redis/redis-py · error · ConnectionError

To maximize compatibility with all Redis products…

Error message

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

What it means

Raised in CacheProxyConnection.connect (connection.py:1739-1745) after the server identity is retrieved, when the server name is not 'redis' OR the version is older than MIN_ALLOWED_VERSION ('7.4.0'). Client-side caching via the cache proxy is only supported on genuine Redis >= 7.4 to maximise compatibility across products; anything else (Valkey, older Redis, or Redis < 7.4) is rejected at connect time.

Solutions

1. Upgrade to Redis >= 7.4.0 if you need client-side caching.
2. Disable the cache (remove cache=) on incompatible servers.
3. If on Valkey/other, do not enable this client-side caching feature.
4. Verify with INFO server / HELLO that server name is 'redis' and version >= 7.4.

Example fix

# before
r = redis.Redis(host=h, port=p, protocol=3, cache=my_cache)  # Redis 7.2
# after
r = redis.Redis(host=h, port=p, protocol=3)  # no cache on <7.4

from redis.connection import CacheProxyConnection
MIN = CacheProxyConnection.MIN_ALLOWED_VERSION  # '7.4.0'

info = redis.Redis(host=h, port=p, protocol=3).info('server')
ok = info.get('redis_version') and compare_versions(info['redis_version'], MIN) <= 0
r = redis.Redis(host=h, port=p, protocol=3, cache=my_cache) if ok else \
    redis.Redis(host=h, port=p, protocol=3)  # no cache on older/non-redis

def supports_csc(info: dict) -> bool:
    return (
        info.get('redis_version', '0.0.0') is not None
        and compare_versions(info['redis_version'], '7.4.0') <= 0
    )

from redis.exceptions import ConnectionError
try:
    r = redis.Redis(host=h, port=p, protocol=3, cache=my_cache)
    r.ping()
except ConnectionError as e:
    if 'client-side caching' in str(e):
        r = redis.Redis(host=h, port=p, protocol=3)  # disable cache
    else:
        raise

When it happens

Trigger: Enabling the client-side cache against Valkey, Redis < 7.4, or any server whose HELLO 'server' field is not 'redis'. compare_versions(server_ver,'7.4.0')==1 means the detected version is strictly less than 7.4.0.

Common situations: Dev environment on an older Redis; using Valkey as a Redis replacement; assuming the cache works on any RESP3 server.

Related errors

• Cache must implement CacheInterface
• Cannot retrieve information about server version
• Client caching is only supported with RESP version 3
• Client caching is only supported with RESP version 3
• Eviction policy should be associated with valid cache.

AI-assisted analysis of redis/redis-py@6a6b581b48 (2026-08-10). Data as JSON: /api/errors/3e16bf287ce5e1c7. Report an issue: GitHub.

Appendix: source

Thrown at redis/connection.py:1743

        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

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