StarCluster Plugin: Configure Nodes with Dynamic DNS

starcluster_dns_update.py

"""A starcluster plugin that registers starcluster nodes in DNS
It assumes that nsupdate command can be run from the same machine where you run this plugin.
"""
from starcluster import clustersetup

import subprocess
from os.path import join

# You should configure these to your needs
DNS_ZONE = "example.com"
NAMESERVER = "ns.example.com"
nsupdate_cmd = """
(
cat <<EOF
server {mydnsserver_ip}
zone {dns_zone}.
{update_statement}
send
EOF
) | nsupdate -k /etc/bind/named.conf.local
"""

add_record = "update add {hostname} 60 A {ip}"
delete_record = "update delete {hostname} A"

# for example, string above could create:
#server ns.example.com
#zone example.com
#update delete mystarcluster-node001.example.com. A
#update add mystarcluster-node001.example.com. 86400 A 10.0.0.0
#show
#send


def node_in_dns(node, add):
    """Register or remove a new/old starcluster node with DNS

    `node` a starcluster.node.Node instance, received from plugin
    `add` (bool) whether to add or delete a node's dns record"""

    ip = node.ssh.execute('hostname --ip-address')[0]
    hostname = '%s.%s' % (node.alias, DNS_ZONE)

    if add:
        update_statement = add_record.format(hostname=hostname, ip=ip)
    else:
        update_statement = delete_record.format(hostname=hostname)
    subprocess.check_call(
        nsupdate_cmd.format(update_statement=update_statement,
                            dns_zone=DNS_ZONE, nameserver=NAMESERVER),
        shell=True)


class DNSUpdate(clustersetup.ClusterSetup):
    """Register starcluster nodes with DNS"""
    def __init__(self, add):
        self.add = add

    def run(self, nodes, master, user, user_shell, volumes):
        for node in nodes:
            node_in_dns(node, self.add)
        node_in_dns(master, self.add)

    def on_add_node(self, node, nodes, master, user, user_shell, volumes):
        node_in_dns(node, True)

    def on_remove_node(self, node, nodes, master, user, user_shell, volumes):
        node_in_dns(node, False)