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| -rw-r--r-- | LICENSE | 203 | ||||
| -rw-r--r-- | README.md | 75 | ||||
| -rw-r--r-- | example.py | 29 | ||||
| -rw-r--r-- | kafka.py | 475 |
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It implements the five basic request types (and their responses): Produce, Fetch, MultiFetch, MultiProduce, and Offsets. + +Compatible with Apache Kafka 0.7x. + +# License + +Copyright 2012, David Arthur under Apache License, v2.0. See `LICENSE` + +# Usage + +## Send a message to a topic + +You need to specify the topic and partition + + kafka = KafkaClient("localhost", 9092) + kafka.send_messages_simple("my-topic", 0, "some message") + kafka.close() + +## Send several messages to a topic + +Same as before, just add more arguments to `send_simple` + + kafka = KafkaClient("localhost", 9092) + kafka.send_messages_simple("my-topic", 0, "some message", "another message", "and another") + kafka.close() + +## Recieve some messages from a topic + +Supply `get_message_set` with a `FetchRequest`, get back the messages and new `FetchRequest` + + kafka = KafkaClient("localhost", 9092) + req = FetchRequest("my-topic", 0, 0, 1024*1024) + (messages, req1) = kafka.get_message_set(req) + kafka.close() + +The returned `FetchRequest` includes the offset of the next message. This makes +paging through the queue very simple. + +## Send multiple messages to multiple topics + +For this we use the `send_multi_message_set` method along with `ProduceRequest` objects. + + kafka = KafkaClient("localhost", 9092) + req1 = ProduceRequest("my-topic-1", 0, [ + create_message_from_string("message one"), + create_message_from_string("message two") + ]) + req2 = ProduceRequest("my-topic-2", 0, [ + create_message_from_string("nachricht ein"), + create_message_from_string("nachricht zwei") + ]) + kafka.sent_multi_message_set([req1, req1]) + kafka.close() + +## Iterate through all messages from an offset + +The `iter_messages` method will make the underlying calls to `get_message_set` +to provide a generator that returns every message available. + + kafka = KafkaClient("localhost", 9092) + for msg in kafka.iter_messages(FetchRequest("my-topic", 0, 0, 1024*1024)): + print(msg.payload) + kafka.close() + +An optional `auto` argument will control auto-paging through results + + kafka = KafkaClient("localhost", 9092) + for msg in kafka.iter_messages(FetchRequest("my-topic", 0, 0, 1024*1024), False): + print(msg.payload) + kafka.close() + +This will only iterate through messages in the first byte range of +(0, 1024\*1024) diff --git a/example.py b/example.py new file mode 100644 index 0000000..c58751b --- /dev/null +++ b/example.py @@ -0,0 +1,29 @@ +import logging + +from kafka import KafkaClient, FetchRequest, ProduceRequest +from kafka import create_message_from_string + +def produce_example(kafka): + message = create_message_from_string("test") + request = ProduceRequest("my-topic", 0, [message]) + print("Sending %s" % str(request)) + kafka.send_message_set(request) + +def consume_example(kafka): + request = FetchRequest("my-topic", 0, 0, 64) + print("Sending %s" % str(request)) + (messages, nextRequest) = kafka.get_message_set(request) + print("Got %d messages:" % len(messages)) + for message in messages: + print("\t%s" % message.payload) + print("Next request %s" % str(nextRequest)) + +def main(): + kafka = KafkaClient("localhost", 9092) + produce_example(kafka) + consume_example(kafka) + + +if __name__ == "__main__": + logging.basicConfig(level=logging.DEBUG) + main() 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() |