DEV: Support synchronous mode for uploads:sync_s3_acls rake task (#31091)

This commit updates the `uploads:sync_s3_acls` rake task to accept a
`sync` argument that would run the rake task in a synchronous manner
so that the outcome of running the rake task can easily be determined.

lib/tasks/uploads.rake

@@ -528,13 +528,8 @@ task "uploads:recover" => :environment do
   end
 end
 
-task "uploads:sync_s3_acls" => :environment do
-  RailsMultisite::ConnectionManagement.each_connection do |db|
-    unless Discourse.store.external?
-      puts "This task only works for external storage."
-      exit 1
-    end
-
+def sync_s3_acls(async: true, concurrency: 10)
+  if async
     puts "CAUTION: This task may take a long time to complete! There are #{Upload.count} uploads to sync ACLs for."
     puts ""
     puts "-" * 30
@@ -542,6 +537,40 @@ task "uploads:sync_s3_acls" => :environment do
     puts "Upload ACLs will be updated in Sidekiq jobs in batches of 100 at a time, check Sidekiq queues for SyncAclsForUploads for progress."
     Upload.select(:id).find_in_batches(batch_size: 100) { |uploads| adjust_acls(uploads.map(&:id)) }
     puts "", "Upload ACL sync complete!"
+  else
+    executor =
+      Concurrent::ThreadPoolExecutor.new(min_threads: 1, max_threads: concurrency, max_queue: 0)
+
+    Upload.find_in_batches(batch_size: 100) do |uploads|
+      uploads
+        .map do |upload|
+          Concurrent::Future.execute(executor:) { Discourse.store.update_upload_ACL(upload) }
+        end
+        .each(&:wait)
+    end
+
+    executor.shutdown
+    executor.wait_for_termination
+  end
+end
+
+task "uploads:sync_s3_acls", %i[synchronous parallel] => :environment do |_, args|
+  unless Discourse.store.external?
+    puts "This task only works for external storage."
+    exit 1
+  end
+
+  method = :sync_s3_acls
+
+  method_args = {
+    async: !args.key?(:synchronous) || !(args[:synchronous] == "true"),
+    concurrency: args[:parallel].to_i,
+  }
+
+  if ENV["RAILS_DB"]
+    send(method, method_args)
+  else
+    RailsMultisite::ConnectionManagement.each_connection { send(method, method_args) }
   end
 end