caching on home page and posts, especially for anonymous users

the home page and post pages are the most likely to get slashdotted by mastodon.

app/activitypub/routes.py

@@ -26,7 +26,7 @@ from app.activitypub.util import public_key, users_total, active_half_year, acti
 from app.utils import gibberish, get_setting, is_image_url, allowlist_html, render_template, \
     domain_from_url, markdown_to_html, community_membership, ap_datetime, ip_address, can_downvote, \
     can_upvote, can_create_post, awaken_dormant_instance, shorten_string, can_create_post_reply, sha256_digest, \
-    community_moderators, lemmy_markdown_to_html
+    community_moderators, lemmy_markdown_to_html, make_cache_key
 from sqlalchemy import desc
 import werkzeug.exceptions
 
@@ -1509,6 +1509,7 @@ def post_ap2(post_id):
 
 
 @bp.route('/post/<int:post_id>', methods=['GET', 'POST'])
+@cache.cached(timeout=5, make_cache_key=make_cache_key)
 def post_ap(post_id):
     if request.method == 'GET' and is_activitypub_request():
         post = Post.query.get_or_404(post_id)

app/main/routes.py

@@ -7,6 +7,7 @@ from time import sleep
 import flask
 import markdown2
 import requests
+from flask_caching import CachedResponse
 from sqlalchemy.sql.operators import or_, and_
 
 from app import db, cache
@@ -28,7 +29,8 @@ from app.utils import render_template, get_setting, gibberish, request_etag_matc
     ap_datetime, ip_address, retrieve_block_list, shorten_string, markdown_to_text, user_filters_home, \
     joined_communities, moderating_communities, parse_page, theme_list, get_request, markdown_to_html, allowlist_html, \
     blocked_instances, communities_banned_from, topic_tree, recently_upvoted_posts, recently_downvoted_posts, \
-    generate_image_from_video_url, blocked_users, microblog_content_to_title, menu_topics, languages_for_form
+    generate_image_from_video_url, blocked_users, microblog_content_to_title, menu_topics, languages_for_form, \
+    make_cache_key
 from app.models import Community, CommunityMember, Post, Site, User, utcnow, Domain, Topic, File, Instance, \
     InstanceRole, Notification, Language, community_language, PostReply
 
@@ -36,23 +38,36 @@ from app.models import Community, CommunityMember, Post, Site, User, utcnow, Dom
 @bp.route('/', methods=['HEAD', 'GET', 'POST'])
 @bp.route('/home', methods=['GET', 'POST'])
 @bp.route('/home/<sort>', methods=['GET', 'POST'])
+@cache.cached(make_cache_key=make_cache_key)
 def index(sort=None):
     if 'application/ld+json' in request.headers.get('Accept', '') or 'application/activity+json' in request.headers.get(
             'Accept', ''):
         return activitypub_application()
 
-    return home_page('home', sort)
+    return CachedResponse(
+        response=home_page('home', sort),
+        timeout=50 if current_user.is_anonymous else 5,
+    )
 
 
 @bp.route('/popular', methods=['GET'])
 @bp.route('/popular/<sort>', methods=['GET'])
+@cache.cached(timeout=5, make_cache_key=make_cache_key)
 def popular(sort=None):
-    return home_page('popular', sort)
+    return CachedResponse(
+        response=home_page('popular', sort),
+        timeout=50 if current_user.is_anonymous else 5,
+    )
+
 
 @bp.route('/all', methods=['GET'])
 @bp.route('/all/<sort>', methods=['GET'])
+@cache.cached(timeout=5, make_cache_key=make_cache_key)
 def all_posts(sort=None):
-    return home_page('all', sort)
+    return CachedResponse(
+        response=home_page('all', sort),
+        timeout=50 if current_user.is_anonymous else 5,
+    )
 
 
 def home_page(type, sort):

app/utils.py

@@ -166,6 +166,14 @@ def gibberish(length: int = 10) -> str:
     return "".join([random.choice(random_chars) for x in range(length)])
 
 
+# used by @cache.cached() for home page and post caching
+def make_cache_key(sort=None, post_id=None):
+    if current_user.is_anonymous:
+        return f'{request.url}_{sort}_{post_id}_anon_{request.headers.get("Accept")}_{request.headers.get("Accept-Language")}'  # The Accept header differentiates between activitypub requests and everything else
+    else:
+        return f'{request.url}_{sort}_{post_id}_user_{current_user.id}'
+
+
 def is_image_url(url):
     common_image_extensions = ['.jpg', '.jpeg', '.png', '.gif', '.bmp', '.tiff', '.webp']
     mime_type = mime_type_using_head(url)