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Diffstat (limited to 'kafka/kafka.py')
| -rw-r--r-- | kafka/kafka.py | 629 |
1 files changed, 629 insertions, 0 deletions
diff --git a/kafka/kafka.py b/kafka/kafka.py new file mode 100644 index 0000000..ff9f53d --- /dev/null +++ b/kafka/kafka.py @@ -0,0 +1,629 @@ +from collections import namedtuple +from cStringIO import StringIO +import logging +import gzip +import select +import socket +import struct +import zlib + +log = logging.getLogger("org.apache.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(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"]) + +def gzip_encode(payload): + buf = StringIO() + f = gzip.GzipFile(fileobj=buf, mode='w', compresslevel=6) + f.write(payload) + f.close() + buf.seek(0) + out = buf.read() + buf.close() + return out + +def gzip_decode(payload): + buf = StringIO(payload) + f = gzip.GzipFile(fileobj=buf, mode='r') + out = f.read() + f.close() + buf.close() + return out + + +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): + """ + 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 + + ATTRIBUTE_CODEC_MASK = 0x03 + + 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) + + ###################### + # 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(self.bufsize) + 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 + + @classmethod + def encode_message(cls, message): + """ + Encode 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: + 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) + 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): + """ + Encode a MessageSet + + One or more concatenated Messages + """ + message_set = "" + for message in messages: + encoded_message = cls.encode_message(message) + message_set += encoded_message + return message_set + + @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 + + @classmethod + def encode_multi_produce_request(cls, produceRequests): + """ + Encode a MultiProducerRequest + + 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 + + @classmethod + def encode_multi_fetch_request(cls, fetchRequests): + """ + Encode 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 + + @classmethod + def encode_offset_request(cls, offsetRequest): + """ + Encode 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 + + @classmethod + def decode_message(cls, data): + """ + 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. + + 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 + raise NotImplementedError("Snappy codec is not yet supported") + else: + raise RuntimeError("Unsupported compression type: %d" % (att & KafkaClient.ATTRIBUTE_CODEC_MASK)) + + @classmethod + def read_message_set(cls, data): + """ + Read a MessageSet + + 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 # + ######################### + + @classmethod + def create_message(cls, payload): + """ + Create a standard Message + + Params + ====== + payload, bytes + + Returns + ======= + A Message tuple + """ + return Message(1, 0, zlib.crc32(payload), payload) + + @classmethod + def create_gzip_message(cls, *payloads): + """ + Create a Gzip encoded Message + + Params + ====== + payloads, list of messages (bytes) to be encoded + + 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) + + def send_message_set(self, produceRequest): + """ + Send a ProduceRequest + + Params + ====== + produceRequest: ProduceRequest + """ + req = length_prefix_message(self.encode_produce_request(produceRequest)) + log.debug("Sending %d bytes to Kafka: %r", len(req), req) + sent = self._sock.send(req) + if sent == 0: + raise RuntimeError("Kafka went away") + + + def send_multi_message_set(self, produceRequests): + """ + Send a MultiProduceRequest + + 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.send(req) + if sent == 0: + raise RuntimeError("Kafka went away") + + 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.encode_fetch_request(fetchRequest)) + log.debug("Sending %d bytes to Kafka", len(req)) + sent = self._sock.send(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)) + + 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.encode_multi_fetch_request(fetchRequests)) + log.debug("Sending %d bytes to Kafka", len(req)) + sent = self._sock.send(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 + + 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(encode_offset_request(offsetRequest)) + log.debug("Sending %d bytes to Kafka", len(req)) + sent = self._sock.send(req) + if sent == 0: + raise RuntimeError("Kafka went away") + + 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, *payloads): + """ + Send one or more strings to Kafka + + Params + ====== + topic: string + payloads: strings + """ + messages = tuple([create_message(payload) for payload in payloads]) + self.send_message_set(ProduceRequest(topic, -1, 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() |