Source code for redis.cluster

import copy
import logging
import random
import socket
import sys
import threading
import time
from collections import OrderedDict
from typing import Any, Callable, Dict, Tuple

from redis.client import CaseInsensitiveDict, PubSub, Redis, parse_scan
from redis.commands import READ_COMMANDS, CommandsParser, RedisClusterCommands
from redis.connection import ConnectionPool, DefaultParser, Encoder, parse_url
from redis.crc import REDIS_CLUSTER_HASH_SLOTS, key_slot
from redis.exceptions import (
from redis.lock import Lock
from redis.utils import (

log = logging.getLogger(__name__)

def get_node_name(host: str, port: int) -> str:
    return f"{host}:{port}"

def get_connection(redis_node, *args, **options):
    return redis_node.connection or redis_node.connection_pool.get_connection(
        args[0], **options

def parse_scan_result(command, res, **options):
    cursors = {}
    ret = []
    for node_name, response in res.items():
        cursor, r = parse_scan(response, **options)
        cursors[node_name] = cursor
        ret += r

    return cursors, ret

def parse_pubsub_numsub(command, res, **options):
    numsub_d = OrderedDict()
    for numsub_tups in res.values():
        for channel, numsubbed in numsub_tups:
                numsub_d[channel] += numsubbed
            except KeyError:
                numsub_d[channel] = numsubbed

    ret_numsub = [(channel, numsub) for channel, numsub in numsub_d.items()]
    return ret_numsub

def parse_cluster_slots(
    resp: Any, **options: Any
) -> Dict[Tuple[int, int], Dict[str, Any]]:
    current_host = options.get("current_host", "")

    def fix_server(*args: Any) -> Tuple[str, Any]:
        return str_if_bytes(args[0]) or current_host, args[1]

    slots = {}
    for slot in resp:
        start, end, primary = slot[:3]
        replicas = slot[3:]
        slots[start, end] = {
            "primary": fix_server(*primary),
            "replicas": [fix_server(*replica) for replica in replicas],

    return slots

def parse_cluster_shards(resp, **options):
    Parse CLUSTER SHARDS response.
    shards = []
    for x in resp:
        shard = {"slots": [], "nodes": []}
        for i in range(0, len(x[1]), 2):
            shard["slots"].append((x[1][i], (x[1][i + 1])))
        nodes = x[3]
        for node in nodes:
            dict_node = {}
            for i in range(0, len(node), 2):
                dict_node[node[i]] = node[i + 1]

    return shards

PRIMARY = "primary"
REPLICA = "replica"
SLOT_ID = "slot-id"

KWARGS_DISABLED_KEYS = ("host", "port")

def cleanup_kwargs(**kwargs):
    Remove unsupported or disabled keys from kwargs
    connection_kwargs = {
        k: v
        for k, v in kwargs.items()
        if k in REDIS_ALLOWED_KEYS and k not in KWARGS_DISABLED_KEYS

    return connection_kwargs

class ClusterParser(DefaultParser):
    EXCEPTION_CLASSES = dict_merge(
            "ASK": AskError,
            "TRYAGAIN": TryAgainError,
            "MOVED": MovedError,
            "CLUSTERDOWN": ClusterDownError,
            "CROSSSLOT": ClusterCrossSlotError,
            "MASTERDOWN": MasterDownError,

class AbstractRedisCluster:
    RedisClusterRequestTTL = 16

    PRIMARIES = "primaries"
    REPLICAS = "replicas"
    ALL_NODES = "all"
    RANDOM = "random"
    DEFAULT_NODE = "default-node"


    COMMAND_FLAGS = dict_merge(
                "ACL CAT",
                "ACL DELUSER",
                "ACL DRYRUN",
                "ACL GENPASS",
                "ACL GETUSER",
                "ACL HELP",
                "ACL LIST",
                "ACL LOG",
                "ACL LOAD",
                "ACL SAVE",
                "ACL SETUSER",
                "ACL USERS",
                "ACL WHOAMI",
                "CLIENT LIST",
                "CLIENT SETNAME",
                "CLIENT GETNAME",
                "CONFIG SET",
                "CONFIG REWRITE",
                "CONFIG RESETSTAT",
                "PUBSUB CHANNELS",
                "PUBSUB NUMPAT",
                "PUBSUB NUMSUB",
                "SLOWLOG GET",
                "SLOWLOG LEN",
                "SLOWLOG RESET",
                "MEMORY PURGE",
                "MEMORY MALLOC-STATS",
                "MEMORY STATS",
                "CLIENT TRACKINGINFO",
                "CLIENT PAUSE",
                "CLIENT UNPAUSE",
                "CLIENT UNBLOCK",
                "CLIENT ID",
                "CLIENT REPLY",
                "CLIENT GETREDIR",
                "CLIENT INFO",
                "CLIENT KILL",
                "CLUSTER INFO",
                "CLUSTER MEET",
                "CLUSTER NODES",
                "CLUSTER REPLICAS",
                "CLUSTER RESET",
                "CLUSTER SET-CONFIG-EPOCH",
                "CLUSTER SLOTS",
                "CLUSTER SHARDS",
                "CLUSTER KEYSLOT",
                "COMMAND COUNT",
                "COMMAND LIST",
                "COMMAND GETKEYS",
                "CONFIG GET",
                "FUNCTION DELETE",
                "FUNCTION FLUSH",
                "FUNCTION LIST",
                "FUNCTION LOAD",
                "FUNCTION RESTORE",
                "SCRIPT EXISTS",
                "SCRIPT FLUSH",
                "SCRIPT LOAD",
        list_keys_to_dict(["FUNCTION DUMP"], RANDOM),
                "CLUSTER DELSLOTS",
                "CLUSTER DELSLOTSRANGE",
                "CLUSTER GETKEYSINSLOT",
                "CLUSTER SETSLOT",


        "CLUSTER SLOTS": parse_cluster_slots,
        "CLUSTER SHARDS": parse_cluster_shards,

    RESULT_CALLBACKS = dict_merge(
        list_keys_to_dict(["PUBSUB NUMSUB"], parse_pubsub_numsub),
            ["PUBSUB NUMPAT"], lambda command, res: sum(list(res.values()))
        list_keys_to_dict(["KEYS", "PUBSUB CHANNELS"], merge_result),
                "CONFIG SET",
                "CONFIG REWRITE",
                "CONFIG RESETSTAT",
                "CLIENT SETNAME",
                "SLOWLOG RESET",
                "MEMORY PURGE",
                "CLIENT PAUSE",
                "CLIENT UNPAUSE",
            lambda command, res: all(res.values()) if isinstance(res, dict) else res,
            ["DBSIZE", "WAIT"],
            lambda command, res: sum(res.values()) if isinstance(res, dict) else res,
            ["CLIENT UNBLOCK"], lambda command, res: 1 if sum(res.values()) > 0 else 0
        list_keys_to_dict(["SCAN"], parse_scan_result),
            ["SCRIPT LOAD"], lambda command, res: list(res.values()).pop()
            ["SCRIPT EXISTS"], lambda command, res: [all(k) for k in zip(*res.values())]
        list_keys_to_dict(["SCRIPT FLUSH"], lambda command, res: all(res.values())),

    ERRORS_ALLOW_RETRY = (ConnectionError, TimeoutError, ClusterDownError)

[docs]class RedisCluster(AbstractRedisCluster, RedisClusterCommands):
[docs] @classmethod def from_url(cls, url, **kwargs): """ Return a Redis client object configured from the given URL For example:: redis://[[username]:[password]]@localhost:6379/0 rediss://[[username]:[password]]@localhost:6379/0 unix://[[username]:[password]]@/path/to/socket.sock?db=0 Three URL schemes are supported: - `redis://` creates a TCP socket connection. See more at: <> - `rediss://` creates a SSL wrapped TCP socket connection. See more at: <> - ``unix://``: creates a Unix Domain Socket connection. The username, password, hostname, path and all querystring values are passed through urllib.parse.unquote in order to replace any percent-encoded values with their corresponding characters. There are several ways to specify a database number. The first value found will be used: 1. A ``db`` querystring option, e.g. redis://localhost?db=0 2. If using the redis:// or rediss:// schemes, the path argument of the url, e.g. redis://localhost/0 3. A ``db`` keyword argument to this function. If none of these options are specified, the default db=0 is used. All querystring options are cast to their appropriate Python types. Boolean arguments can be specified with string values "True"/"False" or "Yes"/"No". Values that cannot be properly cast cause a ``ValueError`` to be raised. Once parsed, the querystring arguments and keyword arguments are passed to the ``ConnectionPool``'s class initializer. In the case of conflicting arguments, querystring arguments always win. """ return cls(url=url, **kwargs)
def __init__( self, host=None, port=6379, startup_nodes=None, cluster_error_retry_attempts=3, require_full_coverage=False, reinitialize_steps=10, read_from_replicas=False, dynamic_startup_nodes=True, url=None, **kwargs, ): """ Initialize a new RedisCluster client. :startup_nodes: 'list[ClusterNode]' List of nodes from which initial bootstrapping can be done :host: 'str' Can be used to point to a startup node :port: 'int' Can be used to point to a startup node :require_full_coverage: 'bool' 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 - 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: 'bool' 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: 'bool' Set the RedisCluster's startup nodes to all of the discovered nodes. If true (default value), 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, it is best to set it to false. :cluster_error_retry_attempts: 'int' Retry command execution attempts when encountering ClusterDownError or ConnectionError :reinitialize_steps: 'int' 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. :**kwargs: Extra arguments that will be sent into Redis instance when created (See Official redis-py doc for supported kwargs []) Some kwargs are not supported and will raise a RedisClusterException: - db (Redis do not support database SELECT in cluster mode) """ if startup_nodes is None: startup_nodes = [] if "db" in kwargs: # Argument 'db' is not possible to use in cluster mode raise RedisClusterException( "Argument 'db' is not possible to use in cluster mode" ) # Get the startup node/s from_url = False if url is not None: from_url = True url_options = parse_url(url) if "path" in url_options: raise RedisClusterException( "RedisCluster does not currently support Unix Domain " "Socket connections" ) if "db" in url_options and url_options["db"] != 0: # Argument 'db' is not possible to use in cluster mode raise RedisClusterException( "A ``db`` querystring option can only be 0 in cluster mode" ) kwargs.update(url_options) host = kwargs.get("host") port = kwargs.get("port", port) startup_nodes.append(ClusterNode(host, port)) elif host is not None and port is not None: startup_nodes.append(ClusterNode(host, port)) elif len(startup_nodes) == 0: # No startup node was provided raise RedisClusterException( "RedisCluster requires at least one node to discover the " "cluster. Please provide one of the followings:\n" "1. host and port, for example:\n" " RedisCluster(host='localhost', port=6379)\n" "2. list of startup nodes, for example:\n" " RedisCluster(startup_nodes=[ClusterNode('localhost', 6379)," " ClusterNode('localhost', 6378)])" ) log.debug(f"startup_nodes : {startup_nodes}") # Update the connection arguments # Whenever a new connection is established, RedisCluster's on_connect # method should be run # If the user passed on_connect function we'll save it and run it # inside the RedisCluster.on_connect() function self.user_on_connect_func = kwargs.pop("redis_connect_func", None) kwargs.update({"redis_connect_func": self.on_connect}) kwargs = cleanup_kwargs(**kwargs) self.encoder = Encoder( kwargs.get("encoding", "utf-8"), kwargs.get("encoding_errors", "strict"), kwargs.get("decode_responses", False), ) self.cluster_error_retry_attempts = cluster_error_retry_attempts self.command_flags = self.__class__.COMMAND_FLAGS.copy() self.node_flags = self.__class__.NODE_FLAGS.copy() self.read_from_replicas = read_from_replicas self.reinitialize_counter = 0 self.reinitialize_steps = reinitialize_steps self.nodes_manager = None self.nodes_manager = NodesManager( startup_nodes=startup_nodes, from_url=from_url, require_full_coverage=require_full_coverage, dynamic_startup_nodes=dynamic_startup_nodes, **kwargs, ) self.cluster_response_callbacks = CaseInsensitiveDict( self.__class__.CLUSTER_COMMANDS_RESPONSE_CALLBACKS ) self.result_callbacks = CaseInsensitiveDict(self.__class__.RESULT_CALLBACKS) self.commands_parser = CommandsParser(self) self._lock = threading.Lock() def __enter__(self): return self def __exit__(self, exc_type, exc_value, traceback): self.close() def __del__(self): self.close() def disconnect_connection_pools(self): for node in self.get_nodes(): if node.redis_connection: try: node.redis_connection.connection_pool.disconnect() except OSError: # Client was already disconnected. do nothing pass
[docs] def on_connect(self, connection): """ Initialize the connection, authenticate and select a database and send READONLY if it is set during object initialization. """ connection.set_parser(ClusterParser) connection.on_connect() if self.read_from_replicas: # Sending READONLY command to server to configure connection as # readonly. Since each cluster node may change its server type due # to a failover, we should establish a READONLY connection # regardless of the server type. If this is a primary connection, # READONLY would not affect executing write commands. connection.send_command("READONLY") if str_if_bytes(connection.read_response()) != "OK": raise ConnectionError("READONLY command failed") if self.user_on_connect_func is not None: self.user_on_connect_func(connection)
def get_redis_connection(self, node): if not node.redis_connection: with self._lock: if not node.redis_connection: self.nodes_manager.create_redis_connections([node]) return node.redis_connection def get_node(self, host=None, port=None, node_name=None): return self.nodes_manager.get_node(host, port, node_name) def get_primaries(self): return self.nodes_manager.get_nodes_by_server_type(PRIMARY) def get_replicas(self): return self.nodes_manager.get_nodes_by_server_type(REPLICA) def get_random_node(self): return random.choice(list(self.nodes_manager.nodes_cache.values())) def get_nodes(self): return list(self.nodes_manager.nodes_cache.values())
[docs] def get_node_from_key(self, key, replica=False): """ Get the node that holds the key's slot. If replica set to True but the slot doesn't have any replicas, None is returned. """ slot = self.keyslot(key) slot_cache = self.nodes_manager.slots_cache.get(slot) if slot_cache is None or len(slot_cache) == 0: raise SlotNotCoveredError(f'Slot "{slot}" is not covered by the cluster.') if replica and len(self.nodes_manager.slots_cache[slot]) < 2: return None elif replica: node_idx = 1 else: # primary node_idx = 0 return slot_cache[node_idx]
[docs] def get_default_node(self): """ Get the cluster's default node """ return self.nodes_manager.default_node
[docs] def set_default_node(self, node): """ Set the default node of the cluster. :param node: 'ClusterNode' :return True if the default node was set, else False """ if node is None or self.get_node( is None: "The requested node does not exist in the cluster, so " "the default node was not changed." ) return False self.nodes_manager.default_node = node"Changed the default cluster node to {node}") return True
[docs] def monitor(self, target_node=None): """ Returns a Monitor object for the specified target node. The default cluster node will be selected if no target node was specified. Monitor is useful for handling the MONITOR command to the redis server. next_command() method returns one command from monitor listen() method yields commands from monitor. """ if target_node is None: target_node = self.get_default_node() if target_node.redis_connection is None: raise RedisClusterException( f"Cluster Node {} has no redis_connection" ) return target_node.redis_connection.monitor()
[docs] def pubsub(self, node=None, host=None, port=None, **kwargs): """ Allows passing a ClusterNode, or host&port, to get a pubsub instance connected to the specified node """ return ClusterPubSub(self, node=node, host=host, port=port, **kwargs)
[docs] def pipeline(self, transaction=None, shard_hint=None): """ Cluster impl: Pipelines do not work in cluster mode the same way they do in normal mode. Create a clone of this object so that simulating pipelines will work correctly. Each command will be called directly when used and when calling execute() will only return the result stack. """ if shard_hint: raise RedisClusterException("shard_hint is deprecated in cluster mode") if transaction: raise RedisClusterException("transaction is deprecated in cluster mode") return ClusterPipeline( nodes_manager=self.nodes_manager, commands_parser=self.commands_parser, startup_nodes=self.nodes_manager.startup_nodes, result_callbacks=self.result_callbacks, cluster_response_callbacks=self.cluster_response_callbacks, cluster_error_retry_attempts=self.cluster_error_retry_attempts, read_from_replicas=self.read_from_replicas, reinitialize_steps=self.reinitialize_steps, lock=self._lock, )
[docs] def lock( self, name, timeout=None, sleep=0.1, blocking=True, blocking_timeout=None, lock_class=None, thread_local=True, ): """ Return a new Lock object using key ``name`` that mimics the behavior of threading.Lock. If specified, ``timeout`` indicates a maximum life for the lock. By default, it will remain locked until release() is called. ``sleep`` indicates the amount of time to sleep per loop iteration when the lock is in blocking mode and another client is currently holding the lock. ``blocking`` indicates whether calling ``acquire`` should block until the lock has been acquired or to fail immediately, causing ``acquire`` to return False and the lock not being acquired. Defaults to True. Note this value can be overridden by passing a ``blocking`` argument to ``acquire``. ``blocking_timeout`` indicates the maximum amount of time in seconds to spend trying to acquire the lock. A value of ``None`` indicates continue trying forever. ``blocking_timeout`` can be specified as a float or integer, both representing the number of seconds to wait. ``lock_class`` forces the specified lock implementation. Note that as of redis-py 3.0, the only lock class we implement is ``Lock`` (which is a Lua-based lock). So, it's unlikely you'll need this parameter, unless you have created your own custom lock class. ``thread_local`` indicates whether the lock token is placed in thread-local storage. By default, the token is placed in thread local storage so that a thread only sees its token, not a token set by another thread. Consider the following timeline: time: 0, thread-1 acquires `my-lock`, with a timeout of 5 seconds. thread-1 sets the token to "abc" time: 1, thread-2 blocks trying to acquire `my-lock` using the Lock instance. time: 5, thread-1 has not yet completed. redis expires the lock key. time: 5, thread-2 acquired `my-lock` now that it's available. thread-2 sets the token to "xyz" time: 6, thread-1 finishes its work and calls release(). if the token is *not* stored in thread local storage, then thread-1 would see the token value as "xyz" and would be able to successfully release the thread-2's lock. In some use cases it's necessary to disable thread local storage. For example, if you have code where one thread acquires a lock and passes that lock instance to a worker thread to release later. If thread local storage isn't disabled in this case, the worker thread won't see the token set by the thread that acquired the lock. Our assumption is that these cases aren't common and as such default to using thread local storage.""" if lock_class is None: lock_class = Lock return lock_class( self, name, timeout=timeout, sleep=sleep, blocking=blocking, blocking_timeout=blocking_timeout, thread_local=thread_local, )
[docs] def set_response_callback(self, command, callback): """Set a custom Response Callback""" self.cluster_response_callbacks[command] = callback
def _determine_nodes(self, *args, **kwargs): command = args[0].upper() if len(args) >= 2 and f"{args[0]} {args[1]}".upper() in self.command_flags: command = f"{args[0]} {args[1]}".upper() nodes_flag = kwargs.pop("nodes_flag", None) if nodes_flag is not None: # nodes flag passed by the user command_flag = nodes_flag else: # get the nodes group for this command if it was predefined command_flag = self.command_flags.get(command) if command_flag: log.debug(f"Target node/s for {command}: {command_flag}") if command_flag == self.__class__.RANDOM: # return a random node return [self.get_random_node()] elif command_flag == self.__class__.PRIMARIES: # return all primaries return self.get_primaries() elif command_flag == self.__class__.REPLICAS: # return all replicas return self.get_replicas() elif command_flag == self.__class__.ALL_NODES: # return all nodes return self.get_nodes() elif command_flag == self.__class__.DEFAULT_NODE: # return the cluster's default node return [self.nodes_manager.default_node] elif command in self.__class__.SEARCH_COMMANDS[0]: return [self.nodes_manager.default_node] else: # get the node that holds the key's slot slot = self.determine_slot(*args) node = self.nodes_manager.get_node_from_slot( slot, self.read_from_replicas and command in READ_COMMANDS ) log.debug(f"Target for {args}: slot {slot}") return [node] def _should_reinitialized(self): # 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. if self.reinitialize_steps == 0: return False else: return self.reinitialize_counter % self.reinitialize_steps == 0
[docs] def keyslot(self, key): """ Calculate keyslot for a given key. See Keys distribution model in """ k = self.encoder.encode(key) return key_slot(k)
def _get_command_keys(self, *args): """ Get the keys in the command. If the command has no keys in in, None is returned. NOTE: Due to a bug in redis<7.0, this function does not work properly for EVAL or EVALSHA when the `numkeys` arg is 0. - issue: - fix: So, don't use this function with EVAL or EVALSHA. """ redis_conn = self.get_default_node().redis_connection return self.commands_parser.get_keys(redis_conn, *args)
[docs] def determine_slot(self, *args): """ Figure out what slot to use based on args. Raises a RedisClusterException if there's a missing key and we can't determine what slots to map the command to; or, if the keys don't all map to the same key slot. """ command = args[0] if self.command_flags.get(command) == SLOT_ID: # The command contains the slot ID return args[1] # Get the keys in the command # EVAL and EVALSHA are common enough that it's wasteful to go to the # redis server to parse the keys. Besides, there is a bug in redis<7.0 # where `self._get_command_keys()` fails anyway. So, we special case # EVAL/EVALSHA. if command in ("EVAL", "EVALSHA"): # command syntax: EVAL "script body" num_keys ... if len(args) <= 2: raise RedisClusterException(f"Invalid args in command: {args}") num_actual_keys = args[2] eval_keys = args[3 : 3 + num_actual_keys] # if there are 0 keys, that means the script can be run on any node # so we can just return a random slot if len(eval_keys) == 0: return random.randrange(0, REDIS_CLUSTER_HASH_SLOTS) keys = eval_keys else: keys = self._get_command_keys(*args) if keys is None or len(keys) == 0: # FCALL can call a function with 0 keys, that means the function # can be run on any node so we can just return a random slot if command in ("FCALL", "FCALL_RO"): return random.randrange(0, REDIS_CLUSTER_HASH_SLOTS) raise RedisClusterException( "No way to dispatch this command to Redis Cluster. " "Missing key.\nYou can execute the command by specifying " f"target nodes.\nCommand: {args}" ) # single key command if len(keys) == 1: return self.keyslot(keys[0]) # multi-key command; we need to make sure all keys are mapped to # the same slot slots = {self.keyslot(key) for key in keys} if len(slots) != 1: raise RedisClusterException( f"{command} - all keys must map to the same key slot" ) return slots.pop()
[docs] def get_encoder(self): """ Get the connections' encoder """ return self.encoder
[docs] def get_connection_kwargs(self): """ Get the connections' key-word arguments """ return self.nodes_manager.connection_kwargs
def _is_nodes_flag(self, target_nodes): return isinstance(target_nodes, str) and target_nodes in self.node_flags def _parse_target_nodes(self, target_nodes): if isinstance(target_nodes, list): nodes = target_nodes elif isinstance(target_nodes, ClusterNode): # Supports passing a single ClusterNode as a variable nodes = [target_nodes] elif isinstance(target_nodes, dict): # Supports dictionaries of the format {node_name: node}. # It enables to execute commands with multi nodes as follows: # rc.cluster_save_config(rc.get_primaries()) nodes = target_nodes.values() else: raise TypeError( "target_nodes type can be one of the following: " "node_flag (PRIMARIES, REPLICAS, RANDOM, ALL_NODES)," "ClusterNode, list<ClusterNode>, or dict<any, ClusterNode>. " f"The passed type is {type(target_nodes)}" ) return nodes
[docs] def execute_command(self, *args, **kwargs): """ Wrapper for ERRORS_ALLOW_RETRY error handling. It will try the number of times specified by the config option "self.cluster_error_retry_attempts" which defaults to 3 unless manually configured. If it reaches the number of times, the command will raise the exception Key argument :target_nodes: can be passed with the following types: nodes_flag: PRIMARIES, REPLICAS, ALL_NODES, RANDOM ClusterNode list<ClusterNode> dict<Any, ClusterNode> """ target_nodes_specified = False target_nodes = None passed_targets = kwargs.pop("target_nodes", None) if passed_targets is not None and not self._is_nodes_flag(passed_targets): target_nodes = self._parse_target_nodes(passed_targets) target_nodes_specified = True # If an error that allows retrying was thrown, the nodes and slots # cache were reinitialized. We will retry executing the command with # the updated cluster setup only when the target nodes can be # determined again with the new cache tables. Therefore, when target # nodes were passed to this function, we cannot retry the command # execution since the nodes may not be valid anymore after the tables # were reinitialized. So in case of passed target nodes, # retry_attempts will be set to 1. retry_attempts = ( 1 if target_nodes_specified else self.cluster_error_retry_attempts ) exception = None for _ in range(0, retry_attempts): try: res = {} if not target_nodes_specified: # Determine the nodes to execute the command on target_nodes = self._determine_nodes( *args, **kwargs, nodes_flag=passed_targets ) if not target_nodes: raise RedisClusterException( f"No targets were found to execute {args} command on" ) for node in target_nodes: res[] = self._execute_command(node, *args, **kwargs) # Return the processed result return self._process_result(args[0], res, **kwargs) except BaseException as e: if type(e) in self.__class__.ERRORS_ALLOW_RETRY: # The nodes and slots cache were reinitialized. # Try again with the new cluster setup. exception = e else: # All other errors should be raised. raise e # If it fails the configured number of times then raise exception back # to caller of this method raise exception
def _execute_command(self, target_node, *args, **kwargs): """ Send a command to a node in the cluster """ command = args[0] redis_node = None connection = None redirect_addr = None asking = False moved = False ttl = int(self.RedisClusterRequestTTL) connection_error_retry_counter = 0 while ttl > 0: ttl -= 1 try: if asking: target_node = self.get_node(node_name=redirect_addr) elif moved: # MOVED occurred and the slots cache was updated, # refresh the target node slot = self.determine_slot(*args) target_node = self.nodes_manager.get_node_from_slot( slot, self.read_from_replicas and command in READ_COMMANDS ) moved = False log.debug( f"Executing command {command} on target node: " f"{target_node.server_type} {}" ) redis_node = self.get_redis_connection(target_node) connection = get_connection(redis_node, *args, **kwargs) if asking: connection.send_command("ASKING") redis_node.parse_response(connection, "ASKING", **kwargs) asking = False connection.send_command(*args) response = redis_node.parse_response(connection, command, **kwargs) if command in self.cluster_response_callbacks: response = self.cluster_response_callbacks[command]( response, **kwargs ) return response except (RedisClusterException, BusyLoadingError, AuthenticationError) as e: log.exception(type(e)) raise except (ConnectionError, TimeoutError) as e: log.exception(type(e)) # ConnectionError can also be raised if we couldn't get a # connection from the pool before timing out, so check that # this is an actual connection before attempting to disconnect. if connection is not None: connection.disconnect() connection_error_retry_counter += 1 # Give the node 0.25 seconds to get back up and retry again # with same node and configuration. After 5 attempts then try # to reinitialize the cluster and see if the nodes # configuration has changed or not if connection_error_retry_counter < 5: time.sleep(0.25) else: # Hard force of reinitialize of the node/slots setup # and try again with the new setup target_node.redis_connection = None self.nodes_manager.initialize() raise except MovedError as e: # First, we will try to patch the slots/nodes cache with the # redirected node output and try again. If MovedError exceeds # 'reinitialize_steps' number of times, we will force # reinitializing the tables, and then try again. # 'reinitialize_steps' counter will increase faster when # the same client object is shared between multiple threads. To # reduce the frequency you can set this variable in the # RedisCluster constructor. log.exception("MovedError") self.reinitialize_counter += 1 if self._should_reinitialized(): self.nodes_manager.initialize() # Reset the counter self.reinitialize_counter = 0 else: self.nodes_manager.update_moved_exception(e) moved = True except TryAgainError: log.exception("TryAgainError") if ttl < self.RedisClusterRequestTTL / 2: time.sleep(0.05) except AskError as e: log.exception("AskError") redirect_addr = get_node_name(, port=e.port) asking = True except ClusterDownError as e: log.exception("ClusterDownError") # ClusterDownError can occur during a failover and to get # self-healed, we will try to reinitialize the cluster layout # and retry executing the command time.sleep(0.25) self.nodes_manager.initialize() raise e except ResponseError as e: message = e.__str__() log.exception(f"ResponseError: {message}") raise e except BaseException as e: log.exception("BaseException") if connection: connection.disconnect() raise e finally: if connection is not None: redis_node.connection_pool.release(connection) raise ClusterError("TTL exhausted.") def close(self): try: with self._lock: if self.nodes_manager: self.nodes_manager.close() except AttributeError: # RedisCluster's __init__ can fail before nodes_manager is set pass def _process_result(self, command, res, **kwargs): """ Process the result of the executed command. The function would return a dict or a single value. :type command: str :type res: dict `res` should be in the following format: Dict<node_name, command_result> """ if command in self.result_callbacks: return self.result_callbacks[command](command, res, **kwargs) elif len(res) == 1: # When we execute the command on a single node, we can # remove the dictionary and return a single response return list(res.values())[0] else: return res
[docs] def load_external_module(self, funcname, func): """ This function can be used to add externally defined redis modules, and their namespaces to the redis client. ``funcname`` - A string containing the name of the function to create ``func`` - The function, being added to this class. """ setattr(self, funcname, func)
[docs]class ClusterNode: def __init__(self, host, port, server_type=None, redis_connection=None): if host == "localhost": host = socket.gethostbyname(host) = host self.port = port = get_node_name(host, port) self.server_type = server_type self.redis_connection = redis_connection def __repr__(self): return ( f"[host={}," f"port={self.port}," f"name={}," f"server_type={self.server_type}," f"redis_connection={self.redis_connection}]" ) def __eq__(self, obj): return isinstance(obj, ClusterNode) and == def __del__(self): if self.redis_connection is not None: self.redis_connection.close()
class LoadBalancer: """ Round-Robin Load Balancing """ def __init__(self, start_index: int = 0) -> None: self.primary_to_idx = {} self.start_index = start_index def get_server_index(self, primary: str, list_size: int) -> int: server_index = self.primary_to_idx.setdefault(primary, self.start_index) # Update the index self.primary_to_idx[primary] = (server_index + 1) % list_size return server_index def reset(self) -> None: self.primary_to_idx.clear() class NodesManager: def __init__( self, startup_nodes, from_url=False, require_full_coverage=False, lock=None, dynamic_startup_nodes=True, **kwargs, ): self.nodes_cache = {} self.slots_cache = {} self.startup_nodes = {} self.default_node = None 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() if lock is None: lock = threading.Lock() self._lock = lock self.initialize() def get_node(self, host=None, port=None, node_name=None): """ Get the requested node from the cluster's nodes. nodes. :return: ClusterNode if the node exists, else None """ if host and port: # the user passed host and port if host == "localhost": host = socket.gethostbyname(host) return self.nodes_cache.get(get_node_name(host=host, port=port)) elif node_name: return self.nodes_cache.get(node_name) else: log.error( "get_node requires one of the following: " "1. node name " "2. host and port" ) return None def update_moved_exception(self, exception): self._moved_exception = exception def _update_moved_slots(self): """ Update the slot's node with the redirected one """ e = self._moved_exception redirected_node = self.get_node(, port=e.port) if redirected_node is not None: # The node already exists if redirected_node.server_type is not PRIMARY: # Update the node's server type redirected_node.server_type = PRIMARY else: # This is a new node, we will add it to the nodes cache redirected_node = ClusterNode(, e.port, PRIMARY) self.nodes_cache[] = redirected_node if redirected_node in self.slots_cache[e.slot_id]: # The MOVED error resulted from a failover, and the new slot owner # had previously been a replica. old_primary = self.slots_cache[e.slot_id][0] # Update the old primary to be a replica and add it to the end of # the slot's node list old_primary.server_type = REPLICA self.slots_cache[e.slot_id].append(old_primary) # Remove the old replica, which is now a primary, from the slot's # node list self.slots_cache[e.slot_id].remove(redirected_node) # Override the old primary with the new one self.slots_cache[e.slot_id][0] = redirected_node if self.default_node == old_primary: # Update the default node with the new primary self.default_node = redirected_node else: # The new slot owner is a new server, or a server from a different # shard. We need to remove all current nodes from the slot's list # (including replications) and add just the new node. self.slots_cache[e.slot_id] = [redirected_node] # Reset moved_exception self._moved_exception = None def get_node_from_slot(self, slot, read_from_replicas=False, server_type=None): """ Gets a node that servers this hash slot """ if self._moved_exception: with self._lock: if self._moved_exception: self._update_moved_slots() if self.slots_cache.get(slot) is None or len(self.slots_cache[slot]) == 0: raise SlotNotCoveredError( f'Slot "{slot}" not covered by the cluster. ' f'"require_full_coverage={self._require_full_coverage}"' ) if read_from_replicas is True: # get the server index in a Round-Robin manner primary_name = self.slots_cache[slot][0].name node_idx = self.read_load_balancer.get_server_index( primary_name, len(self.slots_cache[slot]) ) elif ( server_type is None or server_type == PRIMARY or len(self.slots_cache[slot]) == 1 ): # return a primary node_idx = 0 else: # return a replica # randomly choose one of the replicas node_idx = random.randint(1, len(self.slots_cache[slot]) - 1) return self.slots_cache[slot][node_idx] def get_nodes_by_server_type(self, server_type): """ Get all nodes with the specified server type :param server_type: 'primary' or 'replica' :return: list of ClusterNode """ return [ node for node in self.nodes_cache.values() if node.server_type == server_type ] def populate_startup_nodes(self, nodes): """ Populate all startup nodes and filters out any duplicates """ for n in nodes: self.startup_nodes[] = n def check_slots_coverage(self, slots_cache): # Validate if all slots are covered or if we should try next # startup node for i in range(0, REDIS_CLUSTER_HASH_SLOTS): if i not in slots_cache: return False return True def create_redis_connections(self, nodes): """ This function will create a redis connection to all nodes in :nodes: """ for node in nodes: if node.redis_connection is None: node.redis_connection = self.create_redis_node(, port=node.port, **self.connection_kwargs ) def create_redis_node(self, host, port, **kwargs): if self.from_url: # Create a redis node with a costumed connection pool kwargs.update({"host": host}) kwargs.update({"port": port}) r = Redis(connection_pool=ConnectionPool(**kwargs)) else: r = Redis(host=host, port=port, **kwargs) return r def _get_or_create_cluster_node(self, host, port, role, tmp_nodes_cache): node_name = get_node_name(host, port) # check if we already have this node in the tmp_nodes_cache target_node = tmp_nodes_cache.get(node_name) if target_node is None: # before creating a new cluster node, check if the cluster node already # exists in the current nodes cache and has a valid connection so we can # reuse it target_node = self.nodes_cache.get(node_name) if target_node is None or target_node.redis_connection is None: # create new cluster node for this cluster target_node = ClusterNode(host, port, role) return target_node def initialize(self): """ Initializes the nodes cache, slots cache and redis connections. :startup_nodes: Responsible for discovering other nodes in the cluster """ log.debug("Initializing the nodes' topology of the cluster") self.reset() tmp_nodes_cache = {} tmp_slots = {} disagreements = [] startup_nodes_reachable = False fully_covered = False kwargs = self.connection_kwargs for startup_node in self.startup_nodes.values(): try: if startup_node.redis_connection: r = startup_node.redis_connection else: # Create a new Redis connection and let Redis decode the # responses so we won't need to handle that copy_kwargs = copy.deepcopy(kwargs) copy_kwargs.update({"decode_responses": True, "encoding": "utf-8"}) r = self.create_redis_node(, startup_node.port, **copy_kwargs ) self.startup_nodes[].redis_connection = r # Make sure cluster mode is enabled on this node if bool("cluster_enabled")) is False: raise RedisClusterException( "Cluster mode is not enabled on this node" ) cluster_slots = str_if_bytes(r.execute_command("CLUSTER SLOTS")) startup_nodes_reachable = True except (ConnectionError, TimeoutError) as e: msg = e.__str__ log.exception( "An exception occurred while trying to" " initialize the cluster using the seed node" f" {}:\n{msg}" ) continue except ResponseError as e: log.exception('ReseponseError sending "cluster slots" to redis server') # Isn't a cluster connection, so it won't parse these # exceptions automatically message = e.__str__() if "CLUSTERDOWN" in message or "MASTERDOWN" in message: continue else: raise RedisClusterException( 'ERROR sending "cluster slots" command to redis ' f"server: {startup_node}. error: {message}" ) except Exception as e: message = e.__str__() raise RedisClusterException( 'ERROR sending "cluster slots" command to redis ' f"server {}. error: {message}" ) # CLUSTER SLOTS command results in the following output: # [[slot_section[from_slot,to_slot,master,replica1,...,replicaN]]] # where each node contains the following list: [IP, port, node_id] # Therefore, cluster_slots[0][2][0] will be the IP address of the # primary node of the first slot section. # If there's only one server in the cluster, its ``host`` is '' # Fix it to the host in startup_nodes if ( len(cluster_slots) == 1 and len(cluster_slots[0][2][0]) == 0 and len(self.startup_nodes) == 1 ): cluster_slots[0][2][0] = for slot in cluster_slots: primary_node = slot[2] host = str_if_bytes(primary_node[0]) if host == "": host = port = int(primary_node[1]) target_node = self._get_or_create_cluster_node( host, port, PRIMARY, tmp_nodes_cache ) # add this node to the nodes cache tmp_nodes_cache[] = target_node for i in range(int(slot[0]), int(slot[1]) + 1): if i not in tmp_slots: tmp_slots[i] = [] tmp_slots[i].append(target_node) replica_nodes = [slot[j] for j in range(3, len(slot))] for replica_node in replica_nodes: host = str_if_bytes(replica_node[0]) port = replica_node[1] target_replica_node = self._get_or_create_cluster_node( host, port, REPLICA, tmp_nodes_cache ) tmp_slots[i].append(target_replica_node) # add this node to the nodes cache tmp_nodes_cache[ ] = target_replica_node else: # Validate that 2 nodes want to use the same slot cache # setup tmp_slot = tmp_slots[i][0] if != disagreements.append( f"{} vs {} on slot: {i}" ) if len(disagreements) > 5: raise RedisClusterException( f"startup_nodes could not agree on a valid " f'slots cache: {", ".join(disagreements)}' ) fully_covered = self.check_slots_coverage(tmp_slots) if fully_covered: # Don't need to continue to the next startup node if all # slots are covered break if not startup_nodes_reachable: raise RedisClusterException( "Redis Cluster cannot be connected. Please provide at least " "one reachable node. " ) # Create Redis connections to all nodes self.create_redis_connections(list(tmp_nodes_cache.values())) # Check if the slots are not fully covered if not fully_covered and self._require_full_coverage: # Despite the requirement that the slots be covered, there # isn't a full coverage raise RedisClusterException( f"All slots are not covered after query all startup_nodes. " f"{len(tmp_slots)} of {REDIS_CLUSTER_HASH_SLOTS} " f"covered..." ) # Set the tmp variables to the real variables self.nodes_cache = tmp_nodes_cache self.slots_cache = tmp_slots # Set the default node self.default_node = self.get_nodes_by_server_type(PRIMARY)[0] 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 def close(self): self.default_node = None for node in self.nodes_cache.values(): if node.redis_connection: node.redis_connection.close() def reset(self): try: self.read_load_balancer.reset() except TypeError: # The read_load_balancer is None, do nothing pass class ClusterPubSub(PubSub): """ Wrapper for PubSub class. IMPORTANT: before using ClusterPubSub, read about the known limitations with pubsub in Cluster mode and learn how to workaround them: """ def __init__(self, redis_cluster, node=None, host=None, port=None, **kwargs): """ When a pubsub instance is created without specifying a node, a single node will be transparently chosen for the pubsub connection on the first command execution. The node will be determined by: 1. Hashing the channel name in the request to find its keyslot 2. Selecting a node that handles the keyslot: If read_from_replicas is set to true, a replica can be selected. :type redis_cluster: RedisCluster :type node: ClusterNode :type host: str :type port: int """ self.node = None self.set_pubsub_node(redis_cluster, node, host, port) connection_pool = ( None if self.node is None else redis_cluster.get_redis_connection(self.node).connection_pool ) self.cluster = redis_cluster super().__init__( **kwargs, connection_pool=connection_pool, encoder=redis_cluster.encoder ) def set_pubsub_node(self, cluster, node=None, host=None, port=None): """ The pubsub node will be set according to the passed node, host and port When none of the node, host, or port are specified - the node is set to None and will be determined by the keyslot of the channel in the first command to be executed. RedisClusterException will be thrown if the passed node does not exist in the cluster. If host is passed without port, or vice versa, a DataError will be thrown. :type cluster: RedisCluster :type node: ClusterNode :type host: str :type port: int """ if node is not None: # node is passed by the user self._raise_on_invalid_node(cluster, node,, node.port) pubsub_node = node elif host is not None and port is not None: # host and port passed by the user node = cluster.get_node(host=host, port=port) self._raise_on_invalid_node(cluster, node, host, port) pubsub_node = node elif any([host, port]) is True: # only 'host' or 'port' passed raise DataError("Passing a host requires passing a port, " "and vice versa") else: # nothing passed by the user. set node to None pubsub_node = None self.node = pubsub_node def get_pubsub_node(self): """ Get the node that is being used as the pubsub connection """ return self.node def _raise_on_invalid_node(self, redis_cluster, node, host, port): """ Raise a RedisClusterException if the node is None or doesn't exist in the cluster. """ if node is None or redis_cluster.get_node( is None: raise RedisClusterException( f"Node {host}:{port} doesn't exist in the cluster" ) def execute_command(self, *args, **kwargs): """ Execute a publish/subscribe command. Taken code from redis-py and tweak to make it work within a cluster. """ # NOTE: don't parse the response in this function -- it could pull a # legitimate message off the stack if the connection is already # subscribed to one or more channels if self.connection is None: if self.connection_pool is None: if len(args) > 1: # Hash the first channel and get one of the nodes holding # this slot channel = args[1] slot = self.cluster.keyslot(channel) node = self.cluster.nodes_manager.get_node_from_slot( slot, self.cluster.read_from_replicas ) else: # Get a random node node = self.cluster.get_random_node() self.node = node redis_connection = self.cluster.get_redis_connection(node) self.connection_pool = redis_connection.connection_pool self.connection = self.connection_pool.get_connection( "pubsub", self.shard_hint ) # register a callback that re-subscribes to any channels we # were listening to when we were disconnected self.connection.register_connect_callback(self.on_connect) connection = self.connection self._execute(connection, connection.send_command, *args) def get_redis_connection(self): """ Get the Redis connection of the pubsub connected node. """ if self.node is not None: return self.node.redis_connection class ClusterPipeline(RedisCluster): """ Support for Redis pipeline in cluster mode """ ERRORS_ALLOW_RETRY = ( ConnectionError, TimeoutError, MovedError, AskError, TryAgainError, ) def __init__( self, nodes_manager, commands_parser, result_callbacks=None, cluster_response_callbacks=None, startup_nodes=None, read_from_replicas=False, cluster_error_retry_attempts=5, reinitialize_steps=10, lock=None, **kwargs, ): """ """ self.command_stack = [] self.nodes_manager = nodes_manager self.commands_parser = commands_parser self.refresh_table_asap = False self.result_callbacks = ( result_callbacks or self.__class__.RESULT_CALLBACKS.copy() ) self.startup_nodes = startup_nodes if startup_nodes else [] self.read_from_replicas = read_from_replicas self.command_flags = self.__class__.COMMAND_FLAGS.copy() self.cluster_response_callbacks = cluster_response_callbacks self.cluster_error_retry_attempts = cluster_error_retry_attempts self.reinitialize_counter = 0 self.reinitialize_steps = reinitialize_steps self.encoder = Encoder( kwargs.get("encoding", "utf-8"), kwargs.get("encoding_errors", "strict"), kwargs.get("decode_responses", False), ) if lock is None: lock = threading.Lock() self._lock = lock def __repr__(self): """ """ return f"{type(self).__name__}" def __enter__(self): """ """ return self def __exit__(self, exc_type, exc_value, traceback): """ """ self.reset() def __del__(self): try: self.reset() except Exception: pass def __len__(self): """ """ return len(self.command_stack) def __nonzero__(self): "Pipeline instances should always evaluate to True on Python 2.7" return True def __bool__(self): "Pipeline instances should always evaluate to True on Python 3+" return True def execute_command(self, *args, **kwargs): """ Wrapper function for pipeline_execute_command """ return self.pipeline_execute_command(*args, **kwargs) def pipeline_execute_command(self, *args, **options): """ Appends the executed command to the pipeline's command stack """ self.command_stack.append( PipelineCommand(args, options, len(self.command_stack)) ) return self def raise_first_error(self, stack): """ Raise the first exception on the stack """ for c in stack: r = c.result if isinstance(r, Exception): self.annotate_exception(r, c.position + 1, c.args) raise r def annotate_exception(self, exception, number, command): """ Provides extra context to the exception prior to it being handled """ cmd = " ".join(map(safe_str, command)) msg = ( f"Command # {number} ({cmd}) of pipeline " f"caused error: {exception.args[0]}" ) exception.args = (msg,) + exception.args[1:] def execute(self, raise_on_error=True): """ Execute all the commands in the current pipeline """ stack = self.command_stack try: return self.send_cluster_commands(stack, raise_on_error) finally: self.reset() def reset(self): """ Reset back to empty pipeline. """ self.command_stack = [] self.scripts = set() # TODO: Implement # make sure to reset the connection state in the event that we were # watching something # if self.watching and self.connection: # try: # # call this manually since our unwatch or # # immediate_execute_command methods can call reset() # self.connection.send_command('UNWATCH') # self.connection.read_response() # except ConnectionError: # # disconnect will also remove any previous WATCHes # self.connection.disconnect() # clean up the other instance attributes self.watching = False self.explicit_transaction = False # TODO: Implement # we can safely return the connection to the pool here since we're # sure we're no longer WATCHing anything # if self.connection: # self.connection_pool.release(self.connection) # self.connection = None def send_cluster_commands( self, stack, raise_on_error=True, allow_redirections=True ): """ Wrapper for CLUSTERDOWN error handling. If the cluster reports it is down it is assumed that: - connection_pool was disconnected - connection_pool was reseted - refereh_table_asap set to True It will try the number of times specified by the config option "self.cluster_error_retry_attempts" which defaults to 3 unless manually configured. If it reaches the number of times, the command will raises ClusterDownException. """ if not stack: return [] for _ in range(0, self.cluster_error_retry_attempts): try: return self._send_cluster_commands( stack, raise_on_error=raise_on_error, allow_redirections=allow_redirections, ) except ClusterDownError: # Try again with the new cluster setup. All other errors # should be raised. pass # If it fails the configured number of times then raise # exception back to caller of this method raise ClusterDownError("CLUSTERDOWN error. Unable to rebuild the cluster") def _send_cluster_commands( self, stack, raise_on_error=True, allow_redirections=True ): """ Send a bunch of cluster commands to the redis cluster. `allow_redirections` If the pipeline should follow `ASK` & `MOVED` responses automatically. If set to false it will raise RedisClusterException. """ # the first time sending the commands we send all of # the commands that were queued up. # if we have to run through it again, we only retry # the commands that failed. attempt = sorted(stack, key=lambda x: x.position) # build a list of node objects based on node names we need to nodes = {} # as we move through each command that still needs to be processed, # 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: raise RedisClusterException( f"No targets were found to execute {c.args} command on" ) 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 = 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) # send the commands in sequence. # we write to all the open sockets for each node first, # before reading anything # this allows us to flush all the requests out across the # network essentially in parallel # so that we can read them all in parallel as they come back. # we dont' multiplex on the sockets as they come available, # but that shouldn't make too much difference. node_commands = nodes.values() for n in node_commands: n.write() for n in node_commands: # release all of the redis connections we allocated earlier # back into the connection pool. # we used to do this step as part of a try/finally block, # but it is really dangerous to # release connections back into the pool if for some # reason the socket has data still left in it # from a previous operation. The write and # read operations already have try/catch around them for # all known types of errors including connection # and socket level errors. # So if we hit an exception, something really bad # happened and putting any oF # these connections back into the pool is a very bad idea. # the socket might have unread buffer still sitting in it, # and then the next time we read from it we pass the # buffered result back from a previous command and # every single request after to that connection will always get # a mismatched result. for n in nodes.values(): n.connection_pool.release(n.connection) # if the response isn't an exception it is a # valid response from the node # we're all done with that command, YAY! # if we have more commands to attempt, we've run into problems. # collect all the commands we are allowed to retry. # (MOVED, ASK, or connection errors or timeout errors) attempt = sorted( ( c for c in attempt if isinstance(c.result, ClusterPipeline.ERRORS_ALLOW_RETRY) ), key=lambda x: x.position, ) if attempt and allow_redirections: # RETRY MAGIC HAPPENS HERE! # send these remaing comamnds one at a time using `execute_command` # in the main client. This keeps our retry logic # in one place mostly, # and allows us to be more confident in correctness of behavior. # at this point any speed gains from pipelining have been lost # anyway, so we might as well make the best # attempt to get the correct behavior. # # The client command will handle retries for each # individual command sequentially as we pass each # one into `execute_command`. Any exceptions # that bubble out should only appear once all # retries have been exhausted. # # If a lot of commands have failed, we'll be setting the # flag to rebuild the slots table from scratch. # So MOVED errors should correct themselves fairly quickly. log.exception( f"An exception occurred during pipeline execution. " f"args: {attempt[-1].args}, " f"error: {type(attempt[-1].result).__name__} " f"{str(attempt[-1].result)}" ) self.reinitialize_counter += 1 if self._should_reinitialized(): self.nodes_manager.initialize() for c in attempt: try: # send each command individually like we # do in the main client. c.result = super().execute_command(*c.args, **c.options) except RedisError as e: c.result = e # turn the response back into a simple flat array that corresponds # to the sequence of commands issued in the stack in pipeline.execute() response = [] for c in sorted(stack, key=lambda x: x.position): if c.args[0] in self.cluster_response_callbacks: c.result = self.cluster_response_callbacks[c.args[0]]( c.result, **c.options ) response.append(c.result) if raise_on_error: self.raise_first_error(stack) return response def _fail_on_redirect(self, allow_redirections): """ """ if not allow_redirections: raise RedisClusterException( "ASK & MOVED redirection not allowed in this pipeline" ) def exists(self, *keys): return self.execute_command("EXISTS", *keys) def eval(self): """ """ raise RedisClusterException("method eval() is not implemented") def multi(self): """ """ raise RedisClusterException("method multi() is not implemented") def immediate_execute_command(self, *args, **options): """ """ raise RedisClusterException( "method immediate_execute_command() is not implemented" ) def _execute_transaction(self, *args, **kwargs): """ """ raise RedisClusterException("method _execute_transaction() is not implemented") def load_scripts(self): """ """ raise RedisClusterException("method load_scripts() is not implemented") def watch(self, *names): """ """ raise RedisClusterException("method watch() is not implemented") def unwatch(self): """ """ raise RedisClusterException("method unwatch() is not implemented") def script_load_for_pipeline(self, *args, **kwargs): """ """ raise RedisClusterException( "method script_load_for_pipeline() is not implemented" ) def delete(self, *names): """ "Delete a key specified by ``names``" """ if len(names) != 1: raise RedisClusterException( "deleting multiple keys is not " "implemented in pipeline command" ) return self.execute_command("DEL", names[0]) def block_pipeline_command(name: str) -> Callable[..., Any]: """ Prints error because some pipelined commands should be blocked when running in cluster-mode """ def inner(*args, **kwargs): raise RedisClusterException( f"ERROR: Calling pipelined function {name} is blocked " f"when running redis in cluster mode..." ) return inner # Blocked pipeline commands PIPELINE_BLOCKED_COMMANDS = ( "BGREWRITEAOF", "BGSAVE", "BITOP", "BRPOPLPUSH", "CLIENT GETNAME", "CLIENT KILL", "CLIENT LIST", "CLIENT SETNAME", "CLIENT", "CONFIG GET", "CONFIG RESETSTAT", "CONFIG REWRITE", "CONFIG SET", "CONFIG", "DBSIZE", "ECHO", "EVALSHA", "FLUSHALL", "FLUSHDB", "INFO", "KEYS", "LASTSAVE", "MGET", "MGET NONATOMIC", "MOVE", "MSET", "MSET NONATOMIC", "MSETNX", "PFCOUNT", "PFMERGE", "PING", "PUBLISH", "RANDOMKEY", "READONLY", "READWRITE", "RENAME", "RENAMENX", "RPOPLPUSH", "SAVE", "SCAN", "SCRIPT EXISTS", "SCRIPT FLUSH", "SCRIPT KILL", "SCRIPT LOAD", "SCRIPT", "SDIFF", "SDIFFSTORE", "SENTINEL GET MASTER ADDR BY NAME", "SENTINEL MASTER", "SENTINEL MASTERS", "SENTINEL MONITOR", "SENTINEL REMOVE", "SENTINEL SENTINELS", "SENTINEL SET", "SENTINEL SLAVES", "SENTINEL", "SHUTDOWN", "SINTER", "SINTERSTORE", "SLAVEOF", "SLOWLOG GET", "SLOWLOG LEN", "SLOWLOG RESET", "SLOWLOG", "SMOVE", "SORT", "SUNION", "SUNIONSTORE", "TIME", ) for command in PIPELINE_BLOCKED_COMMANDS: command = command.replace(" ", "_").lower() setattr(ClusterPipeline, command, block_pipeline_command(command)) class PipelineCommand: """ """ def __init__(self, args, options=None, position=None): self.args = args if options is None: options = {} self.options = options self.position = position self.result = None self.node = None self.asking = False class NodeCommands: """ """ def __init__(self, parse_response, connection_pool, connection): """ """ self.parse_response = parse_response self.connection_pool = connection_pool self.connection = connection self.commands = [] def append(self, c): """ """ self.commands.append(c) def write(self): """ Code borrowed from Redis so it can be fixed """ connection = self.connection commands = self.commands # We are going to clobber the commands with the write, so go ahead # and ensure that nothing is sitting there from a previous run. for c in commands: c.result = None # build up all commands into a single request to increase network perf # send all the commands and catch connection and timeout errors. try: connection.send_packed_command( connection.pack_commands([c.args for c in commands]) ) except (ConnectionError, TimeoutError) as e: for c in commands: c.result = e def read(self): """ """ connection = self.connection for c in self.commands: # if there is a result on this command, # it means we ran into an exception # like a connection error. Trying to parse # a response on a connection that # is no longer open will result in a # connection error raised by redis-py. # but redis-py doesn't check in parse_response # that the sock object is # still set and if you try to # read from a closed connection, it will # result in an AttributeError because # it will do a readline() call on None. # This can have all kinds of nasty side-effects. # Treating this case as a connection error # is fine because it will dump # the connection object back into the # pool and on the next write, it will # explicitly open the connection and all will be well. if c.result is None: try: c.result = self.parse_response(connection, c.args[0], **c.options) except (ConnectionError, TimeoutError) as e: for c in self.commands: c.result = e return except RedisError: c.result = sys.exc_info()[1]