base for python based tileserver

src/c3nav/tileserver/wsgi.py

@@ -0,0 +1,106 @@
+import base64
+import logging
+import os
+import re
+import time
+from io import BytesIO
+
+import requests
+
+from c3nav.mapdata.utils.cache import CachePackage
+
+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:
+    regex = re.compile(r'^/(?P<level>\d+)/(?P<zoom>\d+)/(?P<x>-?\d+)/(?P<y>-?\d+).png$')
+
+    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
+
+        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(2, wait*2)
+
+    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
+
+        self.cache_package = CachePackage.read(BytesIO(r.content))
+        self.cache_package_etag = r.headers.get('ETag', None)
+        return True
+
+    def not_found(self, start_response, text):
+        start_response('404 Not Found', [('Content-Type', 'text/plain')])
+        return [text]
+
+    def __call__(self, env, start_response):
+        match = self.regex.match(env['PATH_INFO'])
+        if match is None:
+            return self.not_found(start_response, b'invalid tile path.')
+
+        zoom = int(match.group('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  # noqa
+
+        x = int(match.group('x'))  # noqa
+        y = int(match.group('y'))  # noqa
+
+        level = int(match.group('level'))  # noqa
+
+        start_response('200 OK', [('Content-Type', 'text/plain')])
+        return [b'mau?']
+
+
+application = TileServer()