interface-zookeeper's Introduction

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')