Setting up a stand-alone repository for this

1 files changed, 475 insertions, 0 deletions

diff --git a/kafka.py b/kafka.py
new file mode 100644
index 0000000..3439238
--- /dev/null
+++ b/kafka.py
@@ -0,0 +1,475 @@
+from collections import namedtuple
+import logging
+import select
+import socket
+import struct
+import zlib
+
+log = logging.getLogger("org.apache.kafka")
+
+def length_prefix_message(msg):
+    """
+    Prefix a message with it's length as an int
+    """
+    return struct.pack('>i', len(msg)) + msg
+
+
+def create_message_from_string(payload):
+    return Message(1, 0, zlib.crc32(payload), payload)
+
+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(errorType)
+
+
+Message = namedtuple("Message", ["magic", "attributes", "crc", "payload"])
+FetchRequest = namedtuple("FetchRequest", ["topic", "partition", "offset", "size"])
+ProduceRequest = namedtuple("ProduceRequest", ["topic", "partition", "messages"])
+OffsetRequest = namedtuple("OffsetRequest", ["topic", "partition", "time", "maxOffsets"])
+
+class KafkaClient(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
+    """
+
+    PRODUCE_KEY      = 0
+    FETCH_KEY        = 1
+    MULTIFETCH_KEY   = 2
+    MULTIPRODUCE_KEY = 3
+    OFFSET_KEY       = 4
+
+    def __init__(self, host, port):
+        self.host = host
+        self.port = port
+        self._sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+        self._sock.connect((host, port))
+        log.debug("Connected to %s on %d", host, port)
+
+    ######################
+    #   Protocol Stuff   #
+    ######################
+
+    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
+        """
+        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(1024)
+            log.debug("Read %d bytes from Kafka", len(resp))
+            if resp == "":
+                raise Exception("Underflow")
+            total += len(resp)
+            yield resp
+
+    def _consume_response(self):
+        """
+        Fully consumer the response iterator
+        """
+        data = ""
+        for chunk in self._consume_response_iter():
+            data += chunk
+        return data
+
+    
+    def create_message(self, message):
+        """
+        Create a Message from a Message tuple
+
+        Params
+        ======
+        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.
+        """
+        if message.magic == 0:
+            return struct.pack('>Bi%ds' % len(message.payload),
+                               message.magic, message.crc, message.payload)
+        elif message.magic == 1:
+            return struct.pack('>BBi%ds' % len(message.payload),
+                               message.magic, message.attributes, message.crc, message.payload)
+        else:
+            raise Exception("Unknown message version: %d" % message.magic)
+
+    def create_message_set(self, messages):
+        message_set = ""
+        for message in messages:
+            encoded_message = self.create_message(message)
+            message_set += length_prefix_message(encoded_message)
+        return message_set
+
+    def create_produce_request(self, produceRequest):
+        """
+        Create 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 = self.create_message_set(messages)
+        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 create_multi_produce_request(self, produceRequests):
+        req = struct.pack('>HH', KafkaClient.MULTIPRODUCE_KEY, len(produceRequests))
+        for (topic, partition, messages) in produceRequests:
+            message_set = self.create_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
+
+    def create_fetch_request(self, fetchRequest):
+        """
+        Create 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
+
+    def create_multi_fetch_request(self, fetchRequests):
+        """
+        Create the MultiFetchRequest message from a list of FetchRequest objects
+
+        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
+
+    def create_offset_request(self, offsetRequest):
+        """
+        Create an OffsetRequest message
+
+        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 request-key (4) is encoded as a short (int16).
+        """
+        (topic, partition, offset, maxOffsets) = offsetRequest
+        req = struct.pack('>HH%dsiqi' % len(topic), KafkaClient.OFFSET_KEY, len(topic), topic, partition, offset, maxOffsets)
+        return req
+
+    def read_message_set(self, data):
+        """
+        Read a MessageSet
+
+        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:
+            if (cur + 5) > size:
+                # Underflow for the Header
+                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
+            # Read a Message header (length, magic byte)
+            (N, magic) = struct.unpack('>iB', data[cur:(cur+5)])
+
+            if (cur + N + 4) > size:
+                # Underflow for this Message
+                log.debug("Not enough data to read next message")
+                break
+            cur += 5
+
+            if magic == 0: # v0 Message
+                # Read crc; check the crc; append the message
+                (crc,) = struct.unpack('>i', data[cur:(cur+4)])
+                cur += 4
+                payload = data[cur:(cur+N-5)]
+                assert zlib.crc32(payload) == crc
+                cur += (N-5)
+                log.debug("Got v0 Message, %d bytes", len(payload))
+                msgs.append(Message(magic, None, crc, payload))
+            elif magic == 1: # v1 Message
+                # Read attributes, crc; check the crc; append the message
+                (att, crc) = struct.unpack('>Bi', data[cur:(cur+5)])
+                cur += 5
+                payload = data[cur:(cur+N-6)]
+                assert zlib.crc32(payload) == crc
+                cur += (N-6)
+                log.debug("Got v1 Message, %d bytes", len(payload))
+                msgs.append(Message(magic, att, crc, payload))
+
+        # Return the retrieved messages and the cursor position
+        return (msgs, cur)
+
+    #########################
+    #   Advanced User API   #  
+    #########################
+
+    def send_message_set(self, produceRequest):
+        """
+        Send a ProduceRequest
+        
+        Params
+        ======
+        produceRequest: ProduceRequest
+        """
+        req = length_prefix_message(self.create_produce_request(produceRequest))
+        log.debug("Sending %d bytes to Kafka", len(req))
+        self._sock.send(req) 
+
+    def send_multi_message_set(self, produceRequests):
+        """
+        Send a MultiProduceRequest
+        
+        Params
+        ======
+        produceRequests: list of ProduceRequest
+        """
+        req = length_prefix_message(self.create_multi_produce_request(produceRequests))
+        log.debug("Sending %d bytes to Kafka", len(req))
+        self._sock.send(req) 
+
+    def get_message_set(self, fetchRequest):
+        """
+        Send a FetchRequest and return the Messages
+
+        Params
+        ======
+        fetchRequest: FetchRequest named tuple
+
+        Returns
+        =======
+        A tuple of (list(Message), FetchRequest). This FetchRequest will have the offset 
+        starting at the next message. 
+        """
+
+        req = length_prefix_message(self.create_fetch_request(fetchRequest))
+        log.debug("Sending %d bytes to Kafka", len(req))
+        self._sock.send(req) 
+        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))
+
+    def get_multi_message_set(self, fetchRequests):
+        """
+        Send several FetchRequests in a single pipelined request.
+
+        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.create_multi_fetch_request(fetchRequests))
+        log.debug("Sending %d bytes to Kafka", len(req))
+        self._sock.send(req) 
+        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
+
+    def get_offsets(self, offsetRequest):
+        """
+        Get the offsets for a topic
+
+        Params
+        ======
+        offsetRequest: OffsetRequest
+    
+        Returns
+        =======
+        offsets: tuple of offsets
+        
+        Wire Format
+        ===========
+        <OffsetResponse> ::= <num> [ <offsets> ]
+        <num>            ::= <int32>
+        <offsets>        ::= <offset> [ <offsets> ]
+        <offset>         ::= <int64>
+
+        """
+        req = length_prefix_message(create_offset_request(offsetRequest))
+        log.debug("Sending %d bytes to Kafka", len(req))
+        self._sock.send(req) 
+
+        data = self._consume_response()
+        (num,) = struct.unpack('>i', data[0:4])
+        offsets = struct.unpack('>%dq' % num, data[4:])
+        return offsets
+
+    #######################
+    #   Simple User API   #
+    #######################
+
+    def send_messages_simple(self, topic, partition, *payloads):
+        """
+        Send one or more strings to Kafka
+
+        Params
+        ======
+        topic: string
+        partition: int
+        payloads: strings
+        """
+        messages = tuple([create_message_from_string(payload) for payload in payloads])
+        self.send_message_set(ProduceRequest(topic, partition, messages))
+
+    def iter_messages(self, topic, partition, offset, size, auto=True):
+        """
+        Helper method that iterates through all messages starting at the offset
+        in the given FetchRequest
+
+        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()