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381 lines
14 KiB
381 lines
14 KiB
import asyncio
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import random
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import weakref
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from typing import AsyncIterator, Iterable, Mapping, Optional, Sequence, Tuple, Type
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from redis.asyncio.client import Redis
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from redis.asyncio.connection import (
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Connection,
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ConnectionPool,
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EncodableT,
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SSLConnection,
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)
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from redis.commands import AsyncSentinelCommands
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from redis.exceptions import ConnectionError, ReadOnlyError, ResponseError, TimeoutError
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from redis.utils import str_if_bytes
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class MasterNotFoundError(ConnectionError):
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pass
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class SlaveNotFoundError(ConnectionError):
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pass
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class SentinelManagedConnection(Connection):
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def __init__(self, **kwargs):
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self.connection_pool = kwargs.pop("connection_pool")
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super().__init__(**kwargs)
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def __repr__(self):
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pool = self.connection_pool
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s = (
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f"<{self.__class__.__module__}.{self.__class__.__name__}"
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f"(service={pool.service_name}"
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)
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if self.host:
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host_info = f",host={self.host},port={self.port}"
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s += host_info
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return s + ")>"
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async def connect_to(self, address):
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self.host, self.port = address
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await super().connect()
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if self.connection_pool.check_connection:
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await self.send_command("PING")
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if str_if_bytes(await self.read_response()) != "PONG":
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raise ConnectionError("PING failed")
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async def _connect_retry(self):
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if self._reader:
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return # already connected
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if self.connection_pool.is_master:
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await self.connect_to(await self.connection_pool.get_master_address())
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else:
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async for slave in self.connection_pool.rotate_slaves():
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try:
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return await self.connect_to(slave)
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except ConnectionError:
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continue
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raise SlaveNotFoundError # Never be here
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async def connect(self):
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return await self.retry.call_with_retry(
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self._connect_retry,
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lambda error: asyncio.sleep(0),
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)
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async def read_response(
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self,
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disable_decoding: bool = False,
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timeout: Optional[float] = None,
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*,
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disconnect_on_error: Optional[float] = True,
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push_request: Optional[bool] = False,
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):
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try:
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return await super().read_response(
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disable_decoding=disable_decoding,
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timeout=timeout,
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disconnect_on_error=disconnect_on_error,
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push_request=push_request,
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)
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except ReadOnlyError:
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if self.connection_pool.is_master:
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# When talking to a master, a ReadOnlyError when likely
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# indicates that the previous master that we're still connected
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# to has been demoted to a slave and there's a new master.
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# calling disconnect will force the connection to re-query
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# sentinel during the next connect() attempt.
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await self.disconnect()
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raise ConnectionError("The previous master is now a slave")
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raise
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class SentinelManagedSSLConnection(SentinelManagedConnection, SSLConnection):
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pass
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class SentinelConnectionPool(ConnectionPool):
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"""
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Sentinel backed connection pool.
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If ``check_connection`` flag is set to True, SentinelManagedConnection
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sends a PING command right after establishing the connection.
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"""
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def __init__(self, service_name, sentinel_manager, **kwargs):
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kwargs["connection_class"] = kwargs.get(
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"connection_class",
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SentinelManagedSSLConnection
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if kwargs.pop("ssl", False)
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else SentinelManagedConnection,
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)
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self.is_master = kwargs.pop("is_master", True)
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self.check_connection = kwargs.pop("check_connection", False)
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super().__init__(**kwargs)
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self.connection_kwargs["connection_pool"] = weakref.proxy(self)
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self.service_name = service_name
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self.sentinel_manager = sentinel_manager
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self.master_address = None
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self.slave_rr_counter = None
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def __repr__(self):
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return (
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f"<{self.__class__.__module__}.{self.__class__.__name__}"
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f"(service={self.service_name}({self.is_master and 'master' or 'slave'}))>"
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)
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def reset(self):
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super().reset()
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self.master_address = None
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self.slave_rr_counter = None
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def owns_connection(self, connection: Connection):
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check = not self.is_master or (
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self.is_master and self.master_address == (connection.host, connection.port)
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)
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return check and super().owns_connection(connection)
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async def get_master_address(self):
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master_address = await self.sentinel_manager.discover_master(self.service_name)
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if self.is_master:
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if self.master_address != master_address:
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self.master_address = master_address
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# disconnect any idle connections so that they reconnect
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# to the new master the next time that they are used.
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await self.disconnect(inuse_connections=False)
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return master_address
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async def rotate_slaves(self) -> AsyncIterator:
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"""Round-robin slave balancer"""
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slaves = await self.sentinel_manager.discover_slaves(self.service_name)
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if slaves:
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if self.slave_rr_counter is None:
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self.slave_rr_counter = random.randint(0, len(slaves) - 1)
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for _ in range(len(slaves)):
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self.slave_rr_counter = (self.slave_rr_counter + 1) % len(slaves)
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slave = slaves[self.slave_rr_counter]
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yield slave
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# Fallback to the master connection
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try:
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yield await self.get_master_address()
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except MasterNotFoundError:
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pass
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raise SlaveNotFoundError(f"No slave found for {self.service_name!r}")
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class Sentinel(AsyncSentinelCommands):
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"""
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Redis Sentinel cluster client
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>>> from redis.sentinel import Sentinel
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>>> sentinel = Sentinel([('localhost', 26379)], socket_timeout=0.1)
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>>> master = sentinel.master_for('mymaster', socket_timeout=0.1)
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>>> await master.set('foo', 'bar')
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>>> slave = sentinel.slave_for('mymaster', socket_timeout=0.1)
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>>> await slave.get('foo')
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b'bar'
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``sentinels`` is a list of sentinel nodes. Each node is represented by
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a pair (hostname, port).
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``min_other_sentinels`` defined a minimum number of peers for a sentinel.
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When querying a sentinel, if it doesn't meet this threshold, responses
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from that sentinel won't be considered valid.
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``sentinel_kwargs`` is a dictionary of connection arguments used when
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connecting to sentinel instances. Any argument that can be passed to
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a normal Redis connection can be specified here. If ``sentinel_kwargs`` is
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not specified, any socket_timeout and socket_keepalive options specified
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in ``connection_kwargs`` will be used.
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``connection_kwargs`` are keyword arguments that will be used when
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establishing a connection to a Redis server.
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"""
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def __init__(
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self,
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sentinels,
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min_other_sentinels=0,
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sentinel_kwargs=None,
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**connection_kwargs,
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):
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# if sentinel_kwargs isn't defined, use the socket_* options from
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# connection_kwargs
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if sentinel_kwargs is None:
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sentinel_kwargs = {
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k: v for k, v in connection_kwargs.items() if k.startswith("socket_")
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}
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self.sentinel_kwargs = sentinel_kwargs
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self.sentinels = [
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Redis(host=hostname, port=port, **self.sentinel_kwargs)
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for hostname, port in sentinels
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]
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self.min_other_sentinels = min_other_sentinels
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self.connection_kwargs = connection_kwargs
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async def execute_command(self, *args, **kwargs):
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"""
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Execute Sentinel command in sentinel nodes.
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once - If set to True, then execute the resulting command on a single
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node at random, rather than across the entire sentinel cluster.
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"""
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once = bool(kwargs.get("once", False))
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if "once" in kwargs.keys():
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kwargs.pop("once")
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if once:
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await random.choice(self.sentinels).execute_command(*args, **kwargs)
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else:
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tasks = [
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asyncio.Task(sentinel.execute_command(*args, **kwargs))
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for sentinel in self.sentinels
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]
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await asyncio.gather(*tasks)
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return True
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def __repr__(self):
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sentinel_addresses = []
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for sentinel in self.sentinels:
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sentinel_addresses.append(
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f"{sentinel.connection_pool.connection_kwargs['host']}:"
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f"{sentinel.connection_pool.connection_kwargs['port']}"
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)
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return (
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f"<{self.__class__}.{self.__class__.__name__}"
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f"(sentinels=[{','.join(sentinel_addresses)}])>"
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)
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def check_master_state(self, state: dict, service_name: str) -> bool:
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if not state["is_master"] or state["is_sdown"] or state["is_odown"]:
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return False
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# Check if our sentinel doesn't see other nodes
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if state["num-other-sentinels"] < self.min_other_sentinels:
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return False
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return True
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async def discover_master(self, service_name: str):
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"""
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Asks sentinel servers for the Redis master's address corresponding
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to the service labeled ``service_name``.
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Returns a pair (address, port) or raises MasterNotFoundError if no
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master is found.
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"""
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collected_errors = list()
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for sentinel_no, sentinel in enumerate(self.sentinels):
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try:
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masters = await sentinel.sentinel_masters()
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except (ConnectionError, TimeoutError) as e:
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collected_errors.append(f"{sentinel} - {e!r}")
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continue
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state = masters.get(service_name)
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if state and self.check_master_state(state, service_name):
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# Put this sentinel at the top of the list
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self.sentinels[0], self.sentinels[sentinel_no] = (
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sentinel,
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self.sentinels[0],
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)
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return state["ip"], state["port"]
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error_info = ""
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if len(collected_errors) > 0:
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error_info = f" : {', '.join(collected_errors)}"
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raise MasterNotFoundError(f"No master found for {service_name!r}{error_info}")
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def filter_slaves(
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self, slaves: Iterable[Mapping]
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) -> Sequence[Tuple[EncodableT, EncodableT]]:
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"""Remove slaves that are in an ODOWN or SDOWN state"""
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slaves_alive = []
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for slave in slaves:
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if slave["is_odown"] or slave["is_sdown"]:
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continue
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slaves_alive.append((slave["ip"], slave["port"]))
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return slaves_alive
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async def discover_slaves(
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self, service_name: str
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) -> Sequence[Tuple[EncodableT, EncodableT]]:
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"""Returns a list of alive slaves for service ``service_name``"""
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for sentinel in self.sentinels:
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try:
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slaves = await sentinel.sentinel_slaves(service_name)
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except (ConnectionError, ResponseError, TimeoutError):
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continue
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slaves = self.filter_slaves(slaves)
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if slaves:
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return slaves
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return []
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def master_for(
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self,
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service_name: str,
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redis_class: Type[Redis] = Redis,
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connection_pool_class: Type[SentinelConnectionPool] = SentinelConnectionPool,
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**kwargs,
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):
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"""
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Returns a redis client instance for the ``service_name`` master.
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A :py:class:`~redis.sentinel.SentinelConnectionPool` class is
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used to retrieve the master's address before establishing a new
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connection.
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NOTE: If the master's address has changed, any cached connections to
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the old master are closed.
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By default clients will be a :py:class:`~redis.Redis` instance.
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Specify a different class to the ``redis_class`` argument if you
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desire something different.
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The ``connection_pool_class`` specifies the connection pool to
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use. The :py:class:`~redis.sentinel.SentinelConnectionPool`
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will be used by default.
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All other keyword arguments are merged with any connection_kwargs
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passed to this class and passed to the connection pool as keyword
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arguments to be used to initialize Redis connections.
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"""
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kwargs["is_master"] = True
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connection_kwargs = dict(self.connection_kwargs)
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connection_kwargs.update(kwargs)
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connection_pool = connection_pool_class(service_name, self, **connection_kwargs)
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# The Redis object "owns" the pool
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return redis_class.from_pool(connection_pool)
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def slave_for(
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self,
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service_name: str,
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redis_class: Type[Redis] = Redis,
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connection_pool_class: Type[SentinelConnectionPool] = SentinelConnectionPool,
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**kwargs,
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):
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"""
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Returns redis client instance for the ``service_name`` slave(s).
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A SentinelConnectionPool class is used to retrieve the slave's
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address before establishing a new connection.
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By default clients will be a :py:class:`~redis.Redis` instance.
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Specify a different class to the ``redis_class`` argument if you
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desire something different.
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The ``connection_pool_class`` specifies the connection pool to use.
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The SentinelConnectionPool will be used by default.
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All other keyword arguments are merged with any connection_kwargs
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passed to this class and passed to the connection pool as keyword
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arguments to be used to initialize Redis connections.
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"""
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kwargs["is_master"] = False
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connection_kwargs = dict(self.connection_kwargs)
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connection_kwargs.update(kwargs)
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connection_pool = connection_pool_class(service_name, self, **connection_kwargs)
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# The Redis object "owns" the pool
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return redis_class.from_pool(connection_pool)
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