clean_worker_registry cleans in batches to prevent submitting too muc… (#1390)

* clean_worker_registry cleans in batches to prevent submitting too much data to redis at once when there are a large number of invalid keys

* Address code review comments

Rename MAX_REMOVABLE_KEYS to MAX_KEYS

* Fix tests

Co-authored-by: Joel Harris <combolations@gmail.com>

rq/utils.py

@@ -261,3 +261,16 @@ def get_version(connection):
     except ResponseError:  # fakeredis doesn't implement Redis' INFO command
         version_string = "5.0.9"
     return StrictVersion('.'.join(version_string.split('.')[:3]))
+
+
+def ceildiv(a, b):
+    """Ceiling division. Returns the ceiling of the quotient of a division operation"""
+    return -(-a // b)
+
+
+def split_list(a_list, segment_size):
+    """
+    Splits a list into multiple smaller lists having size `segment_size`
+    """
+    for i in range(0, len(a_list), segment_size):
+        yield a_list[i:i + segment_size]

rq/worker_registration.py

@@ -1,8 +1,10 @@
 from .compat import as_text
 
+from rq.utils import split_list
 
 WORKERS_BY_QUEUE_KEY = 'rq:workers:%s'
 REDIS_WORKER_KEYS = 'rq:workers'
+MAX_KEYS = 1000
 
 
 def register(worker, pipeline=None):
@@ -62,6 +64,7 @@ def clean_worker_registry(queue):
                 invalid_keys.append(keys[i])
 
         if invalid_keys:
-            pipeline.srem(WORKERS_BY_QUEUE_KEY % queue.name, *invalid_keys)
-            pipeline.srem(REDIS_WORKER_KEYS, *invalid_keys)
-            pipeline.execute()
+            for invalid_subset in split_list(invalid_keys, MAX_KEYS):
+                pipeline.srem(WORKERS_BY_QUEUE_KEY % queue.name, *invalid_subset)
+                pipeline.srem(REDIS_WORKER_KEYS, *invalid_subset)
+                pipeline.execute()

tests/test_utils.py

@@ -10,7 +10,8 @@ from distutils.version import StrictVersion
 from redis import Redis
 
 from tests import RQTestCase, fixtures
-from rq.utils import backend_class, ensure_list, first, get_version, is_nonstring_iterable, parse_timeout, utcparse
+from rq.utils import backend_class, ensure_list, first, get_version, is_nonstring_iterable, parse_timeout, utcparse, \
+    split_list, ceildiv
 from rq.exceptions import TimeoutFormatError
 
 
@@ -88,4 +89,27 @@ class TestUtils(RQTestCase):
         class DummyRedis(Redis):
             def info(*args):
                 return {'redis_version': '3.0.7.9'}
-        self.assertEqual(get_version(DummyRedis()), StrictVersion('3.0.7'))
+        self.assertEqual(get_version(DummyRedis()), StrictVersion('3.0.7'))
+
+    def test_ceildiv_even(self):
+        """When a number is evenly divisible by another ceildiv returns the quotient"""
+        dividend = 12
+        divisor = 4
+        self.assertEqual(ceildiv(dividend, divisor), dividend // divisor)
+
+    def test_ceildiv_uneven(self):
+        """When a number is not evenly divisible by another ceildiv returns the quotient plus one"""
+        dividend = 13
+        divisor = 4
+        self.assertEqual(ceildiv(dividend, divisor), dividend // divisor + 1)
+
+    def test_split_list(self):
+        """Ensure split_list works properly"""
+        BIG_LIST_SIZE = 42
+        SEGMENT_SIZE = 5
+
+        big_list = ['1'] * BIG_LIST_SIZE
+        small_lists = list(split_list(big_list, SEGMENT_SIZE))
+
+        expected_small_list_count = ceildiv(BIG_LIST_SIZE, SEGMENT_SIZE)
+        self.assertEqual(len(small_lists), expected_small_list_count)

tests/test_worker_registration.py

@@ -1,4 +1,6 @@
+from rq.utils import ceildiv
 from tests import RQTestCase
+from mock.mock import patch
 
 from rq import Queue, Worker
 from rq.worker_registration import (clean_worker_registry, get_keys, register,
@@ -87,3 +89,30 @@ class TestWorkerRegistry(RQTestCase):
         clean_worker_registry(queue)
         self.assertFalse(redis.sismember(worker.redis_workers_keys, worker.key))
         self.assertFalse(redis.sismember(REDIS_WORKER_KEYS, worker.key))
+
+    def test_clean_large_registry(self):
+        """
+        clean_registry() splits invalid_keys into multiple lists for set removal to avoid sending more than redis can
+        receive
+        """
+        MAX_WORKERS = 41
+        MAX_KEYS = 37
+        # srem is called twice per invalid key batch: once for WORKERS_BY_QUEUE_KEY; once for REDIS_WORKER_KEYS
+        SREM_CALL_COUNT = 2
+
+        queue = Queue(name='foo')
+        for i in range(MAX_WORKERS):
+            worker = Worker([queue])
+            register(worker)
+
+        with patch('rq.worker_registration.MAX_KEYS', MAX_KEYS), \
+             patch.object(queue.connection, 'pipeline', wraps=queue.connection.pipeline) as pipeline_mock:
+            # clean_worker_registry creates a pipeline with a context manager. Configure the mock using the context
+            # manager entry method __enter__
+            pipeline_mock.return_value.__enter__.return_value.srem.return_value = None
+            pipeline_mock.return_value.__enter__.return_value.execute.return_value = [0] * MAX_WORKERS
+
+            clean_worker_registry(queue)
+
+            expected_call_count = (ceildiv(MAX_WORKERS, MAX_KEYS)) * SREM_CALL_COUNT
+            self.assertEqual(pipeline_mock.return_value.__enter__.return_value.srem.call_count, expected_call_count)