FIX: Backup/Restore didn't use correct Redis namespace in multisite (#18060)

In a multisite Discourse reported that no backup is running after 60 seconds because the Redis key expired. Also, the thread that listens for a shutdown signal stopped running immediately because it didn't detect a running operation.

lib/backup_restore.rb

@@ -144,8 +144,13 @@ module BackupRestore
   end
 
   def self.keep_it_running
+    db = RailsMultisite::ConnectionManagement.current_db
+
     # extend the expiry by 1 minute every 30 seconds
     Thread.new do
+      RailsMultisite::ConnectionManagement.with_connection(db) do
+        Thread.current.name = "keep_op_running"
+
         # this thread will be killed when the fork dies
         while true
           Discourse.redis.expire(running_key, 1.minute)
@@ -153,6 +158,7 @@ module BackupRestore
         end
       end
     end
+  end
 
   def self.shutdown_signal_key
     "backup_restore_operation_should_shutdown"

lib/backup_restore/backuper.rb

@@ -98,12 +98,16 @@ module BackupRestore
       BackupRestore.clear_shutdown_signal!
 
       Thread.new do
+        Thread.current.name = "shutdown_wait"
+
+        RailsMultisite::ConnectionManagement.with_connection(@current_db) do
           while BackupRestore.is_operation_running?
             exit if BackupRestore.should_shutdown?
             sleep 0.1
           end
         end
       end
+    end
 
     def mark_backup_as_running
       log "Marking backup as running..."

lib/backup_restore/system_interface.rb

@@ -47,12 +47,16 @@ module BackupRestore
       BackupRestore.clear_shutdown_signal!
 
       Thread.new do
+        Thread.current.name = "shutdown_wait"
+
+        RailsMultisite::ConnectionManagement.with_connection(@current_db) do
           while BackupRestore.is_operation_running?
             exit if BackupRestore.should_shutdown?
             sleep 0.1
           end
         end
       end
+    end
 
     def pause_sidekiq(reason)
       return if Sidekiq.paused?

spec/lib/backup_restore/system_interface_multisite_spec.rb

@@ -36,4 +36,21 @@ RSpec.describe BackupRestore::SystemInterface, type: :multisite do
       end
     end
   end
+
+  describe "#listen_for_shutdown_signal" do
+    it "uses the correct Redis namespace" do
+      test_multisite_connection("second") do
+        BackupRestore.mark_as_running!
+
+        expect do
+          thread = subject.listen_for_shutdown_signal
+          BackupRestore.set_shutdown_signal!
+          thread.join
+        end.to raise_error(SystemExit)
+
+        BackupRestore.clear_shutdown_signal!
+        BackupRestore.mark_as_not_running!
+      end
+    end
+  end
 end