add HTTP caching to /r/ redirect URLs

for #432

redirect.py

@@ -27,7 +27,7 @@ from oauth_dropins.webutil.util import json_dumps, json_loads
 
 from activitypub import ActivityPub
 from common import CACHE_TIME, CONTENT_TYPE_HTML
-from flask_app import app, cache
+from flask_app import app
 from protocol import Protocol
 from web import Web
 
@@ -43,7 +43,10 @@ DOMAIN_ALLOWLIST = frozenset((
     'bsky.app',
 ))
 
-VARY_HEADER = {'Vary': 'Accept'}
+HEADERS = {
+    'Vary': 'Accept',
+    'Cache-Control': f'public, max-age={CACHE_TIME.total_seconds()}'
+}
 
 @app.get(r'/r/<path:to>')
 def redir(to):
@@ -95,7 +98,7 @@ def redir(to):
                 break
     else:
         if not accept_as2:
-            return f'No web user found for any of {domains}', 404, VARY_HEADER
+            return f'No web user found for any of {domains}', 404, HEADERS
 
     if not accept_as2:
         # redirect. include rel-alternate link to make posts discoverable by entering
@@ -113,23 +116,23 @@ def redir(to):
     </html>
     """, 301, {
         'Location': to,
-        **VARY_HEADER,
+        **HEADERS,
     }
 
     # AS2 requested, fetch and convert and serve
     proto = Protocol.for_id(to)
     if not proto:
-        return f"Couldn't determine protocol for {to}", 404, VARY_HEADER
+        return f"Couldn't determine protocol for {to}", 404, HEADERS
 
     obj = proto.load(to)
     if not obj or obj.deleted:
-        return f'Object not found: {to}', 404, VARY_HEADER
+        return f'Object not found: {to}', 404, HEADERS
 
     # TODO: do this for other protocols too?
     if proto == Web and not web_user:
         web_user = Web.get_or_create(util.domain_from_link(to), direct=False, obj=obj)
         if not web_user:
-            return f'Object not found: {to}', 404, VARY_HEADER
+            return f'Object not found: {to}', 404, HEADERS
 
     ret = ActivityPub.convert(obj, from_user=web_user)
     # logger.info(f'Returning: {json_dumps(ret, indent=2)}')
@@ -138,6 +141,6 @@ def redir(to):
                          if accept_type == as2.CONTENT_TYPE_LD
                          else accept_type),
         'Access-Control-Allow-Origin': '*',
-        **VARY_HEADER,
+        **HEADERS,
     }