Reuse epoch-verified record snapshots and avoid empty push payloads

app/controllers/concerns/authentication/session_lookup.rb

@@ -1,7 +1,12 @@
 module Authentication::SessionLookup
   def find_session_by_cookie
     if token = cookies.signed[:session_token]
-      Session.find_by(token: token)
+      version = @response_cache_version if @response_cache_version && (request.get? || request.head?)
+      session, user = RecordCache.fetch([ "session", Digest::SHA256.hexdigest(token.to_s) ], version) do
+        session = Session.find_by(token: token)
+        [ session, session&.user ]
+      end
+      session&.tap { |record| record.user = user }
     end
   end
 end

app/controllers/concerns/cached_responses.rb

@@ -35,6 +35,10 @@ module CachedResponses
   end
 
   private
+    def read_record_cache_version
+      @response_cache_version if request.get? || request.head?
+    end
+
     def capture_response_cache_version
       # Capture for native HTML/JSON/stream renders too, even with page reuse off.
       # Detached renderers do not run callbacks and therefore render uncached.
@@ -81,6 +85,10 @@ module CachedResponses
     def cache_completed_response(key, original_session, encoding)
       if response.status == 200 && response.media_type == "text/html" && session.to_hash == original_session && !response.headers["Content-Encoding"]
         body = encoding == "gzip" ? Zlib.gzip(response.body) : response.body
+        unless body.empty? || response.headers["ETag"] || response.headers["Last-Modified"]
+          # Match Rack::ETag once, rather than hashing the same bytes on each hit.
+          response.headers["ETag"] = %(W/"#{Digest::SHA256.hexdigest(body).byteslice(0, 32)}")
+        end
         response.headers["Content-Encoding"] = "gzip" if encoding == "gzip"
         response.headers["Vary"] = (response.headers["Vary"].to_s.split(/,\s*/) | [ "Accept-Encoding" ]).join(", ")
         headers = response.headers.slice(*CACHE_HEADERS).to_h.freeze

app/controllers/concerns/room_scoped.rb

@@ -7,7 +7,10 @@ module RoomScoped
 
   private
     def set_room
-      @membership = Current.user.memberships.find_by!(room_id: params[:room_id])
-      @room = @membership.room
+      @membership, @room = RecordCache.fetch([ "membership", Current.user.id, params[:room_id] ], read_record_cache_version) do
+        membership = Current.user.memberships.find_by!(room_id: params[:room_id])
+        [ membership, membership.room ]
+      end
+      @membership.room = @room
     end
 end

app/controllers/rooms_controller.rb

@@ -21,7 +21,10 @@ class RoomsController < ApplicationController
 
   private
     def set_room
-      if room = room_scope.find_by(id: params[:room_id] || params[:id])
+      room = RecordCache.fetch([ "room", self.class.name, Current.user.id, params[:room_id] || params[:id] ], read_record_cache_version) do
+        [ room_scope.find_by(id: params[:room_id] || params[:id]) ]
+      end.first
+      if room
         @room = room
       else
         redirect_to root_url, alert: "Room not found or inaccessible"

app/models/record_cache.rb

@@ -0,0 +1,24 @@
+# Rebuild request-local models from bounded, immutable database snapshots.
+# The observer must still see the captured epoch after lookup and admission.
+class RecordCache
+  def self.fetch(key, version)
+    return yield unless version && ResponseCache.instance.budget.positive? && !ActiveRecord::Base.connection.transaction_open?
+
+    key = ActiveSupport::Cache.expand_cache_key([ "record-snapshot-v1", version, key ])
+    return yield if key.bytesize > ResponseCache::MAX_KEY_BYTES
+
+    if snapshot = FragmentCache.store.read(key)
+      if ResponseCache.instance.version == version
+        return ActiveSupport::JSON.decode(snapshot).map { |name, attributes| name.constantize.instantiate(attributes) }
+      end
+    end
+
+    records = yield
+    if records.all? { |record| record&.persisted? && !record.changed? } && ResponseCache.instance.version == version
+      # Raw database values retain timestamp precision and native enum binding.
+      snapshot = ActiveSupport::JSON.encode(records.map { |record| [ record.class.name, record.attributes_before_type_cast ] })
+      FragmentCache.store.write(key, snapshot) if snapshot.bytesize <= ResponseCache::MAX_ENTRY_BYTES
+    end
+    records
+  end
+end

app/models/room/message_pusher.rb

@@ -6,9 +6,9 @@ class Room::MessagePusher
   end
 
   def push
-    build_payload.tap do |payload|
-      push_to_users_involved_in_everything(payload)
-      push_to_users_involved_in_mentions(payload)
+    subscriptions = push_subscriptions_for_users_involved_in_everything.or(push_subscriptions_for_mentionable_users(message.mentionees))
+    if subscriptions.exists?
+      Rails.configuration.x.web_push_pool.queue(build_payload, subscriptions)
     end
   end
 
@@ -37,14 +37,6 @@ class Room::MessagePusher
       }
     end
 
-    def push_to_users_involved_in_everything(payload)
-      enqueue_payload_for_delivery payload, push_subscriptions_for_users_involved_in_everything
-    end
-
-    def push_to_users_involved_in_mentions(payload)
-      enqueue_payload_for_delivery payload, push_subscriptions_for_mentionable_users(message.mentionees)
-    end
-
     def push_subscriptions_for_users_involved_in_everything
       relevant_subscriptions.merge(Membership.involved_in_everything)
     end
@@ -59,10 +51,6 @@ class Room::MessagePusher
       Push::Subscription
         .joins(user: :memberships)
         .merge(User.active)
-        .merge(Membership.visible.disconnected.where(room: room).where.not(user: message.creator))
-    end
-
-    def enqueue_payload_for_delivery(payload, subscriptions)
-      Rails.configuration.x.web_push_pool.queue(payload, subscriptions)
+        .merge(Membership.visible.disconnected.where(room: room).where.not(user_id: message.creator_id))
     end
 end

app/views/messages/_actions.html.erb

@@ -11,8 +11,9 @@
 
     <div class="message__actions-menu border shadow" data-popup-target="menu">
       <div class="quick-boosts">
+        <% boost_path = message_boosts_path(message) %>
         <% EmojiHelper::REACTIONS.each do |character, title| %>
-          <%= form_with model: [ message, Boost.new ], data: { turbo_frame: dom_id(message, :boosting), action: "popup#close"} do |form| %>
+          <%= form_with url: boost_path, data: { turbo_frame: dom_id(message, :boosting), action: "popup#close"} do |form| %>
             <%= hidden_field_tag "boost[content]", character %>
             <%= form.button type: "submit", title: title, class: "btn message__action-btn", data: { emoji: character } do %>
               <figure class="margin-none boost-character"><%= character %></figure>