Added dynamic_startup_nodes configuration to RedisCluster.

CHANGES

@@ -11,9 +11,9 @@
     * Fix broken connection writer lock-up for asyncio (#2065)
     * Fix auth bug when provided with no username (#2086)
     * Fix missing ClusterPipeline._lock (#2189)
+    * Added dynaminc_startup_nodes configuration to RedisCluster
     * Fix reusing the old nodes' connections when cluster topology refresh is being done
     * Fix RedisCluster to immediately raise AuthenticationError without a retry
-
 * 4.1.3 (Feb 8, 2022)
     * Fix flushdb and flushall (#1926)
     * Add redis5 and redis4 dockers (#1871)

README.md

@@ -1006,6 +1006,7 @@ a slots cache which maps each of the 16384 slots to the node/s handling them,
 a nodes cache that contains ClusterNode objects (name, host, port, redis connection)
 for all of the cluster's nodes, and a commands cache contains all the server
 supported commands that were retrieved using the Redis 'COMMAND' output.
+See *RedisCluster specific options* below for more.
 
 RedisCluster instance can be directly used to execute Redis commands. When a
 command is being executed through the cluster instance, the target node(s) will
@@ -1245,6 +1246,55 @@ The following commands are not supported:
 
 Using scripting within pipelines in cluster mode is **not supported**.
 
+
+**RedisCluster specific options**
+
+ require_full_coverage: (default=False)
+
+    When set to False (default value): the client will not require a
+    full coverage of the slots. However, if not all slots are covered,
+    and at least one node has 'cluster-require-full-coverage' set to
+    'yes,' the server will throw a ClusterDownError for some key-based
+    commands. See -
+    https://redis.io/topics/cluster-tutorial#redis-cluster-configuration-parameters
+    When set to True: all slots must be covered to construct the
+    cluster client. If not all slots are covered, RedisClusterException
+    will be thrown.
+
+ read_from_replicas: (default=False)
+
+     Enable read from replicas in READONLY mode. You can read possibly
+     stale data.
+     When set to true, read commands will be assigned between the
+     primary and its replications in a Round-Robin manner.
+
+ dynamic_startup_nodes: (default=False)
+
+     Set the RedisCluster's startup nodes to all of the discovered nodes.
+     If true, the cluster's discovered nodes will be used to determine the
+     cluster nodes-slots mapping in the next topology refresh.
+     It will remove the initial passed startup nodes if their endpoints aren't
+     listed in the CLUSTER SLOTS output.
+     If you use dynamic DNS endpoints for startup nodes but CLUSTER SLOTS lists
+     specific IP addresses, keep it at false.
+
+ cluster_error_retry_attempts: (default=3)
+
+     Retry command execution attempts when encountering ClusterDownError
+     or ConnectionError
+
+ reinitialize_steps: (default=10)
+
+    Specifies the number of MOVED errors that need to occur before
+    reinitializing the whole cluster topology. If a MOVED error occurs
+    and the cluster does not need to be reinitialized on this current
+    error handling, only the MOVED slot will be patched with the
+    redirected node.
+    To reinitialize the cluster on every MOVED error, set
+    reinitialize_steps to 1.
+    To avoid reinitializing the cluster on moved errors, set
+    reinitialize_steps to 0.
+
 ### Author
 
 redis-py is developed and maintained by [Redis Inc](https://redis.com). It can be found [here](

redis/cluster.py

@@ -482,6 +482,7 @@ def __init__(
         require_full_coverage=False,
         reinitialize_steps=10,
         read_from_replicas=False,
+        dynamic_startup_nodes=False,
         url=None,
         **kwargs,
     ):
@@ -509,6 +510,14 @@ def __init__(
              stale data.
              When set to true, read commands will be assigned between the
              primary and its replications in a Round-Robin manner.
+         :dynamic_startup_nodes: 'bool'
+             Set the RedisCluster's startup nodes to all of the discovered nodes.
+             If true, the cluster's discovered nodes will be used to determine the
+             cluster nodes-slots mapping in the next topology refresh.
+             It will remove the initial passed startup nodes if their endpoints aren't
+             listed in the CLUSTER SLOTS output.
+             If you use dynamic DNS endpoints for startup nodes but CLUSTER SLOTS lists
+             specific IP addresses, keep it at false.
         :cluster_error_retry_attempts: 'int'
              Retry command execution attempts when encountering ClusterDownError
              or ConnectionError
@@ -598,6 +607,7 @@ def __init__(
             startup_nodes=startup_nodes,
             from_url=from_url,
             require_full_coverage=require_full_coverage,
+            dynamic_startup_nodes=dynamic_startup_nodes,
             **kwargs,
         )
 
@@ -1283,6 +1293,7 @@ def __init__(
         from_url=False,
         require_full_coverage=False,
         lock=None,
+        dynamic_startup_nodes=False,
         **kwargs,
     ):
         self.nodes_cache = {}
@@ -1292,6 +1303,7 @@ def __init__(
         self.populate_startup_nodes(startup_nodes)
         self.from_url = from_url
         self._require_full_coverage = require_full_coverage
+        self._dynamic_startup_nodes = dynamic_startup_nodes
         self._moved_exception = None
         self.connection_kwargs = kwargs
         self.read_load_balancer = LoadBalancer()
@@ -1612,8 +1624,9 @@ def initialize(self):
         self.slots_cache = tmp_slots
         # Set the default node
         self.default_node = self.get_nodes_by_server_type(PRIMARY)[0]
-        # Populate the startup nodes with all discovered nodes
-        self.startup_nodes = tmp_nodes_cache
+        if self._dynamic_startup_nodes:
+            # Populate the startup nodes with all discovered nodes
+            self.startup_nodes = tmp_nodes_cache
         # If initialize was called after a MovedError, clear it
         self._moved_exception = None
 

tests/test_cluster.py

@@ -2285,6 +2285,27 @@ def cmd_init_mock(self, r):
                 assert rc.get_node(host=default_host, port=7001) is not None
                 assert rc.get_node(host=default_host, port=7002) is not None
 
+    @pytest.mark.parametrize("dynamic_startup_nodes", [True, False])
+    def test_init_slots_dynamic_startup_nodes(self, dynamic_startup_nodes):
+        rc = get_mocked_redis_client(
+            host="[email protected]",
+            port=7000,
+            cluster_slots=default_cluster_slots,
+            dynamic_startup_nodes=dynamic_startup_nodes,
+        )
+        # Nodes are taken from default_cluster_slots
+        discovered_nodes = [
+            "127.0.0.1:7000",
+            "127.0.0.1:7001",
+            "127.0.0.1:7002",
+            "127.0.0.1:7003",
+        ]
+        startup_nodes = list(rc.nodes_manager.startup_nodes.keys())
+        if dynamic_startup_nodes is True:
+            assert startup_nodes.sort() == discovered_nodes.sort()
+        else:
+            assert startup_nodes == ["[email protected]:7000"]
+
 
 @pytest.mark.onlycluster
 class TestClusterPubSubObject: