services/dockercleaner/arvados_docker/cleaner.py

   1 #!/usr/bin/env python3
   2 """arvados_docker.cleaner - Remove unused Docker images from compute nodes
   3
   4 Usage:
   5   python3 -m arvados_docker.cleaner --quota 50G
   6 """
   7
   8 import argparse
   9 import collections
  10 import copy
  11 import functools
  12 import json
  13 import logging
  14 import sys
  15 import time
  16
  17 import docker
  18
  19 SUFFIX_SIZES = {suffix: 1024 ** exp for exp, suffix in enumerate('kmgt', 1)}
  20
  21 logger = logging.getLogger('arvados_docker.cleaner')
  22
  23 def return_when_docker_not_found(result=None):
  24     # If the decorated function raises a 404 error from Docker, return
  25     # `result` instead.
  26     def docker_not_found_decorator(orig_func):
  27         @functools.wraps(orig_func)
  28         def docker_not_found_wrapper(*args, **kwargs):
  29             try:
  30                 return orig_func(*args, **kwargs)
  31             except docker.errors.APIError as error:
  32                 if error.response.status_code != 404:
  33                     raise
  34                 return result
  35         return docker_not_found_wrapper
  36     return docker_not_found_decorator
  37
  38 class DockerImage:
  39     def __init__(self, image_hash):
  40         self.docker_id = image_hash['Id']
  41         self.size = image_hash['VirtualSize']
  42         self.last_used = -1
  43
  44     def used_at(self, use_time):
  45         self.last_used = max(self.last_used, use_time)
  46
  47
  48 class DockerImages:
  49     def __init__(self, target_size):
  50         self.target_size = target_size
  51         self.images = {}
  52         self.container_image_map = {}
  53
  54     @classmethod
  55     def from_daemon(cls, target_size, docker_client):
  56         images = cls(target_size)
  57         for image in docker_client.images():
  58             images.add_image(image)
  59         return images
  60
  61     def add_image(self, image_hash):
  62         image = DockerImage(image_hash)
  63         self.images[image.docker_id] = image
  64         logger.debug("Registered image %s", image.docker_id)
  65
  66     def del_image(self, image_id):
  67         if image_id in self.images:
  68             del self.images[image_id]
  69             self.container_image_map = {
  70                 cid: cid_image
  71                 for cid, cid_image in self.container_image_map.items()
  72                 if cid_image != image_id}
  73             logger.debug("Unregistered image %s", image_id)
  74
  75     def has_image(self, image_id):
  76         return image_id in self.images
  77
  78     def add_user(self, container_hash, use_time):
  79         image_id = container_hash['Image']
  80         if image_id in self.images:
  81             self.container_image_map[container_hash['Id']] = image_id
  82             self.images[image_id].used_at(use_time)
  83             logger.debug("Registered container %s using image %s",
  84                          container_hash['Id'], image_id)
  85
  86     def end_user(self, cid):
  87         self.container_image_map.pop(cid, None)
  88         logger.debug("Unregistered container %s", cid)
  89
  90     def should_delete(self):
  91         if not self.images:
  92             return
  93         # Build a list of images, ordered by use time.
  94         lru_images = list(self.images.values())
  95         lru_images.sort(key=lambda image: image.last_used)
  96         # Make sure we don't delete any images in use, or if there are
  97         # none, the most recently used image.
  98         if self.container_image_map:
  99             keep_ids = set(self.container_image_map.values())
 100         else:
 101             keep_ids = {lru_images[-1].docker_id}
 102         space_left = (self.target_size - sum(self.images[image_id].size
 103                                              for image_id in keep_ids))
 104         # Go through the list most recently used first, and note which
 105         # images can be saved with the space allotted.
 106         for image in reversed(lru_images):
 107             if (image.docker_id not in keep_ids) and (image.size <= space_left):
 108                 keep_ids.add(image.docker_id)
 109                 space_left -= image.size
 110         # Yield the Docker IDs of any image we don't want to save, least
 111         # recently used first.
 112         for image in lru_images:
 113             if image.docker_id not in keep_ids:
 114                 yield image.docker_id
 115
 116
 117 class DockerEventHandlers:
 118     # This class maps Docker event types to the names of methods that should
 119     # receive those events.
 120     def __init__(self):
 121         self.handler_names = collections.defaultdict(list)
 122
 123     def on(self, *status_names):
 124         def register_handler(handler_method):
 125             for status in status_names:
 126                 self.handler_names[status].append(handler_method.__name__)
 127             return handler_method
 128         return register_handler
 129
 130     def for_event(self, status):
 131         return iter(self.handler_names[status])
 132
 133     def copy(self):
 134         result = self.__class__()
 135         result.handler_names = copy.deepcopy(self.handler_names)
 136         return result
 137
 138
 139 class DockerEventListener:
 140     # To use this class, define event_handlers as an instance of
 141     # DockerEventHandlers.  Call run() to iterate over events and call the
 142     # handler methods as they come in.
 143     ENCODING = 'utf-8'
 144
 145     def __init__(self, events):
 146         self.events = events
 147
 148     def run(self):
 149         for event in self.events:
 150             event = json.loads(event.decode(self.ENCODING))
 151             for method_name in self.event_handlers.for_event(event['status']):
 152                 getattr(self, method_name)(event)
 153
 154
 155 class DockerImageUseRecorder(DockerEventListener):
 156     event_handlers = DockerEventHandlers()
 157
 158     def __init__(self, images, docker_client, events):
 159         self.images = images
 160         self.docker_client = docker_client
 161         super().__init__(events)
 162
 163     @event_handlers.on('create')
 164     @return_when_docker_not_found()
 165     def load_container(self, event):
 166         container_hash = self.docker_client.inspect_container(event['id'])
 167         self.new_container(event, container_hash)
 168
 169     def new_container(self, event, container_hash):
 170         self.images.add_user(container_hash, event['time'])
 171
 172     @event_handlers.on('destroy')
 173     def container_stopped(self, event):
 174         self.images.end_user(event['id'])
 175
 176
 177 class DockerImageCleaner(DockerImageUseRecorder):
 178     event_handlers = DockerImageUseRecorder.event_handlers.copy()
 179
 180     def __init__(self, images, docker_client, events):
 181         super().__init__(images, docker_client, events)
 182         self.logged_unknown = set()
 183
 184     def new_container(self, event, container_hash):
 185         container_image_id = container_hash['Image']
 186         if not self.images.has_image(container_image_id):
 187             image_hash = self.docker_client.inspect_image(container_image_id)
 188             self.images.add_image(image_hash)
 189         return super().new_container(event, container_hash)
 190
 191     @event_handlers.on('destroy')
 192     def clean_images(self, event=None):
 193         for image_id in self.images.should_delete():
 194             try:
 195                 self.docker_client.remove_image(image_id)
 196             except docker.errors.APIError as error:
 197                 logger.warning("Failed to remove image %s: %s", image_id, error)
 198             else:
 199                 logger.info("Removed image %s", image_id)
 200                 self.images.del_image(image_id)
 201
 202     @event_handlers.on('destroy')
 203     def log_unknown_images(self, event):
 204         unknown_ids = {image['Id'] for image in self.docker_client.images()
 205                        if not self.images.has_image(image['Id'])}
 206         for image_id in (unknown_ids - self.logged_unknown):
 207             logger.info("Image %s is loaded but unused, so it won't be cleaned",
 208                         image_id)
 209         self.logged_unknown = unknown_ids
 210
 211
 212 def human_size(size_str):
 213     size_str = size_str.lower().rstrip('b')
 214     multiplier = SUFFIX_SIZES.get(size_str[-1])
 215     if multiplier is None:
 216         multiplier = 1
 217     else:
 218         size_str = size_str[:-1]
 219     return int(size_str) * multiplier
 220
 221 def parse_arguments(arguments):
 222     parser = argparse.ArgumentParser(
 223         prog="arvados_docker.cleaner",
 224         description="clean old Docker images from Arvados compute nodes")
 225     parser.add_argument(
 226         '--quota', action='store', type=human_size, required=True,
 227         help="space allowance for Docker images, suffixed with K/M/G/T")
 228     parser.add_argument(
 229         '--verbose', '-v', action='count', default=0,
 230         help="log more information")
 231     return parser.parse_args(arguments)
 232
 233 def setup_logging(args):
 234     log_handler = logging.StreamHandler()
 235     log_handler.setFormatter(logging.Formatter(
 236             '%(asctime)s %(name)s[%(process)d] %(levelname)s: %(message)s',
 237             '%Y-%m-%d %H:%M:%S'))
 238     logger.addHandler(log_handler)
 239     logger.setLevel(logging.ERROR - (10 * args.verbose))
 240
 241 def run(args, docker_client):
 242     start_time = int(time.time())
 243     logger.debug("Loading Docker activity through present")
 244     images = DockerImages.from_daemon(args.quota, docker_client)
 245     use_recorder = DockerImageUseRecorder(
 246         images, docker_client, docker_client.events(since=1, until=start_time))
 247     use_recorder.run()
 248     cleaner = DockerImageCleaner(
 249         images, docker_client, docker_client.events(since=start_time))
 250     logger.info("Starting cleanup loop")
 251     cleaner.clean_images()
 252     cleaner.run()
 253
 254 def main(arguments):
 255     args = parse_arguments(arguments)
 256     setup_logging(args)
 257     run(args, docker.Client())
 258
 259 if __name__ == '__main__':
 260     main(sys.argv[1:])