redis/redis-py · error · ConnectionError

Connection closed by server.

Error message

Connection closed by server.

What it means

The lowest-level read: SocketBuffer._read_from_socket raises redis.exceptions.ConnectionError when sock.recv() returns empty bytes (b'') - the OS-level signal that the peer closed the TCP connection. This is where every 'Connection closed by server.' in the pure-Python parsers originates; the RESP2/RESP3 readline EOF (errors 28/32) ultimately traces here (socket.py:66-67).

Solutions

1. Configure retry_on_error=[ConnectionError, TimeoutError] + Retry/backoff.
2. Enable health_check_interval and socket_keepalive.
3. Set socket_timeout larger than any blocking-command block time.
4. Catch redis.exceptions.ConnectionError and reconnect/retry.

Example fix

# before
r = redis.Redis(parser_class=redis.connection.DefaultParser)  # pure-Python, no retry
r.get('k')  # server closed -> ConnectionError: Connection closed by server.

# after
from redis.retry import Retry
from redis.backoff import ExponentialWithJitterBackoff
from redis.exceptions import ConnectionError, TimeoutError
r = redis.Redis(
    health_check_interval=30, socket_keepalive=True, socket_timeout=5,
    retry_on_error=[ConnectionError, TimeoutError],
    retry=Retry(ExponentialWithJitterBackoff(), 3),
)
r.get('k')

from redis.exceptions import ConnectionError

def alive(r):
    try:
        r.ping()
        return True
    except ConnectionError:
        return False

from redis.exceptions import ConnectionError as RCE

def is_socket_eof(e: BaseException) -> bool:
    return isinstance(e, RCE) and 'closed by server' in str(e).lower()

from redis.exceptions import ConnectionError, TimeoutError
try:
    r.get('k')
except (ConnectionError, TimeoutError):
    r.get('k')

When it happens

Trigger: Any sync read path on a pure-Python (non-hiredis) connection whose peer has closed: restart, failover, CLIENT KILL, idle timeout, eviction, network drop, proxy reaper. recv() returning b'' is the precise trigger.

Common situations: Pure-Python parser (hiredis not installed/used) on a long-lived connection behind an idle reaper; Redis failover; server under memory pressure dropping clients; misconfigured 'timeout'.

Understand the failure class

• Connection failures: ECONNREFUSED, ECONNRESET, and friends — why connections get refused, reset, or dropped.

Related errors

• Connection closed by server.
• Connection closed by server.
• Timeout reading from socket
• Bad response from PING health check
• Connection closed by server.

AI-assisted analysis of redis/redis-py@6a6b581b48 (2026-08-10). Data as JSON: /api/errors/6db4f9fbae128bc0. Report an issue: GitHub.

Appendix: source

Thrown at redis/_parsers/socket.py:67

        timeout: Union[float, object] = SENTINEL,
        raise_on_timeout: Optional[bool] = True,
    ) -> bool:
        sock = self._sock
        socket_read_size = self.socket_read_size
        marker = 0
        custom_timeout = timeout is not SENTINEL

        buf = self._buffer
        current_pos = buf.tell()
        buf.seek(0, SEEK_END)
        if custom_timeout:
            sock.settimeout(timeout)
        try:
            while True:
                data = sock.recv(socket_read_size)
                # an empty string indicates the server shutdown the socket
                if isinstance(data, bytes) and len(data) == 0:
                    raise ConnectionError(SERVER_CLOSED_CONNECTION_ERROR)
                buf.write(data)
                data_length = len(data)
                marker += data_length

                if length is not None and length > marker:
                    continue
                return True
        except socket.timeout:
            if raise_on_timeout:
                raise TimeoutError("Timeout reading from socket")
            return False
        except NONBLOCKING_EXCEPTIONS as ex:
            # if we're in nonblocking mode and the recv raises a
            # blocking error, simply return False indicating that
            # there's no data to be read. otherwise raise the
            # original exception.
            allowed = NONBLOCKING_EXCEPTION_ERROR_NUMBERS.get(ex.__class__, -1)
            if ex.errno == allowed:

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