initial commit
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commit
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*.pyc
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hosts
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.idea/
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FROM python:alpine
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COPY docker-etchosts.py /docker-etchosts.py
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CMD python /docker-etchosts.py
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# Automatically add/update/remove containers from hosts-file
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docker-etchosts is a script that monitors dockers event stream, and
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adds/updates/removes containers to your (/etc/)hosts-file on the fly.
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The script is based on [dockermon by CyberInt](http://pythonwise.blogspot.de/2015/07/dockermon-docker-process-monitor.html).
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## Usage
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Started without further parameters the script will connect to `/var/run/docker.sock` and modify `hosts` in the current working directory.
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It will also process all currently running containers.
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To connect to a remote docker node or swarm cluster use `--socket-url`, e.g.
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python docker-etchosts.py --socker-url='tcp:///localhost:2335'
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To specify the full path to your hosts file you would like modified pass `--hosts-file=/etc/hosts`.
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To skip processing running containers on script startup pass `--skip-running`.
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## Running in a container
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The script runs fine dockerized, the supplied Dockerfile creates a image of about 80 MB size,
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running consumes about 15 MB RAM.
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### build
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docker build -t dockerhosts:pre .
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### run
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docker run -v /etc/hosts:/hosts -v /var/run/docker.sock:/var/run/docker.sock --privileged dockerhosts:pre
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### run and use tcp socket
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docker run -v /etc/hosts:/hosts --privileged dockerhosts:pre --socket-url=tcp:///localhost:2335
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### docker-compose
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...or instead of the above, just do:
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docker-compose up -d
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:)
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docker-etchosts:
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build: .
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volumes:
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- "/etc/hosts:/hosts"
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- "/var/run/docker.sock:/var/run/docker.sock"
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privileged: true
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restart: always
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#!/usr/bin/env python
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"""add/remove containers from host-file using
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docker /events HTTP streaming API"""
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from contextlib import closing
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from socket import socket, AF_UNIX
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from sys import stdout, version_info, platform
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import json
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if version_info[:2] < (3, 0):
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from httplib import OK as HTTP_OK
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from urlparse import urlparse
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else:
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from http.client import OK as HTTP_OK
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from urllib.parse import urlparse
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__version__ = '0.0.1'
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buffer_size = 1024
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default_sock_url = 'ipc:///var/run/docker.sock'
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hostsfile = 'hosts'
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class DockermonError(Exception):
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pass
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def read_http_header(sock):
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"""Read HTTP header from socket, return header and rest of data.
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:param sock: socket to send request to
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"""
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buf = []
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hdr_end = '\r\n\r\n'
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while True:
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buf.append(sock.recv(buffer_size).decode('utf-8'))
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data = ''.join(buf)
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i = data.find(hdr_end)
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if i == -1:
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continue
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return data[:i], data[i + len(hdr_end):]
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def header_status(header):
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"""Parse HTTP status line, return status (int) and reason.
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:param header: header data
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"""
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status_line = header[:header.find('\r')]
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# 'HTTP/1.1 200 OK' -> (200, 'OK')
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fields = status_line.split(None, 2)
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return int(fields[1]), fields[2]
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def connect(url):
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"""Connect to UNIX or TCP socket.
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:param url: can be either tcp://<host>:port or ipc://<path>
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"""
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url = urlparse(url)
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if url.scheme == 'tcp':
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sock = socket()
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netloc = tuple(url.netloc.rsplit(':', 1))
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hostname = socket.gethostname()
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elif url.scheme == 'ipc':
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sock = socket(AF_UNIX)
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netloc = url.path
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hostname = 'localhost'
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else:
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raise ValueError('unknown socket type: %s' % url.scheme)
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sock.connect(netloc)
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return sock, hostname
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def lookup_ip(container_id, url=default_sock_url):
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"""Fetch a running containers IP from the docker API.
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:param container_id: id or name to look up IP for
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:param url: docker API. can be either tcp://<host>:port or ipc://<path>
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:return: IPv4
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:rtype: str
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"""
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sock, hostname = connect(url)
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request = 'GET /containers/{}/json HTTP/1.1\nHost: {}\n\n'.format(
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container_id,
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hostname,
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)
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request = request.encode('utf-8')
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with closing(sock):
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sock.sendall(request)
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header, payload = read_http_header(sock)
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status, reason = header_status(header)
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if status != HTTP_OK:
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raise DockermonError('bad HTTP status: %s %s' % (status, reason))
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payload = payload[payload.find('\r\n') + 2:]
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buf = [payload]
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while True:
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chunk = sock.recv(buffer_size)
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buf.append(chunk.decode('utf-8'))
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data = ''.join(buf)
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if data.endswith('\n\r\n0\r\n\r\n'):
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break
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data = json.loads(data[:-6])
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return data.get('NetworkSettings', {}).get('IPAddress')
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def process_all_running_containers(url=default_sock_url):
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"""Add/Update all running containers IPs to hosts-file.
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Used at script startup.
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:param url: docker API. can be either tcp://<host>:port or ipc://<path>
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"""
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sock, hostname = connect(url)
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request = 'GET /containers/json HTTP/1.1\nHost: {}\n\n'.format(hostname)
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request = request.encode('utf-8')
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with closing(sock):
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sock.sendall(request)
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header, payload = read_http_header(sock)
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status, reason = header_status(header)
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if status != HTTP_OK:
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raise DockermonError('bad HTTP status: %s %s' % (status, reason))
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payload = payload[payload.find('\r\n') + 2:]
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buf = [payload]
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while True:
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chunk = sock.recv(buffer_size)
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buf.append(chunk.decode('utf-8'))
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data = ''.join(buf)
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if data.endswith('\n\r\n0\r\n\r\n'):
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break
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data = json.loads(data[:-6])
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for container in data:
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_update_hosts_file(
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container.get('Names', [])[0].strip('/'),
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lookup_ip(container.get("Id"))
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)
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def watch(callback, url=default_sock_url):
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"""Watch docker events. Will call callback with each new event (dict).
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:param callback: callback function for received events.
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:param url: docker API. can be either tcp://<host>:port or ipc://<path>
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"""
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sock, hostname = connect(url)
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request = 'GET /events HTTP/1.1\nHost: {}\n\n'.format(hostname)
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request = request.encode('utf-8')
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with closing(sock):
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sock.sendall(request)
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header, payload = read_http_header(sock)
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status, reason = header_status(header)
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if status != HTTP_OK:
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raise DockermonError('bad HTTP status: %s %s' % (status, reason))
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# Messages are \r\n<size in hex><JSON payload>\r\n
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buf = [payload]
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while True:
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chunk = sock.recv(buffer_size)
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if not chunk:
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raise EOFError('socket closed')
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buf.append(chunk.decode('utf-8'))
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data = ''.join(buf)
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i = data.find('\r\n')
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if i == -1:
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continue
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size = int(data[:i], 16)
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start = i + 2 # Skip initial \r\n
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if len(data) < start + size + 2:
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continue
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payload = data[start:start + size]
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callback(json.loads(payload))
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buf = [data[start + size + 2:]] # Skip \r\n suffix
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def process_callback(msg):
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"""Process events and route to applicable functions.
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:param msg: docker event as received from API.
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"""
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if ('Type' in msg and msg['Type'] == 'container' and
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msg['Action'] == 'start'):
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_container_start(msg)
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if ('Type' in msg and msg['Type'] == 'container' and
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msg['Action'] == 'destroy'):
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_container_destroy(msg)
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# also print all events to stdout for logspout to catch
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json.dump(msg, stdout)
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stdout.write('\n')
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stdout.flush()
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def _container_start(msg):
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"""
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:param msg:
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"""
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container_name = msg.get('Actor', {}).get('Attributes', {}).get("name")
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container_id = msg.get('Actor', {}).get('ID')
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container_ip = lookup_ip(container_id)
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_update_hosts_file(container_name, container_ip)
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def _container_destroy(msg):
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"""
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:param msg:
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"""
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container_name = msg.get('Actor', {}).get('Attributes', {}).get("name")
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_update_hosts_file(container_name)
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def _update_hosts_file(hostname, ip_address=None):
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"""
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The update function takes the ip address and hostname passed into the
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function and adds it to the host file.
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:param ip_address:
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:param hostname:
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"""
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if not ip_address:
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with open(hostsfile, "r+") as f:
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lines = f.readlines()
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f.seek(0)
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f.writelines([line for line in lines if hostname not in line])
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f.truncate()
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return
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with open(hostsfile, "r") as f:
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lines = f.readlines()
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if any(hostname in s for s in lines):
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altered_lines = ["{} {}\n".format(ip_address, hostname)
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if hostname in line else line for line in lines]
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else:
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altered_lines = list(lines) + ["{} {}\n".format(
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ip_address,
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hostname,
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)]
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with open(hostsfile, "w") as f:
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f.writelines(altered_lines)
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if __name__ == '__main__':
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global hostsfile
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from argparse import ArgumentParser
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parser = ArgumentParser(description=__doc__)
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parser.add_argument(
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'--socket-url', default=default_sock_url,
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help='socket url (ipc:///path/to/sock or tcp:///host:port)'
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)
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parser.add_argument(
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'--skip-running', help='do not process already running containers',
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action='store_true', default=False
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)
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parser.add_argument(
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'--hosts-file', help='hosts file to add/update to', default="hosts"
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)
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parser.add_argument(
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'--version', help='print version and exit',
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action='store_true', default=False
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)
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args = parser.parse_args()
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if args.version:
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print('docker-etchosts %s' % __version__)
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raise SystemExit
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if not args.skip_running:
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process_all_running_containers(args.socket_url)
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hostsfile = args.hosts_file
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try:
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watch(process_callback, args.socket_url)
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except (KeyboardInterrupt, EOFError):
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pass
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