Overview

This interface layer handles the communication between Apache Zookeeper and its clients. The provider end of this interface provides the Zookeeper service. The consumer part requires the existence of a provider to function.

Usage

Provides

Charms providing the Apache Zookeeper service provide this interface. This interface layer will set the following states, as appropriate:

• {relation_name}.joined The provider has been related to a client, though the client service may not be available yet. At this point, the provider should broadcast Zookeeper configuration details using:

  • send_port(port, rest_port)

• {relation_name}.ready Zookeeper configuration details have been sent. The provider and client should now be able to communicate.

Zookeeper provider example:

@when('client.joined')
@when_not('client.ready')
def send_config(client):
    client.send_port(get_zookeeper_port(), get_zookeeper_rest_port())

Requires

Clients require this interface to connect to Apache Zookeeper. This interface layer will set the following states, as appropriate:

• {relation_name}.joined The client charm has been related to a Zookeeper provider. At this point, the charm waits for Zookeeper configuration details.

• {relation_name}.ready Zookeeper is now ready for clients. The client charm should get Zookeeper configuration details using:

  • zookeepers() returns a list of zookeeper unit dicts:

    {host: xyz, port: n, rest_port: m}
    

Zookeeper client example:

@when('zookeeper.joined')
@when_not('zookeeper.ready')
def wait_for_zookeeper(zookeeper):
    hookenv.status_set('waiting', 'Waiting for Zookeeper to become available')


@when('zookeeper.ready')
@when_not('myservice.configured')
def configure(zookeeper):
    for zk_unit in zookeeper.zookeepers():
        add_zookeeper(zk_unit['host'], zk_unit['port'])
    set_state('myservice.configured')

Contact Information

• bigdata@lists.ubuntu.com