# Source code for kafka.conn

    from __future__ import absolute_import, division

    import collections
    import copy
    import errno
    import io
    import logging
    from random import shuffle, uniform

    # selectors in stdlib as of py3.4
    try:
        import selectors  # pylint: disable=import-error
    except ImportError:
        # vendored backport module
        from kafka.vendor import selectors34 as selectors

    import socket
    import struct
    import sys
    import threading
    import time

    from kafka.vendor import six

    import kafka.errors as Errors
    from kafka.future import Future
    from kafka.metrics.stats import Avg, Count, Max, Rate
    from kafka.oauth.abstract import AbstractTokenProvider
    from kafka.protocol.admin import SaslHandShakeRequest
    from kafka.protocol.commit import OffsetFetchRequest
    from kafka.protocol.metadata import MetadataRequest
    from kafka.protocol.parser import KafkaProtocol
    from kafka.protocol.types import Int32, Int8
    from kafka.version import __version__

    if six.PY2:
        ConnectionError = socket.error
        BlockingIOError = Exception

    log = logging.getLogger(__name__)

    DEFAULT_KAFKA_PORT = 9092

    SASL_QOP_AUTH = 1
    SASL_QOP_AUTH_INT = 2
    SASL_QOP_AUTH_CONF = 4

    try:
        import ssl
        ssl_available = True
        try:
            SSLEOFError = ssl.SSLEOFError
            SSLWantReadError = ssl.SSLWantReadError
            SSLWantWriteError = ssl.SSLWantWriteError
            SSLZeroReturnError = ssl.SSLZeroReturnError
        except AttributeError:
            # support older ssl libraries
            log.warning('Old SSL module detected.'
                        ' SSL error handling may not operate cleanly.'
                        ' Consider upgrading to Python 3.3 or 2.7.9')
            SSLEOFError = ssl.SSLError
            SSLWantReadError = ssl.SSLError
            SSLWantWriteError = ssl.SSLError
            SSLZeroReturnError = ssl.SSLError
    except ImportError:
        # support Python without ssl libraries
        ssl_available = False
        class SSLWantReadError(Exception):
            pass
        class SSLWantWriteError(Exception):
            pass

    # needed for SASL_GSSAPI authentication:
    try:
        import gssapi
        from gssapi.raw.misc import GSSError
    except ImportError:
        #no gssapi available, will disable gssapi mechanism
        gssapi = None
        GSSError = None

    AFI_NAMES = {
        socket.AF_UNSPEC: "unspecified",
        socket.AF_INET: "IPv4",
        socket.AF_INET6: "IPv6",
    }

    class ConnectionStates(object):
        DISCONNECTING = '<disconnecting>'
        DISCONNECTED = '<disconnected>'
        CONNECTING = '<connecting>'
        HANDSHAKE = '<handshake>'
        CONNECTED = '<connected>'
        AUTHENTICATING = '<authenticating>'

    class BrokerConnection(object):
        """Initialize a Kafka broker connection

        Keyword Arguments:
            client_id (str): a name for this client. This string is passed in
                each request to servers and can be used to identify specific
                server-side log entries that correspond to this client. Also
                submitted to GroupCoordinator for logging with respect to
                consumer group administration. Default: 'kafka-python-{version}'
            reconnect_backoff_ms (int): The amount of time in milliseconds to
                wait before attempting to reconnect to a given host.
                Default: 50.
            reconnect_backoff_max_ms (int): The maximum amount of time in
                milliseconds to wait when reconnecting to a broker that has
                repeatedly failed to connect. If provided, the backoff per host
                will increase exponentially for each consecutive connection
                failure, up to this maximum. To avoid connection storms, a
                randomization factor of 0.2 will be applied to the backoff
                resulting in a random range between 20% below and 20% above
                the computed value. Default: 1000.
            request_timeout_ms (int): Client request timeout in milliseconds.
                Default: 30000.
            max_in_flight_requests_per_connection (int): Requests are pipelined
                to kafka brokers up to this number of maximum requests per
                broker connection. Default: 5.
            receive_buffer_bytes (int): The size of the TCP receive buffer
                (SO_RCVBUF) to use when reading data. Default: None (relies on
                system defaults). Java client defaults to 32768.
            send_buffer_bytes (int): The size of the TCP send buffer
                (SO_SNDBUF) to use when sending data. Default: None (relies on
                system defaults). Java client defaults to 131072.
            socket_options (list): List of tuple-arguments to socket.setsockopt
                to apply to broker connection sockets. Default:
                [(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)]
            security_protocol (str): Protocol used to communicate with brokers.
                Valid values are: PLAINTEXT, SSL, SASL_PLAINTEXT, SASL_SSL.
                Default: PLAINTEXT.
            ssl_context (ssl.SSLContext): pre-configured SSLContext for wrapping
                socket connections. If provided, all other ssl_* configurations
                will be ignored. Default: None.
            ssl_check_hostname (bool): flag to configure whether ssl handshake
                should verify that the certificate matches the brokers hostname.
                default: True.
            ssl_cafile (str): optional filename of ca file to use in certificate
                verification. default: None.
            ssl_certfile (str): optional filename of file in pem format containing
                the client certificate, as well as any ca certificates needed to
                establish the certificate's authenticity. default: None.
            ssl_keyfile (str): optional filename containing the client private key.
                default: None.
            ssl_password (callable, str, bytes, bytearray): optional password or
                callable function that returns a password, for decrypting the
                client private key. Default: None.
            ssl_crlfile (str): optional filename containing the CRL to check for
                certificate expiration. By default, no CRL check is done. When
                providing a file, only the leaf certificate will be checked against
                this CRL. The CRL can only be checked with Python 3.4+ or 2.7.9+.
                default: None.
            ssl_ciphers (str): optionally set the available ciphers for ssl
                connections. It should be a string in the OpenSSL cipher list
                format. If no cipher can be selected (because compile-time options
                or other configuration forbids use of all the specified ciphers),
                an ssl.SSLError will be raised. See ssl.SSLContext.set_ciphers
            api_version (tuple): Specify which Kafka API version to use.
                Accepted values are: (0, 8, 0), (0, 8, 1), (0, 8, 2), (0, 9),
                (0, 10). Default: (0, 8, 2)
            api_version_auto_timeout_ms (int): number of milliseconds to throw a
                timeout exception from the constructor when checking the broker
                api version. Only applies if api_version is None
            selector (selectors.BaseSelector): Provide a specific selector
                implementation to use for I/O multiplexing.
                Default: selectors.DefaultSelector
            state_change_callback (callable): function to be called when the
                connection state changes from CONNECTING to CONNECTED etc.
            metrics (kafka.metrics.Metrics): Optionally provide a metrics
                instance for capturing network IO stats. Default: None.
            metric_group_prefix (str): Prefix for metric names. Default: ''
            sasl_mechanism (str): Authentication mechanism when security_protocol
                is configured for SASL_PLAINTEXT or SASL_SSL. Valid values are:
                PLAIN, GSSAPI, OAUTHBEARER.
            sasl_plain_username (str): username for sasl PLAIN authentication.
                Required if sasl_mechanism is PLAIN.
            sasl_plain_password (str): password for sasl PLAIN authentication.
                Required if sasl_mechanism is PLAIN.
            sasl_kerberos_service_name (str): Service name to include in GSSAPI
                sasl mechanism handshake. Default: 'kafka'
            sasl_kerberos_domain_name (str): kerberos domain name to use in GSSAPI
                sasl mechanism handshake. Default: one of bootstrap servers
            sasl_oauth_token_provider (AbstractTokenProvider): OAuthBearer token provider
                instance. (See kafka.oauth.abstract). Default: None
        """

        DEFAULT_CONFIG = {
            'client_id': 'kafka-python-' + __version__,
            'node_id': 0,
            'request_timeout_ms': 30000,
            'reconnect_backoff_ms': 50,
            'reconnect_backoff_max_ms': 1000,
            'max_in_flight_requests_per_connection': 5,
            'receive_buffer_bytes': None,
            'send_buffer_bytes': None,
            'socket_options': [(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)],
            'sock_chunk_bytes': 4096,  # undocumented experimental option
            'sock_chunk_buffer_count': 1000,  # undocumented experimental option
            'security_protocol': 'PLAINTEXT',
            'ssl_context': None,
            'ssl_check_hostname': True,
            'ssl_cafile': None,
            'ssl_certfile': None,
            'ssl_keyfile': None,
            'ssl_crlfile': None,
            'ssl_password': None,
            'ssl_ciphers': None,
            'api_version': (0, 8, 2),  # default to most restrictive
            'selector': selectors.DefaultSelector,
            'state_change_callback': lambda node_id, sock, conn: True,
            'metrics': None,
            'metric_group_prefix': '',
            'sasl_mechanism': None,
            'sasl_plain_username': None,
            'sasl_plain_password': None,
            'sasl_kerberos_service_name': 'kafka',
            'sasl_kerberos_domain_name': None,
            'sasl_oauth_token_provider': None
        }
        SECURITY_PROTOCOLS = ('PLAINTEXT', 'SSL', 'SASL_PLAINTEXT', 'SASL_SSL')
        SASL_MECHANISMS = ('PLAIN', 'GSSAPI', 'OAUTHBEARER')

        def __init__(self, host, port, afi, **configs):
            self.host = host
            self.port = port
            self.afi = afi
            self._sock_afi = afi
            self._sock_addr = None
            self._api_versions = None

            self.config = copy.copy(self.DEFAULT_CONFIG)
            for key in self.config:
                if key in configs:
                    self.config[key] = configs[key]

            self.node_id = self.config.pop('node_id')

            if self.config['receive_buffer_bytes'] is not None:
                self.config['socket_options'].append(
                    (socket.SOL_SOCKET, socket.SO_RCVBUF,
                     self.config['receive_buffer_bytes']))
            if self.config['send_buffer_bytes'] is not None:
                self.config['socket_options'].append(
                     (socket.SOL_SOCKET, socket.SO_SNDBUF,
                     self.config['send_buffer_bytes']))

            assert self.config['security_protocol'] in self.SECURITY_PROTOCOLS, (
                'security_protcol must be in ' + ', '.join(self.SECURITY_PROTOCOLS))

            if self.config['security_protocol'] in ('SSL', 'SASL_SSL'):
                assert ssl_available, "Python wasn't built with SSL support"

            if self.config['security_protocol'] in ('SASL_PLAINTEXT', 'SASL_SSL'):
                assert self.config['sasl_mechanism'] in self.SASL_MECHANISMS, (
                    'sasl_mechanism must be in ' + ', '.join(self.SASL_MECHANISMS))
                if self.config['sasl_mechanism'] == 'PLAIN':
                    assert self.config['sasl_plain_username'] is not None, 'sasl_plain_username required for PLAIN sasl'
                    assert self.config['sasl_plain_password'] is not None, 'sasl_plain_password required for PLAIN sasl'
                if self.config['sasl_mechanism'] == 'GSSAPI':
                    assert gssapi is not None, 'GSSAPI lib not available'
                    assert self.config['sasl_kerberos_service_name'] is not None, 'sasl_kerberos_service_name required for GSSAPI sasl'
                if self.config['sasl_mechanism'] == 'OAUTHBEARER':
                    token_provider = self.config['sasl_oauth_token_provider']
                    assert token_provider is not None, 'sasl_oauth_token_provider required for OAUTHBEARER sasl'
                    assert callable(getattr(token_provider, "token", None)), 'sasl_oauth_token_provider must implement method #token()'
            # This is not a general lock / this class is not generally thread-safe yet
            # However, to avoid pushing responsibility for maintaining
            # per-connection locks to the upstream client, we will use this lock to
            # make sure that access to the protocol buffer is synchronized
            # when sends happen on multiple threads
            self._lock = threading.Lock()

            # the protocol parser instance manages actual tracking of the
            # sequence of in-flight requests to responses, which should
            # function like a FIFO queue. For additional request data,
            # including tracking request futures and timestamps, we
            # can use a simple dictionary of correlation_id => request data
            self.in_flight_requests = dict()

            self._protocol = KafkaProtocol(
                client_id=self.config['client_id'],
                api_version=self.config['api_version'])
            self.state = ConnectionStates.DISCONNECTED
            self._reset_reconnect_backoff()
            self._sock = None
            self._ssl_context = None
            if self.config['ssl_context'] is not None:
                self._ssl_context = self.config['ssl_context']
            self._sasl_auth_future = None
            self.last_attempt = 0
            self._gai = []
            self._sensors = None
            if self.config['metrics']:
                self._sensors = BrokerConnectionMetrics(self.config['metrics'],
                                                        self.config['metric_group_prefix'],
                                                        self.node_id)

        def _dns_lookup(self):
            self._gai = dns_lookup(self.host, self.port, self.afi)
            if not self._gai:
                log.error('DNS lookup failed for %s:%i (%s)',
                          self.host, self.port, self.afi)
                return False
            return True

        def _next_afi_sockaddr(self):
            if not self._gai:
                if not self._dns_lookup():
                    return
            afi, _, __, ___, sockaddr = self._gai.pop(0)
            return (afi, sockaddr)

        def connect_blocking(self, timeout=float('inf')):
            if self.connected():
                return True
            timeout += time.time()
            # First attempt to perform dns lookup
            # note that the underlying interface, socket.getaddrinfo,
            # has no explicit timeout so we may exceed the user-specified timeout
            self._dns_lookup()

            # Loop once over all returned dns entries
            selector = None
            while self._gai:
                while time.time() < timeout:
                    self.connect()
                    if self.connected():
                        if selector is not None:
                            selector.close()
                        return True
                    elif self.connecting():
                        if selector is None:
                            selector = self.config['selector']()
                            selector.register(self._sock, selectors.EVENT_WRITE)
                        selector.select(1)
                    elif self.disconnected():
                        if selector is not None:
                            selector.close()
                            selector = None
                        break
                else:
                    break
            return False

        def connect(self):
            """Attempt to connect and return ConnectionState"""
            if self.state is ConnectionStates.DISCONNECTED and not self.blacked_out():
                self.last_attempt = time.time()
                next_lookup = self._next_afi_sockaddr()
                if not next_lookup:
                    self.close(Errors.KafkaConnectionError('DNS failure'))
                    return self.state
                else:
                    log.debug('%s: creating new socket', self)
                    assert self._sock is None
                    self._sock_afi, self._sock_addr = next_lookup
                    self._sock = socket.socket(self._sock_afi, socket.SOCK_STREAM)

                for option in self.config['socket_options']:
                    log.debug('%s: setting socket option %s', self, option)
                    self._sock.setsockopt(*option)

                self._sock.setblocking(False)
                self.state = ConnectionStates.CONNECTING
                self.config['state_change_callback'](self.node_id, self._sock, self)
                log.info('%s: connecting to %s:%d [%s %s]', self, self.host,
                         self.port, self._sock_addr, AFI_NAMES[self._sock_afi])

            if self.state is ConnectionStates.CONNECTING:
                # in non-blocking mode, use repeated calls to socket.connect_ex
                # to check connection status
                ret = None
                try:
                    ret = self._sock.connect_ex(self._sock_addr)
                except socket.error as err:
                    ret = err.errno

                # Connection succeeded
                if not ret or ret == errno.EISCONN:
                    log.debug('%s: established TCP connection', self)

                    if self.config['security_protocol'] in ('SSL', 'SASL_SSL'):
                        log.debug('%s: initiating SSL handshake', self)
                        self.state = ConnectionStates.HANDSHAKE
                        self.config['state_change_callback'](self.node_id, self._sock, self)
                        # _wrap_ssl can alter the connection state -- disconnects on failure
                        self._wrap_ssl()

                    elif self.config['security_protocol'] == 'SASL_PLAINTEXT':
                        log.debug('%s: initiating SASL authentication', self)
                        self.state = ConnectionStates.AUTHENTICATING
                        self.config['state_change_callback'](self.node_id, self._sock, self)

                    else:
                        # security_protocol PLAINTEXT
                        log.info('%s: Connection complete.', self)
                        self.state = ConnectionStates.CONNECTED
                        self._reset_reconnect_backoff()
                        self.config['state_change_callback'](self.node_id, self._sock, self)

                # Connection failed
                # WSAEINVAL == 10022, but errno.WSAEINVAL is not available on non-win systems
                elif ret not in (errno.EINPROGRESS, errno.EALREADY, errno.EWOULDBLOCK, 10022):
                    log.error('Connect attempt to %s returned error %s.'
                              ' Disconnecting.', self, ret)
                    errstr = errno.errorcode.get(ret, 'UNKNOWN')
                    self.close(Errors.KafkaConnectionError('{} {}'.format(ret, errstr)))
                    return self.state

                # Needs retry
                else:
                    pass

            if self.state is ConnectionStates.HANDSHAKE:
                if self._try_handshake():
                    log.debug('%s: completed SSL handshake.', self)
                    if self.config['security_protocol'] == 'SASL_SSL':
                        log.debug('%s: initiating SASL authentication', self)
                        self.state = ConnectionStates.AUTHENTICATING
                    else:
                        log.info('%s: Connection complete.', self)
                        self.state = ConnectionStates.CONNECTED
                        self._reset_reconnect_backoff()
                    self.config['state_change_callback'](self.node_id, self._sock, self)

            if self.state is ConnectionStates.AUTHENTICATING:
                assert self.config['security_protocol'] in ('SASL_PLAINTEXT', 'SASL_SSL')
                if self._try_authenticate():
                    # _try_authenticate has side-effects: possibly disconnected on socket errors
                    if self.state is ConnectionStates.AUTHENTICATING:
                        log.info('%s: Connection complete.', self)
                        self.state = ConnectionStates.CONNECTED
                        self._reset_reconnect_backoff()
                        self.config['state_change_callback'](self.node_id, self._sock, self)

            if self.state not in (ConnectionStates.CONNECTED,
                                  ConnectionStates.DISCONNECTED):
                # Connection timed out
                request_timeout = self.config['request_timeout_ms'] / 1000.0
                if time.time() > request_timeout + self.last_attempt:
                    log.error('Connection attempt to %s timed out', self)
                    self.close(Errors.KafkaConnectionError('timeout'))
                    return self.state

            return self.state

        def _wrap_ssl(self):
            assert self.config['security_protocol'] in ('SSL', 'SASL_SSL')
            if self._ssl_context is None:
                log.debug('%s: configuring default SSL Context', self)
                self._ssl_context = ssl.SSLContext(ssl.PROTOCOL_SSLv23)  # pylint: disable=no-member
                self._ssl_context.options |= ssl.OP_NO_SSLv2  # pylint: disable=no-member
                self._ssl_context.options |= ssl.OP_NO_SSLv3  # pylint: disable=no-member
                self._ssl_context.verify_mode = ssl.CERT_OPTIONAL
                if self.config['ssl_check_hostname']:
                    self._ssl_context.check_hostname = True
                if self.config['ssl_cafile']:
                    log.info('%s: Loading SSL CA from %s', self, self.config['ssl_cafile'])
                    self._ssl_context.load_verify_locations(self.config['ssl_cafile'])
                    self._ssl_context.verify_mode = ssl.CERT_REQUIRED
                if self.config['ssl_certfile'] and self.config['ssl_keyfile']:
                    log.info('%s: Loading SSL Cert from %s', self, self.config['ssl_certfile'])
                    log.info('%s: Loading SSL Key from %s', self, self.config['ssl_keyfile'])
                    self._ssl_context.load_cert_chain(
                        certfile=self.config['ssl_certfile'],
                        keyfile=self.config['ssl_keyfile'],
                        password=self.config['ssl_password'])
                if self.config['ssl_crlfile']:
                    if not hasattr(ssl, 'VERIFY_CRL_CHECK_LEAF'):
                        raise RuntimeError('This version of Python does not support ssl_crlfile!')
                    log.info('%s: Loading SSL CRL from %s', self, self.config['ssl_crlfile'])
                    self._ssl_context.load_verify_locations(self.config['ssl_crlfile'])
                    # pylint: disable=no-member
                    self._ssl_context.verify_flags |= ssl.VERIFY_CRL_CHECK_LEAF
                if self.config['ssl_ciphers']:
                    log.info('%s: Setting SSL Ciphers: %s', self, self.config['ssl_ciphers'])
                    self._ssl_context.set_ciphers(self.config['ssl_ciphers'])
            log.debug('%s: wrapping socket in ssl context', self)
            try:
                self._sock = self._ssl_context.wrap_socket(
                    self._sock,
                    server_hostname=self.host,
                    do_handshake_on_connect=False)
            except ssl.SSLError as e:
                log.exception('%s: Failed to wrap socket in SSLContext!', self)
                self.close(e)

        def _try_handshake(self):
            assert self.config['security_protocol'] in ('SSL', 'SASL_SSL')
            try:
                self._sock.do_handshake()
                return True
            # old ssl in python2.6 will swallow all SSLErrors here...
            except (SSLWantReadError, SSLWantWriteError):
                pass
            except (SSLZeroReturnError, ConnectionError, SSLEOFError):
                log.warning('SSL connection closed by server during handshake.')
                self.close(Errors.KafkaConnectionError('SSL connection closed by server during handshake'))
            # Other SSLErrors will be raised to user

            return False

        def _try_authenticate(self):
            assert self.config['api_version'] is None or self.config['api_version'] >= (0, 10)

            if self._sasl_auth_future is None:
                # Build a SaslHandShakeRequest message
                request = SaslHandShakeRequest[0](self.config['sasl_mechanism'])
                future = Future()
                sasl_response = self._send(request)
                sasl_response.add_callback(self._handle_sasl_handshake_response, future)
                sasl_response.add_errback(lambda f, e: f.failure(e), future)
                self._sasl_auth_future = future

            for r, f in self.recv():
                f.success(r)

            # A connection error could trigger close() which will reset the future
            if self._sasl_auth_future is None:
                return False
            elif self._sasl_auth_future.failed():
                ex = self._sasl_auth_future.exception
                if not isinstance(ex, Errors.KafkaConnectionError):
                    raise ex  # pylint: disable-msg=raising-bad-type
            return self._sasl_auth_future.succeeded()

        def _handle_sasl_handshake_response(self, future, response):
            error_type = Errors.for_code(response.error_code)
            if error_type is not Errors.NoError:
                error = error_type(self)
                self.close(error=error)
                return future.failure(error_type(self))

            if self.config['sasl_mechanism'] not in response.enabled_mechanisms:
                return future.failure(
                    Errors.UnsupportedSaslMechanismError(
                        'Kafka broker does not support %s sasl mechanism. Enabled mechanisms are: %s'
                        % (self.config['sasl_mechanism'], response.enabled_mechanisms)))
            elif self.config['sasl_mechanism'] == 'PLAIN':
                return self._try_authenticate_plain(future)
            elif self.config['sasl_mechanism'] == 'GSSAPI':
                return self._try_authenticate_gssapi(future)
            elif self.config['sasl_mechanism'] == 'OAUTHBEARER':
                return self._try_authenticate_oauth(future)
            else:
                return future.failure(
                    Errors.UnsupportedSaslMechanismError(
                        'kafka-python does not support SASL mechanism %s' %
                        self.config['sasl_mechanism']))

        def _send_bytes_blocking(self, data):
            self._sock.settimeout(self.config['request_timeout_ms'] / 1000)
            total_sent = 0
            try:
                while total_sent < len(data):
                    sent_bytes = self._sock.send(data[total_sent:])
                    total_sent += sent_bytes
                if total_sent != len(data):
                    raise ConnectionError('Buffer overrun during socket send')
                return total_sent
            finally:
                self._sock.settimeout(0.0)

        def _recv_bytes_blocking(self, n):
            self._sock.settimeout(self.config['request_timeout_ms'] / 1000)
            try:
                data = b''
                while len(data) < n:
                    fragment = self._sock.recv(n - len(data))
                    if not fragment:
                        raise ConnectionError('Connection reset during recv')
                    data += fragment
                return data
            finally:
                self._sock.settimeout(0.0)

        def _try_authenticate_plain(self, future):
            if self.config['security_protocol'] == 'SASL_PLAINTEXT':
                log.warning('%s: Sending username and password in the clear', self)

            data = b''
            # Send PLAIN credentials per RFC-4616
            msg = bytes('\0'.join([self.config['sasl_plain_username'],
                                   self.config['sasl_plain_username'],
                                   self.config['sasl_plain_password']]).encode('utf-8'))
            size = Int32.encode(len(msg))
            try:
                with self._lock:
                    if not self._can_send_recv():
                        return future.failure(Errors.NodeNotReadyError(str(self)))
                    self._send_bytes_blocking(size + msg)

                    # The server will send a zero sized message (that is Int32(0)) on success.
                    # The connection is closed on failure
                    data = self._recv_bytes_blocking(4)

            except ConnectionError as e:
                log.exception("%s: Error receiving reply from server", self)
                error = Errors.KafkaConnectionError("%s: %s" % (self, e))
                self.close(error=error)
                return future.failure(error)

            if data != b'\x00\x00\x00\x00':
                error = Errors.AuthenticationFailedError('Unrecognized response during authentication')
                return future.failure(error)

            log.info('%s: Authenticated as %s via PLAIN', self, self.config['sasl_plain_username'])
            return future.success(True)

        def _try_authenticate_gssapi(self, future):
            kerberos_damin_name = self.config['sasl_kerberos_domain_name'] or self.host
            auth_id = self.config['sasl_kerberos_service_name'] + '@' + kerberos_damin_name
            gssapi_name = gssapi.Name(
                auth_id,
                name_type=gssapi.NameType.hostbased_service
            ).canonicalize(gssapi.MechType.kerberos)
            log.debug('%s: GSSAPI name: %s', self, gssapi_name)

            self._lock.acquire()
            if not self._can_send_recv():
                return future.failure(Errors.NodeNotReadyError(str(self)))
            # Establish security context and negotiate protection level
            # For reference RFC 2222, section 7.2.1
            try:
                # Exchange tokens until authentication either succeeds or fails
                client_ctx = gssapi.SecurityContext(name=gssapi_name, usage='initiate')
                received_token = None
                while not client_ctx.complete:
                    # calculate an output token from kafka token (or None if first iteration)
                    output_token = client_ctx.step(received_token)

                    # pass output token to kafka, or send empty response if the security
                    # context is complete (output token is None in that case)
                    if output_token is None:
                        self._send_bytes_blocking(Int32.encode(0))
                    else:
                        msg = output_token
                        size = Int32.encode(len(msg))
                        self._send_bytes_blocking(size + msg)

                    # The server will send a token back. Processing of this token either
                    # establishes a security context, or it needs further token exchange.
                    # The gssapi will be able to identify the needed next step.
                    # The connection is closed on failure.
                    header = self._recv_bytes_blocking(4)
                    (token_size,) = struct.unpack('>i', header)
                    received_token = self._recv_bytes_blocking(token_size)

                # Process the security layer negotiation token, sent by the server
                # once the security context is established.

                # unwraps message containing supported protection levels and msg size
                msg = client_ctx.unwrap(received_token).message
                # Kafka currently doesn't support integrity or confidentiality security layers, so we
                # simply set QoP to 'auth' only (first octet). We reuse the max message size proposed
                # by the server
                msg = Int8.encode(SASL_QOP_AUTH & Int8.decode(io.BytesIO(msg[0:1]))) + msg[1:]
                # add authorization identity to the response, GSS-wrap and send it
                msg = client_ctx.wrap(msg + auth_id.encode(), False).message
                size = Int32.encode(len(msg))
                self._send_bytes_blocking(size + msg)

            except ConnectionError as e:
                self._lock.release()
                log.exception("%s: Error receiving reply from server",  self)
                error = Errors.KafkaConnectionError("%s: %s" % (self, e))
                self.close(error=error)
                return future.failure(error)
            except Exception as e:
                self._lock.release()
                return future.failure(e)

            self._lock.release()
            log.info('%s: Authenticated as %s via GSSAPI', self, gssapi_name)
            return future.success(True)

        def _try_authenticate_oauth(self, future):
            data = b''

            msg = bytes(self._build_oauth_client_request().encode("utf-8"))
            size = Int32.encode(len(msg))
            self._lock.acquire()
            if not self._can_send_recv():
                return future.failure(Errors.NodeNotReadyError(str(self)))
            try:
                # Send SASL OAuthBearer request with OAuth token
                self._send_bytes_blocking(size + msg)

                # The server will send a zero sized message (that is Int32(0)) on success.
                # The connection is closed on failure
                data = self._recv_bytes_blocking(4)

            except ConnectionError as e:
                self._lock.release()
                log.exception("%s: Error receiving reply from server", self)
                error = Errors.KafkaConnectionError("%s: %s" % (self, e))
                self.close(error=error)
                return future.failure(error)

            self._lock.release()

            if data != b'\x00\x00\x00\x00':
                error = Errors.AuthenticationFailedError('Unrecognized response during authentication')
                return future.failure(error)

            log.info('%s: Authenticated via OAuth', self)
            return future.success(True)

        def _build_oauth_client_request(self):
            token_provider = self.config['sasl_oauth_token_provider']
            return "n,,\x01auth=Bearer {}{}\x01\x01".format(token_provider.token(), self._token_extensions())

        def _token_extensions(self):
            """
            Return a string representation of the OPTIONAL key-value pairs that can be sent with an OAUTHBEARER
            initial request.
            """
            token_provider = self.config['sasl_oauth_token_provider']

            # Only run if the #extensions() method is implemented by the clients Token Provider class
            # Builds up a string separated by \x01 via a dict of key value pairs
            if callable(getattr(token_provider, "extensions", None)) and len(token_provider.extensions()) > 0:
                msg = "\x01".join(["{}={}".format(k, v) for k, v in token_provider.extensions().items()])
                return "\x01" + msg
            else:
                return ""

        def blacked_out(self):
            """
            Return true if we are disconnected from the given node and can't
            re-establish a connection yet
            """
            if self.state is ConnectionStates.DISCONNECTED:
                if time.time() < self.last_attempt + self._reconnect_backoff:
                    return True
            return False

        def connection_delay(self):
            """
            Return the number of milliseconds to wait, based on the connection
            state, before attempting to send data. When disconnected, this respects
            the reconnect backoff time. When connecting, returns 0 to allow
            non-blocking connect to finish. When connected, returns a very large
            number to handle slow/stalled connections.
            """
            time_waited = time.time() - (self.last_attempt or 0)
            if self.state is ConnectionStates.DISCONNECTED:
                return max(self._reconnect_backoff - time_waited, 0) * 1000
            elif self.connecting():
                return 0
            else:
                return float('inf')

        def connected(self):
            """Return True iff socket is connected."""
            return self.state is ConnectionStates.CONNECTED

        def connecting(self):
            """Returns True if still connecting (this may encompass several
            different states, such as SSL handshake, authorization, etc)."""
            return self.state in (ConnectionStates.CONNECTING,
                                  ConnectionStates.HANDSHAKE,
                                  ConnectionStates.AUTHENTICATING)

        def disconnected(self):
            """Return True iff socket is closed"""
            return self.state is ConnectionStates.DISCONNECTED

        def _reset_reconnect_backoff(self):
            self._failures = 0
            self._reconnect_backoff = self.config['reconnect_backoff_ms'] / 1000.0

        def _update_reconnect_backoff(self):
            # Do not mark as failure if there are more dns entries available to try
            if len(self._gai) > 0:
                return
            if self.config['reconnect_backoff_max_ms'] > self.config['reconnect_backoff_ms']:
                self._failures += 1
                self._reconnect_backoff = self.config['reconnect_backoff_ms'] * 2 ** (self._failures - 1)
                self._reconnect_backoff = min(self._reconnect_backoff, self.config['reconnect_backoff_max_ms'])
                self._reconnect_backoff *= uniform(0.8, 1.2)
                self._reconnect_backoff /= 1000.0
                log.debug('%s: reconnect backoff %s after %s failures', self, self._reconnect_backoff, self._failures)

        def _close_socket(self):
            if hasattr(self, '_sock') and self._sock is not None:
                self._sock.close()
                self._sock = None

        def __del__(self):
            self._close_socket()

        def close(self, error=None):
            """Close socket and fail all in-flight-requests.

            Arguments:
                error (Exception, optional): pending in-flight-requests
                    will be failed with this exception.
                    Default: kafka.errors.KafkaConnectionError.
            """
            if self.state is ConnectionStates.DISCONNECTED:
                return
            with self._lock:
                if self.state is ConnectionStates.DISCONNECTED:
                    return
                log.info('%s: Closing connection. %s', self, error or '')
                self._update_reconnect_backoff()
                self._sasl_auth_future = None
                self._protocol = KafkaProtocol(
                    client_id=self.config['client_id'],
                    api_version=self.config['api_version'])
                if error is None:
                    error = Errors.Cancelled(str(self))
                ifrs = list(self.in_flight_requests.items())
                self.in_flight_requests.clear()
                self.state = ConnectionStates.DISCONNECTED
                # To avoid race conditions and/or deadlocks
                # keep a reference to the socket but leave it
                # open until after the state_change_callback
                # This should give clients a change to deregister
                # the socket fd from selectors cleanly.
                sock = self._sock
                self._sock = None

            # drop lock before state change callback and processing futures
            self.config['state_change_callback'](self.node_id, sock, self)
            sock.close()
            for (_correlation_id, (future, _timestamp)) in ifrs:
                future.failure(error)

        def _can_send_recv(self):
            """Return True iff socket is ready for requests / responses"""
            return self.state in (ConnectionStates.AUTHENTICATING,
                                  ConnectionStates.CONNECTED)

        def send(self, request, blocking=True):
            """Queue request for async network send, return Future()"""
            future = Future()
            if self.connecting():
                return future.failure(Errors.NodeNotReadyError(str(self)))
            elif not self.connected():
                return future.failure(Errors.KafkaConnectionError(str(self)))
            elif not self.can_send_more():
                return future.failure(Errors.TooManyInFlightRequests(str(self)))
            return self._send(request, blocking=blocking)

        def _send(self, request, blocking=True):
            future = Future()
            with self._lock:
                if not self._can_send_recv():
                    return future.failure(Errors.NodeNotReadyError(str(self)))

                correlation_id = self._protocol.send_request(request)

                log.debug('%s Request %d: %s', self, correlation_id, request)
                if request.expect_response():
                    sent_time = time.time()
                    assert correlation_id not in self.in_flight_requests, 'Correlation ID already in-flight!'
                    self.in_flight_requests[correlation_id] = (future, sent_time)
                else:
                    future.success(None)

            # Attempt to replicate behavior from prior to introduction of
            # send_pending_requests() / async sends
            if blocking:
                self.send_pending_requests()

            return future

        def send_pending_requests(self):
            """Can block on network if request is larger than send_buffer_bytes"""
            try:
                with self._lock:
                    if not self._can_send_recv():
                        return Errors.NodeNotReadyError(str(self))
                    # In the future we might manage an internal write buffer
                    # and send bytes asynchronously. For now, just block
                    # sending each request payload
                    data = self._protocol.send_bytes()
                    total_bytes = self._send_bytes_blocking(data)
                if self._sensors:
                    self._sensors.bytes_sent.record(total_bytes)
                return total_bytes
            except ConnectionError as e:
                log.exception("Error sending request data to %s", self)
                error = Errors.KafkaConnectionError("%s: %s" % (self, e))
                self.close(error=error)
                return error

        def can_send_more(self):
            """Return True unless there are max_in_flight_requests_per_connection."""
            max_ifrs = self.config['max_in_flight_requests_per_connection']
            return len(self.in_flight_requests) < max_ifrs

        def recv(self):
            """Non-blocking network receive.

            Return list of (response, future) tuples
            """
            responses = self._recv()
            if not responses and self.requests_timed_out():
                log.warning('%s timed out after %s ms. Closing connection.',
                            self, self.config['request_timeout_ms'])
                self.close(error=Errors.RequestTimedOutError(
                    'Request timed out after %s ms' %
                    self.config['request_timeout_ms']))
                return ()

            # augment respones w/ correlation_id, future, and timestamp
            for i, (correlation_id, response) in enumerate(responses):
                try:
                    with self._lock:
                        (future, timestamp) = self.in_flight_requests.pop(correlation_id)
                except KeyError:
                    self.close(Errors.KafkaConnectionError('Received unrecognized correlation id'))
                    return ()
                latency_ms = (time.time() - timestamp) * 1000
                if self._sensors:
                    self._sensors.request_time.record(latency_ms)

                log.debug('%s Response %d (%s ms): %s', self, correlation_id, latency_ms, response)
                responses[i] = (response, future)

            return responses

        def _recv(self):
            """Take all available bytes from socket, return list of any responses from parser"""
            recvd = []
            self._lock.acquire()
            if not self._can_send_recv():
                log.warning('%s cannot recv: socket not connected', self)
                self._lock.release()
                return ()

            while len(recvd) < self.config['sock_chunk_buffer_count']:
                try:
                    data = self._sock.recv(self.config['sock_chunk_bytes'])
                    # We expect socket.recv to raise an exception if there are no
                    # bytes available to read from the socket in non-blocking mode.
                    # but if the socket is disconnected, we will get empty data
                    # without an exception raised
                    if not data:
                        log.error('%s: socket disconnected', self)
                        self._lock.release()
                        self.close(error=Errors.KafkaConnectionError('socket disconnected'))
                        return []
                    else:
                        recvd.append(data)

                except SSLWantReadError:
                    break
                except ConnectionError as e:
                    if six.PY2 and e.errno == errno.EWOULDBLOCK:
                        break
                    log.exception('%s: Error receiving network data'
                                  ' closing socket', self)
                    self._lock.release()
                    self.close(error=Errors.KafkaConnectionError(e))
                    return []
                except BlockingIOError:
                    if six.PY3:
                        break
                    self._lock.release()
                    raise

            recvd_data = b''.join(recvd)
            if self._sensors:
                self._sensors.bytes_received.record(len(recvd_data))

            try:
                responses = self._protocol.receive_bytes(recvd_data)
            except Errors.KafkaProtocolError as e:
                self._lock.release()
                self.close(e)
                return []
            else:
                self._lock.release()
                return responses

        def requests_timed_out(self):
            with self._lock:
                if self.in_flight_requests:
                    get_timestamp = lambda v: v[1]
                    oldest_at = min(map(get_timestamp,
                                        self.in_flight_requests.values()))
                    timeout = self.config['request_timeout_ms'] / 1000.0
                    if time.time() >= oldest_at + timeout:
                        return True
                return False

        def _handle_api_version_response(self, response):
            error_type = Errors.for_code(response.error_code)
            assert error_type is Errors.NoError, "API version check failed"
            self._api_versions = dict([
                (api_key, (min_version, max_version))
                for api_key, min_version, max_version in response.api_versions
            ])
            return self._api_versions

        def get_api_versions(self):
            if self._api_versions is not None:
                return self._api_versions

            version = self.check_version()
            if version < (0, 10, 0):
                raise Errors.UnsupportedVersionError(
                    "ApiVersion not supported by cluster version {} < 0.10.0"
                    .format(version))
            # _api_versions is set as a side effect of check_versions() on a cluster
            # that supports 0.10.0 or later
            return self._api_versions

        def _infer_broker_version_from_api_versions(self, api_versions):
            # The logic here is to check the list of supported request versions
            # in reverse order. As soon as we find one that works, return it
            test_cases = [
                # format (<broker version>, <needed struct>)
                ((1, 0, 0), MetadataRequest[5]),
                ((0, 11, 0), MetadataRequest[4]),
                ((0, 10, 2), OffsetFetchRequest[2]),
                ((0, 10, 1), MetadataRequest[2]),
            ]

            # Get the best match of test cases
            for broker_version, struct in sorted(test_cases, reverse=True):
                if struct.API_KEY not in api_versions:
                    continue
                min_version, max_version = api_versions[struct.API_KEY]
                if min_version <= struct.API_VERSION <= max_version:
                    return broker_version

            # We know that ApiVersionResponse is only supported in 0.10+
            # so if all else fails, choose that
            return (0, 10, 0)

        def check_version(self, timeout=2, strict=False, topics=[]):
            """Attempt to guess the broker version.

            Note: This is a blocking call.

            Returns: version tuple, i.e. (0, 10), (0, 9), (0, 8, 2), ...
            """
            timeout_at = time.time() + timeout
            log.info('Probing node %s broker version', self.node_id)
            # Monkeypatch some connection configurations to avoid timeouts
            override_config = {
                'request_timeout_ms': timeout * 1000,
                'max_in_flight_requests_per_connection': 5
            }
            stashed = {}
            for key in override_config:
                stashed[key] = self.config[key]
                self.config[key] = override_config[key]

            # kafka kills the connection when it doesn't recognize an API request
            # so we can send a test request and then follow immediately with a
            # vanilla MetadataRequest. If the server did not recognize the first
            # request, both will be failed with a ConnectionError that wraps
            # socket.error (32, 54, or 104)
            from kafka.protocol.admin import ApiVersionRequest, ListGroupsRequest
            from kafka.protocol.commit import OffsetFetchRequest, GroupCoordinatorRequest

            test_cases = [
                # All cases starting from 0.10 will be based on ApiVersionResponse
                ((0, 10), ApiVersionRequest[0]()),
                ((0, 9), ListGroupsRequest[0]()),
                ((0, 8, 2), GroupCoordinatorRequest[0]('kafka-python-default-group')),
                ((0, 8, 1), OffsetFetchRequest[0]('kafka-python-default-group', [])),
                ((0, 8, 0), MetadataRequest[0](topics)),
            ]

            for version, request in test_cases:
                if not self.connect_blocking(timeout_at - time.time()):
                    raise Errors.NodeNotReadyError()
                f = self.send(request)
                # HACK: sleeping to wait for socket to send bytes
                time.sleep(0.1)
                # when broker receives an unrecognized request API
                # it abruptly closes our socket.
                # so we attempt to send a second request immediately
                # that we believe it will definitely recognize (metadata)
                # the attempt to write to a disconnected socket should
                # immediately fail and allow us to infer that the prior
                # request was unrecognized
                mr = self.send(MetadataRequest[0](topics))

                selector = self.config['selector']()
                selector.register(self._sock, selectors.EVENT_READ)
                while not (f.is_done and mr.is_done):
                    selector.select(1)
                    for response, future in self.recv():
                        future.success(response)
                selector.close()

                if f.succeeded():
                    if isinstance(request, ApiVersionRequest[0]):
                        # Starting from 0.10 kafka broker we determine version
                        # by looking at ApiVersionResponse
                        api_versions = self._handle_api_version_response(f.value)
                        version = self._infer_broker_version_from_api_versions(api_versions)
                    log.info('Broker version identifed as %s', '.'.join(map(str, version)))
                    log.info('Set configuration api_version=%s to skip auto'
                             ' check_version requests on startup', version)
                    break

                # Only enable strict checking to verify that we understand failure
                # modes. For most users, the fact that the request failed should be
                # enough to rule out a particular broker version.
                if strict:
                    # If the socket flush hack did not work (which should force the
                    # connection to close and fail all pending requests), then we
                    # get a basic Request Timeout. This is not ideal, but we'll deal
                    if isinstance(f.exception, Errors.RequestTimedOutError):
                        pass

                    # 0.9 brokers do not close the socket on unrecognized api
                    # requests (bug...). In this case we expect to see a correlation
                    # id mismatch
                    elif (isinstance(f.exception, Errors.CorrelationIdError) and
                          version == (0, 10)):
                        pass
                    elif six.PY2:
                        assert isinstance(f.exception.args[0], socket.error)
                        assert f.exception.args[0].errno in (32, 54, 104)
                    else:
                        assert isinstance(f.exception.args[0], ConnectionError)
                log.info("Broker is not v%s -- it did not recognize %s",
                         version, request.__class__.__name__)
            else:
                raise Errors.UnrecognizedBrokerVersion()

            for key in stashed:
                self.config[key] = stashed[key]
            return version

        def __str__(self):
            return "<BrokerConnection node_id=%s host=%s:%d %s [%s %s]>" % (
                self.node_id, self.host, self.port, self.state,
                AFI_NAMES[self._sock_afi], self._sock_addr)

    class BrokerConnectionMetrics(object):
        def __init__(self, metrics, metric_group_prefix, node_id):
            self.metrics = metrics

            # Any broker may have registered summary metrics already
            # but if not, we need to create them so we can set as parents below
            all_conns_transferred = metrics.get_sensor('bytes-sent-received')
            if not all_conns_transferred:
                metric_group_name = metric_group_prefix + '-metrics'

                bytes_transferred = metrics.sensor('bytes-sent-received')
                bytes_transferred.add(metrics.metric_name(
                    'network-io-rate', metric_group_name,
                    'The average number of network operations (reads or writes) on all'
                    ' connections per second.'), Rate(sampled_stat=Count()))

                bytes_sent = metrics.sensor('bytes-sent',
                                            parents=[bytes_transferred])
                bytes_sent.add(metrics.metric_name(
                    'outgoing-byte-rate', metric_group_name,
                    'The average number of outgoing bytes sent per second to all'
                    ' servers.'), Rate())
                bytes_sent.add(metrics.metric_name(
                    'request-rate', metric_group_name,
                    'The average number of requests sent per second.'),
                    Rate(sampled_stat=Count()))
                bytes_sent.add(metrics.metric_name(
                    'request-size-avg', metric_group_name,
                    'The average size of all requests in the window.'), Avg())
                bytes_sent.add(metrics.metric_name(
                    'request-size-max', metric_group_name,
                    'The maximum size of any request sent in the window.'), Max())

                bytes_received = metrics.sensor('bytes-received',
                                                parents=[bytes_transferred])
                bytes_received.add(metrics.metric_name(
                    'incoming-byte-rate', metric_group_name,
                    'Bytes/second read off all sockets'), Rate())
                bytes_received.add(metrics.metric_name(
                    'response-rate', metric_group_name,
                    'Responses received sent per second.'),
                    Rate(sampled_stat=Count()))

                request_latency = metrics.sensor('request-latency')
                request_latency.add(metrics.metric_name(
                    'request-latency-avg', metric_group_name,
                    'The average request latency in ms.'),
                    Avg())
                request_latency.add(metrics.metric_name(
                    'request-latency-max', metric_group_name,
                    'The maximum request latency in ms.'),
                    Max())

            # if one sensor of the metrics has been registered for the connection,
            # then all other sensors should have been registered; and vice versa
            node_str = 'node-{0}'.format(node_id)
            node_sensor = metrics.get_sensor(node_str + '.bytes-sent')
            if not node_sensor:
                metric_group_name = metric_group_prefix + '-node-metrics.' + node_str

                bytes_sent = metrics.sensor(
                    node_str + '.bytes-sent',
                    parents=[metrics.get_sensor('bytes-sent')])
                bytes_sent.add(metrics.metric_name(
                    'outgoing-byte-rate', metric_group_name,
                    'The average number of outgoing bytes sent per second.'),
                    Rate())
                bytes_sent.add(metrics.metric_name(
                    'request-rate', metric_group_name,
                    'The average number of requests sent per second.'),
                    Rate(sampled_stat=Count()))
                bytes_sent.add(metrics.metric_name(
                    'request-size-avg', metric_group_name,
                    'The average size of all requests in the window.'),
                    Avg())
                bytes_sent.add(metrics.metric_name(
                    'request-size-max', metric_group_name,
                    'The maximum size of any request sent in the window.'),
                    Max())

                bytes_received = metrics.sensor(
                    node_str + '.bytes-received',
                    parents=[metrics.get_sensor('bytes-received')])
                bytes_received.add(metrics.metric_name(
                    'incoming-byte-rate', metric_group_name,
                    'Bytes/second read off node-connection socket'),
                    Rate())
                bytes_received.add(metrics.metric_name(
                    'response-rate', metric_group_name,
                    'The average number of responses received per second.'),
                    Rate(sampled_stat=Count()))

                request_time = metrics.sensor(
                    node_str + '.latency',
                    parents=[metrics.get_sensor('request-latency')])
                request_time.add(metrics.metric_name(
                    'request-latency-avg', metric_group_name,
                    'The average request latency in ms.'),
                    Avg())
                request_time.add(metrics.metric_name(
                    'request-latency-max', metric_group_name,
                    'The maximum request latency in ms.'),
                    Max())

            self.bytes_sent = metrics.sensor(node_str + '.bytes-sent')
            self.bytes_received = metrics.sensor(node_str + '.bytes-received')
            self.request_time = metrics.sensor(node_str + '.latency')

    def _address_family(address):
        """
            Attempt to determine the family of an address (or hostname)

            :return: either socket.AF_INET or socket.AF_INET6 or socket.AF_UNSPEC if the address family
                     could not be determined
        """
        if address.startswith('[') and address.endswith(']'):
            return socket.AF_INET6
        for af in (socket.AF_INET, socket.AF_INET6):
            try:
                socket.inet_pton(af, address)
                return af
            except (ValueError, AttributeError, socket.error):
                continue
        return socket.AF_UNSPEC

    def get_ip_port_afi(host_and_port_str):
        """
            Parse the IP and port from a string in the format of:

                * host_or_ip          <- Can be either IPv4 address literal or hostname/fqdn
                * host_or_ipv4:port   <- Can be either IPv4 address literal or hostname/fqdn
                * [host_or_ip]        <- IPv6 address literal
                * [host_or_ip]:port.  <- IPv6 address literal

            .. note:: IPv6 address literals with ports *must* be enclosed in brackets

            .. note:: If the port is not specified, default will be returned.

            :return: tuple (host, port, afi), afi will be socket.AF_INET or socket.AF_INET6 or socket.AF_UNSPEC
        """
        host_and_port_str = host_and_port_str.strip()
        if host_and_port_str.startswith('['):
            af = socket.AF_INET6
            host, rest = host_and_port_str[1:].split(']')
            if rest:
                port = int(rest[1:])
            else:
                port = DEFAULT_KAFKA_PORT
            return host, port, af
        else:
            if ':' not in host_and_port_str:
                af = _address_family(host_and_port_str)
                return host_and_port_str, DEFAULT_KAFKA_PORT, af
            else:
                # now we have something with a colon in it and no square brackets. It could be
                # either an IPv6 address literal (e.g., "::1") or an IP:port pair or a host:port pair
                try:
                    # if it decodes as an IPv6 address, use that
                    socket.inet_pton(socket.AF_INET6, host_and_port_str)
                    return host_and_port_str, DEFAULT_KAFKA_PORT, socket.AF_INET6
                except AttributeError:
                    log.warning('socket.inet_pton not available on this platform.'
                                ' consider `pip install win_inet_pton`')
                    pass
                except (ValueError, socket.error):
                    # it's a host:port pair
                    pass
                host, port = host_and_port_str.rsplit(':', 1)
                port = int(port)

                af = _address_family(host)
                return host, port, af

    def collect_hosts(hosts, randomize=True):
        """
        Collects a comma-separated set of hosts (host:port) and optionally
        randomize the returned list.
        """

        if isinstance(hosts, six.string_types):
            hosts = hosts.strip().split(',')

        result = []
        afi = socket.AF_INET
        for host_port in hosts:

            host, port, afi = get_ip_port_afi(host_port)

            if port < 0:
                port = DEFAULT_KAFKA_PORT

            result.append((host, port, afi))

        if randomize:
            shuffle(result)

        return result

    def is_inet_4_or_6(gai):
        """Given a getaddrinfo struct, return True iff ipv4 or ipv6"""
        return gai[0] in (socket.AF_INET, socket.AF_INET6)

    def dns_lookup(host, port, afi=socket.AF_UNSPEC):
        """Returns a list of getaddrinfo structs, optionally filtered to an afi (ipv4 / ipv6)"""
        # XXX: all DNS functions in Python are blocking. If we really
        # want to be non-blocking here, we need to use a 3rd-party
        # library like python-adns, or move resolution onto its
        # own thread. This will be subject to the default libc
        # name resolution timeout (5s on most Linux boxes)
        try:
            return list(filter(is_inet_4_or_6,
                               socket.getaddrinfo(host, port, afi,
                                                  socket.SOCK_STREAM)))
        except socket.gaierror as ex:
            log.warning('DNS lookup failed for %s:%d,'
                        ' exception was %s. Is your'
                        ' advertised.listeners (called'
                        ' advertised.host.name before Kafka 9)'
                        ' correct and resolvable?',
                        host, port, ex)
            return []