redis/redis-py · error · ConnectionError

To maximize compatibility with all Redis products, client-si

Error message

To maximize compatibility with all Redis products, client-side caching is supported by Redis 7.4 or later

What it means

Raised as a ConnectionError in CacheProxyConnection.connect when the server is not 'redis' or its version is older than 7.4.0. Client-side caching (tracking) is only supported on Redis >= 7.4 for compatibility across Redis products, so the connection is refused. The version comparison uses compare_versions against MIN_ALLOWED_VERSION (7.4.0).

Source

Thrown at redis/connection.py:1727

        self._conn.connect()

        server_name = self._conn.handshake_metadata.get(b"server", None)
        if server_name is None:
            server_name = self._conn.handshake_metadata.get("server", None)
        server_ver = self._conn.handshake_metadata.get(b"version", None)
        if server_ver is None:
            server_ver = self._conn.handshake_metadata.get("version", None)
        if server_ver is None or server_name is None:
            raise ConnectionError("Cannot retrieve information about server version")

        server_ver = ensure_string(server_ver)
        server_name = ensure_string(server_name)

        if (
            server_name != self.DEFAULT_SERVER_NAME
            or compare_versions(server_ver, self.MIN_ALLOWED_VERSION) == 1
        ):
            raise ConnectionError(
                "To maximize compatibility with all Redis products, client-side caching is supported by Redis 7.4 or later"  # noqa: E501
            )

    def on_connect(self):
        self._conn.on_connect()

    def disconnect(self, *args, **kwargs):
        with self._cache_lock:
            self._cache.flush()
        self._conn.disconnect(*args, **kwargs)

    def check_health(self):
        self._conn.check_health()

    def send_packed_command(self, command, check_health=True):
        # TODO: Investigate if it's possible to unpack command
        #  or extract keys from packed command
        # Pre-packed commands are not individually cacheable, so make sure the

View on GitHub (pinned to da03cdc7e8)

Solutions

1. Upgrade the Redis server to 7.4.0 or later before enabling client-side caching.
2. Disable the cache config if you cannot upgrade the server.
3. Confirm the server reports server='redis' and a >= 7.4 version via HELLO.

Example fix

// before
r = redis.Redis(host=h, cache=cache_config)  # server is 7.2
r.ping()
// after
r = redis.Redis(host=h)  # upgrade server to 7.4, then re-enable cache

import redis
info = redis.Redis(host=h, protocol=3).info()
ver = tuple(int(x) for x in info['redis_version'].split('.'))
if ver < (7, 4, 0):
    raise ValueError('Client-side caching requires Redis >= 7.4.0')

try:
    r = redis.Redis(host=h, protocol=3, cache=cache_config)
    r.ping()
except redis.exceptions.ConnectionError as e:
    if '7.4' in str(e):
        r = redis.Redis(host=h, protocol=3)  # disable cache until upgrade
        r.ping()

When it happens

Trigger: Enabling client-side caching (cache config) against a Redis server older than 7.4.0, or against a non-'redis' server (e.g. Valkey/keydb reported under a different server name) that fails the DEFAULT_SERVER_NAME check. Fires at connect() after reading HELLO metadata.

Common situations: Pointing a CSC-enabled client at Redis 7.2 or earlier; using a compatible-but-renamed server; expecting CSC to work on an older self-hosted Redis.

Related errors

• Cannot retrieve information about server version
• Cannot create cache key.
• Client caching is only supported with RESP version 3
• Cache must implement CacheInterface
• Maintenance notifications handlers on connection are only su

AI-assisted analysis of redis/redis-py@da03cdc7e8 (2026-08-04). Data as JSON: /data/errors/3e16bf287ce5e1c7.json. Report an issue: GitHub.