Stop runnable processes when registered process record disappears

If, for some reason, the process failed a heartbeat and the supervisor
pruned it, we shouldn't continue running. Just stop as if we had
received a signal.

This could be used in the future from Mission Control to stop a worker.

lib/solid_queue/processes/registrable.rb

@@ -29,11 +29,11 @@ def register
       end
 
       def deregister
-        process.deregister if registered?
+        process&.deregister
       end
 
       def registered?
-        process&.persisted?
+        process.present?
       end
 
       def launch_heartbeat
@@ -53,7 +53,10 @@ def stop_heartbeat
       end
 
       def heartbeat
-        process.heartbeat
+        process.reload.heartbeat
+      rescue ActiveRecord::RecordNotFound
+        self.process = nil
+        wake_up
       end
   end
 end

lib/solid_queue/processes/runnable.rb

@@ -39,8 +39,12 @@ def boot
         end
       end
 
+      def run
+        raise NotImplementedError
+      end
+
       def shutting_down?
-        stopped? || (running_as_fork? && supervisor_went_away?) || finished?
+        stopped? || (running_as_fork? && supervisor_went_away?) || finished? || !registered?
       end
 
       def run

test/unit/worker_test.rb

@@ -133,6 +133,27 @@ class WorkerTest < ActiveSupport::TestCase
     assert_equal 5, JobResult.where(queue_name: :background, status: "completed", value: :immediate).count
   end
 
+  test "terminate on heartbeat when unregistered" do
+    old_heartbeat_interval, SolidQueue.process_heartbeat_interval = SolidQueue.process_heartbeat_interval, 1.second
+
+    @worker.start
+    wait_for_registered_processes(1, timeout: 1.second)
+
+    assert_not @worker.pool.shutdown?
+
+    process = SolidQueue::Process.first
+    assert_equal "Worker", process.kind
+
+    process.deregister
+
+    # And now just wait until the worker tries to heartbeat and realises
+    # it needs to stop
+    wait_while_with_timeout(2) { !@worker.pool.shutdown? }
+    assert @worker.pool.shutdown?
+  ensure
+    SolidQueue.process_heartbeat_interval = old_heartbeat_interval
+  end
+
   private
     def with_polling(silence:)
       old_silence_polling, SolidQueue.silence_polling = SolidQueue.silence_polling, silence