This interface layer handles the communication with Etcd via the etcd
interface.
This interface layer will set the following states, as appropriate:
{relation_name}.connected The relation is established, but Etcd may not
yet have provided any connection or service information.
{relation_name}.available Etcd has provided its connection string
information, and is ready to serve as a KV store.
The provided information can be accessed via the following methods:
etcd.get_connection_string()etcd.get_version(){relation_name}.tls.available Etcd has provided the connection string
information, and the tls client credentials to communicate with it.
The client credentials can be accessed via:
{relation_name}.get_client_credentials() returning a dictionary of
the clinet certificate, key and CA.{relation_name}.save_client_credentials(key, cert, ca) is a convenience
method to save the client certificate, key and CA to files of your
choosing.For example, a common application for this is configuring an applications backend key/value storage, like Docker.
@when('etcd.available', 'docker.available')
def swarm_etcd_cluster_setup(etcd):
con_string = etcd.connection_string().replace('http', 'etcd')
opts = {}
opts['connection_string'] = con_string
render('docker-compose.yml', 'files/swarm/docker-compose.yml', opts)
A charm providing this interface is providing the Etcd rest api service.
This interface layer will set the following states, as appropriate:
{relation_name}.connected One or more clients of any type have
been related. The charm should call the following methods to provide the
appropriate information to the clients:
{relation_name}.set_connection_string(string, version){relation_name}.set_client_credentials(key, cert, ca)Example:
@when('db.connected')
def send_connection_details(db):
cert = leader_get('client_certificate')
key = leader_get('client_key')
ca = leader_get('certificate_authority')
# Set the key, cert, and ca on the db relation
db.set_client_credentials(key, cert, ca)
port = hookenv.config().get('port')
# Get all the peers participating in the cluster relation.
addresses = cluster.get_peer_addresses()
connections = []
for address in addresses:
connections.append('http://{0}:{1}'.format(address, port))
# Set the connection string on the db relation.
db.set_connection_string(','.join(conections))