Integration tests passing

1 files changed, 741 insertions, 498 deletions

diff --git a/kafka/client.py b/kafka/client.py
index c25e2d2..5da3919 100644
--- a/kafka/client.py
+++ b/kafka/client.py
@@ -1,631 +1,874 @@
-from collections import namedtuple
+import base64
+from collections import namedtuple, defaultdict
+from functools import partial
+from itertools import groupby, count
 import logging
+from operator import attrgetter
 import socket
 import struct
+import time
 import zlib
 
 from .codec import gzip_encode, gzip_decode
 from .codec import snappy_encode, snappy_decode
+from .util import read_short_string, read_int_string
+from .util import relative_unpack
+from .util import write_short_string, write_int_string
+from .util import group_by_topic_and_partition
+from .util import BufferUnderflowError, ChecksumError
 
 log = logging.getLogger("kafka")
 
-error_codes = {
-   -1: "UnknownError",
-    0: None,
-    1: "OffsetOutOfRange",
-    2: "InvalidMessage",
-    3: "WrongPartition",
-    4: "InvalidFetchSize"
-}
-
-class KafkaException(Exception):
-    def __init__(self, errorType):
-        self.errorType = errorType
-    def __str__(self):
-        return str(self.errorType)
+###############
+#   Structs   #
+###############
 
-Message = namedtuple("Message", ["magic", "attributes", "crc", "payload"])
-FetchRequest = namedtuple("FetchRequest", ["topic", "partition", "offset", "size"])
+# Request payloads
 ProduceRequest = namedtuple("ProduceRequest", ["topic", "partition", "messages"])
-OffsetRequest = namedtuple("OffsetRequest", ["topic", "partition", "time", "maxOffsets"])
-
-def length_prefix_message(msg):
-    """
-    Prefix a message with it's length as an int
-    """
-    return struct.pack('>i', len(msg)) + msg
-
-class KafkaClient(object):
+FetchRequest = namedtuple("FetchRequest", ["topic", "partition", "offset", "max_bytes"])
+OffsetRequest = namedtuple("OffsetRequest", ["topic", "partition", "time", "max_offsets"])
+OffsetCommitRequest = namedtuple("OffsetCommitRequest", ["topic", "partition", "offset", "metadata"])
+OffsetFetchRequest = namedtuple("OffsetFetchRequest", ["topic", "partition"])
+
+# Response payloads
+ProduceResponse = namedtuple("ProduceResponse", ["topic", "partition", "error", "offset"])
+FetchResponse = namedtuple("FetchResponse", ["topic", "partition", "error", "highwaterMark", "messages"])
+OffsetResponse = namedtuple("OffsetResponse", ["topic", "partition", "error", "offsets"])
+OffsetCommitResponse = namedtuple("OffsetCommitResponse", ["topic", "partition", "error"])
+OffsetFetchResponse = namedtuple("OffsetFetchResponse", ["topic", "partition", "offset", "metadata", "error"])
+BrokerMetadata = namedtuple("BrokerMetadata", ["nodeId", "host", "port"])
+PartitionMetadata = namedtuple("PartitionMetadata", ["topic", "partition", "leader", "replicas", "isr"])
+
+# Other useful structs 
+OffsetAndMessage = namedtuple("OffsetAndMessage", ["offset", "message"])
+Message = namedtuple("Message", ["magic", "attributes", "key", "value"])
+TopicAndPartition = namedtuple("TopicAndPartition", ["topic", "partition"])
+
+class ErrorMapping(object):
+    # Many of these are not actually used by the client
+    UNKNOWN                   = -1
+    NO_ERROR                  = 0
+    OFFSET_OUT_OF_RANGE       = 1
+    INVALID_MESSAGE           = 2
+    UNKNOWN_TOPIC_OR_PARTITON = 3
+    INVALID_FETCH_SIZE        = 4
+    LEADER_NOT_AVAILABLE      = 5
+    NOT_LEADER_FOR_PARTITION  = 6
+    REQUEST_TIMED_OUT         = 7
+    BROKER_NOT_AVAILABLE      = 8
+    REPLICA_NOT_AVAILABLE     = 9
+    MESSAGE_SIZE_TO_LARGE     = 10
+    STALE_CONTROLLER_EPOCH    = 11
+    OFFSET_METADATA_TOO_LARGE = 12
+
+class KafkaProtocol(object):
     """
-    Request Structure
-    =================
-
-    <Request>     ::= <len> <request-key> <payload>
-    <len>         ::= <int32>
-    <request-key> ::= 0 | 1 | 2 | 3 | 4
-    <payload>     ::= <ProduceRequest> | <FetchRequest> | <MultiFetchRequest> | <MultiProduceRequest> | <OffsetRequest>
-
-    Response Structure
-    ==================
-
-    <Response>    ::= <len> <err> <payload>
-    <len>         ::= <int32>
-    <err>         ::= -1 | 0 | 1 | 2 | 3 | 4
-    <payload>     ::= <ProduceResponse> | <FetchResponse> | <MultiFetchResponse> | <MultiProduceResponse> | <OffsetResponse>
-
-    Messages are big-endian byte order
+    Class to encapsulate all of the protocol encoding/decoding. This class does not
+    have any state associated with it, it is purely for organization.
     """
-
-    PRODUCE_KEY      = 0
-    FETCH_KEY        = 1
-    MULTIFETCH_KEY   = 2
-    MULTIPRODUCE_KEY = 3
-    OFFSET_KEY       = 4
+    PRODUCE_KEY       = 0
+    FETCH_KEY         = 1
+    OFFSET_KEY        = 2
+    METADATA_KEY      = 3
+    OFFSET_COMMIT_KEY = 6
+    OFFSET_FETCH_KEY  = 7
 
     ATTRIBUTE_CODEC_MASK = 0x03
+    CODEC_NONE = 0x00
+    CODEC_GZIP = 0x01
+    CODEC_SNAPPY = 0x02
 
-    def __init__(self, host, port, bufsize=1024):
-        self.host = host
-        self.port = port
-        self.bufsize = bufsize
-        self._sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
-        self._sock.connect((host, port))
-        self._sock.settimeout(10)
-        log.debug("Connected to %s on %d", host, port)
-
-    def __copy__(self):
-        return KafkaClient(self.host, self.port, self.bufsize)
+    ###################
+    #   Private API   #
+    ###################
 
-    ######################
-    #   Protocol Stuff   #
-    ######################
-
-    def _consume_response_iter(self):
+    @classmethod
+    def _encode_message_header(cls, client_id, correlation_id, request_key):
         """
-        This method handles the response header and error messages. It 
-        then returns an iterator for the chunks of the response
+        Encode the common request envelope
         """
-        log.debug("Handling response from Kafka")
-        # Header
-        resp = self._sock.recv(6)
-        if resp == "":
-            raise Exception("Got no response from Kafka")
-        (size, err) = struct.unpack('>iH', resp)
-
-        log.debug("About to read %d bytes from Kafka", size-2)
-        # Handle error
-        error = error_codes.get(err)
-        if error is not None:
-            raise KafkaException(error)
-
-        # Response iterator
-        total = 0
-        while total < (size-2):
-            resp = self._sock.recv(self.bufsize)
-            log.debug("Read %d bytes from Kafka", len(resp))
-            if resp == "":
-                raise Exception("Underflow")
-            total += len(resp)
-            yield resp
+        return struct.pack('>hhih%ds' % len(client_id), 
+                           request_key,          # ApiKey
+                           0,                    # ApiVersion
+                           correlation_id,       # CorrelationId
+                           len(client_id),       #
+                           client_id)            # ClientId
 
-    def _consume_response(self):
+    @classmethod
+    def _encode_message_set(cls, messages):
         """
-        Fully consumer the response iterator
+        Encode a MessageSet. Unlike other arrays in the protocol, MessageSets are 
+        not length-prefixed
+
+        Format
+        ======
+        MessageSet => [Offset MessageSize Message]
+          Offset => int64
+          MessageSize => int32
         """
-        data = ""
-        for chunk in self._consume_response_iter():
-            data += chunk
-        return data
+        message_set = ""
+        for message in messages:
+            encoded_message = KafkaProtocol._encode_message(message)
+            message_set += struct.pack('>qi%ds' % len(encoded_message), 0, len(encoded_message), encoded_message)
+        return message_set
 
     @classmethod
-    def encode_message(cls, message):
+    def _encode_message(cls, message):
         """
-        Encode a Message from a Message tuple
+        Encode a single message.
 
-        Params
+        The magic number of a message is a format version number. The only supported
+        magic number right now is zero
+
+        Format 
         ======
-        message: Message
-
-        Wire Format
-        ===========
-        <Message>    ::= <Message-0> | <Message-1> 
-        <Message-0>  ::= <N> 0 <header-0> <payload>
-        <Message-1>  ::= <N> 1 <header-1> <payload>
-        <N>          ::= <int32>
-        <header-0>   ::= <crc>
-        <header-1>   ::= <attributes><crc>
-        <crc>        ::= <int32>
-        <payload>    ::= <bytes>
-        <attributes> ::= <int8> 
-
-        The crc is a crc32 checksum of the message payload. The attributes are bitmask
-        used for indicating the compression algorithm.
+        Message => Crc MagicByte Attributes Key Value
+          Crc => int32
+          MagicByte => int8
+          Attributes => int8
+          Key => bytes
+          Value => bytes
         """
         if message.magic == 0:
-            msg = struct.pack('>Bi%ds' % len(message.payload),
-                               message.magic, message.crc, message.payload)
-        elif message.magic == 1:
-            msg = struct.pack('>BBi%ds' % len(message.payload),
-                               message.magic, message.attributes, message.crc, message.payload)
+            msg = struct.pack('>BB', message.magic, message.attributes)
+            msg += write_int_string(message.key)
+            msg += write_int_string(message.value)
+            crc = zlib.crc32(msg)
+            msg = struct.pack('>i%ds' % len(msg), crc, msg)
         else:
             raise Exception("Unexpected magic number: %d" % message.magic)
-        msg = length_prefix_message(msg)
-        log.debug("Encoded %s as %r" % (message, msg))
         return msg
 
+
     @classmethod
-    def encode_message_set(cls, messages):
+    def _decode_message_set_iter(cls, data):
         """
-        Encode a MessageSet
+        Iteratively decode a MessageSet
 
-        One or more concatenated Messages
+        Reads repeated elements of (offset, message), calling decode_message to decode a
+        single message. Since compressed messages contain futher MessageSets, these two methods
+        have been decoupled so that they may recurse easily.
         """
-        message_set = ""
-        for message in messages:
-            encoded_message = cls.encode_message(message)
-            message_set += encoded_message
-        return message_set
+        cur = 0
+        while cur < len(data):
+            try:
+                ((offset, ), cur) = relative_unpack('>q', data, cur)
+                (msg, cur) = read_int_string(data, cur)
+                for (offset, message) in KafkaProtocol._decode_message(msg, offset):
+                    yield OffsetAndMessage(offset, message)
+            except BufferUnderflowError: # If we get a partial read of a message, stop
+                raise StopIteration()
 
     @classmethod
-    def encode_produce_request(cls, produceRequest):
-        """
-        Encode a ProduceRequest
-
-        Wire Format
-        ===========
-        <ProduceRequest> ::= <request-key> <topic> <partition> <len> <MessageSet>
-        <request-key>    ::= 0
-        <topic>          ::= <topic-length><string>
-        <topic-length>   ::= <int16>
-        <partition>      ::= <int32>
-        <len>            ::= <int32>
-
-        The request-key (0) is encoded as a short (int16). len is the length of the proceeding MessageSet
-        """
-        (topic, partition, messages) = produceRequest
-        message_set = cls.encode_message_set(messages)
-        log.debug("Sending MessageSet: %r" % message_set)
-        req = struct.pack('>HH%dsii%ds' % (len(topic), len(message_set)), 
-                KafkaClient.PRODUCE_KEY, len(topic), topic, partition, len(message_set), message_set)
-        return req
+    def _decode_message(cls, data, offset):
+        """
+        Decode a single Message
+
+        The only caller of this method is decode_message_set_iter. They are decoupled to 
+        support nested messages (compressed MessageSets). The offset is actually read from
+        decode_message_set_iter (it is part of the MessageSet payload).
+        """
+        ((crc, magic, att), cur) = relative_unpack('>iBB', data, 0)
+        if crc != zlib.crc32(data[4:]):
+            raise ChecksumError("Message checksum failed")
+
+        (key, cur) = read_int_string(data, cur)
+        (value, cur) = read_int_string(data, cur)
+        if att & KafkaProtocol.ATTRIBUTE_CODEC_MASK == KafkaProtocol.CODEC_NONE:
+            yield (offset, Message(magic, att, key, value))
+        elif att & KafkaProtocol.ATTRIBUTE_CODEC_MASK == KafkaProtocol.CODEC_GZIP:
+            gz = gzip_decode(value)
+            for (offset, message) in KafkaProtocol._decode_message_set_iter(gz):
+                yield (offset, message)
+        elif att & KafkaProtocol.ATTRIBUTE_CODEC_MASK == KafkaProtocol.CODEC_SNAPPY:
+            snp = snappy_decode(value)
+            for (offset, message) in KafkaProtocol._decode_message_set_iter(snp):
+                yield (offset, message)
+
+    ##################
+    #   Public API   #
+    ##################
 
     @classmethod
-    def encode_multi_produce_request(cls, produceRequests):
+    def create_message(cls, payload, key=None):
         """
-        Encode a MultiProducerRequest
+        Construct a Message
 
         Params
         ======
-        produceRequest: list of ProduceRequest objects
-
-        Returns
-        =======
-        Encoded request
-
-        Wire Format
-        ===========
-        <MultiProducerReqeust>  ::= <request-key> <num> <ProduceRequests>
-        <num>                   ::= <int16>
-        <ProduceRequests>       ::= <ProduceRequest> [ <ProduceRequests> ]
-        <ProduceRequest>        ::= <topic> <partition> <len> <MessageSet>
-        <topic>                 ::= <topic-length><string>
-        <topic-length>          ::= <int16>
-        <partition>             ::= <int32>
-        <len>                   ::= <int32>
-
-        num is the number of ProduceRequests being encoded
-        """
-        req = struct.pack('>HH', KafkaClient.MULTIPRODUCE_KEY, len(produceRequests))
-        for (topic, partition, messages) in produceRequests:
-            message_set = cls.encode_message_set(messages)
-            req += struct.pack('>H%dsii%ds' % (len(topic), len(message_set)), 
-                               len(topic), topic, partition, len(message_set), message_set)
-        return req
-
-    @classmethod
-    def encode_fetch_request(cls, fetchRequest):
-        """
-        Encode a FetchRequest message
-
-        Wire Format
-        ===========
-        <FetchRequest> ::= <request-key> <topic> <partition> <offset> <size>
-        <request-key>  ::= 1
-        <topic>        ::= <topic-length><string>
-        <topic-length> ::= <int16>
-        <partition>    ::= <int32>
-        <offset>       ::= <int64>
-        <size>         ::= <int32>
-    
-        The request-key (1) is encoded as a short (int16).
-        """
-        (topic, partition, offset, size) = fetchRequest
-        req = struct.pack('>HH%dsiqi' % len(topic), 
-                KafkaClient.FETCH_KEY, len(topic), topic, partition, offset, size)
-        return req
+        payload: bytes, the payload to send to Kafka
+        key: bytes, a key used for partition routing (optional)
+        """
+        return Message(0, 0, key, payload)
 
     @classmethod
-    def encode_multi_fetch_request(cls, fetchRequests):
+    def create_gzip_message(cls, payloads, key=None):
         """
-        Encode the MultiFetchRequest message from a list of FetchRequest objects
+        Construct a Gzipped Message containing multiple Messages
+
+        The given payloads will be encoded, compressed, and sent as a single atomic
+        message to Kafka.
 
         Params
         ======
-        fetchRequests: list of FetchRequest
-
-        Returns
-        =======
-        req: bytes, The message to send to Kafka
-
-        Wire Format
-        ===========
-        <MultiFetchRequest> ::= <request-key> <num> [ <FetchRequests> ]
-        <request-key>       ::= 2
-        <num>               ::= <int16>
-        <FetchRequests>     ::= <FetchRequest> [ <FetchRequests> ]
-        <FetchRequest>      ::= <topic> <partition> <offset> <size>
-        <topic>             ::= <topic-length><string>
-        <topic-length>      ::= <int16>
-        <partition>         ::= <int32>
-        <offset>            ::= <int64>
-        <size>              ::= <int32>
-
-        The request-key (2) is encoded as a short (int16).
-        """
-        req = struct.pack('>HH', KafkaClient.MULTIFETCH_KEY, len(fetchRequests))
-        for (topic, partition, offset, size) in fetchRequests:
-            req += struct.pack('>H%dsiqi' % len(topic), len(topic), topic, partition, offset, size)
-        return req
+        payloads: list(bytes), a list of payload to send be sent to Kafka
+        key: bytes, a key used for partition routing (optional)
+        """
+        message_set = KafkaProtocol._encode_message_set(
+                [KafkaProtocol.create_message(payload) for payload in payloads])
+        gzipped = gzip_encode(message_set) 
+        return Message(0, 0x00 | (KafkaProtocol.ATTRIBUTE_CODEC_MASK & KafkaProtocol.CODEC_GZIP), key, gzipped)
 
     @classmethod
-    def encode_offset_request(cls, offsetRequest):
+    def create_snappy_message(cls, payloads, key=None):
         """
-        Encode an OffsetRequest message
+        Construct a Snappy Message containing multiple Messages
 
-        Wire Format
-        ===========
-        <OffsetRequest> ::= <request-key> <topic> <partition> <time> <max-offsets>
-        <request-key>   ::= 4
-        <topic>         ::= <topic-length><string>
-        <topic-length>  ::= <int16>
-        <partition>     ::= <int32>
-        <time>          ::= <epoch>
-        <epoch>         ::= <int64>
-        <max-offsets>   ::= <int32>
+        The given payloads will be encoded, compressed, and sent as a single atomic
+        message to Kafka.
 
-        The request-key (4) is encoded as a short (int16).
+        Params
+        ======
+        payloads: list(bytes), a list of payload to send be sent to Kafka
+        key: bytes, a key used for partition routing (optional)
         """
-        (topic, partition, offset, maxOffsets) = offsetRequest
-        req = struct.pack('>HH%dsiqi' % len(topic), KafkaClient.OFFSET_KEY, len(topic), topic, partition, offset, maxOffsets)
-        return req
+        message_set = KafkaProtocol._encode_message_set(
+                [KafkaProtocol.create_message(payload) for payload in payloads])
+        snapped = snappy_encode(message_set) 
+        return Message(0, 0x00 | (KafkaProtocol.ATTRIBUTE_CODEC_MASK & KafkaProtocol.CODEC_SNAPPY), key, snapped)
 
     @classmethod
-    def decode_message(cls, data):
+    def encode_produce_request(cls, client_id, correlation_id, payloads=[], acks=1, timeout=1000):
         """
-        Decode a Message
-
-        Verify crc and decode the Message. A compressed Message's payload is actually
-        an encoded MessageSet. This allows Messages to be nested within Messages and 
-        as such, this method will recurse.
+        Encode some ProduceRequest structs
 
         Params
         ======
-        data, bytes
-
-        Returns
-        =======
-        Generator of Messages (depth-first)
-        """
-        N = len(data)
-        (magic,) = struct.unpack('>B', data[0:1])
-        if magic == 0:
-            # version 0
-            (crc,) = struct.unpack('>i', data[1:5])
-            payload = data[5:N]
-            assert zlib.crc32(payload) == crc
-            msg = Message(magic, None, crc, payload)
-            log.debug("Got v0 Message, %s", msg)
-            yield msg
-        elif magic == 1:
-            # version 1
-            (att, crc) = struct.unpack('>Bi', data[1:6])
-            payload = data[6:N]
-            assert zlib.crc32(payload) == crc
-            if att & KafkaClient.ATTRIBUTE_CODEC_MASK == 0:
-                # Uncompressed, just a single Message
-                msg = Message(magic, att, crc, payload)
-                log.debug("Got v1 Message, %s", msg)
-                yield msg
-            elif att & KafkaClient.ATTRIBUTE_CODEC_MASK == 1:
-                # Gzip encoded Message
-                gz = gzip_decode(payload)
-                (msgs, _) = cls.read_message_set(gz)
-                for msg in msgs:
-                    yield msg
-            elif att & KafkaClient.ATTRIBUTE_CODEC_MASK == 2:
-                # Snappy encoded Message
-                snp = snappy_decode(payload)
-                (msgs, _) = cls.read_message_set(snp)
-                for msg in msgs:
-                    yield msg
-            else:
-                raise RuntimeError("Unsupported compression type: %d" % (att & KafkaClient.ATTRIBUTE_CODEC_MASK))
+        client_id: string
+        correlation_id: string
+        payloads: list of ProduceRequest
+        acks: How "acky" you want the request to be
+            0: immediate response
+            1: written to disk by the leader
+            2+: waits for this many number of replicas to sync
+            -1: waits for all replicas to be in sync
+        timeout: Maximum time the server will wait for acks from replicas. This is _not_ a socket timeout
+        """
+        grouped_payloads = group_by_topic_and_partition(payloads)
+        message = cls._encode_message_header(client_id, correlation_id, KafkaProtocol.PRODUCE_KEY)
+        message += struct.pack('>hii', acks, timeout, len(grouped_payloads))
+        for topic, topic_payloads in grouped_payloads.items():
+            message += struct.pack('>h%dsi' % len(topic), len(topic), topic, len(topic_payloads))
+            for partition, payload in topic_payloads.items():
+                message_set = KafkaProtocol._encode_message_set(payload.messages)
+                message += struct.pack('>ii%ds' % len(message_set), partition, len(message_set), message_set)
+        return struct.pack('>i%ds' % len(message), len(message), message)
 
     @classmethod
-    def read_message_set(cls, data):
+    def decode_produce_response(cls, data):
         """
-        Read a MessageSet
+        Decode bytes to a ProduceResponse 
 
-        This method reads through the given bytes and decodes the length-prefixed Messages. It will short 
-        circuit if there are insufficient bytes to read a whole Message. This allows callers to determine
-        the next valid offset
-        
         Params
         ======
-        data: bytes to read
-
-        Returns
-        =======
-        tuple of (list(Message), read), where read is how many bytes were read
-
-        Wire Format
-        ===========
-        <MessageSet> ::= <len> <Message> [ <MessageSet> ]
-        <len>        ::= <int32>
-
-        len is the length of the proceeding Message
-        """
-        
-        # Read the MessageSet
-        cur = 0
-        msgs = []
-        size = len(data)
-        while cur < size:
-            # Make sure we can read this Message
-            if (cur + 4) > size:
-                # Not enough bytes to read the length
-                if len(msgs) == 0:
-                    raise Exception("Message underflow. Did not request enough bytes to consume a single message")
-                else:
-                    log.debug("Not enough data to read header of next message")
-                    break
-            (N,) = struct.unpack('>i', data[cur:(cur+4)])
-            if (cur + N + 4) > size:
-                # Not enough bytes to read this whole Message
-                log.debug("Not enough data to read next message")
-                break
-            else:
-                cur += 4
-
-            # Decode the message(s)
-            for m in cls.decode_message(data[cur:cur+N]):
-                msgs.append(m)
-
-            # Advance the cursor
-            cur += N
-            
-        # Return the retrieved messages and the cursor position
-        return (msgs, cur)
-
-    #########################
-    #   Advanced User API   #  
-    #########################
+        data: bytes to decode
+        """
+        ((correlation_id, num_topics), cur) = relative_unpack('>ii', data, 0)
+        for i in range(num_topics):
+            ((strlen,), cur) = relative_unpack('>h', data, cur)
+            topic = data[cur:cur+strlen]
+            cur += strlen
+            ((num_partitions,), cur) = relative_unpack('>i', data, cur)
+            for i in range(num_partitions):
+                ((partition, error, offset), cur) = relative_unpack('>ihq', data, cur)
+                yield ProduceResponse(topic, partition, error, offset)
 
     @classmethod
-    def create_message(cls, payload):
+    def encode_fetch_request(cls, client_id, correlation_id, payloads=[], max_wait_time=100, min_bytes=4096):
         """
-        Create a standard Message
+        Encodes some FetchRequest structs
 
         Params
         ======
-        payload, bytes
-
-        Returns
-        =======
-        A Message tuple
+        client_id: string
+        correlation_id: string
+        payloads: list of FetchRequest
+        max_wait_time: int, how long to block waiting on min_bytes of data
+        min_bytes: int, the minimum number of bytes to accumulate before returning the response
         """
-        return Message(1, 0, zlib.crc32(payload), payload)
+        
+        grouped_payloads = group_by_topic_and_partition(payloads)
+        message = cls._encode_message_header(client_id, correlation_id, KafkaProtocol.FETCH_KEY)
+        message += struct.pack('>iiii', -1, max_wait_time, min_bytes, len(grouped_payloads)) # -1 is the replica id
+        for topic, topic_payloads in grouped_payloads.items():
+            message += write_short_string(topic)
+            message += struct.pack('>i', len(topic_payloads))
+            for partition, payload in topic_payloads.items():
+                message += struct.pack('>iqi', partition, payload.offset, payload.max_bytes)
+        return struct.pack('>i%ds' % len(message), len(message), message)
 
     @classmethod
-    def create_gzip_message(cls, *payloads):
+    def decode_fetch_response_iter(cls, data):
         """
-        Create a Gzip encoded Message
+        Decode bytes to a FetchResponse
 
         Params
         ======
-        payloads, list of messages (bytes) to be encoded
+        data: bytes to decode
+        """
+        ((correlation_id, num_topics), cur) = relative_unpack('>ii', data, 0)
+        for i in range(num_topics):
+            (topic, cur) = read_short_string(data, cur)
+            ((num_partitions,), cur) = relative_unpack('>i', data, cur)
+            for i in range(num_partitions):
+                ((partition, error, highwater_mark_offset), cur) = relative_unpack('>ihq', data, cur)
+                (message_set, cur) = read_int_string(data, cur)
+                yield FetchResponse(topic, partition, error, highwater_mark_offset,
+                        KafkaProtocol._decode_message_set_iter(message_set))
 
-        Returns
-        =======
-        A Message tuple
-        """
-        messages = [cls.create_message(payload) for payload in payloads]
-        message_set = cls.encode_message_set(messages)
-        gzipped = gzip_encode(message_set) 
-        return Message(1, 0x00 | (KafkaClient.ATTRIBUTE_CODEC_MASK & 0x01), zlib.crc32(gzipped), gzipped)
+    @classmethod
+    def encode_offset_request(cls, client_id, correlation_id, payloads=[]):
+        grouped_payloads = group_by_topic_and_partition(payloads)
+        message = cls._encode_message_header(client_id, correlation_id, KafkaProtocol.OFFSET_KEY)
+        message += struct.pack('>ii', -1, len(grouped_payloads)) # -1 is the replica id
+        for topic, topic_payloads in grouped_payloads.items():
+            message += write_short_string(topic)
+            message += struct.pack('>i', len(topic_payloads))
+            for partition, payload in topic_payloads.items():
+                message += struct.pack('>iqi', partition, payload.time, payload.max_offsets)
+        return struct.pack('>i%ds' % len(message), len(message), message)
 
     @classmethod
-    def create_snappy_message(cls, *payloads):
+    def decode_offset_response(cls, data):
         """
-        Create a Snappy encoded Message
+        Decode bytes to an OffsetResponse
 
         Params
         ======
-        payloads, list of messages (bytes) to be encoded
+        data: bytes to decode
+        """
+        ((correlation_id, num_topics), cur) = relative_unpack('>ii', data, 0)
+        for i in range(num_topics):
+            (topic, cur) = read_short_string(data, cur)
+            ((num_partitions,), cur) = relative_unpack('>i', data, cur)
+            for i in range(num_partitions):
+                ((partition, error, num_offsets,), cur) = relative_unpack('>ihi', data, cur)
+                offsets = []
+                for j in range(num_offsets):
+                    ((offset,), cur) = relative_unpack('>q', data, cur)
+                    offsets.append(offset)
+                yield OffsetResponse(topic, partition, error, tuple(offsets))
 
-        Returns
-        =======
-        A Message tuple
+    @classmethod
+    def encode_metadata_request(cls, client_id, correlation_id, topics=[]):
         """
-        messages = [cls.create_message(payload) for payload in payloads]
-        message_set = cls.encode_message_set(messages)
-        snapped = snappy_encode(message_set)
-        return Message(1, 0x00 | (KafkaClient.ATTRIBUTE_CODEC_MASK & 0x02), zlib.crc32(snapped), snapped)
+        Encode a MetadataRequest
 
-    def send_message_set(self, produceRequest):
-        """
-        Send a ProduceRequest
-        
         Params
         ======
-        produceRequest: ProduceRequest
+        client_id: string
+        correlation_id: string
+        topics: list of strings
         """
-        req = length_prefix_message(self.encode_produce_request(produceRequest))
-        log.debug("Sending %d bytes to Kafka: %r", len(req), req)
-        sent = self._sock.sendall(req) 
-        if sent == 0:
-            raise RuntimeError("Kafka went away")
+        message = cls._encode_message_header(client_id, correlation_id, KafkaProtocol.METADATA_KEY)
+        message += struct.pack('>i', len(topics))
+        for topic in topics:
+            message += struct.pack('>h%ds' % len(topic), len(topic), topic)
+        return write_int_string(message)
 
-    def send_multi_message_set(self, produceRequests):
+    @classmethod
+    def decode_metadata_response(cls, data):
         """
-        Send a MultiProduceRequest
-        
+        Decode bytes to a MetadataResponse
+
         Params
         ======
-        produceRequests: list of ProduceRequest
-        """
-        req = length_prefix_message(self.encode_multi_produce_request(produceRequests))
-        log.debug("Sending %d bytes to Kafka", len(req))
-        sent = self._sock.sendall(req) 
-        if sent == 0:
-            raise RuntimeError("Kafka went away")
+        data: bytes to decode
+        """
+        ((correlation_id, numBrokers), cur) = relative_unpack('>ii', data, 0)
+
+        # Broker info
+        brokers = {}
+        for i in range(numBrokers):
+            ((nodeId, ), cur) = relative_unpack('>i', data, cur)
+            (host, cur) = read_short_string(data, cur)
+            ((port,), cur) = relative_unpack('>i', data, cur)
+            brokers[nodeId] = BrokerMetadata(nodeId, host, port)
+
+        # Topic info
+        ((num_topics,), cur) = relative_unpack('>i', data, cur)
+        topicMetadata = {}
+        for i in range(num_topics):
+            ((topicError,), cur) = relative_unpack('>h', data, cur)
+            (topicName, cur) = read_short_string(data, cur)
+            ((num_partitions,), cur) = relative_unpack('>i', data, cur)
+            partitionMetadata = {}
+            for j in range(num_partitions):
+                ((partitionErrorCode, partition, leader, numReplicas), cur) = relative_unpack('>hiii', data, cur)
+                (replicas, cur) = relative_unpack('>%di' % numReplicas, data, cur)
+                ((numIsr,), cur) = relative_unpack('>i', data, cur)
+                (isr, cur) = relative_unpack('>%di' % numIsr, data, cur)
+                partitionMetadata[partition] = PartitionMetadata(topicName, partition, leader, replicas, isr)
+            topicMetadata[topicName] = partitionMetadata
+        return (brokers, topicMetadata)
 
-    def get_message_set(self, fetchRequest):
+    @classmethod
+    def encode_offset_commit_request(cls, client_id, correlation_id, group, payloads):
         """
-        Send a FetchRequest and return the Messages
+        Encode some OffsetCommitRequest structs
 
         Params
         ======
-        fetchRequest: FetchRequest named tuple
+        client_id: string
+        correlation_id: string
+        group: string, the consumer group you are committing offsets for
+        payloads: list of OffsetCommitRequest
+        """
+        grouped_payloads= group_by_topic_and_partition(payloads)
+        message = cls._encode_message_header(client_id, correlation_id, KafkaProtocol.OFFSET_COMMIT_KEY)
+        message += write_short_string(group)
+        message += struct.pack('>i', len(grouped_payloads))
+        for topic, topic_payloads in grouped_payloads.items():
+            message += write_short_string(topic)
+            message += struct.pack('>i', len(topic_payloads))
+            for partition, payload in topic_payloads.items():
+                message += struct.pack('>iq', partition, payload.offset)
+                message += write_short_string(payload.metadata)
+        return struct.pack('>i%ds' % len(message), len(message), message)
 
-        Returns
-        =======
-        A tuple of (list(Message), FetchRequest). This FetchRequest will have the offset 
-        starting at the next message. 
+    @classmethod
+    def decode_offset_commit_response(cls, data):
         """
+        Decode bytes to an OffsetCommitResponse
 
-        req = length_prefix_message(self.encode_fetch_request(fetchRequest))
-        log.debug("Sending %d bytes to Kafka", len(req))
-        sent = self._sock.sendall(req) 
-        if sent == 0:
-            raise RuntimeError("Kafka went away")
-        data = self._consume_response()
-        (messages, read) = self.read_message_set(data)
-
-        # Return the retrieved messages and the next FetchRequest
-        return (messages, FetchRequest(fetchRequest.topic, fetchRequest.partition, (fetchRequest.offset + read), fetchRequest.size))
+        Params
+        ======
+        data: bytes to decode
+        """
+        data = data[2:] # TODO remove me when versionId is removed
+        ((correlation_id,), cur) = relative_unpack('>i', data, 0)
+        (client_id, cur) = read_short_string(data, cur)
+        ((num_topics,), cur) = relative_unpack('>i', data, cur)
+        for i in xrange(num_topics):
+            (topic, cur) = read_short_string(data, cur)
+            ((num_partitions,), cur) = relative_unpack('>i', data, cur)
+            for i in xrange(num_partitions):
+                ((partition, error), cur) = relative_unpack('>ih', data, cur)
+                yield OffsetCommitResponse(topic, partition, error)
 
-    def get_multi_message_set(self, fetchRequests):
+    @classmethod
+    def encode_offset_fetch_request(cls, client_id, correlation_id, group, payloads):
         """
-        Send several FetchRequests in a single pipelined request.
+        Encode some OffsetFetchRequest structs
 
         Params
         ======
-        fetchRequests: list of FetchRequest 
-
-        Returns
-        =======
-        list of tuples of (list(Message), FetchRequest). This FetchRequest will have the offset 
-        starting at the next message. 
-
-        Wire Format
-        ===========
-        <MultiFetchResponse> ::= <MultiMessageSet>
-        <MultiMessageSet>    ::= <MultiMessage> [ <MultiMessageSet> ]
-        <MultiMessage>       ::= <len> 0 <MessageSet>
-        <len>                ::= <int32>
-        """
-        req = length_prefix_message(self.encode_multi_fetch_request(fetchRequests))
-        log.debug("Sending %d bytes to Kafka", len(req))
-        sent = self._sock.sendall(req) 
-        if sent == 0:
-            raise RuntimeError("Kafka went away")
-        data = self._consume_response()
-        cur = 0
-        responses = []
-        for request in fetchRequests:
-            (size, _) = struct.unpack('>iH', data[cur:(cur+6)])
-            cur += 6
-            (messages, read) = self.read_message_set(data[cur:(cur+size-2)])
-            cur += size-2
-            responses.append((messages, FetchRequest(request.topic, request.partition, request.offset+read, request.size)))
-        return responses
+        client_id: string
+        correlation_id: string
+        group: string, the consumer group you are fetching offsets for
+        payloads: list of OffsetFetchRequest
+        """
+        grouped_payloads = group_by_topic_and_partition(payloads)
+        message = cls._encode_message_header(client_id, correlation_id, KafkaProtocol.OFFSET_FETCH_KEY)
+        message += write_short_string(group)
+        message += struct.pack('>i', len(grouped_payloads))
+        for topic, topic_payloads in grouped_payloads.items():
+            message += write_short_string(topic)
+            message += struct.pack('>i', len(topic_payloads))
+            for partition, payload in topic_payloads.items():
+                message += struct.pack('>i', partition)
+        return struct.pack('>i%ds' % len(message), len(message), message)
 
-    def get_offsets(self, offsetRequest):
+    @classmethod
+    def decode_offset_fetch_response(cls, data):
         """
-        Get the offsets for a topic
+        Decode bytes to an OffsetFetchResponse
 
         Params
         ======
-        offsetRequest: OffsetRequest
-    
-        Returns
-        =======
-        offsets: tuple of offsets
-        
-        Wire Format
-        ===========
-        <OffsetResponse> ::= <num> [ <offsets> ]
-        <num>            ::= <int32>
-        <offsets>        ::= <offset> [ <offsets> ]
-        <offset>         ::= <int64>
+        data: bytes to decode
+        """
+
+        data = data[2:] # TODO remove me when versionId is removed
+        ((correlation_id,), cur) = relative_unpack('>i', data, 0)
+        (client_id, cur) = read_short_string(data, cur)
+        ((num_topics,), cur) = relative_unpack('>i', data, cur)
+        for i in range(num_topics):
+            (topic, cur) = read_short_string(data, cur)
+            ((num_partitions,), cur) = relative_unpack('>i', data, cur)
+            for i in range(num_partitions):
+                ((partition, offset), cur) = relative_unpack('>iq', data, cur)
+                (metadata, cur) = read_short_string(data, cur)
+                ((error,), cur) = relative_unpack('>h', data, cur)
+                yield OffsetFetchResponse(topic, partition, offset, metadata, error)
+
+
+class KafkaConnection(object):
+    """
+    A socket connection to a single Kafka broker
+
+    This class is _not_ thread safe. Each call to `send` must be followed
+    by a call to `recv` in order to get the correct response. Eventually, 
+    we can do something in here to facilitate multiplexed requests/responses
+    since the Kafka API includes a correlation id.
+    """
+    def __init__(self, host, port, bufsize=4096):
+        self.host = host
+        self.port = port
+        self.bufsize = bufsize
+        self._sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+        self._sock.connect((host, port))
+        self._sock.settimeout(10)
+
+    def __str__(self):
+        return "<KafkaConnection host=%s port=%d>" % (self.host, self.port)
+
+    ###################
+    #   Private API   #
+    ###################
+
+    def _consume_response(self):
+        """
+        Fully consumer the response iterator
+        """
+        data = ""
+        for chunk in self._consume_response_iter():
+            data += chunk
+        return data
 
+    def _consume_response_iter(self):
+        """
+        This method handles the response header and error messages. It 
+        then returns an iterator for the chunks of the response
         """
-        req = length_prefix_message(self.encode_offset_request(offsetRequest))
-        log.debug("Sending OffsetRequest of %d bytes to Kafka", len(req))
-        sent = self._sock.sendall(req) 
+        log.debug("Handling response from Kafka")
+
+        # Read the size off of the header
+        resp = self._sock.recv(4)
+        if resp == "":
+            raise Exception("Got no response from Kafka")
+        (size,) = struct.unpack('>i', resp)
+
+        messageSize = size - 4
+        log.debug("About to read %d bytes from Kafka", messageSize)
+
+        # Read the remainder of the response 
+        total = 0
+        while total < messageSize:
+            resp = self._sock.recv(self.bufsize)
+            log.debug("Read %d bytes from Kafka", len(resp))
+            if resp == "":
+                raise BufferUnderflowError("Not enough data to read this response")
+            total += len(resp)
+            yield resp
+
+    ##################
+    #   Public API   #
+    ##################
+
+    # TODO multiplex socket communication to allow for multi-threaded clients
+
+    def send(self, requestId, payload):
+        "Send a request to Kafka"
+        sent = self._sock.sendall(payload)
         if sent == 0:
             raise RuntimeError("Kafka went away")
+        self.data = self._consume_response()
+
+    def recv(self, requestId):
+        "Get a response from Kafka"
+        return self.data
+
+    def close(self):
+        "Close this connection"
+        self._sock.close()
+
+class KafkaClient(object):
+
+    CLIENT_ID = "kafka-python"
+    ID_GEN = count() 
+
+    def __init__(self, host, port, bufsize=4096):
+        # We need one connection to bootstrap 
+        self.bufsize = bufsize
+        self.conns = {              # (host, port) -> KafkaConnection
+            (host, port): KafkaConnection(host, port, bufsize)
+        } 
+        self.brokers = {}           # broker_id -> BrokerMetadata
+        self.topics_to_brokers = {} # topic_id -> broker_id
+        self.load_metadata_for_topics()
 
-        data = self._consume_response()
-        (num,) = struct.unpack('>i', data[0:4])
-        offsets = struct.unpack('>%dq' % num, data[4:])
-        return offsets
+    def close(self):
+        for conn in self.conns.values():
+            conn.close()
+
+    def get_conn_for_broker(self, broker):
+        "Get or create a connection to a broker"
+        if (broker.host, broker.port) not in self.conns:
+            self.conns[(broker.host, broker.port)] = KafkaConnection(broker.host, broker.port, self.bufsize)
+        return self.conns[(broker.host, broker.port)]
+
+    def next_id(self):
+        "Generate a new correlation id"
+        return KafkaClient.ID_GEN.next()
+
+    def load_metadata_for_topics(self, *topics):
+        """
+        Discover brokers and metadata for a set of topics. This method will
+        recurse in the event of a retry.
+        """
+        requestId = self.next_id()
+        request = KafkaProtocol.encode_metadata_request(KafkaClient.CLIENT_ID, requestId, topics) 
+        response = self.try_send_request(requestId, request)
+        if response is None:
+            raise Exception("All servers failed to process request")
+        (brokers, topics) = KafkaProtocol.decode_metadata_response(response)
+        log.debug("Broker metadata: %s", brokers)
+        log.debug("Topic metadata: %s", topics)
+        self.brokers.update(brokers)
+        self.topics_to_brokers = {}
+        for topic, partitions in topics.items():
+            for partition, meta in partitions.items():
+                if meta.leader == -1:
+                    log.info("Partition is unassigned, delay for 1s and retry")
+                    time.sleep(1)
+                    self.load_metadata_for_topics(topic)
+                else:
+                    self.topics_to_brokers[TopicAndPartition(topic, partition)] = brokers[meta.leader]
 
-    #######################
-    #   Simple User API   #
-    #######################
+    def get_leader_for_partition(self, topic, partition):
+        key = TopicAndPartition(topic, partition)
+        if key not in self.topics_to_brokers:
+            self.load_metadata_for_topics(topic)
+        if key not in self.topics_to_brokers:
+            raise Exception("Partition does not exist: %s" % str(key))
+        return self.topics_to_brokers[key]
 
-    def send_messages_simple(self, topic, *payloads):
+    def send_produce_request(self, payloads=[], fail_on_error=True, callback=None):
         """
-        Send one or more strings to Kafka
+        Encode and send some ProduceRequests
+
+        ProduceRequests will be grouped by (topic, partition) and then sent to a specific
+        broker. Output is a list of responses in the same order as the list of payloads
+        specified
 
         Params
         ======
-        topic: string
-        payloads: strings
-        """
-        messages = tuple([self.create_message(payload) for payload in payloads])
-        self.send_message_set(ProduceRequest(topic, -1, messages))
+        payloads: list of ProduceRequest
+        fail_on_error: boolean, should we raise an Exception if we encounter an API error?
+        callback: function, instead of returning the ProduceResponse, first pass it through this function
 
-    def iter_messages(self, topic, partition, offset, size, auto=True):
+        Return
+        ======
+        list of ProduceResponse or callback(ProduceResponse), in the order of input payloads
+        """
+        # Group the produce requests by which broker they go to
+        original_keys = []
+        payloads_by_broker = defaultdict(list)
+        for payload in payloads:
+            payloads_by_broker[self.get_leader_for_partition(payload.topic, payload.partition)] += payloads
+            original_keys.append((payload.topic, payload.partition))
+
+        # Accumulate the responses in a dictionary
+        acc = {}
+
+        # For each broker, send the list of request payloads
+        for broker, payloads in payloads_by_broker.items():
+            conn = self.get_conn_for_broker(broker)
+            requestId = self.next_id()
+            request = KafkaProtocol.encode_produce_request(KafkaClient.CLIENT_ID, requestId, payloads)
+            # Send the request
+            conn.send(requestId, request)
+            response = conn.recv(requestId)
+            for produce_response in KafkaProtocol.decode_produce_response(response):
+                # Check for errors
+                if fail_on_error == True and produce_response.error != 0:
+                    raise Exception("ProduceRequest for %s failed with errorcode=%d", 
+                            (TopicAndPartition(produce_response.topic, produce_response.partition), produce_response.error))
+                # Run the callback
+                if callback is not None:
+                    acc[(produce_response.topic, produce_response.partition)] = callback(produce_response)
+                else:
+                    acc[(produce_response.topic, produce_response.partition)] = produce_response
+
+        # Order the accumulated responses by the original key order
+        return (acc[k] for k in original_keys)
+
+    def send_fetch_request(self, payloads=[], fail_on_error=True, callback=None):
         """
-        Helper method that iterates through all messages starting at the offset
-        in the given FetchRequest
+        Encode and send a FetchRequest
+        
+        Payloads are grouped by topic and partition so they can be pipelined to the same
+        brokers.
+        """
+        # Group the produce requests by which broker they go to
+        original_keys = []
+        payloads_by_broker = defaultdict(list)
+        for payload in payloads:
+            payloads_by_broker[self.get_leader_for_partition(payload.topic, payload.partition)].append(payload)
+            original_keys.append((payload.topic, payload.partition))
+
+        # Accumulate the responses in a dictionary, keyed by topic+partition 
+        acc = {}
+
+        # For each broker, send the list of request payloads
+        for broker, payloads in payloads_by_broker.items():
+            conn = self.get_conn_for_broker(broker)
+            requestId = self.next_id()
+            request = KafkaProtocol.encode_fetch_request(KafkaClient.CLIENT_ID, requestId, payloads)
+            # Send the request
+            conn.send(requestId, request)
+            response = conn.recv(requestId)
+            for fetch_response in KafkaProtocol.decode_fetch_response_iter(response):
+                # Check for errors
+                if fail_on_error == True and fetch_response.error != 0:
+                    raise Exception("FetchRequest %s failed with errorcode=%d" %
+                            (TopicAndPartition(fetch_response.topic, fetch_response.partition), fetch_response.error))
+                # Run the callback
+                if callback is not None:
+                    acc[(fetch_response.topic, fetch_response.partition)] = callback(fetch_response)
+                else:
+                    acc[(fetch_response.topic, fetch_response.partition)] = fetch_response
+
+        # Order the accumulated responses by the original key order
+        return (acc[k] for k in original_keys)
+
+    def try_send_request(self, requestId, request):
+        """
+        Attempt to send a broker-agnostic request to one of the available brokers.
+        Keep trying until you succeed.
+        """
+        for conn in self.conns.values():
+            try:
+                conn.send(requestId, request)
+                response = conn.recv(requestId)
+                return response
+            except Exception, e:
+                log.warning("Could not send request [%r] to server %s, trying next server: %s" % (request, conn, e))
+                continue
+        return None
+
+    def send_offset_request(self, payloads=[], fail_on_error=True, callback=None):
+        requestId = self.next_id()
+        request = KafkaProtocol.encode_offset_request(KafkaClient.CLIENT_ID, requestId, payloads)
+        response = self.try_send_request(requestId, request)
+        if response is None:
+            if fail_on_error is True:
+                raise Exception("All servers failed to process request")
+            else:
+                return None
+        out = []
+        for offset_response in KafkaProtocol.decode_offset_response(response):
+            if fail_on_error == True and offset_response.error != 0:
+                raise Exception("OffsetRequest failed with errorcode=%s", offset_response.error)
+            if callback is not None:
+                out.append(callback(offset_response))
+            else:
+                out.append(offset_response)
+        return out
+
+    def send_offset_commit_request(self, group, payloads=[], fail_on_error=True, callback=None):
+        requestId = self.next_id()
+        request = KafkaProtocol.encode_offset_commit_request(KafkaClient.CLIENT_ID, requestId, group, payloads)
+        response = self.try_send_request(requestId, request)
+        if response is None:
+            if fail_on_error is True:
+                raise Exception("All servers failed to process request")
+            else:
+                return None
+        out = []
+        for offset_commit_response in KafkaProtocol.decode_offset_commit_response(response):
+            log.debug(offset_commit_response)
+            if fail_on_error == True and offset_commit_response.error != 0:
+                raise Exception("OffsetCommitRequest failed with errorcode=%s", offset_commit_response.error)
+            if callback is not None:
+                out.append(callback(offset_commit_response))
+            else:
+                out.append(offset_commit_response)
+        return out
+
+    def send_offset_fetch_request(self, group, payloads=[], fail_on_error=True, callback=None):
+        requestId = self.next_id()
+        request = KafkaProtocol.encode_offset_fetch_request(KafkaClient.CLIENT_ID, requestId, group, payloads)
+        response = self.try_send_request(requestId, request)
+        if response is None:
+            if fail_on_error is True:
+                raise Exception("All servers failed to process request")
+            else:
+                return None
+        out = []
+        for offset_fetch_response in KafkaProtocol.decode_offset_fetch_response(response):
+            if fail_on_error == True and offset_fetch_response.error != 0:
+                raise Exception("OffsetFetchRequest for topic=%s, partition=%d failed with errorcode=%s" % (
+                    offset_fetch_response.topic, offset_fetch_response.partition, offset_fetch_response.error))
+            if callback is not None:
+                out.append(callback(offset_fetch_response))
+            else:
+                out.append(offset_fetch_response)
+        return out
 
-        Params
-        ======
-        topic: string
-        partition: int
-        offset: int, offset to start consuming from
-        size: number of bytes to initially fetch
-        auto: boolean, indicates whether or not to automatically make the next 
-              FetchRequest for more messages
-
-        Returns
-        =======
-        A generator of Messages
-        """
-        fetchRequest = FetchRequest(topic, partition, offset, size)
-        while True:
-            lastOffset = fetchRequest.offset
-            (messages, fetchRequest) = self.get_message_set(fetchRequest)
-            if fetchRequest.offset == lastOffset:
-                break
-            for message in messages:
-                yield message
-            if auto == False:
-                break
 
-    def close(self):
-        self._sock.close()
+if __name__ == "__main__":
+    logging.basicConfig(level=logging.DEBUG)
+
+    topic = "foo8"
+    # Bootstrap connection
+    conn = KafkaClient("localhost", 49720)
+
+    # Create some Messages
+    messages = (KafkaProtocol.create_gzip_message(["GZIPPed"]),
+                KafkaProtocol.create_message("not-gzipped"))
+
+    produce1 = ProduceRequest(topic=topic, partition=0, messages=messages)
+    produce2 = ProduceRequest(topic=topic, partition=1, messages=messages)
+
+    # Send the ProduceRequest
+    produce_resp = conn.send_produce_request(payloads=[produce1, produce2])
+
+    # Check for errors
+    for resp in produce_resp:
+        if resp.error != 0:
+            raise Exception("ProduceRequest failed with errorcode=%d", resp.error)
+        print resp
+
+    # Offset commit/fetch
+    #conn.send_offset_commit_request(group="group", payloads=[OffsetCommitRequest("topic-1", 0, 42, "METADATA?")])
+    #conn.send_offset_fetch_request(group="group", payloads=[OffsetFetchRequest("topic-1", 0)])
+
+    def init_offsets(offset_response):
+        if offset_response.error not in (ErrorMapping.NO_ERROR, ErrorMapping.UNKNOWN_TOPIC_OR_PARTITON):
+            raise Exception("OffsetFetch failed: %s" % (offset_response))
+        elif offset_response.error == ErrorMapping.UNKNOWN_TOPIC_OR_PARTITON:
+            return 0
+        else:
+            return offset_response.offset
+    # Load offsets
+    (offset1, offset2) = conn.send_offset_fetch_request(
+        group="group1", 
+        payloads=[OffsetFetchRequest(topic, 0),OffsetFetchRequest(topic, 1)],
+        fail_on_error=False,
+        callback=init_offsets
+    )
+    print offset1, offset2
+
+    while True:
+        for resp in conn.send_fetch_request(payloads=[FetchRequest(topic=topic, partition=0, offset=offset1, max_bytes=4096)]):
+            i = 0
+            for msg in resp.messages:
+                print msg
+                offset1 = msg.offset+1
+                print offset1, conn.send_offset_commit_request(group="group1", payloads=[OffsetCommitRequest(topic, 0, offset1, "")])
+                i += 1
+            if i == 0:
+                raise StopIteration("no more messages")
+
+        for resp in conn.send_fetch_request(payloads=[FetchRequest(topic=topic, partition=1, offset=offset2, max_bytes=4096)]):
+            i = 0
+            for msg in resp.messages:
+                print msg
+                offset2 = msg.offset+1
+                print offset2, conn.send_offset_commit_request(group="group1", payloads=[OffsetCommitRequest(topic, 1, offset2, "")])
+                i += 1
+            if i == 0:
+                raise StopIteration("no more messages")
+