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A script to generate an SSH config from Consul's HTTP API
#!/usr/bin/env python3
"""
Renders a partial SSH configuration file from Nodes and Services
located in a specified Consul catalog and then merges other partial
config files into the main ~/.ssh/config file. The Consul based SSH
config follows a convention for the SSH host::
Host <consul-cluster-name>-<service-name>-<node-address>
User <ssh-user>
Hostname <consul-node-address>
For example::
Host aws-us-east-1-wsgi-app-http-10-0-0-50
User joe
Hostname 10.0.0.50
To see available options run::
consul-ssh-configurator --help
"""
import argparse
import glob
import json
import os
import shutil
from http.client import HTTPConnection
class Client(object):
def __init__(self, host):
self.connection = HTTPConnection(host, timeout=10)
def open(self, method, url, body=None, headers={}):
self.connection.request(method, url, body, headers)
response = self.connection.getresponse()
return json.loads(response.read().decode())
def get(self, url):
return self.open('GET', url)
class SshHost(object):
def __init__(self, host, ssh_user, hostname):
self.host = host
self.ssh_user = ssh_user
self.hostname = hostname
class Inventory(object):
def __init__(self, ssh_user):
self.services = {}
self.ssh_user = ssh_user
def add_service(self, dc, name, address):
service = '%s-%s' % (dc, name)
self.services.setdefault(service, [])
host = '%s-%s' % (service, address.replace('.', '-'))
ssh_host = SshHost(host, self.ssh_user, address)
self.services[service].append(ssh_host)
def __iter__(self):
for services in self.services.values():
for ssh_host in services:
yield ssh_host
class App(object):
def __init__(self, consul, ssh_user, merge):
self.client = Client(consul)
self.merge = merge
self.inventory = Inventory(ssh_user)
def get_datacenters(self):
return self.client.get('/v1/catalog/datacenters')
def get_nodes(self, dc=''):
return self.client.get('/v1/catalog/nodes?dc=%s' % dc)
def get_node(self, node, dc=''):
return self.client.get('/v1/catalog/node/%s?dc=%s' % (node['Node'], dc))
def get_node_services(self, node):
return [s['Service'] for s in node['Services'].values()]
def get_inventory(self):
for dc in self.get_datacenters():
for node in self.get_nodes(dc):
node = self.get_node(node, dc)
for service in self.get_node_services(node):
self.inventory.add_service(dc, service, node['Node']['Address'])
def write_config(self):
ssh_dir = os.path.join(os.environ['HOME'], '.ssh')
main_config_path = os.path.join(ssh_dir, 'config')
main_config_backup_path = os.path.join(ssh_dir, 'config.old')
consul_config_path = os.path.join(ssh_dir, 'consul.config')
merge_files = os.path.join(ssh_dir, self.merge)
with open(consul_config_path, 'w') as f:
for ssh_host in self.inventory:
f.write('Host %s\n' % ssh_host.host)
f.write(' Hostname %s\n' % ssh_host.hostname)
f.write(' User %s\n\n' % ssh_host.ssh_user)
shutil.copyfile(main_config_path, main_config_backup_path)
with open(main_config_path, 'w') as ssh_config:
for fn in glob.glob(merge_files):
with open(fn, 'r') as config:
ssh_config.write(config.read())
print('config written to %s' % main_config_path)
def run(self):
self.get_inventory()
self.write_config()
def main():
parser = argparse.ArgumentParser()
parser.add_argument(
'-c', '--consul', default='localhost:8500',
help='The Consul host to connect to. Defaults to localhost:8500')
parser.add_argument(
'-u', '--ssh-user', default=os.getlogin(),
help='The SSH user to specify for all hosts. Defaults to %s' % os.getlogin())
parser.add_argument(
'-m', '--merge', default='*.config',
help='A glob pattern to specify files to collect and merge into the main config. '
'Defaults to "*.config"')
args = parser.parse_args()
App(args.consul, args.ssh_user, args.merge).run()
if __name__ == '__main__':
main()
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