ClusterPipeline Doesn't Handle ConnectionError for Dead Hosts (#2225)

* adds a retry that forces the nodes_manager to reinitialize if cluster pipleline connect to the one of the mapped nodes

* fix line length error

* add trailing comma

* move appending cmd

* updates changes

* trigger build

* fix linting errors

Author: grippy

CHANGES

@@ -16,6 +16,8 @@
     * 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
+    * ClusterPipeline Doesn't Handle ConnectionError for Dead Hosts (#2225)
+
 * 4.1.3 (Feb 8, 2022)
     * Fix flushdb and flushall (#1926)
     * Add redis5 and redis4 dockers (#1871)

redis/cluster.py

@@ -1897,34 +1897,53 @@ def _send_cluster_commands(
         # we figure out the slot number that command maps to, then from
         # the slot determine the node.
         for c in attempt:
-            # refer to our internal node -> slot table that
-            # tells us where a given
-            # command should route to.
-            passed_targets = c.options.pop("target_nodes", None)
-            if passed_targets and not self._is_nodes_flag(passed_targets):
-                target_nodes = self._parse_target_nodes(passed_targets)
-            else:
-                target_nodes = self._determine_nodes(*c.args, node_flag=passed_targets)
-                if not target_nodes:
+            connection_error_retry_counter = 0
+            while True:
+                # refer to our internal node -> slot table that
+                # tells us where a given command should route to.
+                # (it might be possible we have a cached node that no longer
+                # exists in the cluster, which is why we do this in a loop)
+                passed_targets = c.options.pop("target_nodes", None)
+                if passed_targets and not self._is_nodes_flag(passed_targets):
+                    target_nodes = self._parse_target_nodes(passed_targets)
+                else:
+                    target_nodes = self._determine_nodes(
+                        *c.args, node_flag=passed_targets
+                    )
+                    if not target_nodes:
+                        raise RedisClusterException(
+                            f"No targets were found to execute {c.args} command on"
+                        )
+                if len(target_nodes) > 1:
                     raise RedisClusterException(
-                        f"No targets were found to execute {c.args} command on"
+                        f"Too many targets for command {c.args}"
                     )
-            if len(target_nodes) > 1:
-                raise RedisClusterException(f"Too many targets for command {c.args}")
-
-            node = target_nodes[0]
-            # now that we know the name of the node
-            # ( it's just a string in the form of host:port )
-            # we can build a list of commands for each node.
-            node_name = node.name
-            if node_name not in nodes:
-                redis_node = self.get_redis_connection(node)
-                connection = get_connection(redis_node, c.args)
-                nodes[node_name] = NodeCommands(
-                    redis_node.parse_response, redis_node.connection_pool, connection
-                )
 
-            nodes[node_name].append(c)
+                node = target_nodes[0]
+
+                # now that we know the name of the node
+                # ( it's just a string in the form of host:port )
+                # we can build a list of commands for each node.
+                node_name = node.name
+                if node_name not in nodes:
+                    redis_node = self.get_redis_connection(node)
+                    try:
+                        connection = get_connection(redis_node, c.args)
+                    except ConnectionError:
+                        connection_error_retry_counter += 1
+                        if connection_error_retry_counter < 5:
+                            # reinitialize the node -> slot table
+                            self.nodes_manager.initialize()
+                            continue
+                        else:
+                            raise
+                    nodes[node_name] = NodeCommands(
+                        redis_node.parse_response,
+                        redis_node.connection_pool,
+                        connection,
+                    )
+                nodes[node_name].append(c)
+                break
 
         # send the commands in sequence.
         # we  write to all the open sockets for each node first,