Fix: validate that cached files on disk are fresh (#85)

If a logged-in user generated a file, LAST_TIME_RENDERED was set,
but the cache on disk is not written. Now if there was an older
version of the cache still on disk, on next request from a visitor
that is not logged-in, the old cache would be served.

Validate that the time set in LAST_TIME_RENDERED is in fact also
the time of the cache-file on disk. If not, the file on disk is
stale and a new page should be rendered.

truewiki/metadata.py

@@ -45,6 +45,11 @@ def page():
 RELOAD_BUSY.set()
 
 
+def _delete_cached_page(page):
+    if page in LAST_TIME_RENDERED:
+        del LAST_TIME_RENDERED[page]
+
+
 def translation_callback(wtp, wiki_page, page):
     for wikilink in wtp.wikilinks:
         if wikilink.target.startswith("Translation:"):
@@ -56,8 +61,7 @@ def translation_callback(wtp, wiki_page, page):
             # Reset the last time rendered for all translations too, as
             # otherwise a new translation won't show up on those pages.
             for translation in TRANSLATIONS[target]:
-                if translation in LAST_TIME_RENDERED:
-                    del LAST_TIME_RENDERED[translation]
+                _delete_cached_page(translation)
 
 
 def category_callback(wtp, wiki_page, page):
@@ -69,8 +73,7 @@ def category_callback(wtp, wiki_page, page):
             CATEGORIES[target].append(page)
 
             # Reset the last time rendered for the category.
-            if f"Category/{target}" in LAST_TIME_RENDERED:
-                del LAST_TIME_RENDERED[f"Category/{target}"]
+            _delete_cached_page(f"Category/{target}")
 
 
 def file_callback(wtp, wiki_page, page):
@@ -82,8 +85,7 @@ def file_callback(wtp, wiki_page, page):
             FILES[target].append(page)
 
             # Reset the last time rendered for the file.
-            if f"File/{target}" in LAST_TIME_RENDERED:
-                del LAST_TIME_RENDERED[f"File/{target}"]
+            _delete_cached_page(f"File/{target}")
 
 
 def links_callback(wtp, wiki_page, page):
@@ -125,14 +127,10 @@ def template_callback(wtp, wiki_page, page):
 def _forget_page(page):
     for category in PAGES[page]["categories"]:
         CATEGORIES[category].remove(page)
-
-        if f"Category/{category}" in LAST_TIME_RENDERED:
-            del LAST_TIME_RENDERED[f"Category/{category}"]
+        _delete_cached_page(f"Category/{category}")
     for file in PAGES[page]["files"]:
         FILES[file].remove(page)
-
-        if f"File/{file}" in LAST_TIME_RENDERED:
-            del LAST_TIME_RENDERED[f"File/{file}"]
+        _delete_cached_page(f"File/{file}")
     for link in PAGES[page]["links"]:
         LINKS[link].remove(page)
     for template in PAGES[page]["templates"]:
@@ -144,9 +142,7 @@ def _forget_page(page):
         # otherwise a removed translation will still show up on those pages.
         if not translation.startswith(("Category/", "File/", "Template/")):
             translation = f"Page/{translation}"
-
-        if translation in LAST_TIME_RENDERED:
-            del LAST_TIME_RENDERED[translation]
+        _delete_cached_page(translation)
 
     PAGES[page]["categories"].clear()
     PAGES[page]["files"].clear()
@@ -200,8 +196,7 @@ async def _page_changed(page, notified=None):
     # As we are invalidating this page, also reset when we last rendered it.
     # This means that on a next request for this page, browsers will be
     # given a new version too.
-    if page in LAST_TIME_RENDERED:
-        del LAST_TIME_RENDERED[page]
+    _delete_cached_page(page)
 
     # Capture the current templates ued. After analysis, this might have
     # changed, but those are still pages that need to be analyzed again.

truewiki/views/page.py

@@ -73,7 +73,12 @@ def view(user, page: str, if_modified_since) -> web.Response:
             # We already rendered this page before. If the browser has it in his
             # cache, he can simply reuse that if we haven't rendered since.
             response = web.HTTPNotModified()
-        elif not user and cache_filename and os.path.exists(cache_filename):
+        elif (
+            not user
+            and cache_filename
+            and os.path.exists(cache_filename)
+            and os.path.getmtime(cache_filename) >= metadata.LAST_TIME_RENDERED[namespaced_page]
+        ):
             # We already rendered this page to disk. Serve from there.
             with open(cache_filename) as fp:
                 body = fp.read()
@@ -85,14 +90,23 @@ def view(user, page: str, if_modified_since) -> web.Response:
 
         # Never cache anything in the Folder/.
         if can_cache:
-            metadata.LAST_TIME_RENDERED[namespaced_page] = time.time()
-
             if not user and cache_filename:
                 # Cache the file on disk
                 os.makedirs(os.path.dirname(cache_filename), exist_ok=True)
                 with open(cache_filename, "w") as fp:
                     fp.write(body)
 
+                page_time = os.path.getmtime(cache_filename)
+            else:
+                # Accuracy of time.time() is higher than getmtime(), so
+                # depending if we cached, use a different clock.
+                page_time = time.time()
+
+            # Only update the time if we don't have one yet. This makes sure
+            # that LAST_TIME_RENDERED has the oldest timestamp possible.
+            if namespaced_page not in metadata.LAST_TIME_RENDERED:
+                metadata.LAST_TIME_RENDERED[namespaced_page] = page_time
+
         response = web.Response(body=body, content_type="text/html", status=status_code)
 
     # Inform the browser under which rules it can cache this page.