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#!/usr/bin/env python
import os, sys, json, re
import docker
import argparse
parser = argparse.ArgumentParser( description="Manage host entries for docker containers")
parser.add_argument('-n', '--native', help='run service on docker host', action='store_true' , dest='NATIVE_MODE')
parser.add_argument('-o','-1', '--once', help='run once and exit (no continuous polling)', action='store_true', dest='ONCE_MODE')
args = parser.parse_args()
if not args.NATIVE_MODE and os.path.exists("/.dockerenv"):
print "Found /.dockerenv... reading from /tmp/hosts"
HOSTS_FILE="/tmp/hosts"
else:
print "Running in native mode... reading from /etc/hosts"
HOSTS_FILE="/etc/hosts"
if os.environ.get("DOCKER_HOST"):
client = docker.from_env()
else:
try:
client = docker.DockerClient(base_url='unix://var/run/docker.sock')
except:
print "Sorry, I can't find a dockerd to connect to."
sys.exit(1)
def get_ip(c):
try:
networks = c.attrs.get("NetworkSettings").get("Networks")
for n in networks:
ip = networks[n]["IPAddress"]
if ip is not None:
return ip
except:
return None
def get_aliases(c):
aliases = []
try:
envs = c.attrs.get("Config").get("Env")
for e in envs:
m = re.match('ALIAS=(?P<aliases>.*)', e)
if m:
for a in m.group('aliases').split(','):
aliases.append(a)
return aliases
except KeyError as e:
return None
def event_remove(event):
container = client.containers.get(event.get("id"))
container_remove(container.name)
def event_add(event):
container = client.containers.get(event.get("id"))
container_add(container.name)
def container_add(name):
try:
container = client.containers.get(name)
except:
return
container_remove(container.name)
ip = get_ip(container)
if ip:
entry = "%s %s" % (ip, container.name)
aliases = get_aliases(container)
if aliases:
entry += " %s" % ' '.join(aliases)
open(HOSTS_FILE, 'a').write(entry+'\n')
print "Added: %s" % entry
def container_remove(name):
if name is None and len(name) > 0:
return
entry = "(.*)\s+%s(.*)" % (name)
lines = open(HOSTS_FILE, 'r').readlines()
outfile = open(HOSTS_FILE, 'w')
for line in lines:
if re.match(entry, line) is None:
outfile.write(line)
outfile.close()
print "removed entry for pattern %s" % name
### Let's start doing something useful.
# first, we catch up with any existing containers that are already deployed.
for container in client.containers.list():
container_add(container.name)
if args.ONCE_MODE:
sys.exit(0)
# calling events will basically poll forever, so after this we're
# essentially in not-quite-a-daemon mode
for event_json in client.events():
print "SAW: %s" % str(event_json)
event = json.loads(str(event_json))
if event.get("status") == "start":
event_add(event)
elif event.get("status") == "kill":
event_remove(event)
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