refactor: simplify lock processing in worker trigger

src/ahriman/core/distributed/worker_trigger.py

@@ -17,7 +17,6 @@
 # You should have received a copy of the GNU General Public License
 # along with this program. If not, see <http://www.gnu.org/licenses/>.
 #
-from collections import deque
 from threading import Lock, Timer
 
 from ahriman.core.configuration import Configuration
@@ -47,15 +46,14 @@ class WorkerTrigger(DistributedSystem):
         self.ping_interval = configuration.getint(section, "time_to_live", fallback=60) / 4.0
 
         self._lock = Lock()
-        self._timers: deque[Timer] = deque()  # because python doesn't have atomics
+        self._timer: Timer | None = None
 
     def create_timer(self) -> None:
         """
         create timer object and put it to queue
         """
-        timer = Timer(self.ping_interval, self.ping)
-        timer.start()
-        self._timers.append(timer)
+        self._timer = Timer(self.ping_interval, self.ping)
+        self._timer.start()
 
     def on_start(self) -> None:
         """
@@ -71,21 +69,19 @@ class WorkerTrigger(DistributedSystem):
         """
         self.logger.info("removing instance %s in %s", self.worker, self.address)
         with self._lock:
-            current_timers = self._timers.copy()  # will be used later
-            self._timers.clear()  # clear timer list
+            if self._timer is None:
+                return
 
-        for timer in current_timers:
-            timer.cancel()  # cancel remaining timers
+            self._timer.cancel()  # cancel remaining timers
+            self._timer = None  # reset state
 
     def ping(self) -> None:
         """
         register itself as alive worker and update the timer
         """
         with self._lock:
-            if not self._timers:  # make sure that there is related specific timer
+            if self._timer is None:  # no active timer set, exit loop
                 return
 
-            self._timers.popleft()  # pop first timer
-
             self.register()
             self.create_timer()

tests/ahriman/core/distributed/test_worker_trigger.py

@@ -1,8 +1,6 @@
+from pytest_mock import MockerFixture
 from threading import Timer
 
-from pytest_mock import MockerFixture
-
-from ahriman.core.configuration import Configuration
 from ahriman.core.distributed import WorkerTrigger
 
 
@@ -11,10 +9,8 @@ def test_create_timer(worker_trigger: WorkerTrigger) -> None:
     must create a timer and put it to queue
     """
     worker_trigger.create_timer()
-
-    timer = worker_trigger._timers.popleft()
-    assert timer.function == worker_trigger.ping
-    timer.cancel()
+    assert worker_trigger._timer.function == worker_trigger.ping
+    worker_trigger._timer.cancel()
 
 
 def test_on_start(worker_trigger: WorkerTrigger, mocker: MockerFixture) -> None:
@@ -31,7 +27,7 @@ def test_on_stop(worker_trigger: WorkerTrigger, mocker: MockerFixture) -> None:
     must unregister itself as worker
     """
     run_mock = mocker.patch("threading.Timer.cancel")
-    worker_trigger._timers.append(Timer(1, print))  # doesn't matter
+    worker_trigger._timer = Timer(1, print)  # doesn't matter
 
     worker_trigger.on_stop()
     run_mock.assert_called_once_with()
@@ -50,7 +46,7 @@ def test_ping(worker_trigger: WorkerTrigger, mocker: MockerFixture) -> None:
     """
     run_mock = mocker.patch("ahriman.core.distributed.WorkerTrigger.register")
     timer_mock = mocker.patch("threading.Timer.start")
-    worker_trigger._timers.append(Timer(1, print))  # doesn't matter
+    worker_trigger._timer = Timer(1, print)  # doesn't matter
 
     worker_trigger.ping()
     run_mock.assert_called_once_with()