Fix performance of home feed regeneration (#12084)

Fetching statuses from all followed accounts at once takes too long
within Postgres. Fetching them one by one and merging in Ruby
could be a lot less resource-intensive

Because the query for dynamically fetching the home timeline is so
heavy, we can no longer offer it when the home timeline is missing

app/controllers/api/v1/timelines/home_controller.rb

@@ -13,7 +13,7 @@ class Api::V1::Timelines::HomeController < Api::BaseController
     render json: @statuses,
            each_serializer: REST::StatusSerializer,
            relationships: StatusRelationshipsPresenter.new(@statuses, current_user&.account_id),
-           status: regeneration_in_progress? ? 206 : 200
+           status: account_home_feed.regenerating? ? 206 : 200
   end
 
   private
@@ -62,8 +62,4 @@ class Api::V1::Timelines::HomeController < Api::BaseController
   def pagination_since_id
     @statuses.first.id
   end
-
-  def regeneration_in_progress?
-    Redis.current.exists("account:#{current_account.id}:regeneration")
-  end
 end

app/javascript/mastodon/actions/timelines.js

@@ -97,7 +97,7 @@ export function expandTimeline(timelineId, path, params = {}, done = noOp) {
     api(getState).get(path, { params }).then(response => {
       const next = getLinks(response).refs.find(link => link.rel === 'next');
       dispatch(importFetchedStatuses(response.data));
-      dispatch(expandTimelineSuccess(timelineId, response.data, next ? next.uri : null, response.code === 206, isLoadingRecent, isLoadingMore, isLoadingRecent && preferPendingItems));
+      dispatch(expandTimelineSuccess(timelineId, response.data, next ? next.uri : null, response.status === 206, isLoadingRecent, isLoadingMore, isLoadingRecent && preferPendingItems));
       done();
     }).catch(error => {
       dispatch(expandTimelineFail(timelineId, error, isLoadingMore));

app/javascript/mastodon/components/missing_indicator.js

@@ -1,17 +1,24 @@
 import React from 'react';
+import PropTypes from 'prop-types';
 import { FormattedMessage } from 'react-intl';
+import illustration from 'mastodon/../images/elephant_ui_disappointed.svg';
+import classNames from 'classnames';
 
-const MissingIndicator = () => (
-  <div className='regeneration-indicator missing-indicator'>
-    <div>
-      <div className='regeneration-indicator__figure' />
+const MissingIndicator = ({ fullPage }) => (
+  <div className={classNames('regeneration-indicator', { 'regeneration-indicator--without-header': fullPage })}>
+    <div className='regeneration-indicator__figure'>
+      <img src={illustration} alt='' />
+    </div>
 
-      <div className='regeneration-indicator__label'>
-        <FormattedMessage id='missing_indicator.label' tagName='strong' defaultMessage='Not found' />
-        <FormattedMessage id='missing_indicator.sublabel' defaultMessage='This resource could not be found' />
-      </div>
+    <div className='regeneration-indicator__label'>
+      <FormattedMessage id='missing_indicator.label' tagName='strong' defaultMessage='Not found' />
+      <FormattedMessage id='missing_indicator.sublabel' defaultMessage='This resource could not be found' />
     </div>
   </div>
 );
 
+MissingIndicator.propTypes = {
+  fullPage: PropTypes.bool,
+};
+
 export default MissingIndicator;

app/javascript/mastodon/components/regeneration_indicator.js

@@ -0,0 +1,18 @@
+import React from 'react';
+import { FormattedMessage } from 'react-intl';
+import illustration from 'mastodon/../images/elephant_ui_working.svg';
+
+const MissingIndicator = () => (
+  <div className='regeneration-indicator'>
+    <div className='regeneration-indicator__figure'>
+      <img src={illustration} alt='' />
+    </div>
+
+    <div className='regeneration-indicator__label'>
+      <FormattedMessage id='regeneration_indicator.label' tagName='strong' defaultMessage='Loading&hellip;' />
+      <FormattedMessage id='regeneration_indicator.sublabel' defaultMessage='Your home feed is being prepared!' />
+    </div>
+  </div>
+);
+
+export default MissingIndicator;

app/javascript/mastodon/components/status_list.js

@@ -1,12 +1,12 @@
 import { debounce } from 'lodash';
 import React from 'react';
-import { FormattedMessage } from 'react-intl';
 import ImmutablePropTypes from 'react-immutable-proptypes';
 import PropTypes from 'prop-types';
 import StatusContainer from '../containers/status_container';
 import ImmutablePureComponent from 'react-immutable-pure-component';
 import LoadGap from './load_gap';
 import ScrollableList from './scrollable_list';
+import RegenerationIndicator from 'mastodon/components/regeneration_indicator';
 
 export default class StatusList extends ImmutablePureComponent {
 
@@ -81,18 +81,7 @@ export default class StatusList extends ImmutablePureComponent {
     const { isLoading, isPartial } = other;
 
     if (isPartial) {
-      return (
-        <div className='regeneration-indicator'>
-          <div>
-            <div className='regeneration-indicator__figure' />
-
-            <div className='regeneration-indicator__label'>
-              <FormattedMessage id='regeneration_indicator.label' tagName='strong' defaultMessage='Loading&hellip;' />
-              <FormattedMessage id='regeneration_indicator.sublabel' defaultMessage='Your home feed is being prepared!' />
-            </div>
-          </div>
-        </div>
-      );
+      return <RegenerationIndicator />;
     }
 
     let scrollableContent = (isLoading || statusIds.size > 0) ? (

app/javascript/mastodon/features/generic_not_found/index.js

@@ -4,7 +4,7 @@ import MissingIndicator from '../../components/missing_indicator';
 
 const GenericNotFound = () => (
   <Column>
-    <MissingIndicator />
+    <MissingIndicator fullPage />
   </Column>
 );
 

app/javascript/styles/mastodon/components.scss

@@ -3127,37 +3127,27 @@ a.status-card.compact:hover {
   cursor: default;
   display: flex;
   flex: 1 1 auto;
+  flex-direction: column;
   align-items: center;
   justify-content: center;
   padding: 20px;
 
-  & > div {
-    width: 100%;
-    background: transparent;
-    padding-top: 0;
-  }
-
   &__figure {
-    background: url('../images/elephant_ui_working.svg') no-repeat center 0;
-    width: 100%;
-    height: 160px;
-    background-size: contain;
-    position: absolute;
-    top: 50%;
-    left: 50%;
-    transform: translate(-50%, -50%);
+    &,
+    img {
+      display: block;
+      width: auto;
+      height: 160px;
+      margin: 0;
+    }
   }
 
-  &.missing-indicator {
+  &--without-header {
     padding-top: 20px + 48px;
-
-    .regeneration-indicator__figure {
-      background-image: url('../images/elephant_ui_disappointed.svg');
-    }
   }
 
   &__label {
-    margin-top: 200px;
+    margin-top: 30px;
 
     strong {
       display: block;

app/javascript/styles/mastodon/introduction.scss

@@ -3,9 +3,10 @@
   flex-direction: column;
   justify-content: center;
   align-items: center;
+  height: 100vh;
+  background: $ui-base-color;
 
   @media screen and (max-width: 920px) {
-    background: darken($ui-base-color, 8%);
     display: block !important;
   }
 

app/lib/feed_manager.rb

@@ -19,7 +19,7 @@ class FeedManager
 
   def filter?(timeline_type, status, receiver_id)
     if timeline_type == :home
-      filter_from_home?(status, receiver_id)
+      filter_from_home?(status, receiver_id, build_crutches(receiver_id, [status]))
     elsif timeline_type == :mentions
       filter_from_mentions?(status, receiver_id)
     else
@@ -29,6 +29,7 @@ class FeedManager
 
   def push_to_home(account, status)
     return false unless add_to_feed(:home, account.id, status, account.user&.aggregates_reblogs?)
+
     trim(:home, account.id)
     PushUpdateWorker.perform_async(account.id, status.id, "timeline:#{account.id}") if push_update_required?("timeline:#{account.id}")
     true
@@ -36,6 +37,7 @@ class FeedManager
 
   def unpush_from_home(account, status)
     return false unless remove_from_feed(:home, account.id, status, account.user&.aggregates_reblogs?)
+
     redis.publish("timeline:#{account.id}", Oj.dump(event: :delete, payload: status.id.to_s))
     true
   end
@@ -46,7 +48,9 @@ class FeedManager
       should_filter &&= !ListAccount.where(list_id: list.id, account_id: status.in_reply_to_account_id).exists?
       return false if should_filter
     end
+
     return false unless add_to_feed(:list, list.id, status, list.account.user&.aggregates_reblogs?)
+
     trim(:list, list.id)
     PushUpdateWorker.perform_async(list.account_id, status.id, "timeline:list:#{list.id}") if push_update_required?("timeline:list:#{list.id}")
     true
@@ -54,6 +58,7 @@ class FeedManager
 
   def unpush_from_list(list, status)
     return false unless remove_from_feed(:list, list.id, status, list.account.user&.aggregates_reblogs?)
+
     redis.publish("timeline:list:#{list.id}", Oj.dump(event: :delete, payload: status.id.to_s))
     true
   end
@@ -85,16 +90,21 @@ class FeedManager
 
   def merge_into_timeline(from_account, into_account)
     timeline_key = key(:home, into_account.id)
-    query        = from_account.statuses.limit(FeedManager::MAX_ITEMS / 4)
+    aggregate    = into_account.user&.aggregates_reblogs?
+    query        = from_account.statuses.where(visibility: [:public, :unlisted, :private]).includes(:preloadable_poll, reblog: :account).limit(FeedManager::MAX_ITEMS / 4)
 
     if redis.zcard(timeline_key) >= FeedManager::MAX_ITEMS / 4
-      oldest_home_score = redis.zrange(timeline_key, 0, 0, with_scores: true)&.first&.last&.to_i || 0
+      oldest_home_score = redis.zrange(timeline_key, 0, 0, with_scores: true).first.last.to_i
       query = query.where('id > ?', oldest_home_score)
     end
 
-    query.each do |status|
-      next if status.direct_visibility? || status.limited_visibility? || filter?(:home, status, into_account)
-      add_to_feed(:home, into_account.id, status, into_account.user&.aggregates_reblogs?)
+    statuses = query.to_a
+    crutches = build_crutches(into_account.id, statuses)
+
+    statuses.each do |status|
+      next if filter_from_home?(status, into_account, crutches)
+
+      add_to_feed(:home, into_account.id, status, aggregate)
     end
 
     trim(:home, into_account.id)
@@ -120,24 +130,35 @@ class FeedManager
   end
 
   def populate_feed(account)
-    added  = 0
-    limit  = FeedManager::MAX_ITEMS / 2
-    max_id = nil
+    limit        = FeedManager::MAX_ITEMS / 2
+    aggregate    = account.user&.aggregates_reblogs?
+    timeline_key = key(:home, account.id)
 
-    loop do
-      statuses = Status.as_home_timeline(account)
-                       .paginate_by_max_id(limit, max_id)
+    account.statuses.where.not(visibility: :direct).limit(limit).each do |status|
+      add_to_feed(:home, account.id, status, aggregate)
+    end
 
-      break if statuses.empty?
+    account.following.includes(:account_stat).find_each do |target_account|
+      if redis.zcard(timeline_key) >= limit
+        oldest_home_score = redis.zrange(timeline_key, 0, 0, with_scores: true).first.last.to_i
+        last_status_score = Mastodon::Snowflake.id_at(account.last_status_at)
 
-      statuses.each do |status|
-        next if filter_from_home?(status, account)
-        added += 1 if add_to_feed(:home, account.id, status, account.user&.aggregates_reblogs?)
+        # If the feed is full and this account has not posted more recently
+        # than the last item on the feed, then we can skip the whole account
+        # because none of its statuses would stay on the feed anyway
+        next if last_status_score < oldest_home_score
       end
 
-      break unless added.zero?
+      statuses = target_account.statuses.where(visibility: [:public, :unlisted, :private]).includes(:preloadable_poll, reblog: :account).limit(limit)
+      crutches = build_crutches(account.id, statuses)
+
+      statuses.each do |status|
+        next if filter_from_home?(status, account, crutches)
+
+        add_to_feed(:home, account.id, status, aggregate)
+      end
 
-      max_id = statuses.last.id
+      trim(:home, account.id)
     end
   end
 
@@ -152,31 +173,33 @@ class FeedManager
       (context == :home ? Mute.where(account_id: receiver_id, target_account_id: account_ids).any? : Mute.where(account_id: receiver_id, target_account_id: account_ids, hide_notifications: true).any?)
   end
 
-  def filter_from_home?(status, receiver_id)
+  def filter_from_home?(status, receiver_id, crutches)
     return false if receiver_id == status.account_id
     return true  if status.reply? && (status.in_reply_to_id.nil? || status.in_reply_to_account_id.nil?)
     return true  if phrase_filtered?(status, receiver_id, :home)
 
-    check_for_blocks = status.active_mentions.pluck(:account_id)
+    check_for_blocks = crutches[:active_mentions][status.id] || []
     check_for_blocks.concat([status.account_id])
 
     if status.reblog?
       check_for_blocks.concat([status.reblog.account_id])
-      check_for_blocks.concat(status.reblog.active_mentions.pluck(:account_id))
+      check_for_blocks.concat(crutches[:active_mentions][status.reblog_of_id] || [])
     end
 
-    return true if blocks_or_mutes?(receiver_id, check_for_blocks, :home)
+    return true if check_for_blocks.any? { |target_account_id| crutches[:blocking][target_account_id] || crutches[:muting][target_account_id] }
 
     if status.reply? && !status.in_reply_to_account_id.nil?                                                                      # Filter out if it's a reply
-      should_filter   = !Follow.where(account_id: receiver_id, target_account_id: status.in_reply_to_account_id).exists?         # and I'm not following the person it's a reply to
+      should_filter   = !crutches[:following][status.in_reply_to_account_id]                                                     # and I'm not following the person it's a reply to
       should_filter &&= receiver_id != status.in_reply_to_account_id                                                             # and it's not a reply to me
       should_filter &&= status.account_id != status.in_reply_to_account_id                                                       # and it's not a self-reply
-      return should_filter
+
+      return !!should_filter
     elsif status.reblog?                                                                                                         # Filter out a reblog
-      should_filter   = Follow.where(account_id: receiver_id, target_account_id: status.account_id, show_reblogs: false).exists? # if the reblogger's reblogs are suppressed
-      should_filter ||= Block.where(account_id: status.reblog.account_id, target_account_id: receiver_id).exists?                # or if the author of the reblogged status is blocking me
-      should_filter ||= AccountDomainBlock.where(account_id: receiver_id, domain: status.reblog.account.domain).exists?          # or the author's domain is blocked
-      return should_filter
+      should_filter   = crutches[:hiding_reblogs][status.account_id]                                                             # if the reblogger's reblogs are suppressed
+      should_filter ||= crutches[:blocked_by][status.reblog.account_id]                                                          # or if the author of the reblogged status is blocking me
+      should_filter ||= crutches[:domain_blocking][status.reblog.account.domain]                                                 # or the author's domain is blocked
+
+      return !!should_filter
     end
 
     false
@@ -308,4 +331,31 @@ class FeedManager
 
     redis.zrem(timeline_key, status.id)
   end
+
+  def build_crutches(receiver_id, statuses)
+    crutches = {}
+
+    crutches[:active_mentions] = Mention.active.where(status_id: statuses.flat_map { |s| [s.id, s.reblog_of_id] }.compact).pluck(:status_id, :account_id).each_with_object({}) { |(id, account_id), mapping| (mapping[id] ||= []).push(account_id) }
+
+    check_for_blocks = statuses.flat_map do |s|
+      arr = crutches[:active_mentions][s.id] || []
+      arr.concat([s.account_id])
+
+      if s.reblog?
+        arr.concat([s.reblog.account_id])
+        arr.concat(crutches[:active_mentions][s.reblog_of_id] || [])
+      end
+
+      arr
+    end
+
+    crutches[:following]       = Follow.where(account_id: receiver_id, target_account_id: statuses.map(&:in_reply_to_account_id).compact).pluck(:target_account_id).each_with_object({}) { |id, mapping| mapping[id] = true }
+    crutches[:hiding_reblogs]  = Follow.where(account_id: receiver_id, target_account_id: statuses.map { |s| s.account_id if s.reblog? }.compact, show_reblogs: false).pluck(:target_account_id).each_with_object({}) { |id, mapping| mapping[id] = true }
+    crutches[:blocking]        = Block.where(account_id: receiver_id, target_account_id: check_for_blocks).pluck(:target_account_id).each_with_object({}) { |id, mapping| mapping[id] = true }
+    crutches[:muting]          = Mute.where(account_id: receiver_id, target_account_id: check_for_blocks).pluck(:target_account_id).each_with_object({}) { |id, mapping| mapping[id] = true }
+    crutches[:domain_blocking] = AccountDomainBlock.where(account_id: receiver_id, domain: statuses.map { |s| s.reblog&.account&.domain }.compact).pluck(:domain).each_with_object({}) { |domain, mapping| mapping[domain] = true }
+    crutches[:blocked_by]      = Block.where(target_account_id: receiver_id, account_id: statuses.map { |s| s.reblog&.account_id }.compact).pluck(:account_id).each_with_object({}) { |id, mapping| mapping[id] = true }
+
+    crutches
+  end
 end

app/models/home_feed.rb

@@ -7,19 +7,7 @@ class HomeFeed < Feed
     @account = account
   end
 
-  def get(limit, max_id = nil, since_id = nil, min_id = nil)
-    if redis.exists("account:#{@account.id}:regeneration")
-      from_database(limit, max_id, since_id, min_id)
-    else
-      super
-    end
-  end
-
-  private
-
-  def from_database(limit, max_id, since_id, min_id)
-    Status.as_home_timeline(@account)
-          .paginate_by_id(limit, max_id: max_id, since_id: since_id, min_id: min_id)
-          .reject { |status| FeedManager.instance.filter?(:home, status, @account.id) }
+  def regenerating?
+    redis.exists("account:#{@id}:regeneration")
   end
 end

app/models/status.rb

@@ -282,10 +282,6 @@ class Status < ApplicationRecord
       where(language: nil).or where(language: account.chosen_languages)
     end
 
-    def as_home_timeline(account)
-      where(account: [account] + account.following).where(visibility: [:public, :unlisted, :private])
-    end
-
     def as_public_timeline(account = nil, local_only = false)
       query = timeline_scope(local_only).without_replies
 

spec/models/home_feed_spec.rb

@@ -34,11 +34,10 @@ RSpec.describe HomeFeed, type: :model do
         Redis.current.set("account:#{account.id}:regeneration", true)
       end
 
-      it 'gets statuses with ids in the range from database' do
+      it 'returns nothing' do
         results = subject.get(3)
 
-        expect(results.map(&:id)).to eq [10, 3, 2]
-        expect(results.first.attributes.keys).to include('id', 'updated_at')
+        expect(results.map(&:id)).to eq []
       end
     end
   end

spec/models/status_spec.rb

@@ -296,49 +296,6 @@ RSpec.describe Status, type: :model do
     end
   end
 
-  describe '.as_home_timeline' do
-    let(:account) { Fabricate(:account) }
-    let(:followed) { Fabricate(:account) }
-    let(:not_followed) { Fabricate(:account) }
-
-    before do
-      Fabricate(:follow, account: account, target_account: followed)
-
-      @self_status = Fabricate(:status, account: account, visibility: :public)
-      @self_direct_status = Fabricate(:status, account: account, visibility: :direct)
-      @followed_status = Fabricate(:status, account: followed, visibility: :public)
-      @followed_direct_status = Fabricate(:status, account: followed, visibility: :direct)
-      @not_followed_status = Fabricate(:status, account: not_followed, visibility: :public)
-
-      @results = Status.as_home_timeline(account)
-    end
-
-    it 'includes statuses from self' do
-      expect(@results).to include(@self_status)
-    end
-
-    it 'does not include direct statuses from self' do
-      expect(@results).to_not include(@self_direct_status)
-    end
-
-    it 'includes statuses from followed' do
-      expect(@results).to include(@followed_status)
-    end
-
-    it 'does not include direct statuses mentioning recipient from followed' do
-      Fabricate(:mention, account: account, status: @followed_direct_status)
-      expect(@results).to_not include(@followed_direct_status)
-    end
-
-    it 'does not include direct statuses not mentioning recipient from followed' do
-      expect(@results).not_to include(@followed_direct_status)
-    end
-
-    it 'does not include statuses from non-followed' do
-      expect(@results).not_to include(@not_followed_status)
-    end
-  end
-
   describe '.as_public_timeline' do
     it 'only includes statuses with public visibility' do
       public_status = Fabricate(:status, visibility: :public)