team-3/src/c3nav/tileserver/wsgi.py

import base64
import logging
import os
import re
import threading
import time
from io import BytesIO

import pylibmc
import requests

from c3nav.mapdata.utils.cache import CachePackage
from c3nav.mapdata.utils.tiles import (build_access_cache_key, build_base_cache_key, build_tile_etag, get_tile_bounds,
                                       parse_tile_access_cookie)

logging.basicConfig(level=logging.DEBUG if os.environ.get('C3NAV_DEBUG') else logging.INFO,
                    format='[%(asctime)s] [%(process)s] [%(levelname)s] %(name)s: %(message)s',
                    datefmt='%Y-%m-%d %H:%M:%S %z')
logger = logging.getLogger('c3nav')


class TileServer:
    path_regex = re.compile(r'^/(\d+)/(\d+)/(-?\d+)/(-?\d+).png$')
    cookie_regex = re.compile(r'[^ ]c3nav_tile_access=([^; ])')

    def __init__(self):
        try:
            self.upstream_base = os.environ['C3NAV_UPSTREAM_BASE'].strip('/')
        except KeyError:
            raise Exception('C3NAV_UPSTREAM_BASE needs to be set.')

        self.tile_secret = os.environ.get('C3NAV_TILE_SECRET', None)
        if not self.tile_secret:
            tile_secret_file = None
            try:
                tile_secret_file = os.environ['C3NAV_TILE_SECRET_FILE']
                self.tile_secret = open(tile_secret_file).read().strip()
            except KeyError:
                raise Exception('C3NAV_TILE_SECRET or C3NAV_TILE_SECRET_FILE need to be set.')
            except FileNotFoundError:
                raise Exception('The C3NAV_TILE_SECRET_FILE (%s) does not exist.' % tile_secret_file)

        self.auth_headers = {'X-Tile-Secret': base64.b64encode(self.tile_secret.encode())}

        self.cache_package = None
        self.cache_package_etag = None

        self.tile_cache = pylibmc.Client(["127.0.0.1"], binary=True, behaviors={"tcp_nodelay": True, "ketama": True})

        wait = 1
        while True:
            success = self.load_cache_package()
            if success:
                logger.info('Cache package successfully loaded.')
                break
            logger.info('Retrying after %s seconds...' % wait)
            time.sleep(wait)
            wait = min(10, wait*2)

        threading.Thread(target=self.update_cache_package_thread, daemon=True).start()

    def update_cache_package_thread(self):
        while True:
            time.sleep(60)
            self.load_cache_package()

    def load_cache_package(self):
        logger.debug('Downloading cache package from upstream...')
        try:
            headers = self.auth_headers.copy()
            if self.cache_package_etag is not None:
                headers['If-None-Match'] = self.cache_package_etag
            r = requests.get(self.upstream_base+'/map/cache/package.tar.xz', headers=headers)

            if r.status_code == 403:
                logger.error('Rejected cache package download with Error 403. Tile secret is probably incorrect.')
                return False

            if r.status_code == 304:
                if self.cache_package is not None:
                    logger.debug('Not modified.')
                    return True
                logger.error('Unexpected not modified.')
                return False

            r.raise_for_status()
        except Exception as e:
            logger.error('Cache package download failed: %s' % e)
            return False

        try:
            self.cache_package = CachePackage.read(BytesIO(r.content))
            self.cache_package_etag = r.headers.get('ETag', None)
        except Exception as e:
            logger.error('Cache package parsing failed: %s' % e)
            return False
        return True

    def not_found(self, start_response, text):
        start_response('404 Not Found', [('Content-Type', 'text/plain')])
        return [text]

    def deliver_tile(self, start_response, etag, data):
        start_response('200 OK', [('Content-Type', 'image/png'),
                                  ('Cache-Control', 'no-cache'),
                                  ('ETag', etag)])
        return [data]

    def __call__(self, env, start_response):
        match = self.path_regex.match(env['PATH_INFO'])
        if match is None:
            return self.not_found(start_response, b'invalid tile path.')

        level, zoom, x, y = match.groups()

        zoom = int(zoom)
        if not (0 <= zoom <= 10):
            return self.not_found(start_response, b'zoom out of bounds.')

        # do this to be thread safe
        cache_package = self.cache_package

        # check if bounds are valid
        x = int(x)
        y = int(y)
        minx, miny, maxx, maxy = get_tile_bounds(zoom, x, y)
        if not cache_package.bounds_valid(minx, miny, maxx, maxy):
            return self.not_found(start_response, b'coordinates out of bounds.')

        # get level
        level = int(level)
        level_data = cache_package.levels.get(level)
        if level_data is None:
            return self.not_found(start_response, b'invalid level.')

        # decode access permissions
        cookie = env.get('HTTP_COOKIE', None)
        if cookie:
            cookie = self.cookie_regex.match(cookie)
            if cookie:
                cookie = cookie.group(1)
        access_permissions = parse_tile_access_cookie(cookie, self.tile_secret) if cookie else set()

        # only access permissions that are affecting this tile
        access_permissions &= set(level_data.restrictions[minx:miny, maxx:maxy])

        # build cache keys
        last_update = level_data.history.last_update(minx, miny, maxx, maxy)
        base_cache_key = build_base_cache_key(last_update)
        access_cache_key = build_access_cache_key(access_permissions)

        # check browser cache
        if_none_match = env.get('HTTP_IF_NONE_MATCH')
        tile_etag = build_tile_etag(level, zoom, x, y, base_cache_key, access_cache_key, self.tile_secret)
        if if_none_match == tile_etag:
            start_response('304 Not Modified', [('Content-Type', 'text/plain'),
                                                ('ETag', tile_etag)])
            return [b'']

        cached_result = self.tile_cache.get(tile_etag)
        if cached_result is not None:
            return self.deliver_tile(start_response, tile_etag, cached_result)

        r = requests.get('%s/map/%d/%d/%d/%d/%s.png' % (self.upstream_base, level, zoom, x, y, access_cache_key),
                         headers=self.auth_headers)

        if r.status_code == 200 and r.headers['Content-Type'] == 'image/png':
            self.tile_cache[tile_etag] = r.content
            return self.deliver_tile(start_response, tile_etag, r.content)

        start_response('%d %s' % (r.status_code, r.reason), [('Content-Type', r.headers['Content-Type'])])
        return [r.content]


application = TileServer()