how to identify connection error in python?

Question

In python we get different exception for diff connection issues like ECONNREFUSED, ECONNRESET, EHOSTUNREACH etc. Is there any standard logic for identifying connection errors in python? Basically I am using suds for connecting to vmware WS SDK and I want to re-try session login on connection errors.

Answer 1

I faced exactly this problem today and I wrote a blog post about it: https://gmpy.dev/blog/2023/recognize-connection-errors

import errno, socket, ssl

# Network errors, usually related to DHCP or wpa_supplicant (Wi-Fi).
NETWORK_ERRNOS = frozenset((
    errno.ENETUNREACH,  # "Network is unreachable"
    errno.ENETDOWN,  # "Network is down"
    errno.ENETRESET,  # "Network dropped connection on reset"
    errno.ENONET,  # "Machine is not on the network"
))

def is_connection_err(exc):
    """Return True if an exception is connection-related."""
    if isinstance(exc, ConnectionError):
        # https://docs.python.org/3/library/exceptions.html#ConnectionError
        # ConnectionError includes:
        # * BrokenPipeError (EPIPE, ESHUTDOWN)
        # * ConnectionAbortedError (ECONNABORTED)
        # * ConnectionRefusedError (ECONNREFUSED)
        # * ConnectionResetError (ECONNRESET)
        return True
    if isinstance(exc, socket.gaierror):
        # failed DNS resolution on connect()
        return True
    if isinstance(exc, (socket.timeout, TimeoutError)):
        # timeout on connect(), recv(), send()
        return True
    if isinstance(exc, OSError):
        # ENOTCONN == "Transport endpoint is not connected"
        return (exc.errno in NETWORK_ERRNOS) or (exc.errno == errno.ENOTCONN)
    if isinstance(exc, ssl.SSLError):
        # Let's consider any SSL error a connection error. Usually this is:
        # * ssl.SSLZeroReturnError: "TLS/SSL connection has been closed"
        # * ssl.SSLError: [SSL: BAD_LENGTH] bad length
        return True
    return False