssl_cert())
    log("ssl_key=%s" % database.ssl_key())

def waiting_mysql(database):
    status_set('waiting', 'Waiting for MySQL')

@when('database.connected', 'database.available')
def unit_ready(database):
    status_set('active', 'Unit is ready')

In Juju 2.0 environments, the interface will automatically determine the network space binding on the local unit to present to the remote mysql-shared service based on the name of the relation. In older Juju versions, the private-address of the unit will be used instead. This can be overridden using the hostname parameter of the configure method.

def setup_database(database):
    database.configure('mydatabase', 'myusername', hostname='hostname.override')