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.
Charms providing the Apache Zookeeper service provide this interface. This interface layer will set the following states, as appropriate:
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{relation_name}.joinedThe 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)
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{relation_name}.readyZookeeper 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())Clients require this interface to connect to Apache Zookeeper. This interface layer will set the following states, as appropriate:
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{relation_name}.joinedThe client charm has been related to a Zookeeper provider. At this point, the charm waits for Zookeeper configuration details. -
{relation_name}.readyZookeeper 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}
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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')