Allow to get job count and job IDs without cleanup (#2133)

Prior to this commit it was not possible to get a number of jobs in a
registry or list job IDs without triggering a cleanup.
Calling cleanup caused issues for:
 * Monitoring tools (see https://github.com/rq/rq/pull/2104) and
 * Cases with high number of jobs in the registries (see
   https://github.com/rq/rq/pull/2003).
 * Cases where a failure callback is registered and but the
   `get_job_ids` is called not from the main thread.

In this commit:
 1. A new `BaseRegistry.get_job_count` method is added. It is a side
    effect free version of `BaseRegistry.count` and runs in O(1).
 2. A `cleanup` parameter added to `get_job_ids` that allows to avoid
    clean up if it is set to `False`.

Resolves https://github.com/rq/rq/pull/2104.
Resolves https://github.com/rq/rq/pull/2003.

rq/registry.py

@@ -83,12 +83,24 @@ class BaseRegistry:
 
     @property
     def count(self) -> int:
-        """Returns the number of jobs in this registry
+        """Returns the number of jobs in this registry after running cleanup
 
         Returns:
             int: _description_
         """
-        self.cleanup()
+        return self.get_job_count(cleanup=True)
+
+    def get_job_count(self, cleanup=True) -> int:
+        """Returns the number of jobs in this registry after optional cleanup.
+
+        Args:
+            cleanup (bool, optional): _description_. Defaults to True.
+
+        Returns:
+            int: _description_
+        """
+        if cleanup:
+            self.cleanup()
         return self.connection.zcard(self.key)
 
     def add(self, job: 'Job', ttl=0, pipeline: Optional['Pipeline'] = None, xx: bool = False) -> int:
@@ -153,18 +165,20 @@ class BaseRegistry:
         expired_jobs = self.connection.zrangebyscore(self.key, 0, score)
         return [as_text(job_id) for job_id in expired_jobs]
 
-    def get_job_ids(self, start: int = 0, end: int = -1, desc: bool = False):
+    def get_job_ids(self, start: int = 0, end: int = -1, desc: bool = False, cleanup: bool = True) -> List[str]:
         """Returns list of all job ids.
 
         Args:
             start (int, optional): _description_. Defaults to 0.
             end (int, optional): _description_. Defaults to -1.
             desc (bool, optional): _description_. Defaults to False.
+            cleanup (bool, optional): _description_. Defaults to True.
 
         Returns:
             _type_: _description_
         """
-        self.cleanup()
+        if cleanup:
+            self.cleanup()
         return [as_text(job_id) for job_id in self.connection.zrange(self.key, start, end, desc=desc)]
 
     def get_queue(self):

tests/test_registry.py

@@ -131,10 +131,19 @@ class TestRegistry(RQTestCase):
     def test_get_job_ids(self):
         """Getting job ids from StartedJobRegistry."""
         timestamp = current_timestamp()
+        self.connection.zadd(self.registry.key, {'will-be-cleaned-up': 1})
         self.connection.zadd(self.registry.key, {'foo': timestamp + 10})
         self.connection.zadd(self.registry.key, {'bar': timestamp + 20})
         self.assertEqual(self.registry.get_job_ids(), ['foo', 'bar'])
 
+    def test_get_job_ids_does_not_cleanup(self):
+        """Getting job ids from StartedJobRegistry without a cleanup."""
+        timestamp = current_timestamp()
+        self.connection.zadd(self.registry.key, {'will-be-returned-despite-outdated': 1})
+        self.connection.zadd(self.registry.key, {'foo': timestamp + 10})
+        self.connection.zadd(self.registry.key, {'bar': timestamp + 20})
+        self.assertEqual(self.registry.get_job_ids(cleanup=False), ['will-be-returned-despite-outdated', 'foo', 'bar'])
+
     def test_get_expired_job_ids(self):
         """Getting expired job ids form StartedJobRegistry."""
         timestamp = current_timestamp()
@@ -242,15 +251,28 @@ class TestRegistry(RQTestCase):
         pipeline.execute()
         self.assertNotIn(execution.composite_key, registry.get_job_ids())
 
-    def test_get_job_count(self):
+    def test_count(self):
         """StartedJobRegistry returns the right number of job count."""
         timestamp = current_timestamp() + 10
+        self.connection.zadd(self.registry.key, {'will-be-cleaned-up': 1})
         self.connection.zadd(self.registry.key, {'foo': timestamp})
         self.connection.zadd(self.registry.key, {'bar': timestamp})
         self.assertEqual(self.registry.count, 2)
         self.assertEqual(len(self.registry), 2)
 
-        # Make sure
+    def test_get_job_count(self):
+        """Ensure cleanup is not called and does not affect the reported number of jobs.
+
+        Note, the original motivation to stop calling cleanup was to make the count operation O(1) to allow usage of
+        monitoring tools and avoid side effects of failure callbacks that cleanup triggers.
+        """
+        timestamp = current_timestamp() + 10
+        self.connection.zadd(self.registry.key, {'will-be-counted-despite-outdated': 1})
+        self.connection.zadd(self.registry.key, {'foo': timestamp})
+        self.connection.zadd(self.registry.key, {'bar': timestamp})
+        with mock.patch.object(self.registry, 'cleanup') as mock_cleanup:
+            self.assertEqual(self.registry.get_job_count(cleanup=False), 3)
+        mock_cleanup.assert_not_called()
 
     def test_clean_registries(self):
         """clean_registries() cleans Started and Finished job registries."""