Add Async Support (#1899)

Co-authored-by: Chayim I. Kirshen <c@kirshen.com>
Co-authored-by: dvora-h <dvora.heller@redis.com>

1 files changed, 353 insertions, 0 deletions

diff --git a/redis/asyncio/sentinel.py b/redis/asyncio/sentinel.py
new file mode 100644
index 0000000..5aefd09
--- /dev/null
+++ b/redis/asyncio/sentinel.py
@@ -0,0 +1,353 @@
+import asyncio
+import random
+import weakref
+from typing import AsyncIterator, Iterable, Mapping, Sequence, Tuple, Type
+
+from redis.asyncio.client import Redis
+from redis.asyncio.connection import (
+    Connection,
+    ConnectionPool,
+    EncodableT,
+    SSLConnection,
+)
+from redis.commands import AsyncSentinelCommands
+from redis.exceptions import ConnectionError, ReadOnlyError, ResponseError, TimeoutError
+from redis.utils import str_if_bytes
+
+
+class MasterNotFoundError(ConnectionError):
+    pass
+
+
+class SlaveNotFoundError(ConnectionError):
+    pass
+
+
+class SentinelManagedConnection(Connection):
+    def __init__(self, **kwargs):
+        self.connection_pool = kwargs.pop("connection_pool")
+        super().__init__(**kwargs)
+
+    def __repr__(self):
+        pool = self.connection_pool
+        s = f"{self.__class__.__name__}<service={pool.service_name}"
+        if self.host:
+            host_info = f",host={self.host},port={self.port}"
+            s += host_info
+        return s + ">"
+
+    async def connect_to(self, address):
+        self.host, self.port = address
+        await super().connect()
+        if self.connection_pool.check_connection:
+            await self.send_command("PING")
+            if str_if_bytes(await self.read_response()) != "PONG":
+                raise ConnectionError("PING failed")
+
+    async def connect(self):
+        if self._reader:
+            return  # already connected
+        if self.connection_pool.is_master:
+            await self.connect_to(await self.connection_pool.get_master_address())
+        else:
+            async for slave in self.connection_pool.rotate_slaves():
+                try:
+                    return await self.connect_to(slave)
+                except ConnectionError:
+                    continue
+            raise SlaveNotFoundError  # Never be here
+
+    async def read_response(self, disable_decoding: bool = False):
+        try:
+            return await super().read_response(disable_decoding=disable_decoding)
+        except ReadOnlyError:
+            if self.connection_pool.is_master:
+                # When talking to a master, a ReadOnlyError when likely
+                # indicates that the previous master that we're still connected
+                # to has been demoted to a slave and there's a new master.
+                # calling disconnect will force the connection to re-query
+                # sentinel during the next connect() attempt.
+                await self.disconnect()
+                raise ConnectionError("The previous master is now a slave")
+            raise
+
+
+class SentinelManagedSSLConnection(SentinelManagedConnection, SSLConnection):
+    pass
+
+
+class SentinelConnectionPool(ConnectionPool):
+    """
+    Sentinel backed connection pool.
+
+    If ``check_connection`` flag is set to True, SentinelManagedConnection
+    sends a PING command right after establishing the connection.
+    """
+
+    def __init__(self, service_name, sentinel_manager, **kwargs):
+        kwargs["connection_class"] = kwargs.get(
+            "connection_class",
+            SentinelManagedSSLConnection
+            if kwargs.pop("ssl", False)
+            else SentinelManagedConnection,
+        )
+        self.is_master = kwargs.pop("is_master", True)
+        self.check_connection = kwargs.pop("check_connection", False)
+        super().__init__(**kwargs)
+        self.connection_kwargs["connection_pool"] = weakref.proxy(self)
+        self.service_name = service_name
+        self.sentinel_manager = sentinel_manager
+        self.master_address = None
+        self.slave_rr_counter = None
+
+    def __repr__(self):
+        return (
+            f"{self.__class__.__name__}"
+            f"<service={self.service_name}({self.is_master and 'master' or 'slave'})>"
+        )
+
+    def reset(self):
+        super().reset()
+        self.master_address = None
+        self.slave_rr_counter = None
+
+    def owns_connection(self, connection: Connection):
+        check = not self.is_master or (
+            self.is_master and self.master_address == (connection.host, connection.port)
+        )
+        return check and super().owns_connection(connection)
+
+    async def get_master_address(self):
+        master_address = await self.sentinel_manager.discover_master(self.service_name)
+        if self.is_master:
+            if self.master_address != master_address:
+                self.master_address = master_address
+                # disconnect any idle connections so that they reconnect
+                # to the new master the next time that they are used.
+                await self.disconnect(inuse_connections=False)
+        return master_address
+
+    async def rotate_slaves(self) -> AsyncIterator:
+        """Round-robin slave balancer"""
+        slaves = await self.sentinel_manager.discover_slaves(self.service_name)
+        if slaves:
+            if self.slave_rr_counter is None:
+                self.slave_rr_counter = random.randint(0, len(slaves) - 1)
+            for _ in range(len(slaves)):
+                self.slave_rr_counter = (self.slave_rr_counter + 1) % len(slaves)
+                slave = slaves[self.slave_rr_counter]
+                yield slave
+        # Fallback to the master connection
+        try:
+            yield await self.get_master_address()
+        except MasterNotFoundError:
+            pass
+        raise SlaveNotFoundError(f"No slave found for {self.service_name!r}")
+
+
+class Sentinel(AsyncSentinelCommands):
+    """
+    Redis Sentinel cluster client
+
+    >>> from redis.sentinel import Sentinel
+    >>> sentinel = Sentinel([('localhost', 26379)], socket_timeout=0.1)
+    >>> master = sentinel.master_for('mymaster', socket_timeout=0.1)
+    >>> await master.set('foo', 'bar')
+    >>> slave = sentinel.slave_for('mymaster', socket_timeout=0.1)
+    >>> await slave.get('foo')
+    b'bar'
+
+    ``sentinels`` is a list of sentinel nodes. Each node is represented by
+    a pair (hostname, port).
+
+    ``min_other_sentinels`` defined a minimum number of peers for a sentinel.
+    When querying a sentinel, if it doesn't meet this threshold, responses
+    from that sentinel won't be considered valid.
+
+    ``sentinel_kwargs`` is a dictionary of connection arguments used when
+    connecting to sentinel instances. Any argument that can be passed to
+    a normal Redis connection can be specified here. If ``sentinel_kwargs`` is
+    not specified, any socket_timeout and socket_keepalive options specified
+    in ``connection_kwargs`` will be used.
+
+    ``connection_kwargs`` are keyword arguments that will be used when
+    establishing a connection to a Redis server.
+    """
+
+    def __init__(
+        self,
+        sentinels,
+        min_other_sentinels=0,
+        sentinel_kwargs=None,
+        **connection_kwargs,
+    ):
+        # if sentinel_kwargs isn't defined, use the socket_* options from
+        # connection_kwargs
+        if sentinel_kwargs is None:
+            sentinel_kwargs = {
+                k: v for k, v in connection_kwargs.items() if k.startswith("socket_")
+            }
+        self.sentinel_kwargs = sentinel_kwargs
+
+        self.sentinels = [
+            Redis(host=hostname, port=port, **self.sentinel_kwargs)
+            for hostname, port in sentinels
+        ]
+        self.min_other_sentinels = min_other_sentinels
+        self.connection_kwargs = connection_kwargs
+
+    async def execute_command(self, *args, **kwargs):
+        """
+        Execute Sentinel command in sentinel nodes.
+        once - If set to True, then execute the resulting command on a single
+               node at random, rather than across the entire sentinel cluster.
+        """
+        once = bool(kwargs.get("once", False))
+        if "once" in kwargs.keys():
+            kwargs.pop("once")
+
+        if once:
+            tasks = [
+                asyncio.Task(sentinel.execute_command(*args, **kwargs))
+                for sentinel in self.sentinels
+            ]
+            await asyncio.gather(*tasks)
+        else:
+            await random.choice(self.sentinels).execute_command(*args, **kwargs)
+        return True
+
+    def __repr__(self):
+        sentinel_addresses = []
+        for sentinel in self.sentinels:
+            sentinel_addresses.append(
+                f"{sentinel.connection_pool.connection_kwargs['host']}:"
+                f"{sentinel.connection_pool.connection_kwargs['port']}"
+            )
+        return f"{self.__class__.__name__}<sentinels=[{','.join(sentinel_addresses)}]>"
+
+    def check_master_state(self, state: dict, service_name: str) -> bool:
+        if not state["is_master"] or state["is_sdown"] or state["is_odown"]:
+            return False
+        # Check if our sentinel doesn't see other nodes
+        if state["num-other-sentinels"] < self.min_other_sentinels:
+            return False
+        return True
+
+    async def discover_master(self, service_name: str):
+        """
+        Asks sentinel servers for the Redis master's address corresponding
+        to the service labeled ``service_name``.
+
+        Returns a pair (address, port) or raises MasterNotFoundError if no
+        master is found.
+        """
+        for sentinel_no, sentinel in enumerate(self.sentinels):
+            try:
+                masters = await sentinel.sentinel_masters()
+            except (ConnectionError, TimeoutError):
+                continue
+            state = masters.get(service_name)
+            if state and self.check_master_state(state, service_name):
+                # Put this sentinel at the top of the list
+                self.sentinels[0], self.sentinels[sentinel_no] = (
+                    sentinel,
+                    self.sentinels[0],
+                )
+                return state["ip"], state["port"]
+        raise MasterNotFoundError(f"No master found for {service_name!r}")
+
+    def filter_slaves(
+        self, slaves: Iterable[Mapping]
+    ) -> Sequence[Tuple[EncodableT, EncodableT]]:
+        """Remove slaves that are in an ODOWN or SDOWN state"""
+        slaves_alive = []
+        for slave in slaves:
+            if slave["is_odown"] or slave["is_sdown"]:
+                continue
+            slaves_alive.append((slave["ip"], slave["port"]))
+        return slaves_alive
+
+    async def discover_slaves(
+        self, service_name: str
+    ) -> Sequence[Tuple[EncodableT, EncodableT]]:
+        """Returns a list of alive slaves for service ``service_name``"""
+        for sentinel in self.sentinels:
+            try:
+                slaves = await sentinel.sentinel_slaves(service_name)
+            except (ConnectionError, ResponseError, TimeoutError):
+                continue
+            slaves = self.filter_slaves(slaves)
+            if slaves:
+                return slaves
+        return []
+
+    def master_for(
+        self,
+        service_name: str,
+        redis_class: Type[Redis] = Redis,
+        connection_pool_class: Type[SentinelConnectionPool] = SentinelConnectionPool,
+        **kwargs,
+    ):
+        """
+        Returns a redis client instance for the ``service_name`` master.
+
+        A :py:class:`~redis.sentinel.SentinelConnectionPool` class is
+        used to retrieve the master's address before establishing a new
+        connection.
+
+        NOTE: If the master's address has changed, any cached connections to
+        the old master are closed.
+
+        By default clients will be a :py:class:`~redis.Redis` instance.
+        Specify a different class to the ``redis_class`` argument if you
+        desire something different.
+
+        The ``connection_pool_class`` specifies the connection pool to
+        use.  The :py:class:`~redis.sentinel.SentinelConnectionPool`
+        will be used by default.
+
+        All other keyword arguments are merged with any connection_kwargs
+        passed to this class and passed to the connection pool as keyword
+        arguments to be used to initialize Redis connections.
+        """
+        kwargs["is_master"] = True
+        connection_kwargs = dict(self.connection_kwargs)
+        connection_kwargs.update(kwargs)
+        return redis_class(
+            connection_pool=connection_pool_class(
+                service_name, self, **connection_kwargs
+            )
+        )
+
+    def slave_for(
+        self,
+        service_name: str,
+        redis_class: Type[Redis] = Redis,
+        connection_pool_class: Type[SentinelConnectionPool] = SentinelConnectionPool,
+        **kwargs,
+    ):
+        """
+        Returns redis client instance for the ``service_name`` slave(s).
+
+        A SentinelConnectionPool class is used to retrieve the slave's
+        address before establishing a new connection.
+
+        By default clients will be a :py:class:`~redis.Redis` instance.
+        Specify a different class to the ``redis_class`` argument if you
+        desire something different.
+
+        The ``connection_pool_class`` specifies the connection pool to use.
+        The SentinelConnectionPool will be used by default.
+
+        All other keyword arguments are merged with any connection_kwargs
+        passed to this class and passed to the connection pool as keyword
+        arguments to be used to initialize Redis connections.
+        """
+        kwargs["is_master"] = False
+        connection_kwargs = dict(self.connection_kwargs)
+        connection_kwargs.update(kwargs)
+        return redis_class(
+            connection_pool=connection_pool_class(
+                service_name, self, **connection_kwargs
+            )
+        )