openstack/deb-python-kafka
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# Kakfa Python client
This module provides low-level protocol support Apache Kafka. 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)

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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()

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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()