3 files changed, 25 insertions, 1 deletions
diff --git a/app/workers/activitypub/delivery_worker.rb b/app/workers/activitypub/delivery_worker.rb
index 60775787a..6c5a576a7 100644
--- a/app/workers/activitypub/delivery_worker.rb
+++ b/app/workers/activitypub/delivery_worker.rb
@@ -2,6 +2,7 @@
 
 class ActivityPub::DeliveryWorker
   include Sidekiq::Worker
+  include RoutingHelper
   include JsonLdHelper
 
   STOPLIGHT_FAILURE_THRESHOLD = 10
@@ -38,9 +39,18 @@ class ActivityPub::DeliveryWorker
     Request.new(:post, @inbox_url, body: @json, http_client: http_client).tap do |request|
       request.on_behalf_of(@source_account, :uri, sign_with: @options[:sign_with])
       request.add_headers(HEADERS)
+      request.add_headers({ 'Collection-Synchronization' => synchronization_header }) if ENV['DISABLE_FOLLOWERS_SYNCHRONIZATION'] != 'true' && @options[:synchronize_followers]
     end
   end
 
+  def synchronization_header
+    "collectionId=\"#{account_followers_url(@source_account)}\", digest=\"#{@source_account.remote_followers_hash(inbox_url_prefix)}\", url=\"#{account_followers_synchronization_url(@source_account)}\""
+  end
+
+  def inbox_url_prefix
+    @inbox_url[/http(s?):\/\/[^\/]+\//]
+  end
+
   def perform_request
     light = Stoplight(@inbox_url) do
       request_pool.with(@host) do |http_client|
diff --git a/app/workers/activitypub/distribution_worker.rb b/app/workers/activitypub/distribution_worker.rb
index e4997ba0e..9b4814644 100644
--- a/app/workers/activitypub/distribution_worker.rb
+++ b/app/workers/activitypub/distribution_worker.rb
@@ -13,7 +13,7 @@ class ActivityPub::DistributionWorker
     return if skip_distribution?
 
     ActivityPub::DeliveryWorker.push_bulk(inboxes) do |inbox_url|
-      [payload, @account.id, inbox_url]
+      [payload, @account.id, inbox_url, { synchronize_followers: !@status.distributable? }]
     end
 
     relay! if relayable?
diff --git a/app/workers/activitypub/followers_synchronization_worker.rb b/app/workers/activitypub/followers_synchronization_worker.rb
new file mode 100644
index 000000000..35a3ef0b9
--- /dev/null
+++ b/app/workers/activitypub/followers_synchronization_worker.rb
@@ -0,0 +1,14 @@
+# frozen_string_literal: true
+
+class ActivityPub::FollowersSynchronizationWorker
+  include Sidekiq::Worker
+
+  sidekiq_options queue: 'push', lock: :until_executed
+
+  def perform(account_id, url)
+    @account = Account.find_by(id: account_id)
+    return true if @account.nil?
+
+    ActivityPub::SynchronizeFollowersService.new.call(@account, url)
+  end
+end