examples/deepzoom: share a tile cache among all multiserver slides

Author: bgilbert

examples/deepzoom/deepzoom_multiserver.py

@@ -3,6 +3,7 @@
 # deepzoom_multiserver - Example web application for viewing multiple slides
 #
 # Copyright (c) 2010-2015 Carnegie Mellon University
+# Copyright (c) 2021      Benjamin Gilbert
 #
 # This library is free software; you can redistribute it and/or modify it
 # under the terms of version 2.1 of the GNU Lesser General Public License
@@ -43,11 +44,12 @@
 else:
     import openslide
 
-from openslide import OpenSlide, OpenSlideError
+from openslide import OpenSlide, OpenSlideCache, OpenSlideError
 from openslide.deepzoom import DeepZoomGenerator
 
 SLIDE_DIR = '.'
 SLIDE_CACHE_SIZE = 10
+SLIDE_TILE_CACHE_MB = 128
 DEEPZOOM_FORMAT = 'jpeg'
 DEEPZOOM_TILE_SIZE = 254
 DEEPZOOM_OVERLAP = 1
@@ -60,11 +62,13 @@
 
 
 class _SlideCache:
-    def __init__(self, cache_size, dz_opts):
+    def __init__(self, cache_size, tile_cache_mb, dz_opts):
         self.cache_size = cache_size
         self.dz_opts = dz_opts
         self._lock = Lock()
         self._cache = OrderedDict()
+        # Share a single tile cache among all slide handles
+        self._tile_cache = OpenSlideCache(tile_cache_mb * 1024 * 1024)
 
     def get(self, path):
         with self._lock:
@@ -75,6 +79,7 @@ def get(self, path):
                 return slide
 
         osr = OpenSlide(path)
+        osr.set_cache(self._tile_cache)
         slide = DeepZoomGenerator(osr, **self.dz_opts)
         try:
             mpp_x = osr.properties[openslide.PROPERTY_NAME_MPP_X]
@@ -121,7 +126,9 @@ def _setup():
         'DEEPZOOM_LIMIT_BOUNDS': 'limit_bounds',
     }
     opts = {v: app.config[k] for k, v in config_map.items()}
-    app.cache = _SlideCache(app.config['SLIDE_CACHE_SIZE'], opts)
+    app.cache = _SlideCache(
+        app.config['SLIDE_CACHE_SIZE'], app.config['SLIDE_TILE_CACHE_MB'], opts
+    )
 
 
 def _get_slide(path):