charm-interface-mysql-router/README.md

Overview

MySQL Router Interface

This interface layer handles the communication between MySQL Router and a MySQL InnoDB Cluster and facilitates proxying database requests from database clients.

* requires handles communication with MySQL InnoDB Cluster
* provides handles communication with database clients

Usage

Requires

On the requires side, the interface handles requesting a user for MySQL Router and also handles proxying database requests to the MySQL InnoDB cluster from its provides side.

All requests over the mysql-router interface are prefixed using the following pattern:

 {prefix}_username
 {prefix}_hostname
 {prefix}_database

Examples:

The mysql-router user request using the prefix, "mysqlrouter":

mysqlrouter_username="myr-user" mysqlrouter_hostname="192.168.1.5"

A proxied DB request using the prefix, "novaapi":

novaapi_username="nova" novaapi_hostname="192.168.1.20" novaapi_databse="nova_api"

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

• {relation_name}.connected The relation is established, but no data has yet been exchanged.

• {relation_name}.available MySQL Router has a user in the MySQL InnoDB Cluster.

• {relation_name}.available.proxy Proxied database requests are complete.

  Received connection information is available via the following methods:

  • allowed_units(prefix)
  • database(prefix)
  • db_host(prefix)
  • hostname(prefix)
  • username(prefix)
  • password(prefix)

Requests can be made of the MySQL InnoDB Cluster with the following methods:

For MySQL Router itself:

    db_router.configure_db_router("myr-user", "192.168.1.5", "mysqlrouter")

For a proxied database request:

    db_router.configure_proxy_db("nova_api", "nova", "192.168.1.20", "novaapi")

For example:

from charms.reactive import when, when_not

@when('db-router.connected')
def setup_database(db_router):
    db_router.configure_db_router("myr-user", "192.168.1.5", "mysqlrouter")

@when('db-router.available')
def use_database(db_router):
    # Multiple Database requests:
    db_router.configure_proxy_db("nova", "nova", "192.168.1.20", "nova")
    db_router.configure_proxy_db("nova_api", "nova", "192.168.1.20", "novaapi")
    db_router.configure_proxy_db("nova_cell0", "nova", "192.168.1.20", "novacell0")

The interface will automatically determine the network space binding on the local unit to present to the remote mysql-router server based on the name of the relation. This can be overridden using the hostname parameter in the configure_db_router and configure_proxy_db methods.

Provides

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

• {relation_name}.connected The relation is established, but the client has not provided the database information yet.
• {relation_name}.available The requested information is complete. The DB, user and hostname can be created.
• Connection information is passed back to the client with the following method:
  • set_db_connection_info()

For example:

@when('shared-db.available')
@when_not('db-router.available.proxy')
def use_database(db_router, shared_db):
  instance.proxy_db_and_user_requests(db_router, shared_db)

@when('shared-db.available')
@when('db-router.available.proxy')
def use_database(db_router, shared_db):
  instance.proxy_db_and_user_responses(db_router, shared_db)

The interface will automatically determine the network space binding on the local unit to present to the remote mysql-shared client based on the name of the relation. This can be overridden using the db_host parameter of the set_db_connection_info method.